Regulation of Arterial Pressure

Question 1

What is MAP?

Answer 1

Measure of our blood pressure

Question 2

How do we calculate MAP?

Answer 2

MAP= CO * TPR

CO= cardiac output

TPR= total peripheral resistance

CO= HR * SV

MAP= HR * SV * TPR

Question 3

What is our normal MAP?

Answer 3

93.3 mmHg (around 100 mmHg)

Question 4

How do we regulate our blood pressure?

Answer 4

There are two main mechanisms to regulate our blood pressure

1. Baroreceptor reflex- regulates our BP on a minute-to-minute basis.
2. RAAS- fixes chronic problems by altering our blood volume

Question 5

What are our baroreceptors and where are they located?

Where do they then, convey signals to?

Answer 5

Baroreceptors are stretch receptors that respond to RATE of change in our MAP.

They are located in our carotid sinus and our aortic sinus.

They convey signals to our NTS (nucleus tractus solitarius)

Question 6

What detectors are involved in the baroreceptor reflex? (2)

Answer 6

1. Mechanorecptors (stretch receptors) that respond to changes in blood pressure
2. Chemoreceptors that respond to pO2, pCO2 and pH.

Question 7

Low BP–> decreased stretch on the walls of the carotid sinus.

How do the baroreceptors respond?

Answer 7

Decrease of firing rate of of the carotid sinus nerve (herings nerve and the CN IX)

Question 8

What are the brain regions involved in the baroreceptor reflex?

Answer 8

1. NTS (nucleus tractus solitarius)– receives and coordinates the peripheral signals
2. Dorsal motor nucleus of the vagus and nucleus ambigiquus–> alters parasympathetic activity
3. Rostral ventrolateral medulla- alters sympthetic activity

Question 9

What is the control center of the baroreceptor reflex?

Answer 9

The NTS (vasomotor center in the medulla).

Question 10

How do we increase and decrease TPR?

Answer 10

Sympathetically stimulate our arterioles.

Question 11

How do we alter our stroke volume?

Answer 11

Sympathetic stimulation

and

Preload

Question 12

HR is dependent on what?

Answer 12

1. Parasympathetic NS

2. Sympathetic NS.

Question 14

What is the mechanism baroreceptor initiates when there is a decrease in BP?

Answer 14

***Not activating our parasympathetics would increase HR

Question 15

What is the mechanism baroreceptor initiates when there is a increase in BP?

Answer 15

Question 16

How does the baroreceptor adapt with people who have chronic high blood pressure?

Answer 16

Hypertension will reset the baroreceptors to regulate BP at a higher set point.

Thus, they can adjust to different conditions.

Question 17

Activation of what receptors causes renin to be released from juxtaglomerular cells in the kidney?

Answer 17

B-1 adrenergic.

Question 18

Describe the RAAS complex to increase our BP.

Answer 18

Question 19

What causes the release of ADH (vasopressin)

Answer 19

1. Angiotensin II
2. Atrial receptors that detect a low preload
3. Increase osmolarity of the blood

Question 20

What are the purposes our our natriuretic peptides (Atrial NP, Brain NP, C-type NP)?

Answer 20

Natriuretic peptides are the opposite of aldosterone. They are secreted when we have too much preload of the atria and the ventricles; thus, they want to get rid of fluid.

1. Dilating the arterioles (decrease TPR)

2. Increase fluid loss

3. Inhibits renin (decreasing both TPR and preload)

Question 21

What helps to protect against overdilation and overstretching of our heart chambers?

Answer 21

Natriuretic peptides

Question 22

What can cause a decrease in blood volume?

Answer 22

1. Hemorrhage

2. Dehydration

3. Loss of body fluids

Question 23

What is the result of a decrease in blood volume?

Answer 23

1. Decrease venous return
2. Decrease preload
3. Decrease SV
4. Decrease CO
5. Decrease MAP
6. Vascular function curve shows a shift to the LEFT

Question 24

What mechanisms are activated to compensate for a hemorrage?

Answer 24

1. Baroreceptor reflex (increases sympathetic activatio and decreases parasympathetic)
2. • RAAS
3. Decrease in capillary hydrostatic pressure–> increase fluid retention–> increase plasma volume

Question 25

Jerry was found on the floor with a BP of 60. What will his compensatory responses be?

Answer 25

1. Carotid sinus nerve (baroreceptor) will decrease firing
2. HR, contractility, CO, TPR will increase
3. Unstressed volume will increase, to produce an increased venous return
4. Renin, angiotensin II, aldosterone EPI and ADH all increase

Question 26

Increased BV (increased or decreased preload)

What does this cause?

Answer 26

Increased BP means a increased preload

• Increase in ANP secretion
• Decrease in ADH secretion
• Renal vasodilation
• Increase HR

Question 27

During most aerobic excercise, how do our activators and inhibitors of chemoreceptors change?

Answer 27

They do not change much.

Question 28

What happens in response to normal aerobic excercise

Answer 28

• Messages sent to cerebral cortex, which will increase our sympathetic response and decrease our parasympathetic response (increase HR only)
• Increase HR, contractility, CO
• Vasoconstriction via B1 of inactive tissue, skin, splanchnic region, kidney
• Increase in VR.
• Vasodilation of active tissue because there is an increase of lactate, K+ and adenosine. Thus, this decreases TPR

–> Increase blood flow to skeletal m (pulse pressure increases, SBP increase, DBP should not change

Question 29

What happens if we are standing upright too long?

Answer 29

Blood pools to the feet.

Venous return will increase in the limbs, increasing venous return to the feet (decreasing central venous pressure) and capillary hydrostatic pressure, causing edema or hypotension.

-Our baroreceptor reflexes will attempt to work to bring shit back together. RAAS is too slow to have an affect.