KMS PHYSIOOO stdy guide ig

Osmotic equilibrium vs. Electrical disequilibrium vs. Chemical disequilibrium

Osmotic equilibrium: Fluid concentrations equal on both sides (total solute equal). Electrical disequilibrium: Difference in net charge across membrane (inside negative). Chemical disequilibrium: Different concentrations of specific solutes across membrane (e.g. high Na+ outside, high K+ inside).

Major intracellular anions

Proteins and organic phosphates.

Nernst Equation formula and function

Calculates Equilibrium Potential (E_ion) for a single specific ion: V_m = (61/z) * log10([C]_out / [C]_in) at 37 °C.

Goldman-Hodgkin-Katz (GHK) Equation function

Calculates overall membrane potential (V_m) considering concentrations and relative permeabilities (P) of K+, Na+, and Cl-.

Average Resting Membrane Potential (RMP) of living cells

Approximately -75 mV (inside negative relative to outside).

Key ionic mechanism setting resting membrane potential

K+ leak channels provide baseline permeability to K+; K+ diffuses out down its chemical gradient, creating an inside-negative electrical gradient until electrochemical equilibrium (E_K) is approached.

Effect of opening Na+ vs. K+ channels on V_m

Na+ channels open: Depolarizes V_m (becomes more positive as Na+ enters). K+ channels open: Hyperpolarizes V_m (becomes more negative as K+ leaves).

Na+/K+ ATPase pump function

Pumps 3 Na+ out and 2 K+ in using ATP; electrogenic nature contributes slightly to inside-negative potential.

Definitions of Depolarization, Repolarization, Hyperpolarization

Depolarization: V_m becomes less negative/more positive. Repolarization: V_m returns toward resting potential. Hyperpolarization: V_m becomes more negative than resting potential.

Three main types of gated channels in graded potentials

Ligand-gated (chemically-gated), mechanically-gated, and voltage-gated channels.

Key characteristics of Graded Potentials

Occur in dendrites/cell body, variable amplitude, local/decremental over distance, can be depolarizing or hyperpolarizing, and can summate.

Spatial vs. Temporal Summation

Spatial: Multiple presynaptic inputs fire simultaneously at different locations. Temporal: A single presynaptic input fires in rapid succession over time.

Threshold potential definition

The minimum membrane potential required to open voltage-gated Na+ channels and trigger an action potential (typically -50 mV to -55 mV).

Key characteristics of Action Potentials

Occur at axon hillock/axon, all-or-none, constant amplitude, non-decremental (regenerative), unidirectional, and exhibit refractory periods.

Phases of a Neuronal Action Potential

1) RMP (-70 mV). 2) Depolarization to threshold. 3) Rapid depolarization/overshoot via fast voltage-gated Na+ influx. 4) Repolarization via Na+ inactivation and voltage-gated K+ efflux. 5) After-hyperpolarization due to slow K+ channel closure.

Axon terminal signal transmission mechanism

Action potential reaching terminal opens voltage-gated Ca2+ channels; Ca2+ influx triggers exocytosis of neurotransmitter vesicles into the synaptic cleft.

Autonomic Nervous System branches

Sympathetic ("fight or flight") and Parasympathetic ("rest and digest").

Sympathetic vs. Parasympathetic anatomical layout

Sympathetic: Short preganglionic (ACh at ganglion) -> Long postganglionic (Norepinephrine at target). Thoracolumbar origin. Parasympathetic: Long preganglionic (ACh at ganglion) -> Short postganglionic (ACh at muscarinic target). Craniosacral origin.

Adrenal Medulla pathway and function

Modified sympathetic ganglion; preganglionic fibers release ACh onto chromaffin cells, secreting Epinephrine (~80%) and Norepinephrine directly into blood.

Blood flow pathway through the heart

Vena Cava -> Right Atrium -> Tricuspid Valve -> Right Ventricle -> Pulmonary Valve -> Pulmonary Artery -> Lungs -> Pulmonary Veins -> Left Atrium -> Bicuspid/Mitral Valve -> Left Ventricle -> Aortic Valve -> Aorta -> Body.

Hemodynamic Flow equation and pressure gradient rule

Q = delta_P / R. Fluid flows only when a positive pressure gradient exists (moves from higher pressure to lower pressure).

Poiseuille's Law and primary determinant of resistance

R = (8 * viscosity * length) / (pi * r^4). Radius (r) is the primary physiological controller of resistance; R is inversely proportional to r^4.

