Anatomy and Physiology Chapter 5 Etymological Breakdown of the Term Integumentar y System: • Integument-: Derived from the Latin root integumentum, which means "a covering," "disguise," or "cloak" (stemging from integere, meaning to cover or protect). • -ary: A standard adjectival suffix meaning "pertaining to" or "relating to.” • System: Derived from the Greek systēma, meaning a "organized whole" or a "combination of parts" working together. Put it all together, and the integumentary system literally translates to the system relating to the body's covering (the skin, hair, nails, and associated glands that protect the body as an organized unit). Overview of the Integumentary System The Skin and Beyond: • While commonly called the skin, the integumentary system is actually a complex organ system. • Includes the skin (cutaneous membrane) plus its accessory structures: hair, nails, and sweat and sebaceous (oil) glands. Scale & Importance: • The skin is the largest organ of the body, accounting for about 16 percent of body weight (16 to 20 pounds average adult) and covering a surface area of 1.5 to 2 square meters. Primary Functions: • Acts as the immediate barrier protecting the body from pathogens, chemicals, and mechanical injury. • Prevents fluid loss and regulates body temperature and sensation. Clinical Significance: • Often reflects overall health; changes in color, texture, or integrity can indicate underlying systemic diseases (e.g., cardiovascular, respiratory, or liver conditions). https://www.researchgate.net/ Overview of Skin Layers Dual-Layered Organ: • The skin consists of two main, distinct layers resting on a supportive subcutaneous layer. 1. Epidermis: • The superficial, outermost layer of the skin. • Composed of keratinized stratified squamous epithelium. • Avascular (receives nutrients via diffusion from the dermis below). 2. Dermis: • The deeper layer lying directly beneath the epidermis. • Composed of connective tissue (areolar and dense irregular). • Vascularized; houses blood vessels, lymphatic vessels, nerves, hair follicles, and sweat glands. Overview of Skin Layers 3. Hypodermis (Subcutaneous Layer / Superficial Fascia): • Technically not part of the skin itself, but closely associated. • Composed of loose areolar and adipose tissue; anchors skin to underlying muscle and bone while providing insulation and cushioning. https://quizlet.com/ Thick Skin vs. Thin Skin (Epidermal Layers) Classification Criteria: • Skin is categorized as either "thick" or "thin" based on the number of epidermal layers and the depth of the stratum corneum, not the total thickness of the skin organ as a whole. Thin Skin: • Contains four layers (stratum basale, spinosum, granulosum, and corneum). NOTE: These are listed from deep to superficial • Lacks the stratum lucidum. • Covers the vast majority of the body surface and contains hair follicles and sebaceous glands. Thick Skin: • Contains five layers (features the translucent stratum lucidum). • Found only on areas subject to heavy friction and abrasion: the palms of the hands and the soles of the feet. • Features a much thicker stratum corneum and lacks hair follicles and sebaceous glands. https://med.libretexts.org/ Cells of the Epidermis 1. Keratinocytes: • The most abundant cells in the epidermis (approx. 90%). • Synthesize keratin, a tough, fibrous protein that gives skin its hardness, durability, and water-resistant properties. • Continuously produced by stem cells in the deepest layer, pushing upward and eventually shedding. 2. Melanocytes: • Located in the deepest epidermal layer. • Produce the pigment melanin, which absorbs UV radiation and protects deeper cell DNA; transferred to keratinocytes. 3. Langerhans Cells: • Dendritic cells functioning as macrophages in the epidermis. • Engulf bacteria, foreign particles, and damaged cells to trigger an immune response. 4. Merkel Cells: • Receptor cells located in the deepest layer that function as touch receptors, associating with sensory nerve endings. Cells of the Epidermis Layers (Strata) of the Epidermis Layers (Strata) of the Epidermis 1. Stratum Basale (Basal Layer / Stratum Germinativum): • Deepest single layer; attached to the basement membrane and underlying dermis. • Forms a wavy boundary by interlocking with upward projections of the dermis called dermal papillae, increasing surface area and strengthening the epidermal-dermal bond to prevent shearing (enhancing grip). • The stratum basale is a single layer of cells primarily made of basal cells. • Site of continuous mitotic cell division (cuboidal stem cells) that continually produce new keratinocytes. • Houses melanocytes (pigment producers) and Merkel cells (touch receptors). 2. Stratum Spinosum ("Spiny Layer"): • 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny appearance under a microscope. • Contains maturing keratinocytes and Langerhans cells. • Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid. https://www.flickr.com/photos/187096960@N06/51172620298 Layers (Strata) of the Epidermis 1. Stratum Basale (Basal Layer / Stratum Germinativum): • Deepest single layer; attached to the basement membrane and underlying dermis. • Forms a wavy boundary by interlocking with upward projections of the dermis called dermal papillae, increasing surface area and strengthening the epidermal-dermal bond to prevent shearing (enhancing grip). • The stratum basale is a single layer of cells primarily made of basal cells. • Site of continuous mitotic cell division (cuboidal stem cells) that continually produce new keratinocytes. • Houses melanocytes (pigment producers) and Merkel cells (touch receptors). 2. Stratum Spinosum ("Spiny Layer"): • 8 to 10 layers of keratinocytes connected by strong desmosomes, giving a spiny appearance under a microscope. • Contains maturing keratinocytes and Langerhans cells. • Keratinocytes in the stratum spinosum begin the synthesis of keratin and release a water-repelling glycolipid. https://www.flickr.com/photos/187096960@N06/51172620298 Layers (Strata) of the Epidermis 3. Stratum Granulosum ("Granular Layer"): • 3–5 layers deep; cells flatten and fill with keratin, keratohyalin granules, and lamellar granules (waterproofing glycolipids). • Organelles disintegrate and cell death occurs as cells are pushed further from the blood supply. 4. Stratum Lucidum ("Clear Layer"): • Thin, translucent layer of dead, flattened cells packed with eleidin. • Found only in thick skin (palms of hands and soles of feet). 5. Stratum Corneum ("Horny Layer"): • Superficial layer consisting of 15–30 layers of flat, dead, keratin-filled cells. • Provides a durable, waterproof barrier against microbes, dehydration, and mechanical abrasion; continuously sloughed off. Layers (Strata) of the Epidermis The Dermis: Regions & Structure General Characteristics: • The "core" of the cutaneous system; houses blood vessels, sweat glands, oil glands, hair follicles, and nerve endings. • Consists of two layers of connective tissue that compose an interconnected mesh of elastin and collagenous fibers, produced by fibroblasts. 