anatomy and physiology review Flashcards
what are the two basic functions of the heart?
maintain good electrical function and good pump function (BP and CO)
what is BP? ___x ____
resistance x blood flow
what is CO?
HR x SV
what is SV?
preload, after load and contractility
out of preload, after load and contractility which does total circulating vol affect?
preload
out of preload, after load and contractility which does blood viscosity affect?
afterlaod
out of preload, after load and contractility which does body position affect?
preload
out of preload, after load and contractility which does acidosis affect?
contractility
where is the right coronary artery and what does it feed?
courses laterally around the right side of the heart int he right atrioventricular groove feeding the anterior right atrium and the anterior right ventricle and the sA node and all the way around to the crux (juncture of the atrioventricular and intraventricular grooves) supplying the AV node
once the right coronary artery descends towards the apex what is ti called and what does it feed
the posterior descending brand of the right coronary and feeds the inferior surface (wall) of both the right and left ventricles, the posterior 1/3 of the intraventricular septum and the posterior fascicle of the left bundle branch
what are the two main branches on the left coronary artery>
the left anterior descending (LAD) and the circumflex (Circ)
what does the LAD feed?
down anterior intraventricular groove feeding the anterior surface (wall) of left atrium and ventricle. and smaller branches (septal) feed the anterior right ventricular walls nd 2/3 anterior ventricular septum including the anterior fascicle of the eft b uncle branch and the r bundle branch
what does the circumflex feed?
circles laterally around the heart in the left atrioventricular groove feeding the left atrium and the lateral surface (wall) of the left ventricle
which layer of the heart contracts first? why is this off? why?
subendocardial (innermost layer). it is the last layer to receive blood bc coronary arteries penetrate the heart muscle from outside in
when do the coronary arteries perfuse the heart?
when the heart is relaxed (diastole)
at what point (PQRST) is the electrical stimulus slowed to allow for filling?
PR interval to allow or ventricular filling in diastole
how much of the atrial kick contributes to CO?
20-30%
does the electrical impulse go to the bundle of his or purkinje fibres first/
bundle of his
where is the SA node located? what does it consist of? what is its intrinsic rate? is it innervated by parasympathetic or sympathetic NS?
right atrium adjacent to the superior vena cava. highly specialized cells that initiate electrical impulses (automaticity) at 60-100bpm. both
where is the AV node located? function? intrinsic rate? does the AV node allow the electrical impulse to go faster or slower? why?
floor of the right atrium. can function as a secondary pacemaker if SA node fails. 40-60 bpm. slows it down to allow the atria to finish emptying its contents into the ventricles
what does the His-Purkinje system consist of? rate?
his bundle, bundle branches and the purkinje fibers. his bundle divides into two main divisions forming the r and l bundle branches and feed into the purkinje fires. can initiate an impulse if SA and AV node fail at 20-40 bpm
the fibres in the sympathetic system supply what? what are these fibres called?
atria and the ventricle. adrenergic fibres which indicates a relationship to adrenaline
what does the SNS stimulate? think location
the adrenal medulla to release epi and norepinephrine that act on the adrenergic receptors in the heart
what is the effect of flight or fight response?
inc HR, inc contraction, inc in conduction resp rate and dec activity in GI
what are drugs called that mimic SNS or block it? para SNS?
sympathomimetic and sympatholytic
parasympathomimetic and parasympatholytic
the paraSNS acts on the heart via the ___
vagus nerve
what does the paraSNS supply?
SA node, AV node and atrial muscle and ventricular muscle to a lesser extent
what mediator is released in paraSNS? what does this do
acetylcholine which occupies cholinergic receptor sites in the heart - “vagal response” which slows down the sinus node and conduction through the AV node. HR dec, resp rate and GI increases
where do beta 1 receptors effect?
effect the heart. when these are occupied or stimulated w catecholamines (primarily norepinephrine) it results in inc heart rate, increased conduction through AV node and inc contractility. influenced by SNS
where do beta 2 receptors effect? what do they do ?
effect bronchial smooth muscle and peripheral vasculature so B2- (2 lungs. causes bronco dilation, peripheral vasodilation, coronary artery vasodilation
what do alpha receptors do?
effect peripheral vasculature. causesvascoconstuiction of peripheral, coronary and renal vessels. i.e.) if BP low give this kind of drug to vasoconstrict
what do dopaminergic receptors do?
located renal, mesenteric, coronary, and intracerebral vessels. inc renal perfusion?
what does inotropic mean? what does it mean if its positive or negative inotropic effect?
means contractility so inc or dec myocardial contractility
what does chronotropic mean? positive and neg?
heart rate so inc or dec heart rate. think chronology- watches, rate
what does dromotropic mean? pos neg?
conduction through AV node. so pos is enhanced conduction thru av node and vice cersa
during an action potential -before it begins, are the Na outside the cell positive or negative? what is this called. what is the mV
positive outside the cell and K are negative inside the cell. resting memrnae potential, which is -90mV
the SA and AV node resting membrane potential is what? the resting cell is said to be what?
