Lecture 13 - Blood Pressure Regulation

Question 1

Define Blood Pressure

Answer 1

The pressure exerted on blood vessel walls as blood flows through

Question 2

State the formula for Blood Pressure

Answer 2

Blood Pressure = Cardiac Output x Total Peripheral Resistance

Question 3

What is the mechanism of local autoregulation of blood pressure (when it is too low)?

Answer 3

The opening of pre-capillary sphincters in response to chemical vasodilators in the blood (e.g., increased CO2, decreased O2, K+, H+) -> decreased resistance, increased blood flow

Question 4

What 3 main things can disturb homeostasis and prompt local autoregulation of blood flow?

Answer 4

1. Physical Stress (e.g., trauma, high temperature)
2. Chemical Changes (e.g., fall in O2 or pH, increase in CO2, increase in vasodilators)
3. Increased tissue metabolism (-> increased lactate)

Question 5

Where in the body do the signals from chemoreceptors and baroreceptors go?

Answer 5

The Cardiovascular Centre in the Medulla Oblongata

Question 6

How do the signals from Baroreceptors in response to a Fall in BP affect the three centres (and which nervous system is activated by the first two)?

Answer 6

• Activation of Cardioacceleratory Centre
• Inhibition of Cardioinhibitory Centre
• Activation of Vasomotor Centre (vasoconstriction)

SYMPATHETIC Nervous System

Question 7

Whence is angiotensinogen secreted?

Answer 7

From the liver

Question 8

What converts angiotensinogen into angiotensin I (and whence and when is THIS secreted)?

Answer 8

Renin (from the kidney following a fall in renal BP)

Question 9

What converts angiotensin I to angiotensin II (and whence is THIS secreted)?

Answer 9

Angiotensin Converting Enzyme (ACE) -> from the endothelial cells in capillaries of the lungs

Question 10

What are the effects of angiotensin II?

Answer 10

Vasoconstriction, and stimulation of adrenals to secrete aldosterone -> increased Na+ reabsorption and fluid retention

Question 11

What are the three main endocrine responses to low Blood Pressure?

Answer 11

1. ADH (pituitary gland) -> Vasoconstriction and Fluid Retention
2. Erythropoietin (Kidney) -> Vasoconstriction and Increased Blood Volume
3. RAAS

Question 12

What two hormones are released in the endocrine response to HIGH Blood Pressure?

Answer 12

ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide)

Question 13

What effects do ANP and BNP have on the body?

Answer 13

Renal effects: Increased Na+ loss in urine, increased water loss in urine, reduced thirst

Vascular effects: inhibition of ADH, aldosterone, noradrenaline and adrenaline; peripheral vasodilation

Question 14

What kind of vasomotion occurs in emergencies to protect the brain?

Answer 14

Vasodilation of cerebral vessels, and vasoconstriction of periphery