1. Papillary Layer: • Upper 20% of the dermis; composed of loose areolar connective tissue with a loose meshwork of collagen and elastic fibers. • Features dermal papillae that project upward into the epidermis, forming unique epidermal ridges (fingerprints) that enhance grip. • Contains rich capillary loops that nourish the avascular epidermis via diffusion and help regulate body temperature and lymphatic capillaries. • Packed with sensory nerve endings, including Meissner corpuscles (receptors sensitive to light touch) and free nerve endings that detect pain and temperature. • 2. Reticular Layer: • Deeper, thicker 80% of the dermis; composed of dense irregular connective tissue. • Packed with thick bundles of collagen fibers (for structural strength and tensile resilience) and elastic fibers (for skin stretch and recoil). • Contains larger blood vessels, sweat/sebaceous glands, and Pacinian corpuscles (deep pressure receptors). Papillary layer also contains fibroblasts, some fat cells (adipocytes), and phagocytes. Meissner corpuscles https://neuroscientificallychallenged.com/glossary/meissners-corpuscles https://histology.siu.edu/intro/Meissners2.htm The Dermis: Regions & Structure • Papillary layer also contains fibroblasts, some fat cells (adipocytes), mast cells, and phagocytes. https://www.enhance-me-training.com/topic/the-dermis/ The Hypodermis (Subcutaneo us Layer) Position & Anatomy: • Located directly beneath the reticular layer of the dermis. • Technically not part of the skin proper, but rather a connective tissue layer that anchors the skin to underlying bone and muscle. • Composed primarily of loose areolar connective tissue and adipose tissue (fat cells). Vascular Supply: • Highly vascularized; contains large blood vessels that supply the skin and serve as a common site for subcutaneous injections (hypodermic needles). Primary Functions: • Energy Storage: Adipocytes store triglycerides as an energy reserve. • Insulation & Protection: The fat layer provides thermal insulation against heat loss and acts as a shock-absorbing cushion to protect underlying structures from mechanical trauma. Skin Pigmentation & Color Determinants 1. Melanin: • Produced by melanocytes; primary pigment determining skin color. • Exists in two primary forms: eumelanin (brown/black) and pheomelanin (red/yellow). • UV exposure stimulates tyrosinase enzyme activity, increasing melanin production (tanning) to shield cell nuclei from DNA damage. • Freckles and moles represent localized accumulations of melanin. 2. Carotene: • A yellow-orange pigment obtained from plant-based foods (e.g., carrots, sweet potatoes) that can accumulate in the stratum corneum and hypodermis. 3. Hemoglobin: • The red oxygen-transporting protein in red blood cells. • Imparts a pinkish or red tint to the skin as blood flows through the dermal capillaries, particularly visible in lighter-skinned individuals when oxygenated. Carotenodermia https://www.nejm.org/doi/abs/10.1056/NEJMicm950425 https://en.wikipedia.org/wiki/Jaundice https://www.azolifesciences.com/ Integumentary System Disorders Overview of Accessory Structures Definition: • Structures that originate from the epidermis and extend down into the dermis or hypodermis. Key Components: • Hair • Nails • Sweat (Sudoriferous) Glands • Sebaceous (Oil) Glands General Function: • While embedded in the skin, these structures play critical roles in protection, sensory input, thermoregulation, and excretion. https://www.mayoclinichealthsystem.org/ https://www.harleystreethairtransplants.org/ Hair Structure and Growth Anatomy of a Hair: • Shaft: The portion of the hair exposed above the skin surface (completely dead, keratinized cells). • Root: The portion of hair anchored within the follicle below the skin surface. • Hair Bulb: The expanded base of the root surrounding the hair papilla (which contains blood vessels and nerves). Layers of the Hair: • Medulla: The central core of the hair. • Cortex: The middle layer providing strength and pigment. • Cuticle: The outermost layer of overlapping, single cells protecting the inner layers. Follicle & Arrector Pili: • Surrounded by a root sheath and connected to an involuntary smooth muscle called the arrector pili, which contracts to pull hair upright ("goosebumps" in response to cold or fear) and is controlled by the sympathetic nervous system. • This traps a layer of air to add insulation https://www.toppik.com/ Internal Root Sheath Layers of the Hair Follicle External Root Sheath • Structure: Surrounds the growing hair root up to the hair shaft. • Origin: Derived from the basal cells of the hair matrix. Wall • Structure: Encloses the hair root as a direct extension of the epidermis. • Characteristics: Composed of basal cells at the base; becomes increasingly keratinous toward the upper regions. Glassy Membrane • Structure: A thick, clear connective tissue sheath covering the hair root. • Function: Connects the hair follicle directly to the surrounding dermal tissue. Root Hair Plexuses (Hair Follicle Receptors) • Histological Definition: Specialized networks of unmyelinated sensory nerve fibers that wrap intricately around and entwine within the external root sheath of hair follicles. • Anatomical Position: Located in the dermal portion of the hair follicle wall, typically positioned just inferior to the entrance of the sebaceous gland ducts. • Functional Role: Act as rapid-adapting mechanoreceptors (tactile receptors) responsible for detecting fine, light-touch stimuli. • Mechanism of Action: • Deflection of the hair shaft (from wind, clothing, or a crawling insect) acts as a mechanical lever. • Movement physically shifts the follicular wall and deforms the entwined nerve endings. • Mechanical deformation opens mechanically- gated ion channels, triggering action potentials that travel via sensory neurons to the central nervous system. • Clinical/Physiological Significance: Highly sensitive to initial directional movement, providing early cutaneous awareness of external environmental contact before deeper touch receptors are engaged. https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/ https://www.nisenet.org/catalog/scientific-image-human-hair Hair Growth Cycle & Dynamics • Anagen Phase (Growth): Rapid cell division at the root pushes the hair shaft upward at ~0.3 mm/day; lasts 2 to 7 years. • Catagen Phase (Transition): A brief 2 to 3 week transitional period marking the end of active follicular growth. • Telogen Phase (Resting): Lasts 2 to 4 months with no new growth, culminating in a new anagen phase that sheds the old hair. • Shedding & Loss: Average daily loss is 50 hairs; excessive loss exceeding replacement results from aging, hormonal fluctuations, or dietary changes. https://www.pinterest.com/pin/halloween-hair--417638565445540250/ Sweat (Sudoriferous) Glands Function: • Produce sweat to cool the body via evaporative cooling and excrete metabolic wastes. 1. Eccrine (Merocrine) Sweat Glands: • More common; distributed across nearly the entire skin surface (especially palms, soles, and forehead). • Produce a hypotonic fluid (water, salts, metabolic wastes) released via exocytosis directly onto the skin surface for thermoregulation. 