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Hypothalamus (Hormones (Growth hormone (Directly stimulates division and…
Hypothalamus
Hormones
Prolactin
- High levels prolactin reduce levels of sex hormones oestrogen and testosterone
- Causes enlargement of mammary glands
- Stimulates glands to produce milk (Progesterone levels need to fall)
Growth hormone
- Directly stimulates division and multiplication of chondrocytes
- Increase calcium retention + strengthen and increase mineralisation bone
- Increases muscle mass through sarcomere hypertrophy
- Promotes lipolysis
- Increases protein syntheis
- Stimulates growth internal organs (except brain)
- Plays role in homeostasis
- Reduces liver uptake of glucose
- Promotes gluconeogenesis in liver
- Contributes maintenance and function pancreatic islets
- Stimulates immune system
- Increases de-iodination of T4 and T3
- Children: Linear growth
- Adults: protein synthesis, carbohydrate metabolism, lipolysis and calcium homeostasis
- GHs increase production of Insulin like growth factors
- IGFs cause cells to grow and multiply by increase uptake AA and accelerating protein synthesis
- Long half life
LH and FSH
Negative feedback:
Stimulation: Hypothalamus - GnRH - Pituitary - FSH & LH - sertoli & leydig cells- Testes & Ovaries-
Testosterone, oestrogen and progesterone
Inhibition: Testosterone, oestrogen and progesterone - Pituitary and hypothalamus
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Anatomy
- Hypothalamus below thalamus
- Pituitary gland connected hypothalamus via pituitary stalk
- Pituitary sits in pituitary fossa (sella turcica) of sphenoid bone. fossa has fenestration in roof for infundibulum
Venous drainage
- From short veins that enter venous drainage between layers of dura mater
Arterial blood
- Internal carotid (posterior lobe supplied directly, anterior lobe supplied by capillaries originated from capillary bed in hypothalamus)
Embryology
Posterior
- Originates from downward extensions neural ectoderm from floor of diencephalon (down growth neural tissue from brain)
Anterior
- Ectoderm of Rathke's pouch (upgrowth of glandular epithelium from pharynx)
Pituitary gland
Neurohypohysis
Median emminence
- Upper section of the neurohypophysis above pars tuberalis
Infundibular stalk
- Stem connects pars nervosa to base of brain
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- Connected to hypothalamus via hypothalamic-hypophyseal tract
(bundle of neurons from nuclei of hypothalamus)
- Nuclei will be neurosecretory: These will synthesize hormone, pack them in vesicles and then exocytose them when they reach axon terminal (in posterior pituitary)
- Exocytosis only happens when signal via nerve impulse
Adenohypohyis
Pars tuberalis
- Collar of tissue usually surrounds infundibular stalk
Pars intermedia
- Narrow band usually separated from pars distalis by hypophysela cleft. Remnants from embryological structure of no use
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- Connected to hypothalamus via hypophyseal-portal system
Histology
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Cortitrophs ACTH & MSH
ACTH: stimulates adrenal gland (cortex): release cortisol
MSH: increase pigmentation of skin (darker)
Lactotrophs - prolactin
- Enables production breast milk from mammary glands
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