Physiology 2130 Lecture Notes - Lecture 46: Posterior Pituitary, Osmoreceptor, Baroreceptor
1 May 2018
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Lecture 46
Antidiuretic Hormone (ADH)
● Only hormone that is released
● Concentration affects how much water is reabsorbed
● Has a very short plasma life (minutes)
○ Need a constant supply
Plasma Osmolarity and ADH Release (RELISTEN)
● Plasma osmolarity
○ Changes easily
○ Small, sensitive detectable change for ADH release
■ Hypothalamic neurons receive this information and decided how much
ADH to release
● Osmoreceptors are near the 3rd ventricles
○ Respond to a change in osmolarity
○ Osmoreceptors physically decrease in size when blood osmol is low
○ Increase in AP
● Posterior pituitary
○ Release more ADH
● Kidney
○ Increase water reabsorption in response to increase ADH in the collecting duct
○ Decrease water excretion
■ Conservation of body water (lowers osmolarity of ECF)
Blood Volume and ADH release
● Blood volume detectors in the atira and baroreceptors (respond to MAP)
● Baroreceptors sends less APs when MAP increase/blood volume decrese
○ This releases the inhibition and activates the hypothalamus neurons
● Get the release in ADH released by the posterior pituitary
Hypothalamic Integration of ADH release
● Activation both osmoreceptors and baroreceptors leads to maximal ADH secretion
○ Increase osmolarity
○ Decrease blood volume
● What if these two input opposed each other?
○ Decrease in plasma osmolarity and a decrease in blood volume
○ Osmoreceptors are more important in normal physiological conditions
■ If osmolarity is increased but the blood volume is also increased you will
still still secrete more ADH
○ However, in a case of extreme low blood volume (hemorrhage), the
baroreceptor will take precedence
■ If the plasma osmolarity is low but the blood volume is also very low
■ Baroreceptors will stimulate the production of ADH
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Document Summary
Concentration affects how much water is reabsorbed. Has a very short plasma life (minutes) Small, sensitive detectable change for adh release. Hypothalamic neurons receive this information and decided how much. Osmoreceptors physically decrease in size when blood osmol is low. Increase water reabsorption in response to increase adh in the collecting duct. Conservation of body water (lowers osmolarity of ecf) Blood volume detectors in the atira and baroreceptors (respond to map) Baroreceptors sends less aps when map increase/blood volume decrese. This releases the inhibition and activates the hypothalamus neurons. Get the release in adh released by the posterior pituitary. Activation both osmoreceptors and baroreceptors leads to maximal adh secretion. Decrease in plasma osmolarity and a decrease in blood volume. Osmoreceptors are more important in normal physiological conditions. If osmolarity is increased but the blood volume is also increased you will still still secrete more adh. However, in a case of extreme low blood volume (hemorrhage), the baroreceptor will take precedence.