2. Apocrine Sweat Glands: • Confined to areas with hair follicles (e.g., armpits and genital regions). • Larger glands that release a thicker, organic-rich (in addition to water and salts) secretion into hair follicles, which is metabolized by bacteria to produce body odor; become active starting at puberty. • The release of this sweat is under both nervous and hormonal control https://en.wikipedia.org/wiki/Apocrine_sweat_gland Sebaceous (Oil) Glands Definition: • Exocrine glands associated with hair follicles found all over the body except on the palms and soles. Secretion (Sebum): • Produce sebum, a mixture of lipids, cholesterol, and proteins. Functions of Sebum: • Lubricates and waterproofs the skin and hair, preventing them from drying out. • Possesses antibacterial properties to inhibit the growth of microorganisms on the skin surface. Mode of Secretion: • Holocrine secretion: cells accumulate sebum until they rupture and destroy themselves, releasing their product (replaced by mitotic division of basal cells). https://quizlet.com/ca/443370620/hair-and-nails-flash-cards/ Nails Structure & Composition: • Specialized accessory structures composed of densely packed, dead, heavily keratinized epidermal cells. Key Anatomical Features: • Nail Body (Plate): The visible hard plate covering the dorsal surface of the fingertip/toe. • Nail Bed: The specialized skin underlying the nail body, richly supplied with blood vessels (giving it a pink color). • Nail Root: The deep epidermal fold under the skin where nail production begins. • Eponychium (Cuticle): The fold of epithelial tissue that overlaps the proximal edge of the nail body. • Lunula: The thick, crescent-shaped whitish area at the base of the nail body overlying the thick nail matrix. Primary Functions: • Protects the distal tips of fingers and toes from trauma and enhances precision grip for picking up small objects. Overview of Integumentary Functions Primary Role: • The skin and its accessory structures function as an integrated organ system that maintains homeostasis and protects the body. Core Physiological Functions: • Protection: Acts as a physical and chemical barrier against external elements. • Sensation: Detects environmental stimuli via specialized receptors. • Thermoregulation: Modulates body temperature through sweat and blood vessel adjustments. • Vitamin D Synthesis: Produces a crucial hormone essential for calcium absorption. Protection (The Body's Armor) Physical & Chemical Barrier: • Protects underlying vital organs from mechanical injury, UV radiation, wind, and water. Dehydration Prevention: • Layers of tough keratin and water-resistant glycolipids in the stratum corneum prevent excessive fluid loss. Microbial Defense: • Acts as a first line of defense against pathogens, abrasive grit, and harmful chemicals. • Sweat contains dermcidin, which possesses antibiotic properties to deter microbe over-colonization. Immune Protection: • Langerhans (dendritic) cells patrol epidermal layers to intercept foreign invaders and trigger immune responses. https://uen.pressbooks.pub/anatomyphysiology/chapter/epidermis/ Langerhan s (Dendritic) Cells (APC’s) https://courses.lumenlearning.com/wm-biology2/chapter/antigen-presenting-cells/ Sensation (Sensory Function) Environmental Awareness: • The integumentary system contains a rich network of specialized nerve endings and receptors across the epidermis, dermis, and hypodermis. Key Sensory Receptors: • Meissner (Tactile) Corpuscles: Highly concentrated in fingertips; respond to light touch. • Pacinian (Lamellated) Corpuscles: Detect deep pressure and vibration. • Merkel Cells & Hair Root Plexuses: Detect fine touch and minor hair disturbances (e.g., sensing an insect crawling on the skin). Pain & Temperature: • Free nerve endings distributed throughout the skin monitor noxious stimuli, temperature shifts, and physical trauma. Sensation (Sensory Function) • Merkel cells (Tactile discs): Located in the deep layer of the epidermis (stratum basale), these are slow-adapting receptors that excel at detecting sustained touch, fine detail, texture, and edges. When pressed, they release signaling molecules that excite adjacent nerve endings, providing high-resolution tactile feedback (like reading Braille or feeling a smooth surface). • Meissner corpuscles (Tactile corpuscles): Situated in the dermal papillae of hairless (glabrous) skin, such as your fingertips and lips, these are rapid-adapting receptors. They fire intensely when skin first makes contact with an object and when it loses contact, making them exceptionally sensitive to light touch, low-frequency vibration, and slippage (helping you adjust your grip on a moving object). • Pacinian corpuscles (Lamellar corpuscles): Found deep in the dermis and subcutaneous layer, these large, onion-shaped receptors are rapidly adapting and exquisitely sensitive to deep pressure and high-frequency vibration. Because of their layered capsule, steady pressure is filtered out, allowing them to fire only when vibration or sudden mechanical shifts occur (such as feeling a drill vibrate or walking on a rough surface). • Hair root plexus (Hair follicle receptors): A web of sensory nerve fibers wrapped around the base of hair follicles. These rapid-adapting mechanoreceptors detect the bending or movement of hairs. Even a light breeze or an insect crawling across your arm displaces a hair, triggering the surrounding nerve plexus and providing an early warning system for tactile movement across hairy skin. Pacinian Corpuscle (Sensory Organ) Pacinian Corpuscle Anatomy: Encapsulated, onion-like mechanoreceptor for deep pressure and vibration. • The Capsule & Outer Lamination: Dense connective tissue outer envelope and flattened lamellar cells that filter out steady pressure. • Viscous Gel: Interstitial fluid between layers that shifts hydraulically to dampen sustained forces, driving rapid adaptation. • Inner Lamination: Tightly packed, specialized modified Schwann cells forming a core around the central nerve terminal. • Terminal Non-Myelinated Axon: Bare, uninsulated nerve tip at the center with stretch-sensitive channels that trigger action potentials when compressed. • Myelinated Axon: Insulated nerve fiber exiting the corpuscle to rapidly transmit electrical impulses toward the central nervous system via saltatory conduction. Thermoregulation Sympathetic Nervous System Control : The integumentary system works closely with the autonomic nervous system (involuntary bodily control) to continuously monitor and adjust core body temperature. Response to Overheating (Cooling): • Sweating: Eccrine sweat glands secrete water and electrolytes; evaporative cooling dissipates body heat. (Note: insensible perspiration secretes ~500 mL/day even without noticeable sweating). • Vasodilation: Dermal blood vessels dilate to bring warm blood closer to the body surface, releasing heat into the environment. Response to Cold (Heat Retention): • Vasoconstriction: Dermal arterioles constrict to minimize blood flow to the skin surface, trapping core heat internally (can cause a pale/whitish hue). • Shivering: Involuntary muscle contractions generate metabolic heat (assisted by the contraction of arrector pili muscles). Vitamin D Synthesis The Pathway: • 1. Skin Activation: When epidermal cells are exposed to ultraviolet (UV) radiation, a cholesterol derivative in the skin converts into cholecalciferol (Vitamin 3). • 2. Liver Processing: The liver converts cholecalciferol into an intermediate