T1 L2 HPA axis Flashcards
pituitary gland location
below brain
encased by skull
in sella turcica
hypothalamus
area of brain directly above pituitary gland
infundibulum
connects pituitary gland to hypothalamus
posterior pituitary gland
aka
neurohypophysis
structures in post PG
neurosecretory cells in hypothalamus -> hypothalamico- hypophyseal tract in infundibulum -> post PG
peptide hormones secreted by post pit gland (neurohypophysis)
- ADH (vasopressin)
2. oxytocin
synthesis of ADH & oxytocin
- inactive hormone precursors synthesised by supraoptic nuclei and paraventricular nucleus (hypothalamus)
- transported along hypothalamico-neurohypophyseal tract
- Then stored in posterior pituitary
ADH
- secretions influenced by plasma osmolarity
- stimulation of V2 receptors causes translocation of aquaporins to the membrane of the kidney tubule (thus allowing water reabsorption)
- stimulation of V1 rs causes vasoconstriction (doesnt occur at physiological concs)
Oxytocin
- Acts via IP3 to cause contraction of smooth muscle of uterus and breast
- secretions stimulated by stimulation of genitals & nipples
- important at parturation & lactation
- synthesis ^ during pregnancy but parallel ^ in oxytocinase to counteract activity
- not necessary to initiate labour but administered to induce labour
oxytocin effect during parturation
- contraction of smooth muscle to aid expulsion
- continued cervical stim. => continued secretion
oxytocin effect after parturation
- oxytocin responsible for milk expulsion
- stimulus = suckling
- delay between start suckling and milk letdown
Anterior Pituitary gland and hormones secreted
up growth from palate
*mneumonic for hormones secreted* Any Prison Guard Laments The Felon ACTH Prolactin GH LH Thyroid stim hormone FSH
Hormones of Ant. Pituitary Gland
Location of synthesis of TSH, ACTH, FSH
- TSH -> Thyrotrophe cells
- ACTH -> corticotrophe cells
- FSH -> gonadotrophe cells
Hormones of Ant. Pituitary Gland
secretion controlled by:
Releasing hormones of the hypothalamus
- TRH
- CRH
- GnRH
- GHRH
releasing hormones secreted by hypothalamus into ___
hypothalamico adenopophyseal portal vessel -> ant. pituitary
- releasing Hs dont enter systemic circ.
Diagnostic test of pituitary function
- measure releasing hormones & effects of hormone administration (-ve feedback)
- diurnal rhythms: timing of test important
sleep duration effects
- secretion of adrenocorticotropin & cortisol depends on sleep duration
- decreases w/ spontaneous awakening
clinical investigations
- signs & symptoms
- biochemical tests (basal levels): TSH & FT4, cortisol, LH & FHS, Prl, Testosterone & periods
- Imaging (MRI)
- Visual field tests: bitemporal hemianopia bc compression of optic chiasm
prolactin primary role
- promote lactation, development of breast tissue
- important in females after puberty and during and after pregnancy
- synthesised in lactotrophe cells in ant. PG (m+f)
secretion of prolactin controlled by
hypothalamus
- by means of prolactin release inhibiting factor (Dopamine)
- TRH stimulates prolactin synthesis
- secretion stimulaed by muld stress, nipple stimulation and sex
Growth hormone synthesis
- in APG: somatotrophe cells
GH effect
^ linear growth in adolescents
- ^ protein synthesis & collage deposition (mediated via nucleus)
- tissue turnover and repair
GH secretion
controlled by hypothalamus
- stimulated by GHRH
- inhibited by GHR inhibiting hormone (somatostatin, GHRIH)
Stimulated by decrease in carbs & fatty acids and an increase in fatty acids
how does growth hormone produce its effects
GH acts via 2ndary messengers which are produced in liver
- Insulin-like growth factor 1
- Insulin like growth factor 2
