Biology 277: Combined Lecture Notes

Sensory Receptors

Structures that respond to stimuli and initiate sensory input to the CNS, providing information about internal and external environments.

Stimulus

A change in the internal or external environment that triggers a response from sensory receptors.

Sensation

The conscious awareness of incoming sensory information, which needs to reach the cerebral cortex for perception.

Transducers

Convert stimulus energy into electrical signals (action potentials) for transmission to the CNS via sensory neurons.

Receptive Field

The area where the dendritic endings of a single sensory neuron are distributed, influencing the precision of sensory information.

Modality

Refers to the type of stimulus being interpreted by the brain, such as light for vision or sound for hearing.

Adaptation

The ability of sensory receptors to adjust their response to a stimulus over time, categorized into tonic and phasic receptors based on their adaptation rates.

Proprioceptors

Specialized mechanoreceptors located in joints, muscles, and tendons that detect stretch and pressure, providing information about body position.

Referred Pain

Sensory nerve signals from internal organs perceived as originating from somatic sensory receptors, leading to mislocalized pain sensations.

Olfaction

The sense of smell, involving chemoreceptors in the olfactory epithelium that detect odorants dissolved in mucus.

Gustation

The sense of taste, where gustatory cells in taste buds on the tongue detect tastants and transmit signals to the brain for perception.

Vision Accessory Structures

Include extrinsic eye muscles, eyelids, conjunctiva, and lacrimal apparatus, supporting and protecting the eye.

Eye Structure

Comprising three tunics (fibrous, vascular, neural), each with specific functions like shape maintenance, light bending, and light transduction.

Retina

Contains photoreceptor cells (rods and cones), bipolar cells, and ganglion cells, responsible for transducing light into neural signals for vision.

Fovea centralis

Depressed pit with mostly cones and few rods for detailed vision

Peripheral retina

Area with mostly rods for dim light vision

Light refraction

Bending of light passing through different densities

Suspensory ligaments

Attach to lens periphery, change lens shape for light refraction

Ciliary muscles

Contract to change lens shape for focusing

Convergence

Medial eye movement for near vision

Accommodation

Ciliary muscle contraction for lens shape change

Phototransduction

Conversion of light into electrical signals in photoreceptors

Rods

Photoreceptors for dim light, no color vision

Cones

Photoreceptors for color vision and visual sharpness

Photopigments

Composed of opsin and retinal, absorb light

Rhodopsin

Photopigment in rods for dim light vision

Photopsin

Photopigment in cones for color vision

Dark adaptation

Transition from bright to low light vision

Light adaptation

Transition from low to bright light vision

Cochlea

Snail-shaped structure for hearing

Semicircular canals

Detect angular acceleration for head rotation

Equilibrium

Awareness of head position and balance

Epidermis

Outer skin layer with keratinocytes and melanocytes

Dermis

Layer beneath epidermis with collagen fibers and nerve endings

Anagen

The active phase of hair growth, which is the longer part of the cycle.

Catagen

A brief regression period during hair growth when cell division stops, and the follicle undergoes involution.

Telogen

The phase of hair growth characterized by shedding of hair and regrowth from the hair bulb.

Exocrine glands

Glands that release their contents onto the skin surface, including sweat glands.

Merocrine

Sweat glands that are the most numerous and release sweat (99% water) onto the skin surface.

Apocrine

Glands located in specific regions like the axillary and pubic areas that release a viscous, cloudy secretion onto hair follicles.

Sebaceous glands

Glands that release sebum, an oily substance, onto hair follicles, acting as an antibacterial lubricant for the hair and scalp.

Ceruminous

Glands in the external ear canal that secrete ear wax to trap foreign particles and lubricate the ear.

Mammary

Glands that produce milk in pregnant and lactating females.

Acne

Skin condition caused by plugged sebaceous gland ducts, leading to acne lesions like comedones, papules, pustules, nodules, and cysts.

Tissue Repair

The process of regeneration or fibrosis to restore tissue function after damage, with stages like wound healing and scabbing.

Burns

Injuries that result in fluid loss, infection, and burned dead skin, categorized into first, second, and third-degree burns based on severity.

Aging of integument

Changes in the skin due to aging, including reduced stem cell activity, collagen loss, decreased immune response, and thinner hair production.

Skin cancer

Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, affecting different layers of the skin and melanocytes.

Blood

A fluid connective tissue transported by the cardiovascular system, consisting of plasma, formed elements like erythrocytes, leukocytes, and platelets, and functions in transportation, regulation, and protection.

Neutrophil

Most numerous white blood cell (50-70%) with light purple granules, multilobed nucleus, and role in phagocytosing pathogens during bacterial infections.

Eosinophil

White blood cell (1-4%) with bilobed nucleus, reddish granules, targeting antibody-antigen complexes, allergens, and parasitic worms via apoptosis.

Basophil

White blood cell (0.5-1%) with dark purple granules containing histamine and heparin, involved in inflammatory responses.

Monocytes

Agranulocyte white blood cell (2-8%) with a C-shaped nucleus, transforming into macrophages to phagocytize various substances.

