Long Term control of Blood Pressure

Question 1

Why dont people think baroreceptors are the main thing regulating long term BP?

Answer 1

They took them out of dogs and they stayed regulated around a normal value, even if theyre BP graphs did get a lot messier now they couldnt control short term BP

Question 2

Basically, how do the kidneys regulate plasma volume?

Answer 2

They control how much water is lost in the urine and how much you reabsorb

Question 3

In what way do the kidneys control water reabsorption?

Answer 3

By altering the osmotic gradient between the collecting duct and the arterioles. And the ducts permeability to water

Question 4

How is the osmotic gradient controlled?

Answer 4

By altering the amount of Na+ pumped out the duct into the arterioles

Question 5

What do we call the system by which the kidneys regulate plasma volume?

Answer 5

The renal counter-current system

Question 6

What do we call it when very little water is reabsorped and you have loads of dilute urine?

Answer 6

Diuresis

Question 7

What 3 hormone systems regulate the renal counter-current system?

Answer 7

• The renin-angiotensin-aldosterone system
• Antidiuretic factor (ADH, vasopressin)
• Atrial/Brain Natriuretic Peptide (ANP/BNP)

Question 8

What cells produce renin?

Answer 8

juxtaglomerular (granule) cells of the kidney

Question 9

Where are juxtaglomerular cells found?

Answer 9

Around the afferent & efferent arteriole clsoe to the glomerulus

Question 10

What do we call the capsule of the glomerulus?

Answer 10

Bowman’s Capsule

Question 11

What 3 things signal the juxtaglomerular cells to release renin?

Answer 11

Symp. innervation signals a lower MAP
Decreased distension in the afferent arteriole signals lower MAP
The macula densa signal a reduced MAP

Question 12

How do the macula densa detect a lower MAP, and what the fuck are they?

Answer 12

Macula Densa is/are a set of eithelial cells in the ascending loop of henle that border on the juxtaglomerular cells on the outside.

They detect a lower flow of Na+ and Cl- ions through the ascending loop of henle.

Question 13

What does renin do?

Answer 13

Converts angiotensinogen to angiotensin I

Question 14

How does angiotensin I become angiotensin II?

Answer 14

By Angiotensin converting enzyme

Question 15

What does angiotensin II do?

Answer 15

Increases ADH release from the pituitary gland
Causes vasconstriction -> TPR increase -> MAP increase
Increases aldosterone release form adrenal cortex

Question 16

Whats the function of Anti-diuretic hormone?

Answer 16

Increases the water permeability of the collecting duct so more is reabsorped and plasma volume increases

It also increases thirst

Question 17

What does aldosterone do to increase MAP?

Answer 17

Increases Na+ reabsorption in the loop of Henle.
-> increased osmotic gradient
-> increased water reabsorption
-> increased plasma volume

Question 18

Summarize the renin-angiotensin-aldosterone system:

Answer 18

A negative Feedback System
Multiple mechanisms detect MAP dropping
-> Stimulates Relase of Renin
-> Multiple mechanisms increase MAP

Question 19

Where is ADH produced?

Answer 19

ADH is made in the hypothalalmus but released from the posterior pituitary

Question 20

When is ADH released?

Answer 20

• Circulating angiotensin II
• Blood volume decreases

(detected by cardiopulmoanry baroreceptors & relayed by medullary baroreceptors…
…also detected by osmoreceptors in hypothalamus which sense increase ISF osmolarity.)

Question 21

What does ADH do?

Answer 21

Increases water permeability of the collecting duct so more is reabsorped and blood volume increases.

Question 22

Where are atrial & brain natriuretic peptide produced?

Answer 22

The myocardial cells of the atria and ventricles respectively

Question 23

When are ANP/BNP released?

Answer 23

When theres increased distension of atria & ventricles, a sign of abnormally high MAP

Question 24

What do ANP & BNP do?

Answer 24

• decrease Na+ reabsorption leading to deceased water reabsorption (natriuresis)
• Inhibits renin release (inhibiting the renin-angiotensin-aldosterone system)
• Acts on the medullary CV centres to reduce MAP

Question 25

Summarize the ANP/BNP function:

Answer 25

A negative feedback system
-> 2 mechanisms detect a MAP drop
-> ANP & BNP released
-> 3 mechanisms act to decrease MAP

Question 26

How many cases of hypertension are secondary (i.e. explained)?

Answer 26

5-10%

Question 27

What do we call unexplained cases of hypertension?

Answer 27

Primary or essential

Question 28

Name 5 treatments for hypertension?

Answer 28

• Ca2+ channel antagonists
• B-adrenoceptor antagonists
• Thiazide diuretics
• angiotensin converting enzyme inhibitors
• angiotensin II antagonists

Question 29

How do B-adrenoceptor antagonists work?

Answer 29

They block B1 receptors in the heart causing a lowered HR & contractility -> lowers CO -> lowers MAP

Question 30

How do thiazide diuretics work?

Answer 30

They increase water excretion to lower MAP

Question 31

What do angiotensin converting enzyme inhibitors and angiotensin II antagonists do?

Answer 31

They both block the production or function of angiotensin II, lowering MAP

Question 32

How do Ca2+ channel antagonists treat hypertension?

Answer 32

They block calcium channels in the cardiac muscle, reducing the force of contraction and so SV, therefore CO and MAP are reduced.

Question 33

In summary what three hormones act on the kidney to control blood pressure?

Answer 33

• Renin-Angiotensin-Aldosterone system
• Antidiuretic Hormone (ADH, vasopressin)
• Atrial/Brain Natriuretic Peptide (ANP/BNP, Atriopeptin)