compound called calcidiol. • 3. Kidney Activation: The kidneys convert calcidiol into calcitriol, which is the active, functional hormone form of Vitamin D. Physiological Importance: • Calcitriol is essential for the normal intestinal absorption of calcium and phosphorus, which are strictly required for bone health, growth, and remodeling. https://www.researchgate.net/ Effects of Aging on the Integumentary System Epidermal & Dermal Changes: • Mitotic activity in the stratum basale slows down, causing the epidermis to thin. • The dermis exhibits a reduced ability to regenerate, leading to a loss of structural elasticity and flexibility (manifesting as wrinkles). • Fibroblast activity declines, resulting in decreased production of collagen and elastic fibers. Vascular & Glandular Decline: • Blood supply to the skin decreases, reducing the skin's capacity to heal quickly and impairing thermoregulation (leading to increased sensitivity to cold). • Functional activity of sweat (sudoriferous) and sebaceous (oil) glands drops, causing dry, scaly skin and a reduced ability to sweat effectively. Subcutaneous & Accessory Alterations: • The hypodermis loses fat storage over time, contributing to a loss of padding, insulation, and a sunken appearance. • Melanocyte and hair follicle activity slows down, resulting in graying or thinning hair and a reduced capacity to protect against UV radiation. • Immune responsiveness declines as the number of Langerhans cells drops, increasing susceptibility to skin infections and damage. Overview of Skin Cancer Definition & Cause: • Cancer caused by abnormal, uncontrollable cell division in the skin. • Primary culprit is overexposure to ultraviolet (UV) radiation from the sun or tanning beds, which damages cellular DNA. The Danger of Metastasis: • Metastasis is the process where cancer cells break away from the primary tumor, enter the bloodstream or lymphatic vessels, and spread to secondary sites (such as lymph nodes, lungs, or liver), making treatment significantly more difficult. Types of Skin Cancer: • Basal Cell Carcinoma (BCC): Starts in the stratum basale and spreads along that boundary; the most common form of skin cancer, highly curable with early treatment (common in areas exposed to the sun). • Treatments include surgery, freezing (cryosurgery), and topical ointments • Squamous Cell Carcinoma (SCC): Affects keratinocytes of the stratum spinosum; presents as lesions on the scalp, ears, and hands; more aggressive than BCC and can metastasize if left untreated. • Surgery and radiation are used to cure SCC • Melanoma: Uncontrolled growth of melanocytes, typically developing from a mole; the most fatal form of skin cancer due to high rates of metastasis. • Treatment typically involves surgical excision and immunotherapy Basal Cell Carcinoma Squamous Cell Carcinoma Melanoma Early Detection of Melanoma (The ABCDE Rule) Clinical Screening Guidelines: • A – Asymmetry: The two sides of the mole or lesion do not match. • B – Borders: The edges are irregular, ragged, notched, or blurred. • C – Color: The color is not uniform and may include different shades of brown or black, or patches of pink, red, white, or blue. • D – Diameter: The lesion is larger than 6 mm (about the size of a pencil eraser), though melanomas can sometimes be smaller. • E – Evolving: The mole is changing in size, shape, color, or elevation, or begins to bleed/itch. Common Skin Disorder s Introduction to Skin Disorders: • Skin disorders range from minor localized irritations to chronic systemic conditions, often involving inflammation, immune responses, or blocked glands. • Disorders include psoriasis, cold sores, impetigo, scabies, hives, and warts. Eczema: • An inflammatory, allergic condition that presents as dry, red, itchy patches resembling rashes. • Often accompanied by swelling, flaking, and skin cracking; managed with moisturizers, corticosteroid creams, and immunosuppressants. Acne: • A skin disturbance involving the overproduction of sebum and keratin that blocks hair follicles. • Most common during puberty due to hormonal surges (androgens) that stimulate sebaceous glands, leading to bacterial infection and inflammation. Skin Injuries & The Healing Process Types of Injuries: • Cuts, punctures, scrapes, and burns caused by physical trauma, heat, chemicals, or electricity. • Step-by-Step Wound Healing Stages: 1. Hemostasis & Clotting: A blood clot forms immediately to stop bleeding and eventually dries into a protective scab. 2. Inflammation: White blood cells (macrophages) clear out debris and fight potential infection. 3. Proliferation: Fibroblasts migrate into the wound bed to produce new collagen and blood vessels (granulation tissue). 4. Remodeling & Scarring: Epithelial cells regenerate across the wound under the scab, while scar tissue (dense collagen) replaces normal tissue depending on the depth of the injury. https://www.shieldhealthcare.com/ https://jetem.org/thermal_burns/ Burns and Classification s Nature of Burns: • Caused by intense heat, radiation, electricity, or chemicals, resulting in massive cell death and fluid loss. Severity Classifications: • First-Degree (Superficial): Affects only the epidermis; results in redness and minor pain (e.g., mild sunburn) that heals within days. • Second-Degree (Partial-Thickness): Damages both the epidermis and upper dermis; results in blistering and significant pain. • Third-Degree (Full-Thickness): Destroys the full thickness of the skin (epidermis and dermis), charring tissue and destroying nerve endings (often requiring skin grafts). • Fourth-Degree (Full-Thickness with Deep Tissue Damage): Extends completely through the skin down to underlying muscle, tendons, and bone; requires extensive surgical intervention and often amputation. Major Systemic Risks: • Severe dehydration, electrolyte imbalance, renal/circulatory failure, and rampant secondary infections due to lost skin barrier function. Fourth degree Burn https://burncenters.com/burns/evaluate-a-burn/ Common Integumentary Abnormalities and Injury Responses Scars & Keloids: • Scars: Formed when the skin repairs deep dermal damage using collagen-rich connective tissue rather than regenerating normal tissue. • Lacks accessory structures (e.g., hair follicles, sweat glands, and sebaceous glands) • Keloids: Result from an overproduction of scar tissue (collagen) that extends beyond the original boundaries of the wound. Bedsores (Decubitus Ulcers): • Caused by constant, long-term pressure on bony areas that cuts off blood supply to the skin, leading to tissue necrosis and breakdown. Stretch Marks (Striae): • Occur when the dermis is stretched beyond its elastic limits (e.g., during rapid growth, weight gain, or pregnancy), causing collagen and elastin fibers to tear. Calluses & Corns: • A protective response where the stratum basale increases mitotic activity in areas subjected to constant friction or pressure, resulting in a thickened, hardened layer of dead cells. https://www.healthline.com/health/keloid-ear https://www.mayoclinic.org/diseases-conditions/corns-and- calluses/multimedia/callus/img-20007285 https://myexpertmidwife.com/blogs/my-expert-midwife/stretch-marks-101 https://blog.xoxoday.com/empuls/get-to-know-you-questions-for-coworkers/

