Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
53 Cards in this Set
- Front
- Back
Cardiac myocytes: |
have single nucleus, are striated (due to sarcomeres; sothey have myosin, troponin-tropomyosin, etc.) - gap junctions allow cells to synchronize - Heart muscles don’t sum. If they did, they would fatigue |
|
Myocyte refractory period |
the refractory period is 250 ms in a cardiac myocyte (25 times longer than in amuscle) Long refractory period means: contractile cell completelyrelaxes before refractory period ends, which prevents summation and tetanus. |
|
Calcium in myocytes |
Ca imbalance will lead to irregularity in the heart. |
|
Autorhythmic (pacemaker) cells |
- spontaneously depolarize - unstable resting membrane potential - depolarize via Ca++ & Na+ influx - repolarize via K+ efflux - gap junctions allow other cells to fire when these cells fire - are in clusters like SA node, A-V node |
|
depolarization of: - SA node - AV node - purkinje fibers |
SA Node: 90 x's per minute AV node: 50x's per minute Purkinje: 35 x's per minute |
|
___ percent of the cells are contractile cells; ___ percent areautorhythmic/pacemaker cells |
99, 1 |
|
T or F: two atria contract simultaneously, then two ventricles contractsimultaneously |
True |
|
Systole |
contraction of a heart chamber; blood leaves the chamberduring systole. - period of atrial systole and ventricular systole, whichfollows - atria beat separately from the ventricles, so atrialsystole and ventricular systole happen separately - atria contract and push blood into the ventricles |
|
Diastole |
relaxation of the heart chamber; blood fills the chamberduring diastole - atrial are relaxing while ventricles are contracting - there is a time (about .4 of a sec) when all fourchambers are in diastole |
|
semilunar valvesseparate.... |
- ventricles and aorta - open during ventricular systole when ventricles contract and push the blood up and out topulmonary/systemic circuit), close during ventricular diastole |
|
Right A-V (tricuspid) & Left A-V (mitral/bicuspid)... |
- Separate atria and ventricles - close during ventricular systole, open duringventricular diastole. - Atrial systole/diastole doesn’t have anything to dowith A-V valves - Open when there’s no pressure to push up against them |
|
Valve pathologies: stenosis & incompentence |
Stenosis: failure of valve to open Incompetence: failure to close |
|
Trace Blood Flow |
Ratrium → tricuspid valve→ R ventricle → pulmonary semilunar valve → pulmonarytrunk → lungs → L atrium → Bicuspid valve → L ventricle → Aortic semilunar valve → systemiccircuit |
|
During atrial systole... |
- A-V valves are open,pushing blood down through A/V valves - blood is flowing from the atria to the ventricle- ventricles are in diastole (relaxed) |
|
During ventricular systole.... |
- semilunar valves are open - Blood is flowing to pulmonary/systemic circuit- atria are in diastole |
|
When both atria and ventricles are relaxing (in diastole): |
- this stage happens after ventricles finish systole. - A-V valves are open - Blood is flowing into the atria and the ventricles |
|
T or F: atrial systole begins immediately once ventricularsystole is complete? |
False (unless you’re working out) –there’s a period when all 4 chambers are in diastole |
|
What electrical events are happening during: - P wave - QRS wave - T wave |
P wave: atrial depolarization QRS: ventricles depolarizing, atria repolarizing T wave: ventricles are repolarizing |
|
End Systolic Volume |
At end of ventricular systole. The least amount of blood in theheart |
|
End Diastolic Volume |
At the end of atrial systole (right before the ventricles contract) - when the most blood is in the heart - happens at top of QRS |
|
Formula for Stroke Volume |
EDV-ESV = Stroke volume |
|
functional reserve |
Heart fills entirely but only pushes out about 50% of theblood (so average ESV is 50%). This is called functional reserve of the heart. It doesn't have to beat faster to pump more blood. It can justincrease its stroke volume by pumping more fully. |
|
Ejection fraction |
stroke volume made into a percent (about 50% is normal) |
|
Lub |
