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35 Cards in this Set

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what is the mechanism of adrenergic influence upon cardiac cellular functions?
epinephrine from adrenal medualla or norepinephrine from sympathetic neurons binds B1 receptors on myocardial contractile cell that activates cAMP second messenger system that phophorylates 2 paths for 3 mechanisms for 2 results: more forceful contraction (iontropic) and shorter duration of contraction (chronotropic)
the adrenergic affect of phosphorylating voltage gated CA++ channels results in what?
open time increases, increasing Ca++ entry from the extracellular fluid that causes increases in Ca++ stores in SR and increases Ca++ released through Ca++ induced Ca++ release, causing more forceful contractions
the adrenergic affect of phosphorylating phospholamban results in what?
increasing Ca++-ATPase activity of SR, resulting in increasing stores in SR and increasing Ca++ released through Ca++-induced Ca++ release causing more forceful contraction AND Ca++ removed from cytosol faster and time of Ca-troponin binding shorter creating shorter duration of contraction
what is the mechanism of cholinergic influence upon cardiac cellular functions?
acetylcholine affect G-protein with inhibits cAMP second messenger system (preventing phosphorylation)
how does the central cardioinhibitory center sends inhibitory impulese to the SA and AV nodes via what?
the vagus nerve
what does the central cardioinhibitory center send via the vagus nerve?
inhibitory impulses to the SA and AV nodes
the vagus nerve sends inhibitory impulses to the SA and AV nodes from what?
the central cardioinhibitory center
what type of impulses does the central cardioinhibitory center send ote the SA and AV nodes via the vagus nerve?
inhibitory impulses
what is the only nervous system input that influences cardiac function?
autonomic nervous system
what do autonomic neurotransmitters do to the intrinsic myocardial electrical events?
modulate but do not initiate
what is the adrenergic affect on the AV nodal function on slow conduction velocity (AV delay)?
shortens delay
what is the cholinergic affect on the AV nodal function on slow conduction velocity (AV delay)?
lengthens delay
what is the adrenergic affect on the AV nodal function on long refractory period?
shortens - ventricles keep pace at increased sinus HR
what is the cholinergic affect on the AV nodal function on long refractory period?
lengthens
what is the adrenergic affect on the AV nodal function on spontaneous depolarization to threshold as an auxiliary pacemaker (slower than SA)?
faster depolarization
what is the cholinergic affect on the AV nodal function on spontaneous depolarization to threshold as an auxiliary pacemaker (slower than SA)?
slower depolarization
where are sympathetic, adrenergic neurons distributed in the heart?
all cardiac cells
all cardiac cells receive what type of ennervation?
sympathetic, adrenergic neurons
what does activation of B1-adrenergic receptors lead to?
action potentials that are of greater magnitue and velocity (faster, shorter duration) and stronger, quicker contractions
what does stimulation of B1-adrenergic receptors cause?
increased number of Ca++ channels open, increasing amount of extracellular Ca++ entering the cardiac myocites
Ca++ is the primary triggering influence for what during the plateau phase?
cardiac muscle depolarization
what does increased intracellular Ca++ do to membrane potential?
makes it more positive
More positive membrane potential does what to the action potential?
shortens the duration because the more positive the membrane potential is in the plateau phase, the sooner the slow K+ channels open and lead to repolarization
B1-adrenergic receptor stimulation leads to AP's that are what?
greater amplitude and shorter duration that propagate more quickly from cell-to cell and causes muscle to contract more vigorously (positive inotropic affect)
what is positive inotropic affect?
more vigorous muscle contractions
A shorter AP refractory period facilitates what?
a higher HR
parasympathetic, cholinergic influences are generally opposite of what affect?
sympathetic adrenergic
parasympathetic, cholinergic influences are limited to where?
the SA node, AV node, and atrial myocardium
cardiac arrhythmias arise as the result of what?
abnormalities of impulse generation or abnormalities of impulse conduction
organic disease of the intrinsic conduction system can be the underlying cause of what?
arrhyhmia
extrinsic influence upon the activity of the intrinsic conduction system or the contractile myocardium can lead to what?
arrythmia
any disruption of normal sinus rhythm (NSR) renders the heart what?
as a less efficient pump
what does NSR stand for?
normal sinu rhythm
what is the major clinical relevance of any arrhythmia?
the negative impace upon cardiac output, a hemodynamic consideration
what are the relevant generic concepts that apply to any given disturbance of normal cardiac rate and rhythm from a clinical perspective?
location, frequency, and timing