Heart Problems and Smooth Muscle

This set of flashcards covers key concepts related to heart problems and smooth muscle physiology based on the lecture notes.

AV node

A part of the heart conduction system that can take over pacing the heart when the SA node is nonfunctional, generating a heart rate of 40-60 beats/min.

Tachycardia

An abnormally fast heart rate (>100 beats/min) that can lead to fibrillation if persistent.

Bradycardia

A slower than normal heart rate (<60 beats/min) that may lead to inadequate blood circulation in non-athletes.

Ectopic focus

An abnormal area in the heart where electrical impulses originate, potentially leading to arrhythmias.

Fibrillation

Rapid, irregular contractions of the heart muscles that are ineffective for pumping blood.

Stroke volume

The amount of blood pumped by each ventricle per cycle, calculated as End Diastolic Volume minus End Systolic Volume.

Cardiac Output

The volume of blood pumped by each ventricle in one minute, calculated by heart rate multiplied by stroke volume.

Preload (Starling's Law)

The degree to which the ventricles are filled with blood before contraction; increases in filling enhance contractile strength.

Afterload

The pressure the ventricles must overcome to eject blood through the semilunar valves.

Single-unit smooth muscle

Smooth muscle type that behaves like cardiac muscle, exhibits spontaneous action potentials, and is found in hollow organs.

Multi-unit smooth muscle

Smooth muscle type that behaves like skeletal muscle, found in large airways and arteries, with independent contraction due to graded neural stimuli.

Myofilaments in smooth muscle

Contain fewer thick filaments (1:13 ratio to thin filaments), lack troponin, and are arranged spirally.

Excitation-contraction coupling

The process in smooth muscle where calcium influx activates calmodulin, which then activates myosin light chain kinase to initiate contraction.

Stress-relaxation response

The ability of smooth muscle to respond to stretch briefly and then adapt to a new length while retaining the ability to contract on demand.