Flashcards - Réticulum Endoplasmique et Appareil de Golgi

Section 2.1 Ribosomes and Endoplasmic Reticulum

Endoplasmic Reticulum lecture 2

Conditions of the Rumen and Reticulum

Brainstem & Reticular formation

Conditions of the Rumen and Reticulum

part 5: Limbic System, Reticular Formation & Brain Protection

Chapter 4 Skin and Body Membranes Body Membranes Functions of body membranes Cover body surfaces Line body cavities Form protective sheets around organs Classified according to tissue types Body Membranes Two major categories Epithelial membranes Cutaneous membranes Mucous membranes Serous membranes Connective tissue membranes Synovial membranes Epithelial Membranes Epithelial membranes are simple organs Also called covering and lining membranes These membranes contain both: Epithelial tissue layer Connective tissue layer Epithelial Membranes Cutaneous membrane = skin Dry membrane Outermost protective boundary Consists of two layers Epidermis is composed of keratinized stratified squamous epithelium Dermis is mostly dense (fibrous) connective tissue Epithelial Membranes • Mucous membranes (mucosae) • I Moist membranes Some mucosae secrete protective, lubricating mucus Line all body cavities that open to the exterior body surface • Adapted for absorption or secretion • ' Consists of two layers • Epithelium type depends on site • Loose connective tissue (lamina propria) Epithelial Membranes Serous membranes (serosae) Line compartments in the ventral body cavity that are ciosed to the exterior of the body Occur in pairs, separated by serous fluid, with a visceral and parietal layer Consists of two layers Simple squamous epithelium Areolar connective tissue Epithelial Membranes Specific serous membranes Peritoneum Cover organs in the abdominal cavity Pleurae Surround the lungs Pericardia Surround the heart Connective Tissue Membranes Synovial membranes Loose areolar connective tissue only (no epithelial tissue) Line fibrous capsules surrounding joints Line bursae Line tendon sheaths Secrete a lubricating fluid to cushion organs moving against each other during muscle activity Integumentary System Integumentary system consists of the: Skin (cutaneous membrane) Skin appendages Sweat glands Oil glands Hair Nails Functions of the Integumentary System Insulates and cushion deeper body organs Protects the entire body from: Mechanical damage (bumps and cuts) Chemical damage (acids and bases) Thermal damage (heat or cold) Ultraviolet (UV) radiation (sunlight) Microbes (bacteria) • Water loss Functions of the Integumentary System Regulates heat loss as controlled by the nervous system Acts as a mini-excretory system; sweat aids in the loss of Urea Salts Water Synthesizes vitamin D Secretions create a protective acid mantle Structure of the Skin Two kinds of tissue compose the skin Epidermis Dermis Subcutaneous tissue (hypodermis) Anchors the skin to underlying organs Not technically part of the integumentary system Composed mostly of adipose tissue Serves as a shock absorber and insulates deeper tissues Structure of the Skin Epidermisouter layer Composed of stratified squamous epithelium Most cells are keratinocytes which produce a fibrous protein called keratin Keratinization makes the epidermis tough Desmosomes connect keratinocytes together Avascular Composed of five layers (strata) Structure of the Skin Summary of strata (layers) of the epidermis from deepest to most superficial Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (thick, hairless skin only) Stratum corneum Structure of the Skin Stratum basale (stratum germinativum) Deepest layer of epidermis Lies next to dermis Wavy borderline with the dermis anchors the two together Cells undergoing mitosis Daughter cells are pushed upward to become the more superficial layers Stratum spinosum Cells become increasingly flatter and more keratinized Structure of the Skin Stratum granulosum Stratum lucidum Formed from dead cells of the deeper strata Occurs only in thick, hairless skin of the palms of hands and soles of feet Stratum corneum Outermost layer of epidermis Shingle-like dead cells are filled with keratin (protective protein prevents wat loss from skin Structure of the Skin Melanin Melanin is a pigment produced by melanocytes Melanocytes are mostly in the stratum basale of the epidermis Color is yellow to brown to black Structure of the Skin Epidermal dendritic cells Alert and activate immune cells to a threat (bacterial or viral invasion) Merkel cells Associated with sensory nerve endings Serve as touch receptors called Merkel discs Structure of the Skin Dermis Connective tissue Underlies the epidermis Two regions Papillary Reticular Structure of the Skin Two regions of the dermis Papillary layer (upper dermal region) contain projections called dermal papillae Areolar connective tissue Indent the epidermis above Many projections contain capillary loops, and others house pain and touch receptors On palm and sole surfaces, papillae increase friction and gripping ability Fingerprints are identifying films of sweat Structure of the Skin Two regions of the dermis Reticular layer (deepest skin layer) Dense irregular connective tissue Blood vessels Sweat and oil glands Deep pressure receptors (lamellar corpuscles) Structure of the Skin Other dermal features Cutaneous sensory receptors Phagocytes Collagen and elastic fibers Blood vessels I Nerve supply Skin Color • Three pigments contribute to skin color 1. Melanin • Yellow, reddish brown, or black pigments 2. Carotene • Orange-yellow pigment (also found in some vegetables) 3. Hemoglobin Red coloring from blood cells in dermal capillaries Oxygen content determines the extent of red coloring Skin Color Redness (erythema) due to embarrassment, inflammation, hypertension, fever, or allergy Pallor (blanching) due to emotional stress (such as fear), anemia, low blood pressure, impaired blood flow to an area Jaundice (yellow cast)-indicates a liver disorder • Bruises (black and blue marks)-hematomas Appendages of the Skin Cutaneous glands are all exocrine glands Sebaceous glands Sweat glands Hair and hair follicles Nails Appendages of the Skin Sebaceous (oil) glands Located all over the skin except for palms and soles Produce sebum (oil) Makes skin soft and moist Prevents hair from becoming brittle Kills bacteria Most have ducts that empty into hair follicles; others open directly onto skin surface Glands are activated at puberty with increased androgens Appendages of the Skin Sweat (sudoriferous) glands Produce sweat Widely distributed in skin Two types of sudoriferous glands Eccrine glands Apocrine glands Appendages of the Skin Eccrine glands More numerous, located all over the body Open via duct to sweat pores on the skin's surface Produce acidic sweat Water, salts, vitamin C, traces of metabolic waste Function in body temperature regulation Appendages of the Skin Apocrine glands Ducts empty into hair follicles in the armpit and genitals Begin to function at puberty Release sweat that also contains fatty acids and proteins (milky or yellowish color) • Play a minimal role in body temperature regulation Appendages of the Skin Hair Located body-wide except for palms, soles, nipples, lips Produced by hair follicle Root is enclosed in the follicle Shaft projects from the surface of the scalp or skin Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale Appendages of the Skin Hair anatomy Central medulla Cortex surrounds medulla Cuticle on outside of cortex Most heavily keratinized region of the hair Melanin provides color Appendages of the Skin Associated hair structures Hair follicle Composed of an inner epithelial root sheath andan outer fibrous sheath Dermal region provides a blood supply to the hair bulb (deepest part of the follicle) Arrector pili muscle connects to the hair follicle to pull hairs upright when we are cold or frightened Appendages of the Skin Nails Heavily keratinized, scalelike modifications of the epidermis Stratum basale extends beneath the nail bed, which is responsible for growth Lack of pigment makes nails colorless Appendages of the Skin Parts of a nail Free edge Body is the visible attached portion Nail folds are skin folds that overlap the edges of the nail; the cuticle is the proximal edge Root of nail is embedded in skin Growth of the nail occurs from nail matrix of nail bed Homeostatic Imbalances of Skin Infections and allergies Athlete's foot Caused by fungal infection (Tinea pedis) Itchy, red peeling skin between the toes Boils (furuncles) and carbuncles Caused by inflammation of hair follicles Carbuncles are clusters of boils caused by bacteria Cold sores (fever blisters) Caused by human herpesvirus 1 Blisters itch and sting Homeostatic Imbalances of Skin Infections and allergies Contact dermatitis Caused by exposure to chemicals that provoke allergic responses Itching, redness, and swelling of the skin Impetigo Caused by bacterial infection Pink, fluid-filled raised lesions around mouth/nose Psoriasis Triggered by trauma, infection, hormonal changes, or stress Red, epidermal lesions covered with dry, silvery scales that itch, burn, Crack, or sometimes bleed Homeostatic Imbalances of Skin • Burns Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals Associated dangers Protein denaturation and cell death Dehydration and electrolyte imbalance Circulatory shock Result in loss of body fluids and infection from the invasion of bacteria Homeostatic Imbalances of Skin Extent of a burn is estimated using the rule of nines Body is divided into 11 areas for quick estimation Each area represents about 9 percent of total body surface area The area surrounding the genitals (the perineum) represents 1 percent of body surface area Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA replication, mitosis, or both. Cells experiencing rapid, uncontrolled growth become cancerous and can metastasize (spread) to other parts of the body. Homeostatic Imbalances of Skin . First-degree burn (superficial burn) Only epidermis is damaged Skin is red and swollen Second-degree burn (superficial partial-thickness burn) Epidermis and superficial part of dermis are damaged Skin is red, painful, and blistered Regrowth of the epithelium can occur Homeostatic Imbalances of Skin Third-degree burn (full-thickness burn) Destroys epidermis and dermis; burned area is painless Requires skin grafts, as regeneration is not possible Burned area is blanched (gray-white) or black Fourth-degree burn (full-thickness burn) Extends into deeper tissues (bone, muscle, tendons) Appears dry and leathery Requires surgery and grafting May require amputation Homeostatic Imbalances of Skin Criteria for deeming burns critical (if any one is met): Over 30 percent of body has second-degree burns Over 10 percent of the body has third-or fourth-degree burns Third-or fourth-degree burns of the face, hands, feet, or genitals Burns affect the airways Circumferential (around the body or limb) burns have occurred Homeostatic Imbalances of Skin Skin cancer Most common form of cancer in humans Most important risk factor is overexposure to ultraviolet (V) radiation in sunlight and tanning beds Cancer can be classified two ways Benign means the neoplasm (tumor) has not spread Malignant means the neoplasm has invaded other body areas Concept Link Recall that mitosis gone wild is the basis for cancer (Chapter 3, pp. 82-83). These cells lack normal control of cell division and divide quickly, resulting in errors during DNA • One or more of the ABCD characteristics is evolving Developmental Aspects of Skin and Body Membranes Lanugo, a downy hair, covers the body by the fifth or sixth month of fetal development but disappears by birth Vernix caseosa, an oily covering, is apparent at birth Milia, small white spots, are common at birth and disappear by the third week Acne may appear during adolescence Pimples, scales, and dermatitis are more common with aging skin Developmental Aspects of Skin and Body Membranes In youth, skin is thick, resilient, and well hydrated With aging, skin loses elasticity and thins Skin cancer is a major threat to skin exposed to excessive sunlight Balding (alopecia) and/or graying occurs with aging; both are genetically determined other factors that may contribute include drugs and emotional stress

