Blood Pressure Feedback Mechanisms Flashcards
What is blood pressure?
The hydrostatic pressure exerted by the blood on blood vessel walls.
What is systolic arterial blood pressure?
The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts
What is systolic arterial blood pressure usually?
<140 mm/Hg
What is diastolic arterial blood pressure?
Is the pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes
What is the diastolic pressure normally?
<90 mm/Hg
What is hypertension defined as?
Clinic blood pressure of 140/90 mmHg or higher and day time average of 135/85 mmHg or higher
What is pulse pressure?
The difference between systolic and diastolic blood pressures
What is MAP?
The average arterial blood pressure during a single cardiac cycle, which involves contraction and relaxation of the heart
What is twice as long as what?
Diastolic portion is to systolic.
How do you calculate MAP?
MAP = [(2x Diastolic) + Systolic] divided by 3
How do you calculate MAP?
MAP = DBP + 1/3 difference between SBP and DBP
What is the normal range for MAP?
70 - 105
What is the lowest value of MAP needed to perfuse the brain, heart and kidneys?
60
Why is a very high pressure not wanted?
It damages blood vessels and puts extra strain on the heart.
Why is a very low pressure not wanted?
Not enough perfusion of internal organs.
Where are the baroreceptors?
In the aortic arch and carotid sinus.
What nerve links the aortic baroreceptors to the brain?
Herings nerve.
What nerve links the carotid baroreceptors to the brain?
Vagus.
What is the control centre for blood pressure regulation?
Medulla (brain stem).
What kind of receptors are baroreceptors?
Mechanoreceptors.
What are mechanoreceptors sensitive to?
Stretch.
What happens to the firing rate of the baroreceptors when the MAP increases?
Increases
What happens to the firing rate of the baroreceptors when the MAP decreases?
Decreases
MAP=?
CO x SVR
What is CO?
the volume of blood pumped by each ventricle of the heart per minute
CO=?
SV x HR
What is the Stroke Volume (SV) ?
the volume of blood pumped by each ventricle of the heart per heart beat
What is SVR?
the sum of resistance of all vasculature in the systemic circulation
What is the heart rate regulated by?
ANS
What does the sympathetic division of the ANS do?
Accelerates the heart rate.
What does the parasympathetic division of the ANS do?
Stimulates the vagus nerve which slows down the heart rate.
What are the main resistance vessels?
Arterioles.
What is the SVR regulated by?
Vascular smooth muscles.
What is the main site of SVR?
Arterioles.
What is vasoconstriction?
The contraction of smooth muscles
What does vasoconstriction increase?
MAP and SVR
What is vasodilation?
The relaxation of smooth muscles
What nerves are the smooth muscles supplied with?
sympathetic nerves.
What is the neurotransmitter for sympathetic nerves?
Noradrenaline acting on alpha receptors.
What is the vasomotor tone?
The vascular smooth muscles being partially constricted at rest.
What causes the vasomotor tone?
By tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline