Human Physiology and Systems Lecture Review

Comprehensive vocabulary flashcards covering major physiological systems including the cardiac cycle, hormone regulation, renal function, neuroglia, and respiratory processes.

Cardiac Cycle

One complete heartbeat lasting about $0.8\,\text{seconds}$, consisting of relaxation (diastole) and contraction (systole) phases.

Diastole

A $0.4\,\text{sec}$ relaxation phase where heart muscle relaxes, AV valves open, and the heart fills with blood.

Atrial Systole

A $0.1\,\text{sec}$ contraction phase, also known as the "atrial kick," pushing the final $20-30\%$ of blood into the ventricles.

Ventricular Systole

A $0.3\,\text{sec}$ contraction phase where AV valves close ("Lub" sound), semilunar valves open, and blood is ejected from the heart.

Isovolumetric Relaxation

A $0.1\,\text{sec}$ phase where ventricles relax, semilunar valves close ("Dub" sound), and all valves are briefly closed until pressure drops.

IGF-1

A substance released by the liver when stimulated by Growth Hormone (GH) to promote bone and muscle growth.

Lipolysis

The process of breaking down stored fat to be used as energy, stimulated by Growth Hormone.

Somatostatin

A hormone from the hypothalamus (or pancreas) that acts as an inhibitor to Growth Hormone and Insulin.

GHRH

Growth Hormone Releasing Hormone; a stimulator from the brain's hypothalamus that increases GH production.

SA Node

Known as the "Pacemaker," located in the right atrium; it fires electrical signals at $60-100\,\text{bpm}$ to initiate the heartbeat.

AV Node

A component of the conduction system that delays the electrical signal for $0.1\,\text{seconds}$ to allow atria to fully empty into the ventricles.

Bundle of His

The only electrical bridge connecting the atria to the ventricles, carrying signals down the interventricular wall.

Purkinje Fibers

Fibers that spread electrical signals throughout the ventricular muscle from the bottom up to ensure efficient blood ejection.

GLUT4

Transporters on muscle and fat cells that open in response to insulin to allow glucose to enter the cells.

Incretins (GLP-1 & GIP)

Hormones released from the gut after eating that stimulate the production of insulin.

Partial Pressure Gradient

The difference in gas pressure between the alveoli and blood; a larger gradient results in faster diffusion of oxygen and $CO_2$.

Ventilation/Perfusion (V/Q) Match

The requirement that airflow (ventilation) must match blood flow (perfusion) for successful gas exchange.

Reflex Arc

A rapid, automatic pathway bypassing the brain, consisting of a receptor, sensory neuron, integration center, motor neuron, and effector.

Afferent Neuron

A sensory neuron that carries signals from the receptor toward the spinal cord.

Efferent Neuron

A motor neuron that carries signals from the spinal cord out to a muscle or gland.

t-PA

A tissue-released activator that converts inactive Plasminogen into active Plasmin to dissolve blood clots.

Fibrinolysis

The body's natural process for dissolving blood clots after an injury has healed by breaking down the fibrin mesh.

Emulsification

The breakdown of large fat globules into tiny droplets by bile salts in the small intestine to increase surface area.

Micelles

Tiny spheres of monoglycerides, free fatty acids, and bile salts that transport lipid breakdown products to the intestinal lining.

Chylomicrons

Re-packed fat molecules inside intestinal cells that enter lacteals to be transported to the bloodstream.

Renin

An enzyme released by the kidneys in response to low blood pressure to initiate the RAAS pathway.

Angiotensin II

A powerful hormone that causes vasoconstriction, stimulates aldosterone and ADH release, and increases thirst.

Cortical Nephrons

Nephrons making up $85\%$ of the total, located in the outer cortex with short Loops of Henle, primarily for general filtration.

Juxtamedullary Nephrons

Nephrons ($15\%$) with long Loops of Henle diving deep into the medulla, specialized for concentrating urine.

External Respiration

The movement of $O_2$ from the alveoli into the blood and $CO_2$ from the blood into the alveoli.

Astrocytes

Star-shaped CNS neuroglia that feed neurons and form the Blood-Brain Barrier (BBB).

Oligodendrocytes

Neuroglia in the CNS that wrap around multiple nerve fibers to create myelin insulation.

Microglia

Phagocytic cells in the CNS that serve as the brain's "immune clean-up crew."

Erythropoiesis

The process of red blood cell production, requiring Iron, Vitamin $B_{12}$, Folic Acid, and Protein.

Glomerular Filtration Rate (GFR)

The volume of fluid filtered by the glomeruli per minute; normal rate is about $125\,\text{mL/min}$ ($180\,\text{liters/day}$).

Resting Potential

The electrical state of a cell (~$-70\,\text{mV}$) maintained by the $Na^+/K^+$ pump where the inside is negative relative to the outside.

Action Potential

A brief reversal of membrane potential from $-70\,\text{mV}$ to $+30\,\text{mV}$ following the "All-or-None" law.

Acrosome Reaction

The process where sperm release digestive enzymes like acrosin to dissolve the zona pellucida of the egg.

Filtration Fraction

The percentage of plasma filtered by the kidneys, normally about $20\%$.