When ventricles contract, the A-V valves close and opens thesemi lunar valves. Happens atQRS. |
|
Dup |
|
|
Formula for cardiac output |
heart rate x stroke volume (L per min) |
|
Parasympathetic Response (cardiac) |
heart slows down |
|
sympathetic (cardiac) response |
heart beats faster and with more force |
|
What determines heart rate? |
- pacemakercells. inherent rate = 90 bpm. - SANode is dually innervated by sympathetic & Parasympathetic nervous system - parasympathetic slows it down and sympathetic speeds itup - to increase the heartbeat, you can decrease PSstimulation or increase symp stimulation. |
|
sympathetic NS increases HR through |
norepinephrine binding to Beta 1’s - affects heart rate and contractility |
|
Parasympathetic decreases HR through |
releasing acetylcholine onto muscarinic receptors (mACH-R) - Has no effect on muscle/contractile cells |
|
Stroke Volume is determined by |
force of contraction. |
|
force of contraction is determined by |
preload, contractility, and afterload |
|
Preload |
- the degree of stress on the ventricle walls at the end of diastole (directly related to volume) - More volume = more force. Less volume = less force - duration of diastole and rate of venous return both affect EDV. longer duration = more volume, increased venous return = less volume |
|
Contractility |
- How forcefully is the heart beating? Strength ofcontraction at any preload. - depends on how much calcium is inside it (intracellularcalcium) - sympathetic activity innervates the muscle of the heart toincrease contractility |
|
Afterload |
- the degree of stress on ventricle walls at the start ofsystole; ventricular pressure needed to overcome peripheral resistance |
|
peripheral resistance |
- blood pressure in the rest of the body (systemiccircuit) - if it’s low, the heart has an easier time pushing bloodout into the systemic circuit; if it’s high in the systemic circuit, it’sharder for the heart to get the blood out. |
|
Inotropic Agent |
a drug that affects contractility of the heart - positive inotropic effect makes heart beat moreforcefully - negative - less forcefully |
|
How do increases in preload, contractility, and afterload affect stroke volume? |
- if preload increases, stroke volume increases - if contractility increases, stroke volume increases - if afterload increases, stroke volume decreases |
|
Systolic & Diastolic pressure |
Systolic pressure: max pressure created byventricular systole in an artery Diastolic Pressure: arterial pressure duringventricular diastole |
|
Pulse pressure |
Pulse pressure = systolic pressure – diastolicpressure |
|
Mean arterial pressure |
diastolic pressure + 1/3 (systolic – diastolic) |
|
Vasoconstriction |
Norepinephrine from sympathetic system binds to alpha receptors on vascular smooth muscle - epinephrine binding to alpha receptors causes vasoconstriction |
|
Vasodilation |
epinephrine binds to beta-2 receptors and causes vasodilation - decreased sympathetic stimulation also causes vasodilation |
|
hyperemia |
- matching blood flow to demand --> matches resistance --> increases flow |
|
which receptors are dually innervated? |
alpha and Beta-1 |
|
what will a non-specific beta blocker due toMAP/cardiac output? |
- decrease heart rate, decrease stroke volume –bc of Beta1 |
|
Baroceptor reflex |
- pressure sensors that are monitoring yourblood pressure. They initiate a reflexthat keeps the blood pressure homeostatic. - Found in your carotid arteries and your aortic arch - Tonic Mechanoreceptors -> stretch/pressure causes them to depolarizeMedullaoblongata is the integrating center, which monitors whether you’re above orbelow your set point. |
|
Orthostatic hypotension |
drop in blood pressure based on change in bodyposition (usually standing up) |
|
hypo/hypervolemia |
Hypovolemicshock: when your blood volume isdangerously low Hypervolemia: when your blood volume is dangerously high |
|
Alpha receptors |
target cells: systemic arterioles response NE → constrict |
|
Beta-1 receptors |
Target cells: SA Node & contractile Response: Increased HR, increased stroke volume |
|
Beta-2 receptors |
Target cells: coronary artery, hepatic artery, skeletal muscle Response: epinephrine --> dilates |