The hypothalamo-adenohypophysial axis Flashcards
Where does the pituitary gland/ hypophysis lie?
Sella Turcica (bony dip at base of brain)
Diagram of brain, pituitary gland, hypothalamus and other structures
Slide 3, lecture 2
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Diagram of adenohypohysis
Slide 4, lecture 2
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Diagram of hypothalamic- hypophysial portal circulation
Slide 5, lecture 2
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Hypothalmic nucleus definition
Collection of neuronal cell bodies
Situated in hypothalamus
Hypothalmic neurone start+ possible terminations
Property?
Neurotransmitter fate?
Neurone starts in hypothalamus from hypothalamic nuclei
Leaky
Can go to posterior hypothalamus or:
Median eminence, lie on primary capillary plexus= hypothalamus controls anterior pituitary function
Neurones release neurosecretion which get into the blood flowing through primary capillary plexus+ transported to secondary capillary plexus anterior pituitary+ stimulate release of anterior pituitary hormones from secretory cells only responsive to particular neurosecretion
Somatotrophs produce?
What regulates it?
Target cells?
Stimulated by?
Growth hormone (Somatotrophin)
Growth hormone releasing hormone (GHRH), also called somatotrophin releasing hormone= stimulatory
Stomatostatin= inhibitory
General body tissues, particularly liver
Fasting Exercise Oestrogens Stress Sleep
Adenohypophysial cells
Somatotrophs Lactotrophs Thyrotrophs Gonadotrophs Corticotrophs
Lactotrophs produce?
What regulates it?
Target cells?
Prolactin
Dopamine= inhibitory (increased hormone= decreased prolactin)
Thyrotrophin releasing hormone (TRH)
Breasts (lactating women)
Thyrotrophs produce?
What regulates it?
Target cells?
Thyroid Stimulating Hormone (TSH)
Other name= thyrotrophin
Thyrotrophin releasing hormone (TRH)= stimulatory
Thyroid
Gonadotrophs produce?
What regulates it?
Target cells?
Luteinising Hormone (LH) Follicle Stimulating Hormone (FSH)
Gonadotrophin Releasing Hormone (GnRH)= stimulatory
Testes (Men)
Ovaries (Women)
Corticotrophs
Hormone acts on?
What regulates it?
Target cells?
Adrenocorticotrophic Hormone (ACTH)
Also named Corticotrophin
Acts on adrenal cortex
Corticotrophin releasing hormone (CRH)= stimulatory
Vasopressin (VP)= stimulatory
Adrenal Cortex
Where are adenohypophysial hormones stored?
Secretory granules
Released by exocytosis
Protein hormones
Growth hormone (somatotrophin)
Prolactin
Both quite big
Glycoprotein hormones
Thyroid Stimulating Hormone (Thyrotrophin)
2 gonadotrophins
Leuteinising Hormone (LH)
Follicle Stimulating Hormone (FSH)
both have same α subunit, have different β subunits
Polypeptide hormones
Adrenocorticotrophic Hormone (Corticotrophin) (ACTH) smaller than protein hormones
Action of GH
Negative feedback loops?
Adenohypophysis- stomatotrophs→ Growth Hormone→Body tissues+ metabolic actions→ growth+ development
Adenohypophysis- somatotrophs → Growth hormone→ Liver (hepatocyte receptors)→ Somatomedins (IGF1+ IGF II (more relevant in foetus))→ body tissues+ metabolic actions→ growth+ development
Somatomedins negative feedback on hypothalamic nuclei= decreased GHRH+ increased SS, also on secretory cells releasing GH
GH negative feedback on hypothalamic nuclei= decreased GHRH
Metabolic effects of GH
GH excess?
Stimulation of amino acid transport into cells+ protein synthesis Increased gluconeogenesis (diabetes in excess) Lipolysis stimulation= increased fatty acid production Increased cartilaginous growth+ somatic cell growth (predispose to malignancy in excess)
Milk production
Suckling= stimulation of tactile receptors → afferent neural pathway→ suppression of hypothalamic dopaminergic neurones→ less dopamine produced→more prolactin secreted → efferent endocrine pathway→ milk production