Chapter 1: Structure and Function of the Muscular, Nervous, and Skeletal Systems I. The Muscular System. A. Gross Anatomy (Macrostructure) of Skeletal Muscle Connective Tissue Coverings: Epimysium: Outer layer of connective tissue surrounding the entire muscle belly.  Perimysium: Connective tissue surrounding bundles of muscle fibers (fascicles).  Endomysium: Connective tissue surrounding individual muscle fibers.  Tendon: Extension of connective tissues that connects muscle to bone to transmit force.  B. Microscopic Anatomy of Skeletal Muscle Muscle Fiber (Cell): Sarcolemma: The muscle cell membrane that encloses cell contents and conducts electrical impulses.  Sarcoplasm: Cytoplasm of the muscle cell containing ATP, glycogen, enzymes, and organelles.  Multinucleated: Muscle cells contain multiple nuclei located along the cell membrane.  Mitochondria: Organelles responsible for aerobic ATP production.  Sarcoplasmic Reticulum (SR): Internal network storing calcium ions (\bm{\text{Ca}^{2+}}) necessary for muscle action.  Transverse Tubules (T-Tubules): Channels running perpendicular to the myofibrils that carry action potentials deep into the cell.  C. Myofibrils & Sarcomere Structure Myofibril: Columnar protein structures containing contractile filaments.  Myofilaments: Myosin (Thick Filament): Consists of a head, neck, and tail; forms cross-bridges with actin.  Actin (Thin Filament): Globular protein structures containing binding sites for myosin heads. Associated with troponin and tropomyosin (regulatory proteins).  Sarcomere: The basic contractile unit of a muscle fiber bounded by Z-lines.  Z-line: Anchors actin filaments; marks the boundary of a sarcomere.  A-band: Alignment of myosin filaments (dark area).  I-band: Region containing only thin (actin) filaments (light area).  H-zone: Center of the A-band containing only thick (myosin) filaments.  M-line: Center anchor line for adjacent myosin filaments.  II. Neuromuscular Junction & Sliding Filament Theory A. Neuromuscular Junction (NMJ) Point of communication between a motor neuron and a skeletal muscle fiber.  Acetylcholine (ACh): Neurotransmitter released from the axon terminal into the synaptic cleft upon arrival of an action potential.  B. Steps in the Sliding Filament Theory 1. Action Potential: An impulse travels down the motor neuron to the axon terminal.  2. ACh Release: ACh is released into the synaptic cleft and binds to receptors on the sarcolemma.  3. Depolarization & \bm{\text{Ca}^{2+}} Release: The action potential travels along the T-tubules, triggering the release of calcium (\bm{\text{Ca}^{2+}}) from the sarcoplasmic reticulum into the sarcoplasm.  4. Troponin-Tropomyosin Shift: Calcium binds to troponin, causing a conformational change that moves tropomyosin away from myosin-binding sites on actin.  5. Cross-Bridge Formation: Energized myosin heads bind to open active sites on actin.  6. Power Stroke: Hydrolysis of ATP drives the power stroke; myosin pulls actin filaments toward the center of the sarcomere (H-zone shortens).  7. Detachment & Reset: A fresh ATP molecule binds to the myosin head, causing detachment from actin. ATP is hydrolyzed by myosin ATPase, re-energizing the head for subsequent cycles as long as calcium and ATP remain present.  III. Muscle Fiber Types & Actions A. Types of Muscle Actions Concentric: Muscle force exceeds external resistance; muscle shortens.  Eccentric: External force exceeds muscle force; muscle lengthens while developing tension.  Isometric: Muscle force equals external resistance; muscle length does not change.  B. Classification of Muscle Fibers Type I (Slow-Twitch / Slow Oxidative): High fatigue resistance, high aerobic capacity, high myoglobin content, lower force output, and slower contraction speed.  Dominant during endurance activities (e.g., walking, marathon running).  Type IIa (Fast-Twitch / Fast Oxidative-Glycolytic): Moderate fatigue resistance, hybrid aerobic/anaerobic capacity, moderate force production, fast contraction speed.  Type IIx (Fast-Twitch / Fast Glycolytic): Low fatigue resistance, high power/force output, high glycolytic capacity, very fast contraction speed.  Dominant during short-duration explosive movements (e.g., sprinting, heavy resistance training).  IV. The Nervous System A. Organization Central Nervous System (CNS): Brain and spinal cord.  Peripheral Nervous System (PNS): Nerve fibers outside the CNS.  Motor (Efferent) Neurons: Carry impulses from the CNS to peripheral effectors (muscles).  Sensory (Afferent) Neurons: Relay sensory inputs from sensory receptors (muscle, skin) back to the CNS.  Autonomic vs. Somatic: Somatic: Controls voluntary functions (e.g., skeletal muscle activation).  Autonomic: Controls involuntary functions (heart rate, digestion) via Sympathetic ("fight-or-flight") and Parasympathetic ("rest-and-digest") branches.  B. Proprioceptors Muscle Spindle: Sensory organs aligned in parallel with extrafusal muscle fibers.  Sensitive to changes in muscle length and rate of length change.  Triggers the myotatic (stretch) reflex, causing rapid concentric contraction of the stretched muscle to prevent overstretching.  Golgi Tendon Organ (GTO): Sensory receptors located in series within tendons near the neuromuscular junction.  Activated by excessive tension produced within the muscle. Causes reflex inhibition (relaxation) of the active muscle to protect against tendon damage or injury.

