L2: Hypothalamus and Pituitary Gland Phys Flashcards
The interface between the nervous and endocrine systems?
Hypothalamus
Main endocrine function of the hypopthalamus? (7)
- growth
- fertility and reproduction
- osmoregulation (water balance)
- metabolism (thermoregulation)
- energy balance
- stress response
- lactation
Connections between the hypothalamus and Pituitary Gland?
Morphology and Function of each?
Magnocellular Neruons (large, long)
–large cell bodies with long axons projecting down to (posterior) pituitary
–oxytocin and vasopressin (ADH) released into systemic circulation
Parvocellular Neurons (small, short)
–small cell bodies w/ shorter axons projecting to top of pituitary stalk (infundibulum)
–6 hormones (hypophysiotropic hormones) released into Portal Circulation
Hormones secreted by Parvocellular Neurons?
Posterior Pituitary is made of __________ tissue
Pituitary gland is made of NEURAL tissue
Collection of axonal projections from the hypothalamus that serve as a site for the secretion of neurohypophysial hormones directly into the blood?
Posterior Pituitary
_____________: Unmyelinated nerve axons of neurons cells whose cell bodies are located in hypothalamus
Neurohypohysis (aka. Posterior Pituitary): Unmyelinated nerve axons of neurons cells whose cell bodies are located in hypothalamus
Another name for glial cells?
Pituicytes
______________: Secretory granules containing oxytocin and vasopressin in terminal region of axon of Posterior Pituitary
Herring bodies: Secretory granules containing oxytocin and vasopressin in terminal region of axon
Vasopressin is released from the _____________
Vasopressin is released from the Posterior Pituitary
Vasopressin’s physiological effects? (V1 vs. V2)
V1 receptors:
□ abundant in vascular smooth muscle cells
□ activation of V1 receptors => VSMC contraction (‘vasopressin’)
V2 receptors:
□ abundant in renal tubule epithelial cells
□ activation of V2 receptors => increased renal H2O reabsorption
___________ plays essential role in maintaining water balance in kidney
Vasopressin
How does Vasopressin (ADH/AVP) Function to regulate water balance?
Plasma osmolality of > 280mOsm/kg => AVP release
AVP acts on renal epithelial cells to promote reabsorption of H2O
Plasma volume is increased and its osmolality decreased
Urine volume is decreased and its osmolality is increased
Independently, thirst centers in the hypothalamus are activated increasing the urge to consume H2O
What 3 stimuli control Vasopressin Release?
- Blood Osmolality > 280mOsM (sensed by hypothalamus osmoreceptors)
- Hypovolemia (decreased atrial stretch receptor activation)
- Hypotension ( decreased carotid and aortic baroreceptor activation
ADH Action on Kidney Tubule Epithelia?
ADH acts on renal epithelial cells V2 receptors to promote reabsorption of H2O
Leads to water channels (Aquaporin II ) insertion on apical membrane => allows water to enter cell and be returned to vasculature=> Smaller volume of more concentrated urine secreted
Inability of kidney to reabsorb H2O =>excretion of large volumes of dilute urine (25l/day)?
DIabetes Insipidus (ADH Deficiency)
Types of Diabetes Insipidus?
NEURAL (cranial) DI (hypothalamus/pituitary lesion)
NEPHROGENIC DI (renal ‘resistance’ to ADH)
- Inherited -mutations in V2 receptor (X-linked) or aquaporin 2 (autosomal)
- acquired -drug-induced (amphotericin B)