Anatomy & Physiology: Homeostasis, Cell Physiology, and Endocrine System Study Guide

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Homeostasis: The maintenance of a stable internal environment despite external changes. It is essential for normal cell function and overall health.
Electrical Equilibrium: A state where the net charge is balanced across a membrane or within a compartment.
Chemical Equilibrium: A state where the concentration of ions or molecules is equal on both sides of a membrane.
Osmotic Equilibrium: A state where the total number of particles (solutes) is equal on both sides of a membrane, affecting water movement.

Intracellular Fluid (ICF): Fluid inside cells; high in potassium (K+), low in sodium (Na+).
Extracellular Fluid (ECF): Fluid outside cells; high in sodium (Na+), low in potassium (K+).
Blood Plasma: The liquid component of blood, part of the ECF.
Interstitial Fluid: Fluid between cells, also part of the ECF.
Buffer Zones: Blood plasma acts as a buffer zone between the outside world and most cells, helping to maintain homeostasis.

Cranial cavity: Contains the brain.
Thoracic cavity: Contains the heart (pericardial sac) and lungs (pleural sacs).
Abdominal cavity: Contains digestive organs.
Pelvic cavity: Contains reproductive and some excretory organs.

Nervous: Controls sensory ability and coordinates body functions via electrical signals.
Digestive: Breaks down food, absorbs nutrients, eliminates waste.
Respiratory: Facilitates gas exchange (CO2 and O2).
Reproductive: Produces gametes and hormones.
Cardiovascular: Transports nutrients and waste in blood.
Integumentary: Protects from environment, regulates temperature, excretes sweat.
Urinary/Excretory: Removes waste, filters blood.
Muscular: Enables movement, heat production.
Endocrine: Regulates body processes via hormones.
Lymphatic: Defends against pathogens, transports fats.
Skeletal: Provides structure, protection, and blood cell production.

Plasma Membrane: Controls movement of substances in and out of cells; composed of a phospholipid bilayer with embedded proteins.
Types of Molecules Crossing the Membrane:
- Lipid-soluble (nonpolar): Pass freely through the lipid bilayer.
- Small, nonpolar molecules: Also diffuse easily.
- Polar or large molecules: Require transport proteins.
Concentration Gradient: The difference in concentration of a substance across a space or membrane.
Passive Transport: Movement down the concentration gradient without energy input (e.g., simple diffusion, facilitated diffusion).
Active Transport: Movement against the concentration gradient, requiring energy (usually ATP).

Simple Diffusion: Passive movement of molecules directly through the lipid bilayer.
Facilitated Diffusion: Passive movement using channel or carrier proteins.
Osmosis: Diffusion of water across a selectively permeable membrane.
Carrier-Mediated Transport: Uses carrier proteins; can be uniport (one substance), symport (two substances same direction), or antiport (two substances opposite directions).

Structural Proteins: Maintain cell shape and structure.
Enzymes: Catalyze metabolic reactions and signal transfer.
Receptors: Bind signaling molecules (ligands) and initiate cellular responses.
Specificity: Receptors are specific to certain ligands.
Affinity: The strength of ligand binding to a receptor.
Agonist: A molecule that activates a receptor.
Antagonist: A molecule that blocks receptor activation.

Negative Feedback: The response counteracts the stimulus, maintaining homeostasis. Example: Blood glucose regulation—insulin lowers blood glucose when it is high.
Positive Feedback: The response reinforces the stimulus. Example: Childbirth—oxytocin increases contractions until delivery.

Epithelial Tissue: Covers surfaces, lines cavities, involved in secretion and absorption. Example: Skin, lining of the gut.
Connective Tissue: Supports, connects, and protects other tissues. Example: Bone, blood, cartilage.
Muscle Tissue: Enables movement. Example: Skeletal muscle, cardiac muscle.
Nervous Tissue: Transmits electrical signals. Example: Brain, spinal cord, nerves.

Thyroid Hormones: T3 (triiodothyronine), T4 (thyroxine), and calcitonin. Regulate metabolism and calcium balance.
Adrenal Gland Hormones: Glucocorticoids (e.g., cortisol), catecholamines (e.g., adrenaline, noradrenaline).
Posterior Pituitary Hormones: Vasopressin (ADH) and oxytocin.
Growth Hormone: Stimulates growth and metabolism.

Hypothalamic-Pituitary Axis: Hypothalamus releases hormones that regulate the anterior pituitary, which in turn controls other endocrine glands.
Negative Feedback in Hormone Regulation: Hormone levels are regulated by feedback loops to maintain balance.

Hypothyroidism: Low thyroid hormone levels; symptoms include fatigue, weight gain, cold intolerance.
Hyperthyroidism: High thyroid hormone levels; symptoms include weight loss, heat intolerance, irritability.
Osteoporosis: Weakening of bones due to loss of calcium; can be prevented by adequate calcium and vitamin D intake.

Signal Transduction: The process by which a cell converts an extracellular signal into a functional response. Involves first messengers (ligands), membrane receptors, G proteins, and second messengers.
Osmolarity and Tonicity: Osmolarity refers to the concentration of solutes in a solution; tonicity describes the effect of a solution on cell volume.

Compartment	Main Ions	Location
Intracellular Fluid (ICF)	K+, Mg2+, PO43-	Inside cells
Extracellular Fluid (ECF)	Na+, Cl-, Ca2+	Outside cells (includes plasma and interstitial fluid)
Blood Plasma	Na+, Cl-, proteins	Liquid part of blood
Interstitial Fluid	Na+, Cl-	Between cells

Osmosis: Water moves from areas of low solute concentration to high solute concentration.
Osmotic Pressure Equation:

$\Pi = iMRT$

Where $\Pi$ = osmotic pressure, $i$ = van 't Hoff factor, $M$ = molarity, $R$ = gas constant, $T$ = temperature (Kelvin).

Additional info: Some explanations and examples have been expanded for clarity and completeness based on standard Anatomy & Physiology curriculum.