renal physiology

Question 1

define tonicity

Answer 1

refers to what happens to cells in solution

hypotonic = cells take up water and swell

Question 2

describe the hormone ADH

Answer 2

• produced in the hypothalamus, secreted in pituitary
• increased production if decreased BP or increased osmolarity
• increases water reabsorption in collecting ducts

Question 3

describe the effect of the hormone angiotensin 2

Answer 3

• vasoconstriction
• ADH release
• Na reabsorption in proximal tubule
• constriction of efferent arteriole
• aldosterone release
• thirst

Question 4

describe the effect of the hormone aldosterone

Answer 4

• acts on distal tubule & CD to increase Na reabsorption and K excretion
• stimulated by angiotensin 2 and increased K

Question 5

what are the causes of hypernatraemia

Answer 5

• impaired thirst or consciousness
• no access to fluid
• burns
• diarrhoea
• blood loss
• solute diuresis

Question 6

describe diabetes insipidus and the types

Answer 6

• reduction in amount or efficacy of ADH
• polyuria w/ dilute urine
• gives hypernatraemia, dehydration, increased plasma Oslo

central = relates to production or release

nephrogenic = aquaporin dysfunction, gives partial or complete resistance

Question 7

describe hyponatremia

Answer 7

• excessive Na loss or excessive water retention
• check urine osmo
  - if dilute urine = polydipsia
• pseudohyponatremia = high glucose can give false reading, check if serum Oslo normal

Question 8

symptoms of hyponatremia

Answer 8

if slow development

• brain adaption to cerebral oedema, some confusion
  - correct gradually with fluid retention

if rapid development

 - cerebral oedema with confusion, seizure, coma
 - may need more vigorous treatment

Question 9

types of hyponatremia

Answer 9

• hypovolaemic (dehydrated)
• hypervolaemic (fluid overload)
• euvolaemic

Question 10

hypovolaemic hyponatremia

Answer 10

• Na loss with relatively less water loss
• diarrhoea, vomiting, bowel obstruction
• skin loss = burns, sweating
• urinary loss = diuretics, Addison’s disease

Question 11

hypervolaemic hyponatremia

Answer 11

• Na retention with more water retention

- cirrhosis, nephrotic syndrome, HF, renal failure

Question 12

euvolaemic hyponatraemia

Answer 12

• endocrinopathies (hypothyroid)
• diuretics
• fluid replacement
• SIADH
  
  • plasma osmo will be low however not urine

Question 13

causes of SIADH

Answer 13

• trauma e.g. surgery
• medication
• head injury
• tumour
• medication (e.g. SSRI’s)
• chronic lung disease

Question 14

key roles of the kidney

Answer 14

• Elimination of waste products
• Control of fluid balance
• Control of minerals
• Regulate acid-base balance
• Produce hormones