Quarterly #1 Sem 2

Homeostasis

Maintain dynamic equilibrium in the body. Organisms maintain a stable, relatively constant internal environment despite fluctuating external conditions.

Negative feedback loop!

Set point

Midpoint or target point in homeostasis. While there are normal fluctuations, the body’s systems will usually attempt to go back to this point.

Stimulus

Anything (an object, event, or change) that causes a reaction or response in an organism or system, triggering a physical or behavioral change

Ex) Seeing light (a stimulus) causing your pupil to constrict

Receptor

(The detector) A specialized cell or group of cells that detects that specific stimulus and converts it into a nerve signal.

Negative Feedback Loop

Feedback to a control mechanism that increases or decreases a stimulus instead of maintaining it.

In other words, if a level is too high, the body does something to bring it down, and conversely, if a level is too low, the body does something to make it go up.

Predominant mechanism used in homeostasis.

Positive Feedback Loop

Maintains the direction of the stimulus, possibly accelerating it.

Ex) Childbirth, blood clotting

Ectotherms

Animals that rely on external temperatures to set their body temperature

Endotherms

Animals that rely on internal sources for maintenance of relatively constant body temperature in varying environmental temperatures

Thermoregulation

The vital physiological process by which the body maintains a stable core temperature (typically 37∘C or 98.6 ∘ F) by balancing heat production and loss

Homeostatic Control System Sequence

Stimulus → Sensor → Control (change is compared to the set point)→ Effector (The control center sends signals to the effector which then performs an action (e.g., releases insulin, shivers) to counteract or enhance the initial stimulus. 

Anatomy

Study of body’s internal and external structures, and relationship between body’s parts
• Traditionally subdivided into gross & microscopic

Anatomy affects physiology

Physiology

Study of how these structures work as an integrated whole
• Focuses on the chemical, electrical & physical process of the body
• Traditionally deals with organs and organ systems

Asymmetrical Animals

Animals with no pattern or symmetry; an example is a sponge.

Radial Symmetry

Describes when an animal has an up-and-down orientation: any plane cut along its longitudinal axis through the organism produces equal halves, but not a definite right or left side.

Bilateral Symmetry

A plane cut from front to back separates the animal into definite right and left sides.

Sagittal plane

Divides the body into right and left portions.

Frontal plane

Separates the front from the back.

Transverse plane or cross section

Divides the animal into upper and lower portions.

Dorsal Cavity

Contains the cranial and the vertebral (or spinal) cavities.

Ventral cavity

Contains the thoracic cavity, which in turn contains the pleural cavity around the lungs and the pericardial cavity, which surrounds the heart. Also contains the abdominopelvic cavity, which can be separated into the abdominal and the pelvic cavities.

Epithelial tissues

Cover the outside of organs and structures in the body and line the lumens of organs in a single layer or multiple layers of cells. Smooth inner lining.

Epithelia composed of a single layer of cells is called simple epithelia; epithelial tissue composed of multiple layers is called stratified epithelia

Squamous

Flat, irregular round shape

Located in:

Simple: lung alveoli, capillaries

Stratified: skin, mouth, vagina (think about where the body faces abrasion)

Cuboidal

Cube shaped, central nucleus

Located in:

glands, renal tubules

Columnar

Tall, narrow, nucleus toward base; tall, narrow, nucleus along cell

Located in:

Simple: digestive tract

Pseudostratified: respiratory tract (think where cilia needs to help move stuff)

Transitional

Round, simple but appear stratified

Located in:

Urinary bladder

Connective Tissues

Made up of a matrix consisting of living cells and a nonliving substance, called the ground substance. Contains blood vessels.

The organic portion or protein fibers found are either collagen, elastic, or reticular fibers.

• Fibers provide strength to the tissue, preventing it from being torn or separated from the surrounding tissues.

