Long term control of blood pressure

Question 1

how is blood pressure controlled in the long term?

Answer 1

control of plasma volume by the kidney

Question 2

what is not involved in the long term control of blood pressure?

Answer 2

arterial baroreflex

Question 3

what 3 hormone systems are involved in the control of blood plasma

Answer 3

Renin-angiotensin-aldosterone system

Antidiuretic factor (ADH, vasopressin)

Atrial natriuretic peptide

Question 4

what are some functions of the kidney? (5)

Answer 4

Excretion of waste products 
Maintenance of ion balance
Regulation of pH 
Regulation of osmolarity 
Regulation of plasma volume

Question 5

what happens if the collecting duct is very permeable to water?

Answer 5

results in lots of water reabsorption, little urine, and conserve plasma volume

Question 6

what happens if the collecting duct is very impermeable to water?

Answer 6

little reabsorption, lots of urine (= diuresis), and a reduction in plasma volume

Question 7

Describe how the kidney regulates plasma volume

Answer 7

the kidney is made up of 1000s of units called nephrons that filter waste and fluid out of the blood

Blood is filtered under pressure in the glomerulus out into Bowman’s capsule.

the waste, nutrients, H20 etc move through the proximal tubueles to the loop of Henle, the distal tubule and finally into the collecting duct that leads to the bladder for excretion

Question 8

What does blood enter and leave the glomerulus through?

Answer 8

afferent and efferent arterioles

Question 9

what happens with Na+ and H20 in the loop of Henle?

Answer 9

Na+ can move across through transporters on thick ascending tubule
this causes water to move across thin descending tubule due to decrease in H20 conc as Na+ displaces it (increase in osmolarity). H20 moves from high to low conc.
continuous shuttling of high conc filtrate in and low conc filtrate out until max conc of 1200 is reached

this is called the counter current system

Question 10

what is the max concentration that can be reached in medulla

Answer 10

1200 mOsM

Question 11

what does the counter current system do

Answer 11

it creates a very high osmolarity outside the collecting duct

Question 12

what does the counter current system do

Answer 12

it creates a very high osmolarity outside the collecting duct (high Na+ and H20 conc)

Question 13

define osmolarity

Answer 13

total number of particles in solution both penetrating and non-penetrating

Question 14

what control can you have over the counter current system?

Answer 14

you can control Na+ transport which determines how big the osmotic gradient is

or control over the permeability of collecting duct to H2O which determines if H2O follows the osmotic gradient or not

Question 15

a very permeable collecting duct results in small volume of…

Answer 15

hyper-osmotic urine (ie low H20 conc, high Na+ conc) ie small vol of very concentrated urine

Question 16

a very impermeable collecting duct results in small volume of…

Answer 16

hypo-osmotic urine (ie high conc H20, low Na+ conc)

Question 17

where is renin produced

Answer 17

from the juxtaglomerular (granule cells) of the kidney on the side of the afferent arteriole near bowman’s capsule

Question 18

what triggers renin production

Answer 18

Activation of sympathetic nerves to the juxtaglomerular apparatus

Decreased distension (dilation) of afferent arterioles (the “renal baroreflex”)

Decreased delivery of Na+/Cl- through the tubule

Question 19

the three triggers of renin production are signs of what?

Answer 19

low mean arterial pressure/low BP

Question 20

what does angiotensin II do?

Answer 20

Stimulates release of aldosterone from the adrenal cortex
which increases Na+ reabsorption in the loop of Henle and therefore reduces diuresis (too much fluid in urine) and increases plasma volume

increases release of ADH from the pituitary - which increases water permeability of the collecting duct therefore reduces diuresis and increases plasma vol and increases sense of thirst

is a vasoconstrictor therefor increases TPR

Question 21

define tubular reabsorption

Answer 21

process by which the nephron removes water and solutes from the tubular fluid (pre-urine) and returns them to the circulating blood

Question 22

how is the Renin-angiotensin-aldosterone system a negative feedback system?

Answer 22

Multiple mechanism detect any decrease in MAP

Stimulates release of renin
This evokes multiple mechanisms which increase MAP

Question 23

where is ADH antidiuretic hormone synthesised

Answer 23

in the hypothalmus

Question 24

where is ADH antidiuretic hormone released from

Answer 24

posterior pituitary

Question 25

what triggers ADH release?

Answer 25

A decrease in blood volume (as sensed by cardioplumonary baroreceptors and relayed via medullary cardiovascular centres)

An increase in osmolarity of interstitial fluid (as sensed by osmoreceptors in the hypothalamus)

Circulating angiotensin II (triggered by the renin-angiotensin-aldosterone system)

all are signs of low plasma volume or MAP

Question 26

what does ADH do?

Answer 26

Increases the permeability of the collecting duct to H2O, therefore reduces diuresis and increases plasma volume - increases MAP

Causes vasoconstriction (hence its alternative name, vasopressin), therefore increasing MAP

Question 27

How is ADH release involved in a negative feedback system

Answer 27

Multiple mechanism detect any decrease in MAP
Stimulates release of ADH
This evokes multiple mechanisms which increase MAP

Question 28

where is atrial natriuretic peptide produced?

Answer 28

produced in and released from myocardial cells in the atria

Question 29

what triggers ANP release?

Answer 29

increased distension (dilation) of the atrium ie atrium expanding ie when MAP increases

Question 30

what does ANP do?

Answer 30

Increases excretion of Na+ (natriuresis) - decrease in plasma volume

Inhibits the release of renin
Acts on medullary CV centres to reduce MAP

Question 31

how is ANP involved in a negative feeback system

Answer 31

A mechanism that detects any increase in MAP
Stimulates release of ANP
This evokes multiple mechanisms which reduce MAP

Question 32

what 2 hormone systems work to increase MAP

Answer 32

Antidiuretic hormone system

Renin-angiotensin-aldosterone system

Question 33

which hormone system results in a reduced MAP

Answer 33

atrial natriuretic peptide hormone system

Question 34

common drugs/treatment for hypertension

Answer 34

Ca2+ channel antagonists
beta adrenoceptor antagonists
Thiazide diuretics - increase water and salt in urine - increased calcium re-absorption into the blood - lower blood pressure though as lower plasma volume
Angiotensin converting enzyme inhibitors