regulation of the cardiovascular system 1 Flashcards
what is end diastolic volume
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what is end systolic volume
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how to calculate stroke volume
EDV - ESV
define venous return
Venous return - the volume of blood that comes back to the right atrium per unit time
define cardiac output
Cardiac output - volume of blood pumped into the aorta per unit time
how to calculate cardiac output
stroke volume x heart rate
what happen if cardiac output does not equal to venous return
diseases occur
unit of cardiac output
CO: Litres/min
SV: mL
HR: beats/minq
what are the 3 components that affect stroke volume
- preload
- afterload
- contractility
what does preload, afterload and contractility affect respectively
EDV
- Preload
ESV
- Afterload
- Contractility
what is the primary and secondary pacemaker
Primary pacemaker - SA node
Secondary pacemaker - AV node
what is the parasympathetic nerve for heart regulation
vagus nerve
what is the sympathetic nerve for heart regulation
adrenergic nerve
2 ways to increase heart rate
- decreasing vagal tone
- Increasing sympathetic tone
process of parasympathetic control of heart rate (SA node)
- Release of acetylcholine -
○ slows heart rate
○ By binding to muscarinic receptors (Muscarinic receptors are a type of acetylcholine receptor)
○ Muscarinic receptor antagonist wil increases heart rate (blocking the vagal response)
Release acetylcholine open fewer Na channels, less amount of sodium entering the cell, so the rate at which it takes to reach the threshold potential is slower, and hence triggering the action potential slower
process of sympathetic control of heart rate (SA node)
Sympathetic control
- Release noradrenaline
○ Increases heart rate
○ By binding to beta-adrenoreceptors
○ Beta-adrenoreceptor antagonist will decrease heart rate (blocking the sympathetic activity)
Release noradrenaline open more Na+ channels, greater amount of sodium entering the cell, so the rate at which it takes to reach the threshold potential is quicker, and hence triggering the action potential quicker
process of parasympathetic control of heart rate (AV node)
Parasympathetic control:
- Increases refractory period (time at which the AV node cannot receive action potential)
- Decreasing AV conduction, hence decreasing the heart rate
process of sympathetic control of heart rate (AV node)
Sympathetic control
- Decreases refractory period
- Increasing the AV conduction, hence increasing the heart rate
what is contractility
a measure of the force produced by the cardiomyocytes
how is contractility regulated
For atrial myocytes:
- The sympathetic nerve terminal releases noradrenaline which binds to beta-adrenoreceptors on atrial myocytes
- The parasympathetic vagal nerve releases acetylcholine which will bind to muscarinic receptors on the sympathetic nerve terminal, this blocks the release of noradrenaline
what is the frank-starling law
- The relationship between myofibre length (stretch), dictated by left ventricular EDV (or EDP = preload), and force generated by contraction
- The more blood that returns to the heart = the greater the stretch of the cardiomyocytes, that greater degree stretch optimizes the heart to contract harder in order to expel the volume put into it
is the frank-starling law linear
It is not a linear relationship (you cannot pour more and more blood into the heart, there is a limit)wha
what affects the venous pressure
- Blood returns to the right atrium due to forward motion resulting from contraction of the left ventricle
- Vasoconstriction of blood from the peripheral to central vein increases venous return and increases the stroke volume
- Lower limb skeletal muscle activity helps transport blood back to the heart, increases the central venous pressure and increases stroke volume
- Thoracic pump:
Inspiration - pressure gradient favors venous return