Loose/areolar

Connective tissue

Cells: Fibroblasts, macrophages, some lymphocytes, some neutrophils

Fibers: Collagen, elastic, reticular

Location: Around blood vessels; anchors epithelia

Dense, fibrous

Connective tissue

Cells: Fibroblasts, macrophages

Fibers: Mostly collagen

Location:

Irregular: skin

Regular: tendons, ligaments

Cartilage

Connective Tissue

Cells: chondrocytes, chondroblasts

Fibers:

Hyaline: The collagen fibers are very thin and spread out, so you usually don’t see them easily under a microscope. Resulting properties: smooth, flexible, good at reducing friction and absorbing shock

Fibrocartilage: Large amount of collagen, thick, densely packed collagen fibers that are clearly visible. Resulting properties: Very strong, resistant to compression and pulling forces

Location: Shark skeleton, fetal bones, human ears, intervertebral discs

Bone

Connective Tissue

Cells: Osteoblasts, osteocytes, osteoclasts

Fibers: (Some) collagen, elastic

Location: Vertebrate skeletons

Adipose

Connective tissue

Cells: Adipocytes

Fibers: Few

Location: Adipose (fat)

Blood

Connective tissue

Cells: Red blood cells, white blood cells

Fibers: None

Location: Blood

What are the three types of muscle tissue?

Smooth, skeletal, and cardiac

Smooth muscle

Does not have striations in its cells, has a single, centrally located nucleus. Non-striated as it lacks the banded appearance of skeletal and cardiac muscle.

Constriction of smooth muscle occurs under involuntary, autonomic nervous control and in response to local conditions in the tissues.

Neuron

The structural and functional unit of nervous tissue

Skeletal muscle

Muscle has striations across its cells caused by the arrangement of the contractile proteins actin and myosin.

These muscle cells are relatively long and have multiple nuclei along the edge of the cell. Skeletal muscle is under voluntary, somatic nervous system control and is found in the muscles that move bones.

Cardiac Muscle

Found only in the heart. Has cross striations in its cells, but cardiac muscle has a single, centrally located nucleus.

Not under voluntary control but can be influenced by the autonomic nervous system to speed up or slow down.

Has intercalated discs: which assist in passing electrical impulse efficiently from one cell to the next and maintains the strong connection between neighboring cardiac cells.

Nervous Tissue

Made of cells specialized to receive and transmit electrical impulses from specific areas of the body and to send them to specific locations in the body.

Clinical Care

Prevention, treatment, and management of illness and the preservation of mental and physical well- being through the services offered by medical and allied health professions; also known as health care

Clinical care team

Consists of the health professionals with the training and skills needed to provide high-quality, coordinated care specific to the patient’s clinical needs and circumstances

Epidemic / Outbreak

Occurrence in a community or region of cases of an illness, specific health-related behavior, or other health-related event clearly in excess of normal expectancy.

(Both terms are used interchangeably)

• epidemic usually refers to a larger geographic distribution of illness or health-related events

Public Health Approach

Surveillance → Risk Factor Identification → Intervention Evaluation → Implementation

John Snow

Best known for his work tracing the source of the cholera outbreak and is considered the father of modern epidemiology.

Three core functions of public health

Assessment, policy development, assurance

Epidermis (skin layer)

Forms the surface of the skin

• Stratified squamous epithelium

Dermis (skin layer)

Forms a deeper skin layer
• composed of dense connective tissue with many resilient elastic fibers and strong
collagen fibers
• contains hair follicles, oil and sweat glands, muscle cells, nerves, sensory receptors,
and blood vessels

Integumentary system

The body's largest organ system, comprising the skin, hair, nails, and glands, which acts as a protective, regulatory barrier

Pathogen

Agents, usually microorganisms, that cause diseases in their hosts

Include bacteria, protists, fungi and other infectious organisms.

Innate immunity

Occurs naturally because of genetic factors or physiology; it is not induced by infection or vaccination but works to reduce the workload for the adaptive immune response.

