Principles of neuroendocrinology Flashcards
neuroendocrinology
study of physiological processes involved in integrating neural and endocrine functions
brain produces neurohormones
neuroendocrine systems
set of neurons, glands, non-endocrine tissues and neurochemical, hormones, humoral signals they produce and receive, that function in an integrated manner to collectively regulate a physiological or behavioural state
neuroendocrine integration
process by which neuroendocrine signals register/transduce/interpret important signals/internal and external environment & direct adaptive changes in prevailing physiological and behavioural states
what do NTs/neurohormones/hormones cause
AP cause depolarisation of the nerve terminal
increase permeability
Ca2+ influx
NT release via exocytosis
hormones released by endocrine cells into bloodstream act at a distance to target cells
neurosecretion
production and secretion of neurohormones by neurons into the bloodstream
vesicles are larger (100-400um) longer AP duration = more Ca2+ influx per AP
neurosecretory cells
posterior pituitary (cell bodies in SON/PVN)
similar structure to other neurons/dendrites/perikarya/axons
different morphology for specialised function
peptidergic
peptides with varying size 3-50AA chains
peptide synthesised in cell body (larger inactive precursor polypeptide) on RER
golgi packages precursor material into granules, transported to terminals by axonal transport - copackaged peptidase enzyme processes the final secretory product within vesicles
e.g magnocellular neurons in PVN/SON product OT/AVP
neuropeptide processing
neuropeptide - prepro - pro - hormone
evidence for neuropeptide processing
cysteine (aa) associated with OT/AVP
radiolabelled cysteine injected in rat cerebral ventricles
radioactivity accumulates in SON/PVN of hypothalamus - radioactivity in pituitary stalk and posterior lobe
rat given hypertonic salt solution (for AVP secretion) causes faster accumulation and cysteine transport
axonal transport via radioactive phosphorus is identical
excitation/secretion coupling
depolarisation (AP) causes AVP secretion
depolarisation by increasing K+ concentration
increase in Ca2+ conc causes hormone release, agents which block Ca2+ interfere with secretory response
define homeostasis
process requiring co-ordinated control over endocrine, behavioural, autonomic nervous responses to the environment
hypothalamus at the base of the brain - sends projections to circulatory system and higher brain centres
what is the circumventricular organ
present in many sites in the ventricular system
lacks the BBB - endothelial cells are fenestrated allowing diffusion
hormones out/circulating factors in (median eminence)
types of nuclei in the hypothalamus
feeding: ARC/VMH/LH
drinking: PVN/SON
sexual behaviour: pre optic/VMH
stress response: PVN
electrolyte and water balance: SON/PVN
centre concept is outdated - fine tuning
what are the tissues which form the neurohypophysis and adenohypophysis
invagniation of FB (diencephalon) which form the posterior lob (neurohypophysis) - SON/PVN
outgrowth of the buccal cavity (rathke’s pouch) - forms anterior lobe (adenohypophysis) - glandular
pars intermedia forms MSH (not in adult humans)
secretion of the anterior and posterior pituitary
anterior: LH/FSH/TSH/ACTH/PRL/GH
posterior: AVP/OT