PHYSIO L1: phys & homeostasis

"Physiology"

"Study of how the living body normally functions

"Function vs. Mechanism"

"Function = WHY something happens/its purpose. Mechanism = HOW it happens physiologically."

"Levels of Organization"

"Cells → tissues → organs → organ systems → organism."

"4 Major Cell Types"

"Nerve, muscle, epithelial, & connective tissue

"Homeostasis"

"Keeping the body's internal environment within a normal RANGE. It does not mean conditions stay perfectly constant."

"Why Homeostasis Matters"

"most cells can't directly interact with the outside world, so they depend on the body maintaining their internal environment.

"Internal Environment of Cells"

"Extracellular fluid (ECF) surrounding the cells."

"Main Homeostatic Control Systems"

"Nervous system + endocrine system."

"Nervous vs. Endocrine"

"Nervous = generally FAST (water slide). Endocrine = generally SLOWER and can be widespread (lazy river)."

"2 Major Fluid Compartments"

"ICF = fluid INSIDE cells. ECF = fluid OUTSIDE cells."

"ICF"

"Intracellular fluid = inside cells ≈ 2/3 of total body water ≈ 28 L."

"ECF"

"Extracellular fluid = outside cells ≈ 1/3 of total body water ≈ 14 L."

"ECF Breakdown"

"≈ 11 L interstitial fluid + 3 L plasma = 14 L ECF."

"Interstitial Fluid vs. Plasma"

"Interstitial fluid surrounds tissue cells; plasma is the fluid portion of blood."

"Body Fluid Memory Map"

"42 L total → 28 L ICF + 14 L ECF → 11 L interstitial + 3 L plasma."

"Negative Feedback"

"OPPOSES the initial change and moves a variable back toward its normal range. Memory: Negative = REVERSE."

"Negative Feedback Example"

"Blood glucose ↑ → response involving insulin → blood glucose moves ↓ toward normal."

"Negative Feedback Pathway"

"Stimulus → Receptor → Afferent pathway → Integrating center → Efferent pathway → Effector → Response."

"Receptor"

"Detects the stimulus/change in a regulated variable."

"Afferent vs. Efferent"

"Afferent carries information TOWARD the integrating center; efferent carries instructions AWAY toward the effector. Memory: Afferent ARRIVES

"Integrating Center"

"Receives/processes information and coordinates the appropriate response."

"Effector"

"Tissue or organ that carries out the response."

"Positive Feedback"

"REINFORCES the initial change instead of opposing it. Memory: Positive = REINFORCE."

"Positive Feedback Example"

"Childbirth: cervical stretch → oxytocin/contractions → more cervical stretch → stronger contractions. Delivery ends the loop."

"Feedforward"

"Body ANTICIPATES an upcoming change and responds beforehand. Memory: Feedforward = PREPARE. Example: salivating before eating or heart rate rising before exercise."

"3 Types of Regulation"

"Negative = REVERSE; Positive = REINFORCE; Feedforward = PREPARE."