endo 2 - linking nerves and hormones an introduction to neuroendocrinology historical perspectives...
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Endo 2 - Linking nerves and hormones
An introduction to neuroendocrinology
•Historical perspectives
•Neurosecretory cells
•Embryology of the pituitary gland
•Anatomy and blood supply of the hypothalamic-pituitary axis
•Hormones of the posterior pituitary gland
•Hormones of the anterior pituitary gland
•Control of hormone secretions
NEUROENDOCRINE INTEGRATION
NERVES HORMONES
EFFECTOR ORGANS
The hypothalamic-pituitary axis
Historical Persepctives
• 130 A.D. Galen: pituitary gland ‘phlegmatic glandule’ secreting waste products (pituita) into the nose
• 1838 Rathke (viz Rathke’s pouch): development of the pituitary gland
• 1886 Pierre Marie: acromegaly associated with enlarged pituitary gland
• 1909 Harvey William Cushing: described the symptoms associated with hypo- and hyper- pituitarism
Phlegmatic glandule
Development of pituitary gland - Rathke (1838)
Rathke’s pouch
Pierre Marie (1886) enlarged pituitary gland associated with acromegaly
Brain-pituitary connections• 1930’s Bargmann and the Scharrers: histological studies
identified neurosecretory cells in brain projecting to the posterior pituitary
• 1930 Popa & Fielding: identified hypophyseal portal veins capillaries. Dispute as to direction of blood flow
• 1950’s Geoffrey Harris: established neurohumoral control of anterior pituitary gland
• 1969 Guilleman & Schally: identified structure of TRH
• 1970’s The decade of neuropeptides• 1980’s Gene sequencing.
Brain-pituitary connections• 1930’s Bargmann and the Scharrers:
histological studies identified neurosecretory cells in brain projecting to the posterior pituitary
• 1930 Popa & Fielding: identified hypophyseal portal veins capillaries. Dispute as to direction of blood flow
• 1950’s Geoffrey Harris: established neurohumoral control of anterior pituitary gland
• 1969 Guilleman & Schally: identified structure of TRH
• 1970’s The decade of neuropeptides• 1980’s Gene sequencing.
DEFINING HORMONES
• ENDOCRINE
• NEUROENDOCRINE
• PARACRINE
• AUTOCRINE
• INTRACRINE
Active hormone
Circulating hormone
INTRACRINE
Transduction of Transduction of nervous signal nervous signal
into an endocrine into an endocrine signalsignal
Neurosecretory Neurosecretory cellcell
Classical neurosecretory neurones• Chromaffin cells of the adrenal medulla
• Magnocellular neurones (SON & PVN) projecting to the posterior pituitary gland
• Parvicellular neurones projecting to the hypophyseal portal capillaries
C
Magnocellular Parvicellular
Neurosecretory cells (A) and sympathetic innervation of endocrine glands (B)
ANTERIOR PITUITARY
Parvicellular neurones
Magnocellular neurones
Neurosecretory cells of the
hypothalamus
Embryology of the pituitary gland
Gross anatomy of the pituitary gland
Hypothalamic nuclei
Aminergic and serotonergic
pathways of the brain
Blood supply of the neurohypophysis and adenohypophysis
Superior hypophyseal artery
Portal veins
Inferior hypophyseal artery
Hypophyseal veinsHypophyseal veins
Blood supply of the median eminence and pituitary gland
Internal carotid artery
Venous drainage of the pituitary gland
Neurones in the hypothalamus synthesise and release hormones from the posterior pituitary
Other neurosecretory cells in the hypothalamus release their hormones into the portal capillaries in which they are transported directly to endocrine cells of the anterior pituitary gland
LH, FSH, ACTH, TSH, PRL, GH
Oxytocin, vasopressin
Structure of oxytocin and vasopressin (ADH
Control of posterior pituitary hormones
Oxytocin
• Cervix/uterus
uterine contractions
• Nipples
milk ejection(neuroendocrine reflex)
Vasopressin (ADH)
• Osmoreceptors/
volume receptors
permeability of
collecting ducts(V2 receptors)
• Vasoconstriction(V1 receptors)
Control of vasopressin release and its actions
Control of anterior pituitary secretions
• Adrenocorticotrophic hormone – ACTH CRH
• Thyroid stimulating hormone – TSH TRH
GHIH (somatostatin)• Luteinizing hormone and follicle stimulating hormone
- LH & FSH GnRH
• Prolactin – PRL dopamine
(dominant control)
TRH/others
• Growth hormone – GH GHRH GHIH
(somatostatin)
Feedback control of the H-P axis
HYPOTHALAMUS
PITUITARY GLAND
EFFECTOR ORGAN
Feed
back
External stimuli
Factors controlling the release of growth hormone
and prolactin and feedback control
Factors controlling the secretion of TSH and
feedback control
Factors controlling the secretion of ACTH and
feedback control
Hypopituitary patient resulting from a tumour
Note loss of secondary sexual characteristics
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