Lecture 3 Cardio Flashcards
(35 cards)
What is the cardiac output?
vol of blood pumped by each ventricle per minute (L/Min)
For an avg sized adult, the cardiac output is ~ ____
50 L/min
The amount of blood ejected by each ventricle with each beat is called the
Stroke volume
How is cardiac output calculated?
stroke volume x heart rate
SV(HR) = CO
During max exercise in a well-trained athlete, CO can increase to ~ ___
35 L/min
The SA node, which normally determines the ___, is innervated by the _____
The SA node, which normally determines the resting heart rate, is innervated by the parasympathetic and sympathetic postganglionic nerve fibers
Parasympathetic activity causes the rate of SA node firing to ____ and therefore the heart rate ___
Parasympathetic activity causes the rate of SA node firing to decrease and therefore the heart rate decreases
Sympathetic activity causes the rate of SA node firing to ___ and therefore the heart rate ___
Sympathetic activity causes the rate of SA node firing to increase and therefore the heart rate increases
With HR, parasympathetic activity normally…
dominates over sympathetic activity and thus the resting HR is approximately 7- BPM rather than 100 that would result from the intrinsic, unregulated depolarization of the SA node
Increasing sympathetic activity increases the number of ____ and ____, resulting in the membrane potential…
Increasing sympathetic activity increases the number of Sodium and Calcium (L type) channels that open, resulting in the membrane potential reaching threshold faster than it would under the resting level of parasympathetic stimulus
Increasing parasympathetic activity results in fewer
SA node discharges (APs) per minute and thus a decreased heart rate
Increasing parasympathetic activity ___ the cell and this contributes to the increased….
Increasing parasympathetic activity hyperpolarizes the cell and this contributes to the increased amount of time it takes the membrane potential to reach threshold.
___ causes more of the special Na+ and Ca2+ (T) to open and, thus, enhances the movement of positive charge into the cell
Norepinephrine
___ causes more of the special Na+ and Ca2+ (T) to be closed, thus slowing down the movement of positive charge into the cell
Acetylcholine
___ from the adrenal medulla increases HR by interacting with the same beta-adrenergic receptors as norepinephrine
epinephrine
The AV node is innervated by..
both the sympathetic and parasympathetic nerve fibers
Increasing the relative amount of sympathetic activity increases the…
Increasing the relative amount of sympathetic activity increases the velocity of conduction of APs through the AV node
Increasing the amount of parasympathetic activity decreases the…
Increasing the amount of parasympathetic activity decreases the velocity of conduction of APs through the AV node
Other factors that affect the resting HR:
Body temp, alterations in serum electrolyte concentrations, and adenosine
Since the ventricles do not empty completely with each heart beat, it is possible to alter the __ by___.
This can be accomplished by…
stroke volume by altering the forcefulness of the ventricular contraction
altering the end-diastolic volume (EDV) or by altering the amount of sympathetic activity, or BOTH.
A basic phys principle is that the ventricles contract more forcefully if…
they have been filled to a greater degree during the preceding diastole
Stroke volume increases as the ___ increases
this is known as:
ventricular end-diastole volume
this is called the Frank-Starling mechanism
The frank-staling mechanism is an intrinsic property of cardiac muscle that is related to…
It is not….
the length-tension properties of this tissue
not the result of the ANS or circulating hormones
One important consequence of this mechanism is that…
the cardiac output of the L and R ventricles are maintained equal
