Body Fluid Homeostasis Flashcards
What does vasopressin/ADH regulate?
Body fluid osmolality
- conserves H2O
Which peptide hormone does ADH share the same pathway as?
Oxytocin
Mechanism of ADH secretion
- Change in osmolality is detected by hypothalamic osmoreceptors
- Neurosecretory neurons produce ADH. Cell body lies in hypothalamus axon leads to posterior pituitary gland where ADH is released
- Increases feeling of thirst
Which nuclei are stimulated in body fluid homeostasis?
Supra-optic and paraventricular nuclei
When is ADH released?
H2O deficiency, decreased blood volume
What is osmolality proportional to?
The number of particles per kg of solvent
What is osmolarity proportional to?
The number of particles per L of solution
Mechanism of vasopressin on principal cell
Binds to V2 receptor on basolateral membrane
activate protein kinase A
Inserts AQP2 channels into apical membrane
takes in more water –> fall I’m osmolality
Which receptors does vasopressin bind to?
V2 receptors on basolateral membrane of principal cell
What are the two types of diabetes insipidus?
- Central DI
- Nephrogenic DI
What is central DI?
No vasopressin release so kidneys can’t regulate how much H2O is excreted
What is nephrogenic DI?
The kidney cells have no response to ADH due to a defect in the V2 receptor and aquaporin defect
How can the two types of diabetes insipidus be treated?
Central - nasal spray DDAVP (synthetic analogue of ADH)
Nephrogenic - No treatment
Where is aldosterone released?
Mineralocorticoid released from the adrenal cortex
What does aldosterone regulate?
Na+, K+ and body fluid volume
What does aldosterone act on? What effect does it have?
Distal tubule and collecting duct
Increases reabsorption of Na+
Increases secretion of K+ and H+
With which system does aldosterone coordinate regulation?
Renin-angiotensin system
What is Liddle’s syndrome?
- High Na+ reabsorption - mutation in ENaC
- Low aldosterone
- Increase Na+ channels in principal cell
leads to hypertension
What is pseudohypoaldosteronism?
- Salt loss but high aldosterone
- Loss response to aldosterone
- Mineralocorticoid receptor problem
Where is renin released from?
Juxtaglomerular apparatus (JGA)
What is the macula densa?
Part of the distal tubule which detects [Na+] - regulates blood pressure and filtration rate
Renin-angiotensin cascade
- Decrease ECF volume
- Renin released from JGA
- Angiotensinogen converted to angiotensin I in blood
- Angiotensin-converting eznyme converts to angiotensin II
Angiotensin II effects
- aldosterone release
- vasoconstriction
- increases bp
- increases plasma Na+ and ECF volume
What happens when you ingest salt?
- Increases plasma Na+ and H2O
- H2O moves out ICF into blood
- Increases ECF volume and osmolality plasma
What does a decrease in aldosterone cause?
- Increases Na+ loss
- Increases H2O loss
- Decreases ECF volume
What does an increase in vasopressin cause?
- Increases H2O reabsorption
- Decreases osmolality but increases ECF volume
