Physiology - Endocrine Flashcards
Where is the pituitary gland?
In the sella tercica - the pituitary fossa, part of the sphenoid bone. Separated from the brain by the diaphragm sellae, a reflection of the dura mata. It is connected to the hypothalamus by the neural stalk. It sits below the optic chiasm.
What are the pituitary subdivisions?
The neurohypophyses (posterior pituitary) and the adenohypophyses (anterior pituitary)
Functions of the neurohypophyses
Neural cells which are an extension of the hypothalamus. They secrete oxytocin and ADH
Functions of the adenohypophyses
Glandular cells. Releases
LH, FSH, GH, Prolactin, ACTH, TSH, Melanocyte stimulating hormone
Relationship between hypothalamus and pituitary
Hypothalamus sits above pituitary and releases hormones which act on the pituitary.
What hormones come from hypothalamus?
CRH, TRH and dopamine
What does CRH do?
Released from paraventricular nucleus in response to stress. Stimulates ACTH which causes the adrenal gland to produce cortisol. Cortisol prepares for stress by increasing BP, mobilising energy stores.
CRH also acts on the CNS to increase sympathetic response and mediate central arousal.
What does TRH do?
Released from paraventricular nucleus in response to thermal and energy requirements. It stimulates TSH which causes the thyroid gland to produce T3 and T4 to increase metabolic rate and negatively feedback to pituitary and hypothalamus.
What does dopamine do?
Released from multiple sites including the arcuate nucleus of the hypothalamus. It acts on the pituitary to inhibit prolactin responsible for lactation and sexual arousal.
