physiology endocrine control of body fluid volume and composition Flashcards
role of ADH?
increases water reabsorption (this is also known as vasopressin)
role of aldosterone?
- increases Na+ reabsorption
- increases H+ and K+ secretion
role of atrial natriuretic hormone?
-decreases Na+ reabsorption
role of PTH?
- increases calcium reabsorption
- decreases phosphate reabsorption
what is the permeability like for water and urea in distal tubule?
-low permeability to water and urea
what increases the distal tubules permeability for water and urea?
-ADH
what can the distal tubule be split into?
-early and late segment
role of early distal tubule?
NaCl reabsorption using Na+-K+- 2Cl transporter
role of late distal tubule?
Ca2+ reabsorption
H+ secretion
Na+ reabsorption
K+ reabsorption
what can the collecting duct be split into?
early and late portions
what is the late collecting ducts permeability like for ions and water?
- low ion permeability
- permeability to water (and urea) influenced by ADH
what secreted ADH?
-posterior pituitary
what triggers secretion of ADH?
- when you become dehydrated
- causing increase in plasma osmolarity which is detected in the hypothalamus causing secretion of ADH
what occurs to water in collecting ducts in presence of ADH?
-water moves from collecting duct lumen along the osmotic gradient into the medullary interstitial fluid this enabling hypertonic urine formation
what occurs to water permeability and urine in high ADH?
- high water permeability
- hypertonic urine (up to 1400 mos mol/l)
what occurs to water permeability and urine in low ADH?
- low water permeability
- hypotonic urine (<50 mosmol/l)
what does hypertonic urine mean?
-small amount very concentrated urine
what are the receptors in the hypothalamus that detect dehydration called?
osmoreceptors
what can diabetes insipidus be split into?
- central diabetes insipidus
- nephrogenic diabetes insipidus
what are some symptoms of diabetes insipidus?
- large volumes of dilute urine (up to 20 litres per day)
- constant thirst
what is diabetes insipidus?
-rare form of diabetes where they do not produce enough ADH
what is treatment for diabetes insipidus?
ADH replacement
what stimulates ADH?
- hypothalamic osmoreceptors
- activation of left atrial stretch receptors (decreased atrial pressure leads to increased ADH release)
what occurs to ADH if there is stimulation of stretch receptors in upper GI tract?
-this exceeds feed forwards inhibition of ADH
what is the effect of nicotine and alcohol on ADH?
- nicotine stimulates ADH release
- alcohol inhibits ADH release
what is aldosterone?
-steroid hormone secreted by adrenal cortex
when is aldosterone secreted?
- In response to rising [K+] or falling [Na+]. in the blood
- activation of the renin angiotensin system
what does aldosterone do?
-stimulates Na+ reabsorption and K+ secretion (Na+ retention contributes to an increased blood volume and pressure)
control of renin release from granular cells in JGA slide
what produces ANP?
-atrial cella in the heart
when is ANP released?
-when the atrial muscle cells are stretched due to an increase in circulating plasma volume
what does ANP promote?
- excretion of Na+ and diuresis, thus decreasing plasma volume
- also exerts effects on the cardiovascular system to lower blood pressure
