PSC1002/L13 Kidneys

Question 1

What occurs to volume as the filtrate passes through the nephron?

Answer 1

Volume decreases most in the PCT

Question 2

What is the normal composition of fluid entering the collecting duct? (2)

Answer 2

High H2O content
Low [Na+]

Question 3

What is diuresis?

Answer 3

Removal of excess water in urine

Question 4

Why is there no reabsorption of water from the collecting duct?

Answer 4

Collecting duct is impermeable to H2O

Question 5

What hormone controls the permeability of cells in the collecting duct to H2O?

Answer 5

ADH/ vasopressin

Question 6

Describe regulation of water volume by ADH. (3)

Answer 6

ADH makes collecting duct more permeable to H2O
H2O reabsorbed passively driven by osmotic gradient in medullary interstitium
Results in concentrated urine and water conservation

Question 7

Describe cellular action of ADH. (6)

Answer 7

ADH binds to receptor on basolateral cell surface
Stimulates adenylyl cyclase to generate cAMP and activate protein kinases
Increased insertion of Aquaporin 2 into apical membrane
Increased water permeability
Increased water reabsorption
Concentrated urine and water conservation

Question 8

Describe release of ADH. (4)

Answer 8

AVP made and packaged in cell body of neuron
Vesicles transported down the cell
Vesicles containing AVP stored in posterior pituitary
AVP released into blood

Question 9

What is the full range of osmolar control over?

Answer 9

280-300mOsm
20mOsm

Question 10

Give 3 physiological stimuli for ADH secretion.

Answer 10

Heightened emotions
Stress
High temperature
Exercise
Pain

Question 11

Give 3 reasons for inappropriate secretion of ADH.

Answer 11

Post-operative pain
Intracranial disease/injury
Ectopic disease/injury
Opiates: Vinblastine Tricyclics
Chlorpropamide, MDMA - ecstasy
Pneumonia
TB
Pulmonary disease
Nicotine

Question 12

What is nocturnal enuresis?

Answer 12

Delay in development of normal circadian rhythm of ADH

Question 13

Describe how MDMA alters fluid balance. (2)

Answer 13

Stimulates thirst reflex and repetitive behaviour
Stimulates ADH secretion

Question 14

What is diabetes insipidus? (3)

Answer 14

Polyurea due to deficiency of ADH or its action
Central - deficiency of ADH secretion
Nephrogenic - nephrons do not respond to ADH

Question 15

Describe where Na+ is filtered and reabsorbed. (2)

Answer 15

Filtered in glomerulus
No reabsorption from thin LOH

Question 16

Give 3 ways in which renin release is stimulated.

Answer 16

Stretch receptors in afferent arteriole sense decreased BP
Increased sympathetic nerve stimulation due to central decreased BP
Decreased NaCl at Macula Densa

Question 17

Describe the renin-angiotensin-aldosterone axis. (6)

Answer 17

Angiotensinogen (plasma)
Angiotensin I (plasma)
Angiotensin II (plasma)
Aldosterone (AC)
Increased Na+ reabsorption (DCT & CD)
Increase extracellular fluid

Question 18

Describe cellular action of aldosterone. (4)

Answer 18

Aldosterone binds to receptor in cytoplasm
Initiates transcription
Increased number of ENaC channels in apical surface increased Na+-K+ pumps
Na+ reabsorption, Cl- follows, K+ secretion

Question 19

Give 2 functions of angiotensin II.

Answer 19

Increase BP
Increase blood volume to maintain osmolarity

Question 20

What is the function of atrial natriuretic peptide?

Answer 20

Increased NaCl and H2O excretion
Decreased blood volume

Question 21

What is nephrolithiasis?

Answer 21

Formation of renal calculi (kidney stones) crystalline structures composed most commonly of calcium oxalate salts

Question 22

Why does nephrolithiasis occur?

Answer 22

Due to higher than normal ion and solute concentrations in filtrate (supersaturation)

Question 23

Where do kidney stones form?

Answer 23

In nephron loop, distal tubule, and/or collecting duct

Question 24

Describe the internal ring of the sphincter muscles.

Answer 24

Smooth muscle, has normal tone that keeps it contracted

Question 25

Describe the external rings of sphincter muscles.

Answer 25

Skeletal muscle controlled by somatic motor neurones
Tonic stimulation from CNS maintains contractions

Question 26

Describe the mechanism of micturition. (5)

Answer 26

Stretch receptors fire
Parasympathetic neurons fire and motor neurons stop firing
Smooth muscle contracts
Internal sphincter pulled open
External sphincter relaxes