Lecture 10

Question 1

Arterial pressure is _______ controlled and is precisely regulated at ________ mmHg

Answer 1

homeostatically controlled

90

Question 2

Why is it important that the arterial pressure is maintained?

Answer 2

so that there is sufficient perfusion pressure to overcome the resistance of arterioles, while flowing at the desired rate

Question 3

What does arterial pressure being homeostatically controlled enable?

Answer 3

it enables precise control of regional blood flow by manipulating only the regional resistance

Question 4

What are the sensors of blood pressure and where are they located?

Answer 4

baroreceptors in the aortic arch and carotid sinus

Question 5

Where is the carotid sinus? Why is it important that there are baroreceptors there?

Answer 5

This is in the neck. We need the blood pressure to be good here because this is going to the brain

Question 6

Baroreceptors are ______ active at rest. What does this mean?

Answer 6

tonically

this means they have a resting firing rate that changes in response to high or low blood pressure

Question 7

How do baroreceptors change in response to an increase in blood pressure?

Answer 7

If there is an increase in BP, there is an increase in stretch. This is detected by the baroreceptors and they increase their rate of firing

Question 8

How do baroreceptors change in response to a decrease in blood pressure?

Answer 8

If there is a decrease in BP, there is a decrease in stretch. This is detected by the baroreceptors and they decrease their rate of firing

Question 9

How do the baroreceptors in the aortic arch and carotid sinus send information to the brain?

Answer 9

The receptors in the carotid sinus send information via the carotid sinus nerve and the receptors in the aortic arch send information via the vagus nerve

Question 10

What is another name for the carotid sinus nerve?

Answer 10

the glossopharyngeal nerve

Question 11

Why is the pressure cyclical?

Answer 11

because it changes between systolic and diastolic pressure

Question 12

Each cycle can give a burst of _______ activity of the nerve

Answer 12

tonic

Question 13

Blood pressure regulation is needed for ______ term regulation such as ________ to _______

Answer 13

short

sitting to standing

Question 14

As the blood pressure goes up, there is an increase/decrease in the rate of firing

Answer 14

increase

Question 15

If you reduce your MABP, the amount of nerve activity is increased/decreased

Answer 15

decreased

Question 16

If the MABP is increased, the amount of nerve activity is increased/decreased

Answer 16

increased

Question 17

How can you increase pulse pressure?

Answer 17

through an increase in systolic and a decrease in diastolic pressure

Question 18

If the pulse pressure increases, the amount of nerve activity is what?

Answer 18

very very large

Question 19

Where is the information about the firing from the baroreceptors processed?

Answer 19

in the integrator: the nucleus tractus solitarius (NTS) in the medulla

Question 20

The information from our nerves is coming up to the NTS and is doing what?

Answer 20

trying to work out if it is different from normal and then sends information out back to the periphery on how to change things to get things back to normal

Question 21

What is the efferent output from the NTS?

Answer 21

parasympathetic and sympathetic output (both pre-gangionlic and post-ganglionic nerves for this)

Question 22

Where is the cardiovascular sensor located?

Answer 22

in the medulla

Question 23

Describe the sympathetic output from the medulla

Answer 23

It comes out of the spinal cord and there is a synapse onto the preganglionic fibre which goes to a sympathetic ganglion just outside the spinal cord and then there is postganglionic fibres which innervate the heart and the blood vessels

Question 24

Describe the parasympathetic output from the medulla

Answer 24

The preganglionic fibre comes out of the medulla towards the heart and synapses in the ganglion in the heart and then the post-ganglionic fibre changes things in the heart

Question 25

What do parasympathetic nerves innervate and how does this affect MABP?

Answer 25

they innervate the heart which acts to reduce the flow/CO and this decreases MABP

Question 26

What do sympathetic nerves innervate and how does this affect the MABP?

Answer 26

Some of them innervate the heart which acts to increase flow/CO and some innervate the blood vessels which act to increase TPR and this increase MABP

Question 27

What happens when there is an increase in MABP?

Answer 27

- arterial baroreceptors increase their firing - this decreases sympathetic outflow to the heart, arterioles and veins and - increase parasympathetic outflow to the heart - there is decreased contractility, decreased TPR, decreased HR, decreased MABP

Question 28

What happens when there is a decrease in MABP?

Answer 28

- arterial baroreceptors decrease their firing - this decreases parasympathetic outflow to the heart and - increases sympathetic outflow to the heart, arterioles and veins - there is increased contractility, increased TPR, increased HR, increased MABP

Question 29

Defne a haemorrhage

Answer 29

an escape of blood from a ruptured blood vessel

Question 30

When you haemorrhage, your blood pressure decreases. What are the three stages of restoration?

Answer 30

- baroreflex - cardiovascular volume restoration - total body volume restoration

Question 31

How does arterial blood pressure fall after a haemorrhage? | 9

Answer 31

- blood loss - decreased blood volume - decreased venous pressure - decreased venous return - decreased atrial pressure - decreased ventricular end-diastolic volume - decreased stroke volume (detected by baroreceptors) - decreased cardiac output - decreased arterial blood pressure

Question 32

How does the baroreflex act immediately to try and restore blood pressure after a haemmorhage?

Answer 32

``` it acts on the heart to - increase HR - increase SV - increase CO - increase MABP it acts on the veins to - cause venoconstriction to - increase VR - increase EDV - increase CO - increase MABP it acts on the arterioles to - cause vasoconstriction to - increase TPR - increase MABP ```

Question 33

What is the issue with the baroreflex when you have haemorrhaged?

Answer 33

it does not restore blood volume

Question 34

Describe the cardiac volume restoration process in response to a haemorrhage?

Answer 34

If there is a reduction in pressure, an increase in vasoconstriction of the arterioles will lead to a bigger drop in pressure across the arterioles so the capillary pressure is lower. In the normal capillary pressure, H2O tends to be driven out of the capillary but after the haemorrhage there is a change in pressure and so instead of water leaving the capillaries, water enters the capillaries which restores blood volume

Question 35

What is the purpose of the cardiovascular volume restoration function?

Answer 35

If we have a reduction in MABP, we can pull water into the capillaries

Question 36

Where are large amounts of water absorbed in the body?

Answer 36

from the skin and the gut (non-vital places)

Question 37

How long does blood pressure take to be restored after water is pulled from the capillaries?

Answer 37

just a few minutes

Question 38

What is the long-term total body volume restoration system?

Answer 38

this is the renin angiotensin aldosterone system

Question 39

Describe the renin angiotensin aldosterone system

Answer 39

- the kidneys produce renin and the liver produces angiotensinogen - the renin converts the angiotensinogen to angiotensin | - enzymes in the lungs and blood vessels called angiotensin converting enzymes convert angiotensin | to angiotensin || - angiotensin || causes vasoconstriction which can help with the maintenance and BP - angiotensin || also acts on the adrenal cortex and kidney to produce aldosterone

Question 40

What is the effect of aldosterone?

Answer 40

it stimulates Na+ and H2O reabsorption in the kidney which decreases urine output and increase total body water

Question 41

What is renin production controlled by?

Answer 41

- regulated by perfusion pressure (reduction in this leads to increase in renin production) - sympathetic stimulation (via the baroreflex)

Question 42

``` Which statement is INCORRECT? An increase in sympathetic nerve activity will : A) Decrease heart rate B) Increase venous return C) Increase ventricular contractility D) Increase the production of renin ```

Answer 42

A) Decrease heart rate

Question 43

The baroreceptors are tonically inactive at rest BECAUSE at rest arterial blood pressure is maintained at approximately 120/80 mmHg to silence the baroreceptors.

Answer 43

false, false