• No “memory”

• External barriers (skin/exoskeleton, acidic environment, secretions, mucous membranes, hairs, cilia) internal barriers (phagocytic cells, natural killer cells, defensive proteins, inflammatory response)

Macrophage

A large phagocytic cell that engulfs foreign particles and pathogens.

Lymphocytes

Leukocytes that are histologically identifiable by their large, darkly staining nuclei; they are small cells with very little cytoplasm. Can kill cells infected with viruses or tumor cells (abnormal cells that uncontrollably divide and invade other tissue).

T cells

Lymphocytes that mature in the thymus gland.

Kill infected cells or help other immune cells

B cells

Lymphocytes that mature in the bone marrow.
Make antibodies

Lymphatic System

Involved in innate and adaptive immunity
• consists of a network
• lymphatic vessels, lymph nodes, and lymph

Circulating lymph

Collects
• microbes, parts of microbes, and microbial toxins
• transports them to lymphatic organs
• macrophages in lymphatic organs engulf the invaders
• lymphocytes may mount an adaptive immune response

Perforin

A destructive protein that creates a pore in the target cell.

Adaptive Immunity

An immunity that occurs after exposure to an antigen either from a pathogen or a vaccination.

Activated when the innate immune response is insufficient to control an infection.

Antigen

Foreign molecules recognized by our immune systems
• elicit the adaptive immune response

Active immunity

Occurs when the body is exposed to an antigen and responds by producing its own antibodies and memory cells

Humoral immune response

An adaptive immune response in which B cells produce antibodies that circulate in blood and lymph to target antigens.

Cell-mediated immune response

The part of the adaptive immune system that uses T cells (not antibodies) to fight infected or abnormal cells.

Microphages

A large white blood cell that locates and eats particles such as bacteria, viruses, fungi, and parasites. Use a process known as phagocytosis to destroy unwanted particles in the body.

Include neutrophils and eosinophils.
Normally in blood but can leave bloodstream to enter infected or injured tissue

Macrophages

Specialized white blood cell that acts as the body's "clean-up crew" and first responder, engulfing and digesting pathogens (like bacteria), dead cells, and debris, while also coordinating other immune cells and promoting tissue repair and homeostasis

Derived from monocytes
• pervade almost every body tissue

Mast Cells

Immune cells in connective tissues that act as the body's "alarm system," releasing chemicals to fight infections and parasites, but also causing allergies and anaphylaxis when triggered inappropriately.

Secrete histamine and heparin

Interferons

Small proteins released by activated lymphocytes, macrophages, infected cells
• Cause normal cells to produce antiviral compounds
• May also stimulate macrophages and natural killer (NK) cells into action

Antigens

Foreign molecules recognized by our immune systems
• elicit the adaptive immune response

Effector Cells

Selected lymphocyte cells multiply into clones of short-lived effector cells, specialized for defending against the antigen that triggered the response

Clonal selection

When a specific antigen shows up, it “selects” the one lymphocyte that matches it, that cell multiplies, and the clones become fighters now (effector/plasma cells) and rememberers later (memory cells).

Think: Find → Copy → Fight → Remember

Plasma cells (B-cell effector cells)

• If the selected lymphocyte is a B cell, its effector cells are called plasma cells.

• Plasma cells:

  • Secrete large amounts of antibodies

  • Target that specific antigen

Plasma cells = antibody factories

Memory cells (long-term immunity)

• Some clones become memory cells instead of effector cells.

• Memory cells:

  • Live a long time

  • Respond faster and stronger if the antigen returns

This is why you don’t get sick again (or get much milder illness).

Helper T-cells

1. Receptors recognize the self–nonself complexes
2. Interaction activates the helper T cells
3. Then cytotoxic T cells attack body cells that are infected with pathogens and B cells

Cytotoxic T cells

Only T cells that kill infected cells
• bind to infected body cells and destroy them
• play a role in protecting the body against the spread of some cancers

Self-/non-self discrimination

The immune system’s ability to tell your own cells (“self”) from foreign invaders (“non-self”).

When do T-cells learn self-/non-self discrimination?

