Lecture 12: Integration salt and water balance 1 Flashcards
1
Q
What happens when you are dehydrated?
A
- Water defecit –> increased extracellular osmolarity –> increased ADH secretion from posterior pituitary –> increased plasma ADH –> Increased H2O permiability in collecting ducts –> Increased H2O reabsorption –> decreased H2O excretion
2
Q
Where is ADH produced and where is dehyration sensed?
A
- Sensed in hypothalamus
- Released in posterior pituitary
3
Q
What are the non-physiological causes of ADH release?
A
- Pain, stress
- Drugs
- Carcinomas
- Pulmonary disorders
- CNS disorders
- Alcohol inhibits ADH release
4
Q
What happens if ADH levels are low?
A
- You can get diabetes insipidus
- Can be central or nephrogenic
5
Q
What is the difference between central DI and nephrogenic DI?
A
- Central:
- ADH not secreted
- problems with hypothalamus or posterior pituitary
- Due to brain tumour, injury or infection. Not heriditary
- treat with ADH analogs
- Nephrogenic:
- Collecting tubules not responsive to ADH
- Can be caused by drugs (Li+)
- Less commonly heriditary
- Not currently treatable
6
Q
What test can you preform to establish if DI is nephrogenic or central?
A
- Water deprevation test
- Deprive someone of water for sometime (hours)
- give analog of ADH
- if central urine osmolarity will increase
7
Q
What is SIADH?
A
- Syndrome of inappropriate ADH secretion
- usually plasma ADH levels higher than normal
- patient inappropriately retains water
- causes drop in plasma osmolarity
- treated by limiting water intake
- may be caused by brain injury, tumor or lung tumour
8
Q
Factors that promote renin secretion?
A
- decreased afferent arteriole pressure
- increased sympathetic activity
- Decreased macula dense NaCl delivery
9
Q
Effects of angiotensin II?
A
- Efferent arteriole constriction
- increased aldosterone production
- binds to AT1 receptors which allows reabsorptiopn of Na+ pg98
10
Q
What are antihypertensive drugs?
A
- ACE inhibitors
