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The Renal System > Physiology - Endocrine Control of Body Fluid Volume and Composition > Flashcards

Physiology - Endocrine Control of Body Fluid Volume and Composition Flashcards

1
Q

The tubular fluid leaving the ascending loop of henle is ____________

A

The tubular fluid leaving the asceneding loop of henle is hypo-osmotic

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2
Q

Where does the collecting duct originate?

A

Cortex

(then descends into the medulla)

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3
Q

Hormones such as vasopressin affect which cells in the nephron?

A

Those of the distal tubule and collecting duct

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4
Q

What are the key hormones which regulate fluid and salt regulation the the distal tubule and collecting duct?

A

Antidiuretic hormone

Aldosterone

Atrial natriuretic hormone

Parathyroid hormone

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5
Q

What affect does ADH have?

A

Increases water reabsorption

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6
Q

What affect does parathyroid hormone have?

A

Calcium reabsorption and phosphate excretion

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7
Q

What effect does atrial natriuretic hormone have?

A

Reduces sodium reabsorption

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8
Q

What effect does parathyroid hormone have?

A

Increases Calcium reabsorption

Decreases phosphate reabsorption

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9
Q

The corticomedullary gradient is set up by which two things?

A

Salt and urea

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10
Q

The distal tubule has what type of permeability to water and urea?

A

Low

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11
Q

The distal tubule has two segments, which is each responsible fore reabsorbing?

A

Early distal tubule: Na+/K+/2Cl- = NaCl

Late distal tubule: Ca2+, Na+, K+ (K+ is secreted under influence of aldosterone, but in the basal state, reabsorbed)

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12
Q

What are the two key properties of the late collecting duct?

A

Low ion permeability

Permeability to water and urea (influenced by ADH)

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13
Q

Where is ADH synthesised?

A

Supraoptic and paraventricular nuclei in hypothalamus

Transported down nerves to terminals where it is stored and then secreted from granules in posterior pituitary

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14
Q

How does vasopressin (ADH) affect the distal tubule and late collecting duct

A

Type 2 vasopressin receptor on basolateral membrane

Cell signalling response

Increase in cAMP

Insertion of aquaporins at apical membrane

Increases reabsorptive capability of cells to water

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15
Q

What happens to the aquaporins on the apical membrane of the collecting duct cells when there is no vasopressin?

A

They are internalised

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16
Q

High concentrations of ADH results in what?

A

Hypertonic urine

(concentrated urine, low volume)

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17
Q

Why does water leave the distal tubule and collecting duct?

A

Osmosis

In order to match the high osmolarity created by the corticomedullary gradient

(this occurs to different degrees depending on the conc of ADH)

18
Q

Without ADH, the distal tubule and collecting duct are essentially ___________ to water reabsorption

A

Without ADH, the distal tubule and collecting duct are essentially impermeable to water reabsorption

19
Q

Why can ADH only affect water reabsorption and not solute reabsorption?

A

Due to ADH only affecting aquaporin channel insertion into apical membranes

20
Q

If there is a severe decrease in ECF (e.g. haemorrhage) which receptors can detect this?

A

Stretch receptors in left artria

(then increase secretion of ADH)

21
Q

What is the second effect of ADH which acts only in severe decreases in ECF?

A

Arteriolar vasoconstriction

22
Q

What are the two types of diabetes insipidus?

A

Central DI

Nephrogenic DI

23
Q

What is the cause of central DI?

A

Unable to produce or secrete ADH

24
Q

What is the cause of nephrogenic DI?

A

Failure of ADH produced to have an impact on target cells

25
Q

What is the treatment for

a) Central DI
b) Nephrogenic

A

a) ADH replacement
b) Drugs to reduce urine output

26
Q

Which drug can induce nephrogenic DI?

A

Lithium

(around 20% of long term users)

27
Q

Nicotine will _________ ADH release and alcohol will _________ it

A

Nicotine will stimulate ADH release and alcohol will reduce it

28
Q

When will aldosterone be secreted?

A
  1. Rising potassium or falling sodium in the blood
  2. Activation of RAAS system
29
Q

What is the action of aldosterone?

A

Stimulates sodium reabsorption and potassium secretion

This raises blood pressure and blood volume as water follows sodium

30
Q

An increase which ion will stimulate the adrenal cortex?

A

Potassium

31
Q

A decrease in which ion promotes the indirect secretion of aldosterone and by which means?

A

Sodium

Juxtaglomerular apparatus detects low sodium levels (at macula densa)

32
Q

What are the actions of angiotensin II?

A

Increases ADH secretion

Thirst

Arteriolar constriction

33
Q

In which 3 ways is renin release controlled from granular cells in juxtaglomerular apparatus?

A

Reduced pressure in afferent arteriole

Macular densa cells sense amount of NaCl in distal tubule

Increase sympathetic activity as a result of reduced BP

(all of these function to increase renin secretion and increase blood pressure)

34
Q

How does aldosterone impact the cells in the distal and collecting tubules?

A

Increases Na+/K+ATPases on basolateral membrane

Increases sodium channels on apical membrane

(this allows for a sodium gradient to be set up into the blood)

35
Q

How is fluid retention related to the RAAS?

A

Heart failure →

Decreased BP →

RAAS stimulated →

Salt and water retention →

More pressure on failing heart

36
Q

How can the issue of a failing heart and increasing RAAS activity problem be treated?

A

Low salt diet

Loop diuretics

ACEI

37
Q

Where is atrial natriuretic peptide produced?

A

Heart

(stored in atrial muscle cells)

38
Q

When is ANP released?

A

Atrial cells stretched

(due to increased circulatory volume)

39
Q

What is the effect of ANP?

A

Increases sodium (and water) excretion

40
Q

What are the four effects of ANP?

A

Minimises Na+ reabsorption

Decreases RAAS system activity

Decreases smooth muscle constricion of afferent arterioles (which increases GFR)

Decreases effects of sympathetic system reducing TPR

41
Q

Which two mechanism govern the process of bladder emptying?

A
  1. Micturation reflex
  2. Voluntary control
42
Q

How much fluid can the bladder hold before stretch receptors become activated?

A

250-400ml

(micturation reflex is then activated)

The Renal System (37 decks)

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