Control of arterial blood pressure - 1

Question 1

What is blood pressure?

Answer 1

The outwards (hydrostatic) pressure exerted by the blood on blood vessel walls

Question 2

What is systemic systolic arterial blood pressure?

Answer 2

The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart contracts (not exceed 140mmHg)

Question 3

What is systemic diastolic arterial blood pressure?

Answer 3

The pressure exerted by the blood on the walls of the aorta and systemic arteries when the heart relaxes (not exceed 90mmHg)

Question 4

What is pulse pressure?

Answer 4

The difference between systolic and diastolic blood pressure

Question 5

What is mean arterial blood pressure and why is the value closer to the diastolic arterial pressure?

Answer 5

Its the average arterial blood pressure during a single cardiac cycle which involves both contraction and relaxation of the heart
-The diastolic portion of the cardiac cycle is twice as long as systolic

Question 6

How is mean arterial blood pressure estimated?

Answer 6

MAP= [(2 x diastolic) + systolic] divided by 3

Question 7

What is the normal mean arterial pressure?

Answer 7

70-105mmHg

Question 8

Why is mean arterial blood pressure needed to be regulated within a narrow range?

Answer 8

• pressure is high enough to perfuse internal organs including the brain, heart and kidneys
• pressure is not too high to damage the blood vessels or place an extra strain on the heart

Question 9

What is total peripheral resistance?

Answer 9

The sum of resistance of all peripheral vasculature in the systemic circulation

Question 10

What are the major resistance vessels?

Answer 10

Arterioles

Question 11

What does contraction of vascular smooth muscles cause?

Answer 11

• vasoconstriction

- increase TPR and MAP(i.e. pressure upstream)

Question 12

What does relaxation of vascular smooth muscles cause?

Answer 12

• vasodilation

- decreases TPR and MAP

Question 13

What is vasomotor tone?

Answer 13

When vascular smooth muscles are partially constricted at rest

Question 14

What causes vasomotor tone?

Answer 14

Caused by tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline

Question 15

What does increased sympathetic discharge have on vasomotor and what does it result in?

Answer 15

Increase vasomotor tone and results in vasoconstriction (increase TPR and MAP- pressure upstream)

Question 16

What does decreased sympathetic discharge have on vasomotor tone and what does it result in?

Answer 16

Decrease in vasomotor tone resulting in vasodilation (decrease TPR and MAP)

Question 17

What is the effect of parasympathetic on arterial smooth muscles?

Answer 17

No significant parasympathetic innveration of arterial smooth muscles - except penis and clitoris

Question 18

What are the 2 types of baroreceptors?

Answer 18

• Carotid ( in carotid sinus)

- Aortic (in aorta)

Question 19

What does the baroreceptor reflex do?

Answer 19

Short term regulation of mean arterial pressure

Question 20

How does the baroreceptors work?

Answer 20

The baroreceptors ( pressure centres) detect signal, move to the medulla (control centre) and goes to the heart and blood vessels ( effectors)

Question 21

What is the only type of changes that baroreceptors respond to?

Answer 21

Acute changes

Question 22

After “re-set” of baroreceptors, when will they fire again and what does this show?

Answer 22

Fire again only if there is an acute change in MAP above the new higher steady state level
-this shows baroreceptor cannot supply information about prevailing steady state blood pressure

Question 23

What is control of MAP in the long-term?

Answer 23

Control of blood volume