Cardiovascular System Fundamentals

Study Notes

Striated, involuntary muscle: Cardiac muscle is a type of striated muscle that is under involuntary control.
Branching fibers: Cardiac muscle fibers are branching, allowing for rapid transmission of electrical signals.
Intercalated discs: Specialized regions that connect adjacent fibers, enabling coordinated contraction.
T-tubules: Deep invaginations of the sarcolemma, allowing for rapid transmission of electrical signals.

SA node (sinoatrial node): The natural pacemaker, generating an electrical impulse at a rate of 60-100 bpm.
AV node (atrioventricular node): Relays the electrical impulse from the SA node to the ventricles, causing contraction.
Bundle of His: A group of specialized fibers that transmit the electrical impulse from the AV node to the ventricles.
Purkinje fibers: Specialized fibers that rapidly transmit the electrical impulse to the ventricular muscle.

Stroke volume: The volume of blood pumped by the heart per beat.
Heart rate: The number of times the heart beats per minute.
Cardiac output: The product of stroke volume and heart rate, measured in liters per minute (L/min).
Factors affecting cardiac output: Heart rate, stroke volume, preload, afterload, and contractility.

Short-term regulation: Mediated by the autonomic nervous system, which adjusts heart rate and vasodilation/constriction to maintain blood pressure.
Long-term regulation: Mediated by the kidneys, which regulate blood volume and vasoconstriction to maintain blood pressure.
Baroreceptors: Specialized sensors that detect changes in blood pressure and send signals to the brain for adjustment.

Autonomic nervous system: The sympathetic and parasympathetic nervous systems work together to regulate heart rate.
Sympathetic nervous system: Increases heart rate and contractility through the release of norepinephrine.
Parasympathetic nervous system: Decreases heart rate through the release of acetylcholine.
Intrinsic control: The heart's intrinsic rate, which is around 100 bpm.