cardiovascular function and electrical activity of the heart

What are the three main components of the cardiovascular system?

Heart, blood vessels, and blood.

What is the main function of the cardiovascular system?

Transport of gases, nutrients, wastes, hormones, and heat.

Name the four chambers of the heart.

Right atrium, right ventricle, left atrium, left ventricle.

Name the four valves of the heart.

Tricuspid, pulmonary, mitral (bicuspid), aortic.

Describe systemic circulation.

Blood flow between the aorta and venae cavae; supplies the body tissues.

Describe pulmonary circulation.

Blood flow between the heart and lungs for gas exchange.

Describe coronary circulation.

Blood flow through the heart’s own vessels to nourish cardiac tissue.

What is systolic aortic pressure?

Peak pressure during left ventricular contraction (~120 mmHg).

What is diastolic aortic pressure?

Minimum pressure before the next ejection (~80 mmHg).

Define mean aortic pressure.

Average blood pressure in the aorta (~98 mmHg), drives systemic blood flow.

Define systemic perfusion pressure.

Pressure difference between mean aortic and vena cava pressure (~95 mmHg).

Define pulmonary perfusion pressure.

Pressure difference between pulmonary artery and vein (~8 mmHg).

Which circulation is high pressure and resistance?

Systemic circulation.

Which circulation is low pressure and resistance?

Pulmonary circulation.

What vessels carry blood away from the heart?

Arteries.

What vessels return blood to the heart?

Veins.

Where does nutrient and gas exchange occur?

Capillaries.

What is a portal system?

Two capillary beds arranged in series for specialized transport.

Name three portal systems in the body.

Splanchnic, renal, hypothalamic-hypophyseal.

What percentage of blood is found in systemic circulation?

75%.

Which vessels contain most of the blood volume?

Venules and veins (~80% of systemic blood volume).

What is hematocrit?

Percentage of blood volume occupied by red blood cells.

Define polycythemia.

Abnormally high hematocrit → increased blood viscosity and heart workload.

Define anemia.

Low hematocrit or hemoglobin → reduced oxygen-carrying capacity.

What are the main plasma proteins?

Albumin, globulins, fibrinogen.

What is the difference between plasma and serum?

Plasma contains clotting factors; serum lacks them.

What is bulk flow?

Movement of blood driven by pressure differences.

What is diffusion (in circulation)?

Slow movement of molecules across capillaries for gas and nutrient exchange.

What are the three main types of pacemaker cells in the heart?

SA node, AV node, and Purkinje fibers.

Where is the SA node located?

Right atrial wall near the venae cavae; initiates heartbeat.

Where is the AV node located?

Lower interatrial septum near coronary sinus; delays impulse.

What is the ventricular rate from SA node pacemaking in a dog?

80–90 beats per minute.

What is the ventricular rate from AV node pacemaking?

30–40 beats per minute.

What structure conducts impulses rapidly through ventricles?

Purkinje fibers.

What is a pacemaker potential?

Spontaneous depolarization in SA node cells that initiates action potentials.

Which ions are involved in pacemaker depolarization?

Na+, Ca2+ influx and decreased K+ efflux.

Which channels cause depolarization in pacemaker cells?

Ca2+ (L-type) channels.

What maintains the resting membrane potential?

Na+/K+ ATPase pump and K+ leak channels.

Describe the phases of cardiac action potential.

Phase 0: Na+ influx; Phase 1: Na+ inactivation; Phase 2: Ca2+ plateau; Phase 3: K+ repolarization; Phase 4: resting potential.

Which ion triggers cardiac muscle contraction?

Ca2+, entering via slow channels and released from SR.

Why is the cardiac refractory period long?

Prevents tetanus and allows refilling between contractions.

Which cells have shorter action potentials: atrial or ventricular?

Atrial cells.

What neurotransmitter increases heart rate?

Norepinephrine (β-adrenergic effect).

What neurotransmitter decreases heart rate?

Acetylcholine (muscarinic effect).

How do norepinephrine and epinephrine affect cardiac muscle?

Increase Ca2+ influx → stronger, faster contractions.

How does acetylcholine affect cardiac muscle?

Decreases heart rate; weakens sympathetic effects.

What is the intrinsic heart rate in dogs (no neural input)?

~140 beats per minute.

What is sick sinus syndrome?

SA node dysfunction causing bradycardia or sinus arrest.

What are tachyarrhythmias?

Rapid heart rhythms from abnormal pacemaker activity.

Name three types of supraventricular tachycardia.

Sinus tachycardia, atrial tachycardia, junctional tachycardia.

What is ventricular fibrillation?

Random ventricular depolarizations → no coordinated contraction; fatal without defibrillation.

What is a first-degree AV block?

Slow conduction from atria to ventricles.

What is a second-degree AV block?

Some atrial impulses fail to reach ventricles.

What is a third-degree AV block?

Complete block; atria and ventricles beat independently.

How do beta-blockers (e.g., propranolol) affect the heart?

Reduce heart rate, contractility, and conduction velocity.

How do calcium channel blockers (e.g., verapamil) act?

Block L-type Ca2+ channels; lower plateau, weaken contractions.

What is the effect of cardiac glycosides (e.g., digitalis)?

Inhibit Na+/K+ pump → increased intracellular Ca2+ → stronger contraction.