Feedback control in the cardiovascular system Flashcards
What is measured when blood pressure is taken?
The systemic arterial blood pressure during systole and diastole
What is systemic systolic arterial blood pressure?
The outwards, hydrostatic pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
What is systemic diastolic arterial blood pressure?
The outwards, hydrostatic pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
What is the ideal systolic arterial blood pressure range for a person under 80?
90-120 mmHg
What is the ideal diastolic arterial blood pressure range for a person under 80?
60-80 mmHg
What clinic blood pressure is defined as hypertension?
140/90 mmHg or higher
What day time average pressure is defined as hypertension?
135/85 mmHg or higher
What is pulse pressure?
The difference between systolic and diastolic blood pressures
What is the ideal pulse pressure range?
30-50 mmHg
What is mean arterial blood pressure (MAP)?
The average arterial blood pressure during a single cardiac cycle, which involves systole and diastole
Why is the mean arterial blood pressure not the value half way between systolic and diastolic blood pressure?
Because during the cardiac cycle, the diastolic portion is twice as long as the systolic
How do you calculate mean arterial blood pressure?
MAP=(2D+S)/3, where S is systolic pressure and D is diastolic
What is the ideal mean arterial blood pressure range?
70-105 mmHG
What is the minimum mean arterial blood pressure required to perfuse vital organs such as the brain?
60 mmHg
Why can blood pressure not get too high?
If pressure is too high, blood vessels can become damaged and extra strain can be placed on the heart and other vital organs such as the brain or kidneys
What type of receptor detects changes in blood pressure?
Baroreceptors
What is the control centre within the brain for blood pressure?
The medulla oblongata
What are the 2 main types of baroreceptors?
Carotid and aortic baroreceptors
What nerve carries impulses from the aortic baroreceptors to the medulla oblongata?
The vagus nerve (the 10th cranial nerve)
What nerve carries impulses from the carotid baroreceptors to the medulla oblongata?
The Hering’s nerve, which is a branch of the glossopharyngeal nerve (the 9th cranial nerve)
What kind of receptors are baroreceptors?
They are mechanoceptors that are sensitive to stretch
How does an increase in mean arterial blood pressure affect the firing rate of a baroreceptor?
The firing rate increases
How does a decrease in mean arterial blood pressure affect the firing rate of a baroreceptor?
The firing rate decreases
What is the site of first synapse for all cardiovascular system afferents in the medulla?
The nucleus tractus solitarius
What is the function of the nucleus tractus solitarius?
It integrates and relays information to other regions that control the pathways of the two divisions of the autonomic nervous system to the heart and blood vessels
What is the formula for MAP using cardiac output and systemic vascular resistance?
MAP= CO x SVR
What is the formula for cardiac output using stroke volume and heart rate?
CO = SV x HR
What is the formula for MAP using stroke volume, heart rate and systemic vascular resistance?
MAP = SV x HR x SVR
What is cardiac output?
The volume of blood pumped out by each ventricle per minute
What is stroke volume?
The volume of blood pumped out by each ventricle per heart beat
What is systemic vascular resistance?
The sum of resistance of all vasculature in the systemic circulation
What is autorhymicity?
The capability of the heart to beat rhythmically in the absence of an external stimuli
What does stimulation of the sympathetic division cause?
Tachycardia
What is tachycardia?
Acceleration of the heart rate
What does stimulation of the parasympathetic division cause?
Bradycardia
What is bradycardia?
Deceleration of the heart rate
What nerve is stimulated in the parasympathetic division to cause bradycardia?
The vagus nerve
What neurotransmitter is present in the sympathetic division and causes bradycardia?
Noradrenaline (norepinephrine)
What type of receptors does noradrenaline act on during bradycardia?
ß1 receptors in the heart
What neurotransmitter is present in the parasympathetic division and causes tachycardia?
Acetylcholine
What type of receptor does acetylcholine act on during tachycardia?
Muscarinic (M2) receptors in the heart
How does stimulation of the sympathetic division affect stroke volume?
Stroke volume increases as the contractile strength of the heart increases.
How does the sympathetic nerve increase the contractile strength of the heart?
Sympathetic nerves innervate the ventricular myocardium and stimulation increases the force of contraction
How does intrinsic control of stroke volume occur?
Through the Frank-Starling mechanism
What vessel is the main site of systemic vascular resistance?
The arterioles
What causes an increase in SVR and MAP?
Contraction of smooth muscle causing vasoconstriction
What causes a decrease in SVR and MAP?
Relaxation of smooth muscle causing vasodilation
What causes the vasomotor tone?
The tonic discharge of sympathetic nerves, resulting in continuous release of noradrenaline
How does the sympathetic division increase SVR?
Sympathetic nerve fibres stimulate contraction of vascular smooth muscle
What neurotransmitter is released by sympathetic nerve fibres during vasoconstriction?
Noradrenaline
What receptor does noradrenaline act upon during vasoconstriction?
α receptors
What is the name given to the partial constriction of smooth muscle when at rest?
The vasomotor tone
What effect does increased sympathetic stimulation have on the vasomotor tone?
The vasomotor tone will increase, therefore causing vasoconstriction
What effect does decreased sympathetic stimulation have on the vasomotor tone?
The vasomotor tone will decrease, therefore causing vasodilation
Where in the body is there parasympathetic innervation of arterial smooth muscle?
The penis and clitoris
What happens to the firing rate of baroreceptors if high arterial blood pressure is sustained?
It decreases and baroreceptors reset and will only fire again if an MAP is detected above the new high level
