Ex Phys Lecture 6

3 main components of the cardiovascular system

The heart (pump), blood vessels (pulmonary and systemic channels), and blood (fluid medium).

Right Ventricle vs. Left Ventricle

RV: Pulmonary circulation, thinner muscle, one-way. LV: Systemic circulation, thicker muscle, generates higher pressure.

3 layers of the heart wall

Epicardium (outer protective), Myocardium (thick middle cardiac muscle with mitochondria), Endocardium (inner impermeable layer).

Myocardial blood flow

Coronary arteries deliver blood to the myocardium primarily during diastole.

Intrinsic conduction & electrical properties

Automaticity (nodes leak Na/Ca to generate impulses without neural stimulation) and Conductivity (gap junctions/intercalated discs).

Stroke Volume (SV), EDV, Cardiac Output (Q), EF

SV = blood per beat; EDV = volume at end of filling; Q = HR x SV; EF = ejection fraction % (60-70%).

Blood vessel structures

Arteries (vasodilation/vasoconstriction), Arterioles (lack adventitia), Capillaries (intima/endothelium only), Veins (less muscle, must constrict).

Blood flow formula & main factor

Blood Flow = Blood Pressure / Vascular Resistance. Biggest factor is the radius of blood vessels.

Mechanisms of Venous Return

Breathing (thoracic pressure changes), Muscle Pump (muscular contractions), Valves (one-way flow), Venoconstriction.

Blood components & Hematocrit

Plasma, Erythrocytes (RBCs/hemoglobin), Leukocytes (WBCs), Platelets. Hematocrit = % of blood made of RBCs (40-45%). Total volume = 4-6L.

Cardiovascular control center regulators

Medulla oblongata responds to hypothalamus (temp), baroreceptors (blood pressure), chemoreceptors (CO2, pH, O2), and autonomic nervous system.

Parasympathetic vs. Sympathetic NS on the heart

Parasympathetic (Vagus): Dominant at rest, decreases HR/contraction. Sympathetic (Accelerator): Dominant during exercise, increases HR/contraction.

Adrenergic Receptors (Alpha 1, Beta 1, Beta 2)

Alpha 1: Constricts vessels/viscera. Beta 1: Increases HR, contractility, renin release. Beta 2: Dilates coronary arteries/bronchioles, relaxes smooth muscle.

ECG (Electrocardiogram) basics

Measures heart's electrical activity. Horizontal = time (1 box = 0.04s); Vertical = voltage; Isoelectric line = baseline.

Hormones/factors affecting heart rate & tone

Epi/Norepi (B1), T3/T4, chemoreceptors (CO2/H+), thermoreceptors, baroreceptors, increased sympathetic / decreased parasympathetic impulses.

ECG ST segment indications

Depressed = reduced blood flow (ischemia); Elevated = injury to the heart.

Why stroke volume increases during exercise

Frank-Starling Mechanism (greater ventricular stretch/force), increased ventricular contractility (Epi/Norepi), and decreased total peripheral resistance.

Long-term aerobic training adaptations

Increased heart size (LV chamber/thickness), increased SV at rest/exercise, decreased HR at rest/exercise, unchanged resting Q (increased during exercise), decreased resting BP.