Hypothalamus and Pituitary Gland Flashcards
Describe the embryonic origins of the pituitary gland and how this relates to gland function.
Ant. Pos (Adenohypophysis): Grows upwards from glandular tissue (Pars distalis and Pars Intermedialis).
This eants ant.pit. hormones are produced and released in ant.pit.
Wide range of hormones
Controlled by direct neg. feedback from hypothalamic hormones
Pos.Pit (Neurohypophysis): Grows downwards from diencephalon (Pars nervosa)
Pos.pit hormones produed in HypoT nerve bodies and released through pos. pit when required
Axons start in HypoT-> Infundibulum-> pos pit.-> Vesicles released.
Where are posterior pituitary gland hormones formed and how are they released?
Oxytocin produced in paraventricular nucleus
Vasopressin produced in supraoptic nucleus
Axons of cell bodies in hypothalamus, travel via hypothalamohypophysel tract. Released from pos.pit from axons into the blood.
What mechanisms control the release of oxytocin?
Positive Feeback system
Baby Pushing on cervix= Oxy released
Contractions increase -> greater pushing on cervix
-> Oxy release
Baby delivered
Oxytocin release stops
Same w/ letdown reflex of lactating nipple
What mechanisms control the release of ADH (vasopressin)?
Hypothalamic osmoreceptors detect high osmolarity of blood. Supraoptic nuc. produces vesicles of ADH. Released in the pos.pit= Water retention in the DCT = Decreases osmolarity. INhibitive feedback to hypoT osmoreceptors. ADH release Stopped.
Left atria baroreceptor detects low blood pressure. Supraoptic nuc. produces vesicles of ADH. Released in the pos.pit. = vasoconstriction. Increases BP, inhibiion at baroreceptors. ADH release stopped.
Where are anterior pituitary gland hormones formed and how are they released?
Anterior Pituitary Hormones are synthesized in the anterior pituitary.
Hypophysiotropic hormones are release from hypothalamus. Travel down hypothalamohypophyseal portal systems into anterior pituitary capilaries.
Trigger Anterior Pituitary to release hormones into the blood stream.
Describe the different roles of releasing hormones with named examples.
Thyrotropin releasing hormone = Increase thyrotropin
Corticotropin releasing hormone = Increase adrenocorticotropin
Gonadotropin releasing hormone = Increase FSH and LH
Growth Hormone releasing hormone = Increase Growth Hormone
Prolactin releasing factor = Increase Prolactin
Growth hormone inhibiting hormone = Decreases Growth hormone
Prolacting inhibiting factor (dopamine) = Decreases Prolactin
