Regulation of Blood Pressure Flashcards

1
Q

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?

A

Short term = baroreceptor reflex

Long term = regulation of blood volume

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2
Q

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

A

To perfume vital organs

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3
Q

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

A

To stop damage to organs

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4
Q

Explain the steps of the baroreceptor reflex?

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

A

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.

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5
Q

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

A

The nucleus tractus solitarius

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

What does the PNS do to BP?

A

Decreases it.

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9
Q

What does the SNS do to BP?

A

Increases it.

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10
Q

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

A

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

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11
Q

How does PNS stimulation decrease BP?

Which receptors are involved in this process?

A

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

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12
Q

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

A

Alpha-1 adrenergic receptors.

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13
Q

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

A

Beta-1 adrenergic receptors.

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14
Q

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?

A

The vasculature = alpha-1 adrenergic receptors

The heart = beta-1 adrenergic receptors

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15
Q

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

A

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

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16
Q

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

A

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

17
Q

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

A

80-150mmHg

18
Q

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

A

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

19
Q

What is the main influence on blood volume?

A

Salt composition

20
Q

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

A

Natriuresis (the excretion of sodium in the urine).

This process takes weeks.

21
Q

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

A

Pressure natriuresis.

22
Q

What is pressure natriuresis?

A

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.

23
Q

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

A

The RAAS system

24
Q

What does the RAAS system do?

A

Conserves sodium to increase the retention of water.

25
Q

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

A

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.

26
Q

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

A

They release atrial natriuretic peptide which causes renal sodium excretion.

27
Q

What X3 things trigger the RAAS system?

A

Decreases in:

  • BP
  • Blood volume
  • Blood sodium concentration (usually 135-145mEq/L)
28
Q

What is the first stage of the RAAS system?

A

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

29
Q

What does renin do when in the blood?

A

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

30
Q

Where is angiotensinogen produced?

A

In the liver.

31
Q

What does angiotensin 1 do?

A

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

32
Q

What does angiotensin 2 do?

A

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

33
Q

What is ADH also called?

A

Vasopressin

34
Q

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

A

Guyton’s model