Regulation of Blood Pressure

Question 1

Regulation of blood pressure is split into short and long term regulation. Which methods are employed by the body for each of these to regulate blood pressure?

Answer 1

Short term = baroreceptor reflex

Long term = regulation of blood volume

Question 2

Why is it important to keep the blood pressure high enough?

Answer 2

To perfume vital organs

Question 3

Why is it important to keep the blood pressure low enough?

Answer 3

To stop damage to organs

Question 4

Explain the steps of the baroreceptor reflex?

Include: the nerve fibres involved in each step and the locations of structures.

Answer 4

1) BP is monitored by baroreceptors (afferent nerve fibres) in the aortic arch and carotid sinus (“bulge” where common carotid bifurcated).
2) BP is relayed to the medulla (lowest part of the brain stem) where it is compared to a set point.
3) ANS efferents send correct impulses to cause a response in the heart and the vasculature to bring the BP closer to the set point.

Question 5

Which area of the medulla in the brainstem do the baroreceptor afferent signals travel to?

Answer 5

The nucleus tractus solitarius

Question 6

Describe the nerve pathway from the aortic arch to the nucleus tractus solitarius.

Answer 6

Aortic arch —-> aortic nerve —-> vagus nerve —-> nucleus tractus solitarius

Question 7

Describe the nerve pathway from the carotid sinus to the nucleus tractus solitarius.

Answer 7

Carotid sinus —-> carotid sinus nerve —-> glossopharnygeal nerve —-> nucleus tractus solitarius

Question 8

What does the PNS do to BP?

Answer 8

Decreases it.

Question 9

What does the SNS do to BP?

Answer 9

Increases it.

Question 10

Which receptors in the heart are the target for PNS outflow aiming to reduce the heart rate?

Answer 10

Muscarinic (M2) receptors (a subset of cholinergic receptors)

Question 11

How does PNS stimulation decrease BP?

Which receptors are involved in this process?

Answer 11

Slows HR via M2 receptors, which decreases cardiac output and therefore heart rate.

Question 12

Which receptors in the vasculature are the target for SNS outflow aiming to increase BP?

Answer 12

Alpha-1 adrenergic receptors.

Question 13

Which receptors in the heart are the target for SNS outflow aiming to increase BP?

Answer 13

Beta-1 adrenergic receptors.

Question 14

Which X2 areas of the CV system are targeted by the SNS to increase BP, and which receptors at each of these locations are responsible for this?

Answer 14

The vasculature = alpha-1 adrenergic receptors

The heart = beta-1 adrenergic receptors

Question 15

What X2 ways does the SNS alter the vasculature to increase BP?

Answer 15

1) increases arterial tone = increases TPR = increases BP
2) increases venous tone = decreases venous capacitance = increases CVP/preload = increases stroke volume = increases cardiac output = increases BP

Question 16

What X2 ways does the SNS alter the heart to increase BP?

Answer 16

1) increases inotropy = increases stroke volume = increases cardiac output = increases BP
2) increases chronotropy = increases cardiac output = increases BP

Question 17

Between what range of systolic pressures is the barororeceptor reflex effective?

Answer 17

80-150mmHg

Question 18

How does blood volume (the method of long term BP regulation) effect cardiac output?

Answer 18

Decreased volume = decreased CVP/preload = decreases stroke volume = decreased cardiac output (= decreased BP)

Question 19

What is the main influence on blood volume?

Answer 19

Salt composition

Question 20

By what process is increase blood volume reversed and how long does this process take?

Answer 20

Natriuresis (the excretion of sodium in the urine).

This process takes weeks.

Question 21

What process does an increased blood pressure stimulate to drive natriuresis?

Answer 21

Pressure natriuresis.

Question 22

What is pressure natriuresis?

Answer 22

A direct effect of increased blood volume causing increased BP which leads to increased renal sodium excretion in an effort to decrease blood volume and restore BP. The exact mechanism is unknown.

Question 23

Which system does increases in blood volume and BP down regulate?

Answer 23

The RAAS system

Question 24

What does the RAAS system do?

Answer 24

Conserves sodium to increase the retention of water.

Question 25

How does increased blood volume trigger down regulation of the RAAS system (other than directly) via the atria?

Answer 25

Increases blood volume causes atrial stretch receptors (cardiopulmonary receptors) to stretch and respond by decreasing SNS outflow to the kidney, which increases renal sodium excretion and down regulates the RAAS system.

Question 26

In what other way do the atria stretching in response to increased blood volume lead to increased renal sodium excretion?

Answer 26

They release atrial natriuretic peptide which causes renal sodium excretion.

Question 27

What X3 things trigger the RAAS system?

Answer 27

Decreases in:

• BP
• Blood volume
• Blood sodium concentration (usually 135-145mEq/L)

Question 28

What is the first stage of the RAAS system?

Answer 28

The juxtaglomerular cells of the kidney detect low blood pressure/volume/sodium concentration and secrete renin.

Question 29

What does renin do when in the blood?

Answer 29

Cleaves the protein angiotensinogen (freely circulating) into angiotensin 1.

Question 30

Where is angiotensinogen produced?

Answer 30

In the liver.

Question 31

What does angiotensin 1 do?

Answer 31

It gets converted by angiotensin converting enzyme (ACE) (found at the lungs) into angiotensin 2.

Question 32

What does angiotensin 2 do?

Answer 32

X3 things to increase BP:

1) Causes aldosterone to be released from the adrenal cortex which causes increased sodium and water reabsorption from the renal tubules
2) Causes vasoconstriction
3) Causes ADH to be released from the posterior pituitary which causes water reabsorption in the renal tubules

Question 33

What is ADH also called?

Answer 33

Vasopressin

Question 34

What is the name of a long term model of BP regulation?

Answer 34

Guyton’s model