Series vs. Parallel vessel arrangement

Vessel types (arteries, arterioles, capillaries, veins) are in SERIES (total flow Q is equal across levels). Individual vessels within a bed are in PARALLEL (allows independent flow control and reduces total resistance).

Velocity of blood flow equation and relation to area

Velocity = Flow / Cross-sectional area (v = Q / A). Velocity is slowest in capillaries because total cross-sectional area is largest, facilitating exchange.

Two major types of cardiac muscle cells

Contractile cells (99%, mechanical work) and Autorhythmic/Conducting cells (1%, generate and spread electrical signals).

Intrinsic cardiac conduction pathway and firing rates

SA node (70-80 bpm, primary pacemaker) -> AV node (40-60 bpm) -> Bundle of His -> Bundle Branches -> Purkinje fibers (15-40 bpm).

Pacemaker potential mechanism in SA node

I_f ("funny") channels open upon hyperpolarization to allow Na+ influx; T-type and L-type Ca2+ channels then depolarize the cell to threshold.

Cardiac Contractile Cell Action Potential phases

Phase 0: Rapid Na+ influx. Phase 1: Brief Na+ closure/K+ exit. Phase 2: Plateau (L-type Ca2+ influx balances K+ efflux). Phase 3: Repolarization (Ca2+ closes, K+ efflux). Phase 4: Resting membrane potential.

Role of intercalated discs and gap junctions

Connect cardiac cells mechanically (desmosomes) and electrically (gap junctions), allowing rapid ion flow so myocardium contracts as a functional syncytium.

Autonomic control of Heart Rate (Chronotropy)

Sympathetic (NE/Epi on Beta-1): Increases cAMP, speeds I_f and Ca2+ entry -> increases HR. Parasympathetic (ACh on Muscarinic M2): Increases K+ exit, decreases cAMP -> hyperpolarizes and slows HR.

ECG Waves, Segments, and Intervals

P wave: Atrial depolarization. PR segment: AV node conduction delay. QRS complex: Ventricular depolarization. ST segment: Ventricular plateau/contraction. T wave: Ventricular repolarization.

First-Degree vs. Third-Degree AV Block on ECG

First-Degree: Consistently prolonged PR interval (delay at AV node). Third-Degree (Complete): P waves and QRS complexes are completely dissociated (no conduction through AV node).

Five main phases of the Cardiac Cycle

1) Late Diastole (passive filling). 2) Atrial Systole (atrial kick). 3) Isovolumetric Ventricular Contraction (S1 sound, all valves closed). 4) Ventricular Ejection (semilunar valves open). 5) Isovolumetric Ventricular Relaxation (S2 sound, semilunar valves close).

End-Diastolic Volume (EDV) vs. End-Systolic Volume (ESV)

EDV: Volume in ventricle at end of filling (~135 mL). ESV: Volume remaining in ventricle after contraction (~65 mL).

Stroke Volume (SV) formula and normal value

SV = EDV - ESV (e.g., 135 mL - 65 mL = 70 mL per beat).

Ejection Fraction (EF) formula

EF = (SV / EDV) * 100 (Normal is ~55-70%).

Cardiac Output (CO) formula and average resting value

CO = Heart Rate * Stroke Volume (Normal resting value is ~5 L/min).

Determinants of Venous Return

1) Skeletal muscle pump. 2) Respiratory pump. 3) Sympathetic venoconstriction. 4) Blood volume.

Frank-Starling Law of the Heart (Preload)

Increasing EDV stretches ventricular muscle fibers, increasing myocardial cross-bridge formation and resulting in a more forceful contraction and increased Stroke Volume.

Cardiac Contractility (Inotropy) definition and mechanism

Intrinsic strength of contraction at a given EDV; increased by sympathetic stimulation (Beta-1) increasing intracellular Ca2+ during contraction.

Afterload definition and effect on SV

The arterial pressure/resistance the ventricle must overcome to eject blood. Elevated afterload decreases Stroke Volume and increases ESV.

Mean Arterial Pressure (MAP) formulas

MAP = Diastolic BP + (1/3 * Pulse Pressure) OR MAP = Cardiac Output * Total Peripheral Resistance (TPR).

Baroreceptor Reflex mechanism for low blood pressure

Decreased BP -> Decreased stretch on carotid/aortic baroreceptors -> Decreased firing to Medullary CVCC -> Increased Sympathetic / Decreased Parasympathetic output -> Increased HR, Contractility, and Vasoconstriction (TPR) -> Restores MAP.