4: Feedback control of the cardiovascular system Flashcards
What is blood pressure?
The outward pressure exerted by the blood on blood vessel walls
What is systolic blood pressure?
The pressure exerted on the walls of the blood vessels when the heart contracts
What value (mm Hg) is systolic blood pressure usually LESS THAN?
140
What is diastolic blood pressure?
The pressure exerted on the walls of the blood vessels when the heart relaxes
What value (mm Hg) is diastolic blood pressure usually LESS THAN?
90
What is Mean Arterial Blood Pressure (MAP)?
The average arterial blood pressure during a single cardiac cycle
Why ISN’T MAP taken by averaging the systolic and diastolic blood pressures?
Time taken for relaxation is twice as long as that taken for contraction
How is MAP calculated
MAP = [(2x Diastolic) + Systolic)] divided by 3
What is the normal range of Mean Arterial Blood Pressure (MAP) in mm Hg?
70 - 105
What is the minimum MAP (in mm Hg) needed to perfuse the coronary arteries, brain and kidneys?
60
In which two areas are baroreceptors found?
- Aortic arch (Aortic baroreceptors)
2. Carotid sinus (Carotid baroreceptors)
What are baroreceptors?
Receptors responsible for regulating blood pressure
What happens to the firing rate of baroreceptors when MAP increases?
It also increases
What happens to the firing rate of baroreceptors when MAP decreases?
It also decreases
What is the cardiovascular control centre called?
Medulla
What is the cardiac output (CO)?
The volume of blood pumped by EACH VENTRICLE of the heart PER MINUTE
What is the stroke volume?
The volume of blood pumped by EACH VENTRICLE of the heart PER HEARTBEAT
Give an equation for cardiac output.
Cardiac output = Stroke volume x Heart rate
Give an equation for MAP.
Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance
What is Total Peripheral Resistance?
The sum of all the resistance in all of the systemic circulation
What is autorhythmicity?
The heart being able to beat automatically in the absence of any external stimuli
Which nervous division ACCELERATES the heart rate?
Sympathetic
Which nervous division SLOWS the heart rate?
Parasympathetic
What is tachycardia?
Increase in heart rate
What is bradycardia?
Decrease in heart rate?
Which nervous division is involved in regulating stroke volume?
Sympathetic
What type of controls regulate stroke volume?
Intrinsic (within the heart)
What type of muscle regulates total peripheral resistance?
Smooth muscle
Where is the majority of TPR found?
Arterioles
What does vasoconstriction do to TPR and MAP?
Increases them both
What does vasodilation do to TPR and MAP?
Decreases them both
Vascular smooth muscles are partially constricted at rest. This is called _____ ____.
Vasomotor tone
What controls vasomotor tone?
Discharge of sympathetic nerves resulting in continuous release of noradrenaline
What neurotransmitter is involved in sympathetic control of vascular smooth muscle?
Noradrenaline
Increased sympathetic discharge will ____ vasomotor tone resulting in ________.
increase , vasoconstriction
Decreased sympathetic discharge will ____ vasomotor tone resulting in ________.
decrease , vasodilation
Baroreceptors only respond to _____ changes in blood pressure.
acute
