Hypothalamus & Pituitary Gland Flashcards
Name the parts
Name the parts
Control of hormone secretion by neurons
CNS
- Autonomic nervous system
- adrenal gland
- endocrine gland cell
- Hypothalamus
- Anterior pituitary
- posterior pituitary
Hypothalamus endocrine cells of the posterior pituitary
- supraoptic nucleus → cells secrete oxytocin
- paraventricular nucleus → cells secrete ADH
Hormone secretion from hypthalamus to posterior pituitary
Hypthalamus triggers hormone production in its endocrine cells which signal down to terminate in capillary beds within the posterior pituitary whereby the hormones synthesized in hypothalamus are released and they drain into the venous system and are circulated
ADH
antidiuretic hormone = vasopresson
2 main functions of ADH
- Conserves body water and blood volume by increasing water reabsorption at the kidneys
- Increases blood pressure by constricting arteries and the arterioles (= vasoconstriction)
ADH effects at kidney basolateral membrane
- ADH moves from circulation (peritubular capillary) through the pertubular fluid and acts on receptors on basolateral membrane of the principle cell. The receptor is a G coupled protein receptor
- Adenylate cyclase is activated stimulating the cAMP second messenger.
- cAMP phosphorylates protein kinase A
- Activation of protein kinase A on aquaporin
ADH effects on kidney at the apical membrane
So ADH stimulates thw principle cell which leads to translocation of vesicle cell containing aquaporin 2 and it splices with the apical membrane which is in contact with the tubular fluid and allows fluid to be absorbed from tubular into the cell. Withdrawal of ADH leads to the vesicles leaving the apical membrane and water is shuttled out into the peritubular through the basolateral membrane via aquaporin 3 which is always active. ADH not only causes insertion of the aquaporion 2 for water reabsorption but can also regulate the expression of aquaporion 2 and 3.
What regulates the release of ADH?
- low blood pressure detected by reduced stretch of:
- → walls of the atria of the heart
- → aortic and carotid arteries
- High plasma polarity detected by osmoreceptors in the hypthalamus
Both have a stimulating affect to release ADH from the periventricular neuron and will get negative feedback to stop working once water reabsorption levels have been fixed.
What is nocturnal enuresis?
Bed wetting
- Typically effects school-aged children - most have a physiological cause. ADH secretion has circadian rhythm and levels increase at night so reduced nocturnal producing of more urine concentrated production so urine output stays filled and may release spontaneously.
- Desmopressin helps this
Where is oxytocin secreted from?
The supraocta nucleus in the hypothalamus
What is oxytocin important for?
Preceding and following birth
- Effect: Stimulates contraction of the uterine muscle to aid in labor
- Regulation: secreted in response to stretch of the uterine neck by fetus
- Is the most common pharmacological agent to induce labor
Effect and regulation of oxytocin and nursing
- Effect: causes smooth muscle contraction in mammary gland breast tissue - responsible for milk let down
- Regulation: secreted in response to sucking
How do hormones travel from the hypothalamus to the anterior pituitary?
- The neurosecretory cells release hypothalamic hormones into the capillary bed in the median eminence, so the neuron extends and terminates here, not in the anterior pituitary
- The hormones then travel via a portal system to the anterior pituitary
- Hypothalamic hormones regulate the secretion of hormones produced in cells of the anterior pituitary such that once they arrive at the anterior pituitary they are released from the circulation into the tissue and
- Anterior pituitary hormones release into the blood and travel to the rest of body; so the hypothalamic hormones and anterior pituitary hormones exchange places
General feedback system of the anterior pituitary
What are the hypothalamic and anterior pituitary hormones