During embryonic or newborn stages of life in the thymus.

What happens to T-cells that recognize self-antigens?

They are eliminated in the thymus by clonal deletion.

Clonal deletion

The removal of self-reactive T-cell clones to prevent autoimmunity.

If it fails → Self-reactive T-cells persist and can cause autoimmune diseases.

Autoimmune diseases

Occur when the immune system turns against the body’s own molecules

Include:

• lupus

• rheumatoid arthritis

• insulin-dependent diabetes mellitus

• multiple sclerosis

Immunodeficiency diseases

Occur when an immune response is defective or absent

Allergies

Produced when body mounts massive inflammatory response to foreign substance (allergen) that is not in itself harmful

• Triggers release of histamine and heparin

“Over-reaction” by body
• Response ranges from mild to life-threatening (sneezing vs. asthma)

Passive immunity

Transfer of antibodies from one individual to another to provide temporary protection against pathogens

Ex: Breastfeeding

Axon

The long threadlike part of a nerve cell along which impulses are conducted from the cell body to other cells.

Dendrite

The branched, tree-like extensions of a neuron that receive chemical and electrical signals from other neurons and transmit them to the cell body

Open circulatory system

System in which the blood is mixed with interstitial fluid and directly covers the organs

Pumps hemolymph into body cavities where it directly bathes organs before returning to the heart, making it a low-pressure and less efficient system.

Found in: All arthropods and most mollusks

Closed circulatory system

System in which the blood is separated from the bodily interstitial fluid and contained in blood vessels

Found in: vertebrates, earthworms, squids, and octopuses

Arteries (arterioles)

Carry blood away from the heart to body organs and tissues; most high O2

Veins (venules)

Return blood to the heart; most high CO2

• Have valves

Double circulation

Blood is pumped a second time after it loses pressure in the lungs

Pulmonary circuit

Carries blood between the heart and gas exchange tissues in the lungs

Systemic circuit

Carries blood between the heart and the rest of the body

Three chambered heart

Exists in: Amphibians & Reptiles

Consists of:
• Two atria
• Right – receives blood from body
• Left – receives blood from the lungs
• One ventricle
• Sends blood out of the heart

Four chambered heart

Consists of:
• Two atria
• Right – receives blood from body
• Left – receives blood from the lungs
• Two ventricles
• Right – sends blood to lungs
• Left – sends blood to body
• No mixing, divided sides
• Right = No O2
• Left = O2

“Lub” sound

When valves between atria and ventricles close
• Valves = atrioventricular (bi- & tricuspid)

“Dub” sound

Produced by closing of valves between ventricles and arteries
• Valves = Semi-lunar (aortic & pulmonary)

Capillaries

Thin walls consisting of a single layer of epithelial cell
• Narrow = about as wide as one red blood cell
• Allows RBCs to squeeze through
• exchange gas and fluid with the interstitial fluid
• Only 5-10% f the time is blood flowing through

Blood Pressure

Force blood exerts on vessel walls
• depends on cardiac output and resistance of vessels to expansion
• decreases as blood moves away from the heart

Systolic Pressure

Ventricular contraction

Top # in blood pressure reading

Diastolic pressure

Low pressure between contractions.

Bottom # in blood pressure reading

Hypertension

Simply means high blood pressure.

• The heart has to work harder, weakening the heart over time

Arteriosclerosis

(Umbrella term)

Increased plaque formation from tiny ruptures

“Hardening of the arteries”

• Arteries become thick, stiff, and less elastic

• Happens with aging, hypertension, diabetes

• Reduces the artery’s ability to expand

• Broad term that includes several conditions

Think: overall stiffness

Atherosclerosis

Increased risk of blood clot formation

“Fatty hardening of the arteries”

• Caused by plaque buildup (fat, cholesterol, calcium)

• Plaque forms inside the arterial wall

• Narrows the artery → reduced blood flow

• Can lead to heart attacks, strokes

Think: plaque clogging