Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Urinary System Physiology SA > Regulation of Osmolarity > Flashcards

Regulation of Osmolarity Flashcards

1
Q

What hormone is responsible for water regulation

A

ADH (vasopressin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the hormone ADH composed of

A

A polypeptide hormone, composed of 9 amino acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where is the ADH hormone, synthesised and stored

A

synthesised in the supraoptic (SO) and the paraventricular nuclei (PVN) of the hypothalamus in the brain

Stored in Posterior pituitary hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why is the Half life of ADH 10 minutes

A

So can rapidly be adjusted depending on the body’s needs for H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does control of ADH secretion depend upon

A

Plasma osmolarity (primary control)

ECF volume

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is normal plasma osmolarity

A

280-290mOsm/kg H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does increased plasma osmolarity increases ADH secretion

A

Due to osmoreceptors

as high osmolarity, causes water to move out the osmoreceptor cells, causing them to shrink activating the stretch sensitive ion channel, increasing neural discharge, stimulating the release of ADH from the posterior pituitary

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where is the osmoreceptors located

A

Anterior hypothalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What specifically does the osmoreceptors sense

A

The effective osmotic pressure which is a measure of tonicity, which creates the osmotic drag allowing what osmotic receptors cells to either shrink or expand due to water movement in or out the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What effect does decreased plasma osmolarity, have on osmoreceptors

A

A decreased osmolarity means that water moves into the cells of the osmoreceptors causing them to swell decreasing the neural discharge therefore decreasing ADH secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is the plasma osmolarity regulated very precisely

A

Corrected very quickly and very sensitive to change

as a small change in the plasma osmolarity produces a very strong response to ADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the relationship between ECF volume and ADH secretion

A

Inverse relationship

Increased ECF volume causes a reduced ADH secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What mediates the relationship between ECF volume and ADH secretion

A

Low and High pressure receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where are low pressure receptors found

A

Found in left and right atrial

and great veins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Where are high pressure receptors found

A

Is the carotid and aortic branch baroreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the purpose of low pressure receptors

A

Are volume receptors, monitoring the return of blood from the heart

Normally exert tonic inhibitory discharge of ADH secreting neurones via vagus nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the affect on low pressure receptors when ECF volume moderately decreases

A

ECF volume decreases, decreases atrial receptor discharge of inhibitory vagal block therefore increase ADH release

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

When are high pressure receptors affected in the relationship with ECF volume

A

High pressure receipts are affected when the volume changes enough the affect the mean blood pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

When would high pressure receptors trigger the release of ADH

A

When the ECF volume has decreased enough the decrease BP, decreasing the receptor discharge of the high pressure receptors, resulting in the release of ADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

When are high pressure receipts triggered

A

When going from lying down to standing up - slight increase in ADH release

Very important in haemorrhage

21
Q

What other stimuli increases ADH release

A 
Pain 
emotion
stress
exercise 
nicotine 
morphine 
following traumatic surgery 
inappropriate ADH secretion 
monitoring H2O intake
22
Q

What stimuli decreases ADH release

A

Alcohol surpasses ADH release

23
Q

Where is the site of water regulation

A

The collecting ducts

24
Q

How does ADH control water regulation in the collecting ducts

A

By affecting the permeability of the collecting ducts to water reabsorption

25
Q

What does the amount of urine produced depend upon

A

The concentration of ADH and also the amount of solute to be secreted (so whether the filtrate urine delivered to the tubule is concentrated)

26
Q

What occurs in the collecting ducts when ADH is present

A

The collective ducts become permeable to water and H2O is able to leave the collecting ducts

27
Q

What drives the reabsorption of water from the collecting ducts

A

It is driven by the hypertonic medullary interstitial gradient, created by the countercurrent multiplier of the loop of Henle.

28
Q

What occurs once water is reabsorbed from the collecting ducts

A

The cortical collecting duct becomes equilibrated with that of the cortical interstium (300mOsm)

H2O is then absorbed by the vasa recta

29
Q

What occurs when a maximum concentration of ADH is present at the collecting ducts

A

The collecting duct contents equilibrates with that of the medullary interstium via the reabsorption of water therefore collecting duct contents becomes highly concentrated at the tip of medulla

therefore producing a small volume of highly concentrated urine

30
Q

When is there a maximum concentration of ADH at the collecting ducts

A

When you are compensating for water deficit and want to reabsorb as much H2O as possible

31
Q

In maximum ADH concentration, what happens to the water reabsorbed

A

You are effectively adding pure H2O to the ECF, which is then reabsorbed by the oncotic pressure of the vasa recta which is greater that usual in the presence of H2O deficit

32
Q

What does the presence of ADH cause a secondary affect to

A

Urea reabsorption

33
Q

How does increased ADH cause an increased urea reabsorption

A

The reabsorption of water from the collecting ducts, concentrates the remaining urea in the collecting ducts

and as the collecting ducts as particularly permeable to urea at the medullary tip

as urea approaches the medullary tip, due to its high concentration, there is a tendency for it to be reabsorbed

34
Q

What is the purpose of urea reabsorption, as a secondary affect of ADH

A

It is important that urea should be reabsorbed because if it remained in the tubule, it would exert an osmotic effect to hold H2O in the tubule

Also reinforces the medullary gradient in region of thin ascending limb

35
Q

What does continually reabsorption of urea cause

A

Ureamia syndrome

36
Q

What occurs in the absence of ADH in the collecting ducts

A

In absence the collecting ducts are impermeable to H2O, so the medullary interstitial gradient is ineffective in inducing H2O movements out of the collecting ducts

therefore large volume of dilute urine is excreted

37
Q

When would there be an absence of ADH

A

When compensating to water excess, as osmolarity can fall to 30-50mOsm (basically excreting pure water)

38
Q

What is the normal level of ADH

A

Any level of ADH between the extremes of [max] and absence is possible, so that the Collecting duct permeability can be precisely graded to meet the demands of the body for H2O regulation.

39
Q

How does ADH increase the permeability of the collecting ducts

A

By incorporating H2O channels (aquaporins) into the luminal membrane

40
Q

What occurs when ADH stimulates increased permeability of collecting ducts

A

ADH indicated signaling cascade the tell lipid vesicles in collecting duct cell storing the aquaporin to fuse to the membrane in the side of the collecting duct

increasing the number of aquaporins in the luminal (apical)membrane

41
Q

What occurs in ADH signalling cascade in the collecting duct cell

A

ADH binds to membrane receptor activating cAMP second messenger system,

42
Q

What needs to be present on collecting ducts for water to be reabsorbed

A

Aquaporin

43
Q

What condition is associated with ADH hormone deficit

A

Diabetes inspidus

44
Q

what are the two types of diabetes insipidus

A

Central DI - problems with producing ADH

Peripheral DI - collecting ducts may be impermeable to ADH

45
Q

What is the potential causes of central DI

A

The hypothalamic areas synthesizing ADH may become diseased due to tumours, or in meningitis.

They may be “damaged” during surgery

46
Q

What is the causes of peripheral DI

A

Usually secondary to hypercalcemia and hypokalaemia

Genetic defects in ADH receptors

Defect in genes for aquaporins

47
Q

What is diabetes inspidus characterised by

A

passage of very large volumes of very dilute urine, generally > 10 l/day = polyuria

They drink large volumes of H2O = polydipsia.

48
Q

What is the treatment for diabetes inspidus

A

Central: Give ADH (AVP)

Peripheral: Manage thirst
Treat underlying cause
cant give ADH

Urinary System Physiology SA (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions