Water And Electrolytes

Question 1

What ways can water be gained

Answer 1

• water ingested (food and drink)
• water formed in metabolism

Question 2

Describe ways water can be lost from the body

Answer 2

• excretion - urine, faeces
• evaporation - sweat, in expired air

Question 3

How is water balance controlled

Answer 3

Urinary excretion is the only one of these factors under homeostatic control

Question 4

What factor of water balance is under homeostatic control

Answer 4

Urinary secretion

Question 5

What should renal blood flow be

Answer 5

1200 ml/min

Question 6

What is the function of the glomerulus

Answer 6

• filtration of plasma
• pressures vary along the length of the glomerus

Question 7

What is the capillary hydrostatic blood pressure

Answer 7

45-50mmHg

Question 8

What is the plasma protein oncotic pressure in the glomerus

Answer 8

25-35mmHg

Question 9

What is the capsular pressure in the glomerus

Answer 9

10mmHg

Question 10

What is the net filtration pressure in the glomerus

Answer 10

10-15mmHg

Question 11

What is reabsorbed in the proximal convoluted tube

Answer 11

Ions
Small organic molecules

60-70% of glomerular filtrate

Question 12

What is secreted in the proximal convoluted tube

Answer 12

Secretion of H+ (acid-base balance)

Question 13

What does the concentration of urine depend on

Answer 13

The active transport pumps in thick, ascending limb of the loop of henle

Question 14

What is the loop of Henle important for

Answer 14

Concentration of urine

Question 15

What is the function of the distal convoluted tubule

Answer 15

• reabsorption of water, Na+, Cl-, Ca2+
• secretion of H+ and K+

Question 16

What is activity in the distal convoluted tubule controlled by

Answer 16

Activity controlled by hormones
- aldosterone
- atrial natriuretic hormone
- ADH (in most distal parts)
- parathyroid hormone

Question 17

What hormones regulate water and electrolytes

Answer 17

• antidiuretic hormone (ADH)
• renin-angiotensin-aldosterone
• atrial natriuretic hormone (ANH) also called ANF and ANP

Question 18

What hormone mainly controls water in the body

Answer 18

Antidiuretic hormone (ADH) also known as vasopressin

Question 19

Where is ADH produced

Answer 19

Produced in the hypothalamus and released from posterior pituitary gland

Question 20

What does vasopressin act on

Answer 20

Acts on distal convoluted tubules (distal end) and collecting ducts to increase water permeability

Question 21

What affects the release pf ADH

Answer 21

Decrease in plasma volume
Increase in plasma osmolarity

Question 22

What is ADH secretion increased by

Answer 22

Decreased ECF volume
Increased ECF osmolarity

ADH also causes construction of blood vessels

Question 23

What electrolytes are most important for the body

Answer 23

Na+, K+, H+, Ca+

Question 24

Where is electrolyte concentration controlled

Answer 24

Much of this control operates through the kidneys this determines how much is excreted

Question 25

What promotes reabsorption of Na+

Answer 25

Renin antigiotensin aldosterone

Question 26

What is the function of atrial natriuretic hormone

Answer 26

Increases excretion of Na+ and water

Question 27

Angiotensin can be described as..

Answer 27

A potent vasoconstrictor

Question 28

What will increase ANH release

Answer 28

Increase in plasma volume and increase in atrial distension

Question 29

What can hyposecretion of ADH cause

Answer 29

• diabetes inspidus
• large volumes of insipid (tasteless) urine

Question 30

What can hypersecretion of ADH cause

Answer 30

• syndrome of inappropriate ADH
• excess ADH increased water retention

Question 31

What is the effect of K+ on nerve function

Answer 31

Increasing ECF K+ > depolarisation