ch 18 cardiovascular system- the heart 1/30 Flashcards
3 steps to cardiac muscle contractile
depolarize, plateau, repolarize.
depolarize phase of cardiac muscle cell
fast Na+ opens, ECF Na+ flows into making cell more positive, membrane potential reverses -90 mV to +30 mV. must happen for AP to take place
plateau phase of cardiac muscle cell
Ca+ channels open, Ca+ enters, K+ channels open, K+ leaves. This balances out the membrane potential in the cell. Plateau phase allows contractile cells to do friction, so heart contracts more eventually
repolarization phase of cardiac muscle cell
Ca+ channels close, K+ open, inside cell is more negative now, reaching resting membrane potential once again. tension decreases bc cardiac cells relax
electrocardiogram (ECG)
allows doctor to see heart activity, electrical impulses generated in and out heart, they produce P, QRS, T waves
P wave
depolarization of both atria sides from SA node to atria, first wave on ECG shown, after P wave is when it contracts, once depolarize is complete, depolarization moves to AV node
QRS complex
depolarization of ventricles, impulse goes down inter ventricular septum, hooks L/R apex, travels up via perkinje fibers. R is the peak, Q/S troughs occurs due to changing depolarization waves. current changes directions after.
T wave
relaxation of ventricles, repolarization of ventricles, T wave is wider than QRS complex bc repolarization takes longer than depolarization, heart relaxes at slower rate than contracts.
RR interval on an ECG
interval of actual ventricle contraction, the amount of time between individual heartbeats
junctional rhythms
due to dysfunctional SA node, P wave no longer there so HR slows to like 50 bpm, RR is farther spaced. intrinsic conduction issue here: AV node takes place of SA node to set the rhythm slow and bad
ventricular fibrillation
APs are occur rapid and irregularly chaotic, defibrillator must be used with EPI and heart is not a pump in this situation it is not an efficient blood mover
systole and diastole
systole- period of contraction
diastole- period of relaxation
each cycle occurs 75 x per min
cardiac cycle steps
ventricular filling, isovolumetric contraction phase, ventricular ejection, isovoulemtric relaxation
ventricular filling stop of cardiac cycle
mid to late diastole, low pressure in heart so heart is relaxed, atrial systole occurs atria contracts to push remaining blood into ventricle, AV valves open and end diastolic volume (EDV) occurs, where max blood volume is in ventricle before it contracts.
isovolumetric contraction phase, systole, of cardiac cycle
same value of blood in heart, blood won’t move, ventricle begin contract and pressure rises fast in ventricles, AV valves close and SL valves aren’t open yet, SL valves will open when pressure in ventricles > blood vessels. (blood flows high to low)
ventricular ejection, systole in cardiac cycle
blood flows from ventricles to aorta (left ventricle) and pulmonary trunk (right ventricle).
isovolumetric relaxation in cardiac muslce cycle, early diastole
ventricles relax and pressure drops fast in the ventricles, ESV (end diastolic volume) is reached (where remaining blood volume in ventricles after complete relax and contraction). SL valves closed and ventricles get closed off again. this prevents back flow and nearly empties ventricles
cardiac output
total blood pumped by ventricle in a single minute, cardiac output (CO) = stroke volume (SV) times HR
stroke volume
volume of blood pumped out by ventricle with each beat, EDV-ESV. SV is directly correlated to ventricular contraction. higher contraction = more SV
average adult SV and HR and CO
70 mL blood per beat, and avg 75 bpm making average CO 5,250 mL OR 5.25 L. around same amount of total blood volume.
what happens when to CO when stroke volume increases? HR?
if CO increase, SV and HR increase
how can cardiac output be physically altered
physical exercise, hormones, emotional states
maximal cardiac output
maximum Amt of blood that can be pumped in a single minute, depends on physical fitness. less fit- 20-25 L/min, more fit- 35 L/min, elite athletes can move more blood in a single minute than regular ppl
about 4-5 amt of resting level.
regulating stroke volume
more blood means more force, can change EDV by increasing preload.
