Heart Physiology

what connects cardiac myocytes (muscle cells) together?

intercalated discs + gap junctions and desmosomes

what ion triggers contraction?

calcium enters the cell, binding to troponin

what causes spontaneous depolarization?

Na+ leakage channels

what are the two types of cardiac muscle cells?

conducting cells = spread action potential

contractile cells = contract

what is the pace of the SA node?

80-100

what is the pace of the AV node?

40-60, the cells are smaller so the signal moves slowly / delay

what is an ectopic pacemaker?

disrupts timing between atrial and ventricular contraction

what is an atrial flutter?

ectopic focu în the atria give extra contractions, 200-400

what is a PVD heartbeat?

early firing of ectopic focus, could be irritation

what is a ventricular fibrillation?

electrical signals arrive at different times

what comprises a cardiac cycle?

one contraction and relaxation of all four heart chambers

process of the cardiac cycle

1. arterial contraction adds more blood to relaxed ventricles

2. ventricles contract and push AV valves closed, the atria are relaxed

3. ventricles relax, atria relaxed and fill up with blood

4. ventricles fill passively

what is auscultation?

listening to heart sounds

what is cardiac output?

amount of blood pumped out the heart in one minute

how do you calculate CO?

HR X SV

what is cardiac reserve?

Resting - maximal cardiac output

what influences HR?

autonomic innervation and hormones (epinephrine, norepinephrine, thyroid)

what stimulates chemoreceptors?

fall of O2 or increase in CO2

what is the barostatic reflex?

increased in BP in head region decreases HR

what is the brainbridge reflex?

increase in HR after increase in venous return

what is EDV?

blood in ventricle right before contraction

what is ESV?

blood remaining in ventricle just before relaxation

what is preload?

ventricular cells during diastole

what is afterload?

tension the contracting ventricle produces to eject blood

if venous return increases, what happens to EDV?

increases

if the filling time decreases, what happens to the EDV?

decreases

if EDV increases, what happens to SV?

increases

if ESV decreases, what happens to the SV?

increases

if contractility decreases, what happens to ESV?

increases

if afterload increases, what happens to ESV?

increases

what impacts venous return?

blood volume, peripheral circulation, skeletal muscle activity