-70mV. polarized
when a cell is stimulated by an electrical impulse, the membrane of the polarized cell becomes permeable to what? what is the membrane potential now? what is the cell called following this?
positively charged na ions. rises from -90 to -60. depolarized now.
what kind of channels do the pacemaker cells of the SA and AV node have?
slow calcium channels. allows pos charged Na and Ca into the cell at a slower rate.
why do cardiac channel membranes in the SA and AV nodes set the HR. what is their threshold
higher threshold around -40. therefore can initiate impulse faster than non-pacemaker cells aka takes less time to reach their threshold. so faster and can set the pace of the heart
as soon as cardiac cells depolarize what happens to potassium ions?
flow out of the cel initiating repolarization and inside of cell is negative again
does a cardiac cell need to be completely repolarized before it can be stimulated to depolarize again?
no it does not need to be -90 again it can be -70 (threshold potential) to depolarize again
when is the cell pos and neg during action potential? explain movement of ions
inside of cell is negative during resting potential and when an electrical impulse causes na to flood in then it is pos. at the end of depolarization. process of repolarization begins w Na+ channels closing (rapid influx stops) and K leaves the cell causing cell to be neg again. but to get back to resting potential (polarized) the K has to be pumped back in and Na out
what occurs during phase 0?
represents depolarization. na in cell, inside cell is positive to about +20mV. cell is depolarized and begins to contract
what occurs during phase 1?
first na+ channels close, halting Na from coming into cell and K moves out of cell. cell is positive inside. drop in membrane potential to about 0mV. called EARLY RAPID REPOLARIZATION
what occurs during phase 2?
plateau phase and is slow repolarization. allows cell to finish contracting and begin to relax. remains about 0mV. Ca and Na slowly enter cell and K leaves
what occurs during phase 3?
inside of cell becomes more neg and returns to -90 (resting membrane pot) referred to as TERMINAL PHASE OF RAPID REPOLARIZATION. caused by K leaving the cell
what occurs during phase 4?
period between action potentials. returned to -90. inside of cell is neg. Na/K pump is now activated and Na is transported out of the cel and K in cell bc still lots left in and out
how does the na/K pump work effectively
thru energy- ATP and Mg
what are refractory periods?
the time between depoarization and depolarization during which cardiac cells cannot be stimulated to depolarize.
what is the absolute refractory period?
ends midway through phase 3 (corresponing with the peak of the T wave). cardiac cells have no depolarized enough to reach their threshold potential and can’t depolarize
what is the relative refractory period?
extends through the second half of phase 3 (downslope of the t wave). cardiac cells have now depolarized enough to reach their threshold membrane potential and can be stimulated to depolarize if stimulus is strong enough. called the vulnerable period.
what is the supernormal period?
short period of phase 3 just before the cells return to their resting membrane potential.. a stimulus weaker than is normal ca depolarize the cell
properties of cardiac cells: what is automaticity
the ability to initiate an impulse or stimulus. it is the cardiac cells capacity to depolarize spontaneously during phase 4. spont dep depends on the ability of the cell to become permeable to na during phase 4.
what is excitability?
the ability to respond to impulse. capability of a resting cell to depolarize to stimuli
what is conductivity?
ability to transmit impulses to other areas. who cardiac ells depolarize and stimulate adjacent cells to depolarize
what is contractility?
ability to respond to electrical impulse with PUMP ACTION (the only technical property of heart)
how big are the little boxes on ECG? (time)
0.04 sec
how big are the large squares on ECG?
whole thing is 0.2 seconds so 5 big squares is 1 sec
how long is normal PR interval
0.12-0.20 seconds
how long is normal QRS interval
<0.10 seconds
what occurs during PR interval?
delay of AV node. represents the length of time it takes for the impulse to travel from the atria to ventricles
what occurs during ST segment?
refractory period
what occurs during QT interval?
refractory period. may lead to life-threatening ventricular arrhythmia. normal QT is 0.44 seconds for men and 0.46 sec for women or 1/2 of RR interval
what does a normal P wave indicate?
the electrical impulse originated in the SA node
where is the J point?
just after S
how do you measure big block method?
each large box is 300 beats/min so if there are 2 boxes between each beat then its 300/2 and so on. or memorize 300-150-100-75-60-50-43
