Physiology: Long term control of blood pressure

Question 1

What are the differences between short control of BP and long term control of BP?

Answer 1

Short term control is mediated by arterial baroreceptors whereas long term is not
Long term revolves around control of plasma volume which is controlled by the kidneys
Main Sensors are the cardio-pulmonary baroreceptors

Question 2

What are the 3 main hormone systems that control long term BP?

Answer 2

Renin-angiotensin-aldosterone system
Antidiuretic factor
Atrial natriuretic peptide

Question 3

What are the functions of the kidneys?

Answer 3

Excretion of waste products 
Maintains ion balance 
pH regulation 
Osmolarity regulation  
Plasma Volume regulation

Question 4

What effect does MAP have on the kidneys?

Answer 4

Controls plasma volume

Question 5

How do the kidneys regulate plasma volume?

Answer 5

Renal counter-current system creates high osmolarity outside the collecting ducts
Na+ transport determines the osmotic gradient
Control of permeability of the collecting duct controls if the water goes down the osmotic gradient

Question 6

What does high permeability of the collecting duct cause?

Answer 6

Lots of water re absorption
Little urine
Conserves plasma volume

Question 7

What does low permeability of the collecting duct cause?

Answer 7

Little reabsorption of water
Diuresis (lots of water)
Reduction in plasma volume

Question 8

Where is renin produced?

Answer 8

Juxtaglomerular (granule cells) of the kidneys

Question 9

When is renin produced?

Answer 9

Activation of sympathetic nerves on kidney tissue
Decrease distension (swelling inside the body) of afferent arterioles
Decreased Na+ and Cl- through the tubules
Negative Feedback system

Question 10

What is the function of Renin?

Answer 10

Converts angiotensinogen into angiotensin I which then can be further converted in into angiotensin II by an angiotensin converting enzyme (ACE)

Question 11

What is the function of angiotensin II?

Answer 11

Increase MAP
Stimulate release of aldersterone from the adrenal cortex
Increase the release of ADH from pituitary
Vasoconstrictor

Question 12

What are the effects of aldesterone?

Answer 12

Increase Na+ reabsorption in the loop of henule

Reduce diuresis and increase plasma volume

Question 13

Where is Antidiuretic hormone (ADH) produced?

Answer 13

Synthesised in the hypothalamus and released from the posterior pituitary

Question 14

What triggers the release of ADH?

Answer 14

Low blood volume (sensed by cardiopulmonary baroreceptors)
Increase in osmolarity of the interstitial fluid (sensed by osmoreceptors in hypothalamus)
Circulating Angiotensin II
Negative Feedback System

Question 15

What are the effects of ADH on the body?

Answer 15

Increase permeability of the collecting duct
Causes vasoconstriction
Increases MAP

Question 16

Where is Atrial Natriuretic Peptide (ANP) ?

Answer 16

Produced in myocardial cells in the atria

Question 17

What triggers ANP release?

Answer 17

Distension of atria (sign of high MAP)

Question 18

What effect does ANP have on the body?

Answer 18

Increase excretion of Na+
Inhibits release of renin
Acts on medullary CV centres 
Reduces MAP
Negative Feedback System

Question 19

What % of hypertension is secondary?

Answer 19

5-10%

Question 20

What does secondary hypertension mean?

Answer 20

Due to a known cause

Question 21

What does primary hypertension mean?

Answer 21

Idiopathic

Question 22

What are drugs used for the treatment of hypertension?

Answer 22

Ca2+ Channel Blockers
B-adrenoceptors antagonists
Thiazide diuretics
ACE Inhibitors