Hormones regulating body fluids and electryolytes Flashcards
Wk 11
What are the hormones that regulate body fluid and electrolytes?
Vasopressin (ADH)
Aldosterone
Angiotensin II
Atrial Natriuretic Peptide
Where is ADH synthesised?
cell bodies of supraoptic and paraventricular nucleus
What is the major factor that controls AVP release?
plasma osmolality
Describe the physiology effects of ADH on Target organ.
Reabsorbing water from renal tubules
Induces production and insertion of Aquaporin 2 into the luminal membrane
Enhances permeability of cell to water
Increases water reabsorption = increased osmolality
outline the cellular mechanism of action for vasopression.
Binds to V2 receptor in distal convoluted tubules and medullary collecting ducts –> activate AC –> increases cAMP formation and Aquaporin 2 phosphorylation –> insertion into luminal membrane
What can Vasopressin do at high concentrations in relation to receptors?
ADH constricts arterioles using V1A receptor
How does decreased plasma volume result in increased total water?
Decreased plasma volume = decreased BP = increased ADH = increased reabsorption = increased total water
How does decreased fluid osmolality result in decreased total body water body
Decreased fluid osmolality = decreased ADH secretion = decreased water reabsorption= decreased total body water
What occurs to ADH in when there is water ingestion?
suppression of osmoreceptor firing = shuts of ADH release
What is the cause of Diabetes insipidus?
Vasopressin deficiency or when kidneys fail to respond to vasopressin
What are the four types of diabetes insidious and there association with ADH
Decreased ADH release: Hypothalamic diabetes insipidus (HDI)
- Decreased renal responsiveness to ADH: Nephrogenic diabetes insipidus (NDI)
- Gestational DI
- Inappropriate, excessive water drinking: Dipsogenic diabetes insipidus (DDI)
What test is used to differentiate cranial DI and Nephrogenic DI? What does it show?
Water deprivation test= Synthetic AVP Analougue DDAVP Desmopressin test
Differentiates Cranial Di and Nephrogenic DI
Desmopressin = more renal effect than vasoconstrictor effect
If urine becomes concentrated = Cranial DI
Urines fails to become concentrated = nephrogenic DI
What is Syndrome of inappropriate ADH, what is it caused by and what are some symptoms?
Too much ADH with inappropriate water retention and decreased sodium
cause
brain injury
tumor production of ADH
presentations
low osmolality
concentrated urine
Inability to produce dilute urine –>water
retention –> increased ECF volume –>
hyponatremia (dilutional hyponatremia)
What is the mechanism of Action for Aldosterone.
Acts on cytosolic receptors to alter cell membrane Na transporters and Na/K pump = increased Na+ channels in luminal membrane
increased urinary excretion
What is the site of action for Aldosterone?
Distal convoluted tubule and collecting duct
Principal cells
what are the circulatory effects of Aldosterone?
Increased Blood volume and pressure
What are the overall effects of Aldosterone on plasma Na?
Increases expression of Na Channels and expression of proteins involved in Na transporter synthesis
Increases Ca reabsorption
What are the three disorders that result from hyper-secretion of the three corticosteroids? What are the corticosteroids that cause each of them?
Cushing Syndrome - glucocorticoid
Conn’s Syndrome- Excess mineralocorticoids (primary and secondary)
Adrenogenitial syndrome - excess Adrenal sex steroids- congenital Adrenal Hyperplasia
What is the cause of primary Conn’s syndrome?
result of adrenal hyperplasia and aldosterone producting adenomas
What is the cause of secondary Conn’s syndrome?
high plasma renin –> stimulation of angiotensin II and aldosterone.
What is the effect of Conn’s Syndrome on Na?
hypersectertion = excessive NA+ reabsoprtion = water retention = expansion of ECF volume, Arterial hypertensin
What is the cause and effect of Hypoaldosteronism?
Cause
Reduced renin
Congenital defect (deficiency of enzyme for renin synthesis)
Excision of aldosterone secterting hormone
Effects
Hypotension
Hyperkalaemia
Metabolic acidosis
What are the major effcts of renin?
increased formation of angiotensin II
Increased aldosterone secretion –> increases sodium reabsorption in kidney + blood pressure
What is the stimuli for the renin-Angiotensin system?
renal ischemia, decreased blood volume and pressure and sympathetic nerve stimulation.
