Ch. 20 - Heart Physiology Flashcards
at what period in the cardiac cycle are all 4 valves closed?
isovolumetric ventricular contraction & isovolumetric ventricular relaxation
what type of junction connects myocardiocytes?
intercalated discs, gap junctions
what connects myocardiocytes to underlying connective tissue?
hemidesmisomes
what does depolarization mean?
the cell gets more positive, increase permeability for Na+ (it comes in w + charge)
how do cardiac muscles’ action potential differ from skeletal muscles?
cardiac muscles act slower than skeletal bc they must allow full contraction
what is spontaneous depolarization? what causes it?
cells can reach threshold without help because of leaky Na+ channels
what are the main conducting cells?
pacemaker cells
purpose of conducting cells
spread action potential throughout the heart
purpose of contractile cells
create force of contraction, respond to conducting cell signals
describe impulse conduction pathway through the heart
SA Node AV node atria inter ventricular septum purkinje fibers & papillary muscles ventricular myocardium
purpose of SA node, location?
create HR, natural pacemaker. in right atrium
purpose and location of purkinje fibers
push blood out, help papillary muscles with contraction, in ventricles
purpose and location of AV node
pacemaker activity, delay so atria can fully contract
what is more serious, premature ventricular contractions (PVCs) or ventricular fibrillation?
ventricular fibrillation, bc the ventricles are quivering and aren’t pumping enough blood
possible causes of premature ventricular contractions (PVCs)
early firing of ectopic focus
stress, lack of sleep, irritation of heart
what is ectopic focus?
any part of heart thats doing its own thing
which direction do you want impulse to flow?
apex —> base
other names for semilunar valves
pulmonary & aortic
phases of cardiac cycle
atrial systole
AV valve opens, blood —> ventricles
atrial diastole, AV valve closed
isovolumetric ventricular contraction
end of ventricular systole
semilunar valves closed (isovolumetric relaxation)
AV valve opens, passive atrial filling occurs
formula for stroke volume
end diastolic volume - end systolic volume
what happens to ventricular volume during passive filling?
increases (because ventricles are filling w blood)
what make up walls of ventricles?
papillary muscles, trabeculae carnae, purkenje fibers
what is the name of process of listening to the heart
auscultation
formula for cardiac output
HR x SV
what raises HR?
sympathetic autonomic nervous system, epinephrine (adrenaline)
what is stroke volume?
amount of blood pumped out by heart in 1 min
what makes the “lubb” “dubb” sound
lubb = AV valve closing & semilunars opening dubb = ejection of blood from heart, semilunars closing, AV opens
what is a heart murmur? are they always pathological?
irregularity of blood flow, not always bad
what is cardiac reserve?
resting output - maximal output
which branch of autonomic nervous system increases HR?
sympathetic (fight or flight)
medulla oblongata role in HR
location of autonomic reflex centers, manipulates HR as needed
nerve used to transmit signal through sympathetic nervous system
cardiac nerve
nerve used to transmit signal through parasympathetic nervous system
vagus
hormone affects on heart
inc HR and contractility
what are baroreceptors?
sensory inputs sensitive to pressure (barometer measures pressure)
what are chemoreceptors?
sensory inputs sensitive to gases (CO2 & O2)
what is barostatic reflex?
dec HR bc of inc BP in head and neck region
what is atrial reflex?
inc HR bc of inc venous return (more blood returning to heart through veins)
what is preload
tension in ventricular myocardium right before systole
what is afterload
BP in aorta & pulmonary trunk, opposes opening of semilunar valves and limits stroke volume
what is Frank-Starling Law of the Heart
ventricles will adapt to contract to push out the amount of blood it receives
which cells can spontaneous depolarize
conducting cells, pacemaker cells
