L9- Physiology: parameters of the cardiovascular system Flashcards
With each ventricular ejection of blood by the heart, what happens to BP, SP and DP?
BP blood pressure in the aorta and other arteries sharply rises to a maximum (systolic pressure) and then falls to a minimum as ventricles relax (diastolic pressure). Difference between these extremes is defined as pulse pressure (PP).
Formula of PP (pulse pressure)
PP = SP - DP
Mean Arterial Pressure changes when?
When you exercise or change posture
Heart spends more time in?
more time in diastole than systole
Formula of MAP (mean arterial pressure)
MAP = DP + 1/3 (SP - DP) = DP + 1/3 PP
Formula of MAP in relation to cardiac output and total peripheral resistance
MAP = CO x TPR
Unit of CO (cardiac output)
Volume of blood ejected by the heart per minute (L/min )
TPR is?
Total resistance of peripheral vasculature in the systemic circulation and has the units of mm Hg (L/min)
An increase in firing rate of the autonomic _____ or _____ neurons, which innervate the pacemaker, the sino-atrial node, will increase or decrease heart rate respectively.
Sympathetic or parasympathetic neurons
Adrenaline (epinephrine) released from?
Released from adrenal medulla
Adrenaline (epinephrine) stimulates an increase in?
Increase in heart rate
An increase in the volume of blood returning to the heart (venous return) can indirectly increase?
Heart rate
The force of ventricular contraction is influenced by?
sympathetic neuronal output and an increased volume of blood returning to the heart will induce a greater force of contraction (Starling’s LAw of the Heart) respectively.
The previous DP (if DP increases then the following ____ increases)
Systolic pressure
List determinants of systolic pressure
- Force of ventricular contraction
- Stroke volume
- Previous diastolic pressure
- Distensibility of aortic walls
Systolic pressure will increase with a decrease in?
Decrease in aortic elasticity
List determinants of diastolic pressure
- Heart rate
- Total peripheral resistance
- Previous systolic pressure
An increase in heart rate will increase?
Diastolic pressure
An increase in TPR will increase?
Diastolic pressure
An increase in systolic pressure will cause following ?
Diastolic pressure to increase
Determinants of total peripheral resistance
- Radius of the blood vessel (arterioles mostly)
- Length of the blood vessels
- Viscosity of blood
Radius of the blood vessels controls?
Controls vasoconstriction while local metabolites cause vasodilation
What is baroreceptor reflex?
It regulates homeostatic control of blood pressure automatically restoring any changes in blood pressure back to normal after a posture change.
What are baroreceptor afferent nerve fibres?
Cranial nerves IX (sympathetic) and X (parasympathetic) fibres
Where are baroreceptor afferent nerve fibres located?
Located in the blood vessel walls of the carotid sinuses and aortic arch.
When MAP falls when changing from a sitting to standing position, firing rate of baroreceptor?
Baroreceptor firing rate decreases
Decreased baroreceptor firing rate causes an increased?
Increased firing of efferent sympathetic nerves to the heart and a decreased firing of efferent parasympathetic nerves via interneurons in the brainstem.
Increased efferent sympathetic nerves to the heart increases?
Increased activity of post-ganglionic cardiac sympathetic nerves, resulting in increased pacemaker activity of the sino-atrial node (SA node)
Increased post-ganglionic cardiac sympathetic nerves results in?
Increased pacemaker activity of SA node
Increased pacemaker activity of SA node increases?
Increases contractility of ventricular muscle fibres
Increased contractility of ventricular muscle fibres with decreased cardiac vagal activity results in an?
Results in an increase in heart rate and contractility
Increased activity in sympathetic vasomotor nerves to arterioles and veins causes?
Causes vasoconstriction and venoconstriction respectively.
Sympathetic activation also causes an increase in?
Increase in adrenal medullary hormone secretion, principally adrenalin (epinephrine) which also affects blood vessels and the heart.
Net result of baroreceptor reflex
Rise in CO and TPR, and hence MAP, thereby restoring it to normal.
Change in posture from lying to standing will _____ the pressure in the vessels below the heart and result in?
Increased pressure in the vessels, and results in immediate changes in SP, DP, MAP and HR.
How long till body baroreceptor reflex kicks in to restore MAP after postural change?
5 to 10 seconds
Finapres recording devices allow?
Allow continuous measurement of BP and visualization of the immediate effects of postural change
Finapres recording devices monitors?
Monitors intra-arterial blood pressure changes using a finger cuff.
How does finapres recording device work?
Waves of increasing and decreasing volumes of blood flowing through finger with each cardiac cycle evaluated as pressure changes in the cuff.
Finapres recording devices measures?
Measures the highest and lowest pressures representing the systolic pressure and diastolic pressures respectively, while MAP and CO are derived from the software.