Endoplasmic Reticulum

Brainstem and Reticular Formation

histologija-retikulum

Exam Review Chapters 1, 2, & 3. Chapter 1 The Science of Psychology Behavior: Everything, we do that can be directly observed. Behavioral approach: an approach to psychology emphasizing the scientific study of observable behavioral responses and their environmental determinants. Biological approach: an approach to psychology focusing on the body, especially the brain and nervous system. Case study or case history: an in-depth look at a single individual. Cognitive approach: an approach to psychology emphasizing the mental processes involved in knowing: how we direct our attention, perceive, remember, think, and solve problems. Control group: The participants in an experiment who are as much like the experimental group as possible and who are treated in every way like the experimental group except for a manipulated factor, the independent variable. Correlational research: research that examines the relationships between variables, whose purpose is to examine whether and how two variables change together. Critical thinking: The process of thinking deeply and actively, asking questions, and evaluating the evidence. Dependent variable: The outcome; the factor that can change in an experiment in response to changes in the independent variable. Double-blind experiment: An experimental design in which neither the experimenter nor the participants are aware of which participants are in the experimental group and which are in the control group until the results are calculated. Evolutionary approach: An approach to psychology centered on evolutionary ideas such as adaptation, reproduction, and natural selection as the basis for explaining specific human behaviors. Experiment: A carefully regulated procedure in which the researcher manipulates one or more variables that are believed to influence some other variable. Experimental group: The participants in an experiment who receive the drug or other treatment under study—that is, those who are exposed to the change that the independent variable represents. Functionalism: James’s approach to mental processes, emphasizing the functions and purposes of the mind and behavior in the individual’s adaptation to the environment. Humanistic approach: An approach to psychology emphasizing a person’s positive qualities, the capacity for positive growth, and the freedom to choose any destiny. Hypothesis: A testable prediction that derives logically from a theory. Independent variable: A manipulated experimental factor; the variable that the experimenter changes to see what its effects are. Longitudinal design: A special kind of systematic observation, used by correlational researchers, that involves obtaining measures of the variables of interest in multiple waves over time. Mental processes: The thoughts, feelings, and motives that people experience privately but that cannot be observed directly. Natural selection: Darwin’s principle of an evolutionary process in which organisms that are best adapted to their environment will survive and produce offspring. Naturalistic observation: The observation of behavior in a real-world setting. Placebo: In a drug study, a harmless substance that has no physiological effect, given to participants in a control group so that they are treated identically to the experimental group except for the active agent. Placebo effect: The situation where participants’ expectations, rather than the experimental treatment, produce an experimental outcome. Population: The entire group about which the researcher wants to draw conclusions. Psychoanalysis: techniques involves an analyst unlocking a person's unconscious conflicts by talking with the individual about his or her childhood memories, dreams, thoughts, and feelings. Psychodynamic approach: an approach to psychology emphasizing unconscious thought, the conflict between biological drives (such as the drive for sex) and society’s demands, and early childhood family experiences. Psychology: The scientific study of behavior and mental processes. Sample: The subset of the population chosen by the investigator for study. Sociocultural approach: an approach to psychology that examines the ways in which social and cultural environments influence behavior. Structuralism: Wundt’s approach to discovering the basic elements, or structures, of mental processes. Theory: A broad idea or set of closely related ideas that attempts to explain observations and to make predictions about future observations. Validity: The soundness of the conclusions that a researcher draws from an experiment. In the realm of testing, the extent to which a test measures what it is intended to measure. Variable: Anything that can change. Wilhelm Wundt is most often regarded the "founding father" of modern psychology. He was also the founder of structuralism. William James was the founder of functionalism. J. B. Watson and B. F. Skinner believed that psychology should focus on an organism's visible interactions with the environment—that is, behaviors. Ethical Guidelines developed by the American Psychological Association include: • informed consent. • confidentiality. • deception. • debriefing. Chapter 2 The Brain and Behavior Action potential: The brief wave of positive electrical charge that sweeps down the axon. Adrenal glands: glands at the top of each kidney that are responsible for regulating moods, energy level, and the ability to cope with stress. Amygdala: An almond-shaped structure within the base of the temporal lobe that is involved in the discrimination of objects that are necessary for the organism’s survival, such as appropriate food, mates, and social rivals. Association cortex: Sometimes called association areas, the region of the cerebral cortex that is the site of the highest intellectual functions, such as thinking and problem solving. Autonomic nervous system: The body system that takes messages to and from the body’s internal organs, monitoring such processes as breathing, heart rate, and digestion. Axon The part of the neuron that carries information away from the cell body toward other cells. Basal ganglia Large neuron clusters located above the thalamus and under the cerebral cortex that work with the cerebellum and the cerebral cortex to control and coordinate voluntary movements. Brain stem The stem like brain area that includes much of the hindbrain (excluding the cerebellum) and the midbrain; connects with the spinal cord at its lower end and then extends upward to encase the reticular formation in the midbrain. Cell body The part of the neuron that contains the nucleus, which directs the manufacture of substances that the neuron needs for growth and maintenance. Central nervous system (CNS): The brain and spinal cord. Cerebral cortex: Part of the forebrain, the outer layer of the brain, responsible for the most complex mental functions, such as thinking and planning. Chromosomes: In the human cell, threadlike structures that come in 23 pairs, one member of each pair originating from each parent, and that contain DNA. Corpus callosum: The large bundle of axons that connects the brain’s two hemispheres, responsible for relaying information between the two sides. Dendrites: Treelike fibers projecting from a neuron, which receive information and orient it toward the neuron’s cell body. Deoxyribonucleic acid (DNA): A complex molecule in the cell’s chromosomes that carries genetic information. Dominant-recessive genes principle: The principle that if one gene of a pair is dominant and one is recessive, the dominant gene overrides the recessive gene. A recessive gene exerts its influence only if both genes of a pair are recessive. Endocrine system: The body system consisting of a set of glands that regulate the activities of certain organs by releasing their chemical products into the bloodstream. Forebrain: The brain’s largest division and its most forward part. Frontal lobes: The portion of the cerebral cortex behind the forehead, involved in personality, intelligence, and the control of voluntary muscles. Genes: The units of hereditary information, consisting of short segments of chromosomes composed of DNA. Genotype: An individual’s genetic heritage; his or her actual genetic material. Glands: Organs or tissues in the body that create chemicals that control many bodily functions. Glial cells: The second of two types of cells in the nervous system; glial cells (also called glia) provide support, nutritional benefits, and other functions and keep neurons running smoothly. Hindbrain: Located at the skull’s rear, the lowest portion of the brain, consisting of the medulla, cerebellum, and pons. Hippocampus: The structure in the limbic system that has a special role in the storage of memories. Hormones: Chemical messengers that are produced by the endocrine glands and carried by the bloodstream to all parts of the body. Hypothalamus: A small forebrain structure, located just below the thalamus, that monitors three pleasurable activities—eating, drinking, and sex—as well as emotion, stress, and reward. Limbic system: A set of subcortical brain structures central to emotion, memory, and reward processing. Midbrain: Located between the hindbrain and forebrain, an area in which many nerve-fiber systems ascend and descend to connect the higher and lower portions of the brain; in particular, the midbrain relays information between the brain and the eyes and ears. Motor cortex: A region in the cerebral cortex, located just behind the frontal lobes, that processes information about voluntary movement. Myelin sheath: A layer of fat cells that encases and insulates most axons. Neocortex: The outermost part of the cerebral cortex, making up 80 percent of the human brain’s cortex. Nervous system: The body’s electrochemical communication circuitry. Neural networks: Networks of nerve cells that integrate sensory input and motor output. Neurons: One of two types of cells in the nervous system; neurons are the nerve cells that handle the information-processing function. Neurotransmitters: Chemical substances that are stored in very tiny sacs within the neuron’s terminal buttons and involved in transmitting information across a synaptic gap to the next neuron. Occipital lobes: Structures located at the back of the head that respond to visual stimuli. Ovaries: Sex-related endocrine glands that produce hormones involved in women’s sexual development and reproduction. Pancreas: A dual-purpose gland under the stomach that performs both digestive and endocrine functions. Parasympathetic nervous system: The part of the autonomic nervous system that calms the body. Parietal lobes: Structures at the top and toward the rear of the head that are involved in registering spatial location, attention, and motor control. Peripheral nervous system (PNS): The network of nerves that connects the brain and spinal cord to other parts of the body. Phenotype: An individual’s observable characteristics. Pituitary gland: A pea-sized gland just beneath the hypothalamus that controls growth and regulates other glands. Plasticity: The brain’s special capacity for change. Prefrontal cortex: an important part of the frontal lobes that is involved in higher cognitive functions such as planning, reasoning, and self-control. Resting potential, The stable, negative charge of an inactive neuron. Reticular formation: A system in the midbrain comprising a diffuse collection of neurons involved in stereotyped patterns of behavior such as walking, sleeping, and turning to attend to a sudden noise. Somatic nervous system: The body system consisting of the sensory nerves, whose function is to convey information from the skin and muscles to the central nervous system about conditions such as pain and temperature, and the motor nerves, whose function is to tell muscles what to do. Somatosensory cortex: A region in the cerebral cortex that processes information about body sensations, located at the front of the parietal lobes. Stem cells: Unique primitive cells that have the capacity to develop into most types of human cells. Stress: The responses of individuals to environmental stressors. Stressors: Circumstances and events that threaten individuals and tax their coping abilities and that cause physiological changes to ready the body to handle the assault of stress. Sympathetic nervous system: The part of the autonomic nervous system that arouses the body to mobilize it for action and thus is involved in the experience of stress. Synapses: Tiny spaces between neurons; the gaps between neurons are referred to as synaptic gaps. Temporal lobes: Structures in the cerebral cortex that are located just above the ears and are involved in hearing, language processing, and memory. Testes: Sex-related endocrine glands in the scrotum that produce hormones involved in men’s sexual development and reproduction. Thalamus: The forebrain structure that sits at the top of the brain stem in the brain’s central core and serves as an important relay station. Left Hemisphere • verbal processing, speech, grammar Right Hemisphere • spatial perception • visual recognition • emotion Chapter 3 Sensation and Perception Absolute threshold: The minimum amount of stimulus energy that a person can detect. Apparent movement: The perception that a stationary object is moving. Auditory nerve: The nerve structure that receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas. Binding: In the sense of vision, the bringing together and integration of what is processed by different neural pathways or cells. Binocular cues: Depth cues that depend on the combination of the images in the left and right eyes and on the way the two eyes work together. Bottom-up processing: The operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation. Cones: The receptor cells in the retina that allow for color perception. Convergence: A binocular cue to depth and distance in which the muscle movements in an individual’s two eyes provide information about how deep and/or far away something is. Depth perception: The ability to perceive objects three-dimensionally. Difference threshold: The degree of difference that must exist between two stimuli before the difference is detected. Feature detectors: Neurons in the brain’s visual system that respond to particular features of a stimulus. Figure-ground relationship: The principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground). Frequency theory: Theory on how the inner ear registers the frequency of sound, stating that the perception of a sound’s frequency depends on how often the auditory nerve fires. Gestalt psychology A school of thought interested in how people naturally organize their perceptions according to certain patterns. Inner ear: The part of the ear that includes the oval window, cochlea, and basilar membrane and whose function is to convert sound waves into neural impulses and send them to the brain. Kinesthetic senses: Senses that provide information about movement, posture, and orientation. Middle ear: The part of the ear that channels and amplifies sound through the eardrum, hammer, anvil, and stirrup to the inner ear. Monocular cues: Powerful depth cues available from the image in one eye, either the right or the left. Noise: Irrelevant and competing stimuli—not only sounds but also any distracting stimuli for the senses. Olfactory epithelium: The lining of the roof of the nasal cavity, containing a sheet of receptor cells for smell. Opponent-process theory: Theory stating that cells in the visual system respond to complementary pairs of red-green and blue-yellow colors; a given cell might be excited by red and inhibited by green, whereas another cell might be excited by yellow and inhibited by blue. Optic nerve: The structure at the back of the eye, made up of axons of the ganglion cells, that carries visual information to the brain for further processing. Outer ear: The outermost part of the ear, consisting of the pinna and the external auditory canal. Pain: The sensation that warns an individual of damage to the body. Papillae: Rounded bumps above the tongue’s surface that contain the taste buds, the receptors for taste. parallel processing: The simultaneous distribution of information across different neural pathways. Perception: The process of organizing and interpreting sensory information so that it makes sense. perceptual constancy: The recognition that objects are constant and unchanging even though sensory input about them is changing. perceptual set A predisposition or readiness to perceive something in a particular way. place theory: Theory on how the inner ear registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane. retina The multilayered light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain. Rods: The receptor cells in the retina that are sensitive to light but not very useful for color vision. selective attention: The act of focusing on a specific aspect of experience while ignoring others. semicircular canals: Three fluid-filled circular tubes in the inner ear containing the sensory receptors that detect head motion caused when an individual tilts or moves the head and/or the body. Sensation: The process of receiving stimulus energies from the external environment and transforming those energies into neural energy. sensory adaptation: A change in the responsiveness of the sensory system based on the average level of surrounding stimulation. sensory receptors: Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain. signal detection theory: An approach to perception that focuses on decision making about stimuli in the presence of uncertainty. subliminal perception The detection of information below the level of conscious awareness. Thermoreceptors: Sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 98.6 degrees Fahrenheit. top-down processing The operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world. trichromatic theory: Theory stating that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths. vestibular sense: Sense that provides information about balance and movement. visual cortex: Located in the occipital lobe, the part of the cerebral cortex involved in vision. volley principle: Principle addressing limitations of the frequency theory of hearing, stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses. Weber’s law: The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.

Buňka - endoplazmatické retikulum

Smooth Endoplasmic Reticulum bio 353 lecture2

Rough Endoplasmic Reticulum bio 353 lecture 2

The Brainstem and Reticular Formation

Réticulum Endoplasmique - Cartes de Vocabulaire

Cell Organelles: Endoplasmic Reticulum, golgi appratus, and Lysosomes