Hypothalamus and Pituitary Flashcards
(20 cards)
Hypothalamus
▪️Several groups of neutrons called nuclei ▪️Neural cell= neuron. Group of neural cells= nuclei
▪️Forms lower part of the lateral wall and floor of the third ventricle
▪️ Receives information from nervous connections, bloodstream and cerebrospinal fluid.
Infundibulum
▪️Pituitary stalk that connects hypothalamus to Pituitary gland
Functions of hypothalamus
▪️Appetite and hunger ▪️Thirst ▪️Temperature ▪️Autonomic Nervous System ▪️Sleep and Circadian rhythms
Pituitary gland
▪️Sits within pituitary fossa (sella turcica) ▪️Made of Anterior and Posterior sections.
Embryology of Pituitary gland
▪️AP- derived from ectoderm of Rathke’s pouch
▪️PP- originates from downward extension of neural ectoderm from floor of diencephalon.
Blood supply of PG
▪️AP- signals sent by Posterior hypothalamus travel through axons and reach a complex network of capillaries supplied by superior hypophyseal artery. ▪️PP- hormones sent down axons from Anterir hypothalamus and are released immerdiatley and directly into capillaries supplied by inferior hypophyseal artery.
AP stimulated
▪️Hypothalamus receives a signal (stimulatory or inhibitory)
▪️Hypothalamus secretes releasing hormones that travel down the axon then into capillary network at the AP.
▪️The releasing hormones then stimulate AP to release other hormones into the blood that then act on specific target cells.
PA stimulated
▪️Hypothalamus receives a signal (stimulatory or inhibitory)
▪️Hypothalamus release hormones into axons.
▪️Hormones travel down axons into capillary network where they are immediately and directly released into blood.
AP cells
▪️Somatotroph (GH- secreting cells) ▪️Corticotroph (ACTH-secreting cells) ▪️Thyrotroph (TSH- secreting cells) ▪️Gonadotroph (LH/FSH- secreting cells) ▪️Lactotroph (Prolactin- secreting cells)
GH release
▪️ Stimulatory/Inhibitory
▪️Hypothalamus releases Growth Hormone Releasing Hormone (GHRH) or Growth Hormone Inhibiting Hormone (GHIH/Somatostatin) to AP
▪️AP releases GH which stimulates Insulin Growth Factor-1 (IGF1) in liver
▪️GH also binds to fat cells and stimulates them to break down and not take up anymore leaving fatty acids to circulate blood.
▪️High levels of GH inhibits GHRH by negative feedback.
GH function
▪️⬆️Protein synthesis ▪️⬆️Tissue growth in children ▪️⬆️Fat breakdown ▪️⬇️Glucose usage ▪️ Calcium homeostasis
Prolactin inhibition
▪️Dopamine acts as a hormone, traveling to the AP via the axon and capillary network to inhibit prolactin secretion by AP cells.
Oxytocin release
▪️Hypothalamus receives a signal (stimulatory or inhibitory)
▪️Hypothalamus releases oxytocin into axon.
▪️Oxytocin travels down axons into capillary network where it is immediately and directly released into blood.
Oxytocin function
▪️Stimulates myoepthilial contractions
▪️In mammary gland during lactation- milk is ejected due to suckling
▪️In uterus during labour
Antidiuretic Hormone (Vasopressin) release
▪️Hypothalamus receives a signal (stimulatory or inhibitory)
▪️Hypothalamus releases ADH into axons. ▪️ADH travel down axons into capillary network where it is immediately and directly released into blood.
ADH function
▪️Conserves body water and regulates osmotic concentration
▪️Causes movement of Aquaporins to the plasma membrane of kidney cells to allow more reabsorption of water from urine. ▪️Increases blood fluid, therefore, blood pressure and decreases osmotic concentration.
Hypothalamus parasympathetic responses
▪️ Preoptic nucleus and anterior hypothalamic area ▪️⬇️Blood pressure- vasodilation ▪️⬇️Heart rate ▪️Contraction of bladder ▪️⬆️Movement of GI tract ▪️Salivation ▪️Sweating
Hypothalamus sympathetic responses
▪️Posterior and lateral hypothalamic area ▪️⬆️Blood pressure - vasoconstriction ▪️⬆️Heart rate ▪️⬇️Movement of GI tract ▪️ Shivering
Food and water uptake
▪️Lateral region- hunger and thirst centre
▪️ Satiety centre
Emotion and behaviour
▪️ Blushing due to increased heart rate
▪️Lateral nuclei cause rage
