Water And Electrolytes Flashcards
What ways can water be gained
- water ingested (food and drink)
- water formed in metabolism
Describe ways water can be lost from the body
- excretion - urine, faeces
- evaporation - sweat, in expired air
How is water balance controlled
Urinary excretion is the only one of these factors under homeostatic control
What factor of water balance is under homeostatic control
Urinary secretion
What should renal blood flow be
1200 ml/min
What is the function of the glomerulus
- filtration of plasma
- pressures vary along the length of the glomerus
What is the capillary hydrostatic blood pressure
45-50mmHg
What is the plasma protein oncotic pressure in the glomerus
25-35mmHg
What is the capsular pressure in the glomerus
10mmHg
What is the net filtration pressure in the glomerus
10-15mmHg
What is reabsorbed in the proximal convoluted tube
Ions
Small organic molecules
60-70% of glomerular filtrate
What is secreted in the proximal convoluted tube
Secretion of H+ (acid-base balance)
What does the concentration of urine depend on
The active transport pumps in thick, ascending limb of the loop of henle
What is the loop of Henle important for
Concentration of urine
What is the function of the distal convoluted tubule
- reabsorption of water, Na+, Cl-, Ca2+
- secretion of H+ and K+
What is activity in the distal convoluted tubule controlled by
Activity controlled by hormones
- aldosterone
- atrial natriuretic hormone
- ADH (in most distal parts)
- parathyroid hormone
What hormones regulate water and electrolytes
- antidiuretic hormone (ADH)
- renin-angiotensin-aldosterone
- atrial natriuretic hormone (ANH) also called ANF and ANP
What hormone mainly controls water in the body
Antidiuretic hormone (ADH) also known as vasopressin
Where is ADH produced
Produced in the hypothalamus and released from posterior pituitary gland
What does vasopressin act on
Acts on distal convoluted tubules (distal end) and collecting ducts to increase water permeability
What affects the release pf ADH
Decrease in plasma volume
Increase in plasma osmolarity
What is ADH secretion increased by
Decreased ECF volume
Increased ECF osmolarity
ADH also causes construction of blood vessels
What electrolytes are most important for the body
Na+, K+, H+, Ca+
Where is electrolyte concentration controlled
Much of this control operates through the kidneys this determines how much is excreted
What promotes reabsorption of Na+
Renin antigiotensin aldosterone
What is the function of atrial natriuretic hormone
Increases excretion of Na+ and water
Angiotensin can be described as..
A potent vasoconstrictor
What will increase ANH release
Increase in plasma volume and increase in atrial distension
What can hyposecretion of ADH cause
- diabetes inspidus
- large volumes of insipid (tasteless) urine
What can hypersecretion of ADH cause
- syndrome of inappropriate ADH
- excess ADH increased water retention
What is the effect of K+ on nerve function
Increasing ECF K+ > depolarisation