Lymphocytes

White blood cells (20-40%) with dark-stained nucleus, including T-lymphocytes managing immune responses, B-lymphocytes producing antibodies, and Natural Killer cells inducing apoptosis in abnormal cells.

Platelets

Irregularly shaped cell fragments from megakaryocytes, crucial for homeostasis and blood clotting (hemostasis).

Thrombocytopenia

Condition characterized by a low platelet count, leading to impaired blood clotting.

Hemostasis

Process involving vascular spasm, platelet plug formation, and coagulation cascade to prevent excessive bleeding.

Coagulation Cascade

Series of events converting inactive proteins to active forms, forming fibrin strands for blood clotting.

Coronary Circulation

Blood flow through coronary arteries and veins supplying the heart muscle with oxygen and nutrients.

Cardiac Conduction System

Includes SA node, AV node, bundle of His, Purkinje fibers, regulating the heart's electrical activity and contraction.

Cardiac Cycle

Sequence of events in a heartbeat, including atrial and ventricular relaxation, contraction, and blood ejection.

Cardiac Output

Volume of blood pumped by the heart per minute, determined by heart rate and stroke volume.

Variables Influencing Heart Rate

Factors like autonomic nervous system, hormones, and drugs affecting the heart's beating rate.

Variables Influencing Stroke Volume

Factors like venous return, inotropic agents, and preload affecting the volume of blood ejected by the heart.

Drugs

Substances that can have various effects on the body, such as altering cardiac output or blood pressure.

Digitalis

A drug that boosts cardiac output by increasing contractility.

Afterload

The resistance in arteries to the ejection of blood from the heart.

Arteries

Blood vessels that carry blood away from the heart, consisting of three layers:tunica intima, tunica media, and tunica externa.

Capillaries

Microscopic blood vessels where solutes diffuse, with three types:continuous, fenestrated, and sinusoid.

Bulk flow

Movement of large amounts of fluid and dissolved substances down a pressure gradient.

Blood pressure

The force per unit area that blood exerts against the inside wall of a vessel.

Baroreceptors

Sensors that detect changes in blood pressure and send signals to regulate heart rate and blood vessel constriction.

Chemoreceptor Reflexes

Receptors that respond to changes in blood chemistry, such as high CO2 or low pH, to regulate blood pressure.

Lymphatic System

A network of vessels and organs that transport lymph, house immune cells, and return excess fluid to the blood.

Antigen-Presenting Cells (APCs)

Immune cells that present antigens to T-lymphocytes for adaptive immunity.

Respiratory Burst

Release of reactive oxygen-containing molecules by immune cells to destroy microbes.

Basophils and Mast Cells

Immune cells involved in proinflammatory responses and allergic reactions.

Complement System

Group of proteins that enhance inflammation, opsonization, and cytolysis in the immune response.

Fever

Abnormal elevation of body temperature that can inhibit microbial growth and promote immune activity.

Adaptive Immunity

Specific immune response involving T-lymphocytes and B-lymphocytes to target antigens.

T-Lymphocytes

Immune cells that differentiate into cytotoxic or helper-T lymphocytes for cell-mediated immunity.

B-Lymphocytes

Immune cells that develop into plasma cells to produce antibodies for antibody-mediated immunity.

MHC Class I and II Molecules

Transmembrane proteins that present antigens to T-lymphocytes for immune recognition.

Effector Response

Actions of activated lymphocytes to eliminate antigens, including cytokine release and antibody production.

Respiratory bronchiole to alveolar duct to alveoli

Pathway of air from the smallest airways to the site of gas exchange in the lungs.

Mucosa (mucosa membrane)

The lining of the respiratory tract that includes respiratory epithelium, cilia, and goblet cells.

Lamina propria

Connective tissue layer beneath the respiratory epithelium in the conducting zone of the respiratory system.

Paranasal Sinuses

Air-filled cavities connected to the nasal passages that help humidify and filter air.

Larynx

Structure containing vocal cords that functions in air passage, sound production, and preventing foreign materials from entering the respiratory tract.

Alveolar type I cells

Cells that make up most of the alveolar wall and are involved in gas exchange in the lungs.

Pulmonary circulation

Blood flow to and from the lungs for gas exchange and removal of carbon dioxide.

Intrapleural Pressure

Pressure within the pleural cavity that is lower than intrapulmonary pressure to keep the lungs inflated.

Boyle’s Gas Law

Describes the inverse relationship between gas pressure and volume, influencing lung expansion and air movement.

Compliance

The ease with which the lungs and chest wall expand, determined by surface tension and elasticity.

Bronchodilation

Increases PCO2 in the air of the bronchiole.

Bronchoconstriction

Decreases PCO2 in the air of the bronchiole.

Perfusion

Changes within pulmonary arteries.

Gas Transport

Movement of respiratory gases within the blood between the lungs and systemic cells.

Oxygen Transport

Process facilitated by hemoglobin binding with oxygen.

Carbon Dioxide Transport

Movement of carbon dioxide in the blood.