Principles of neuroendocrinology

Question 1

neuroendocrinology

Answer 1

study of physiological processes involved in integrating neural and endocrine functions
brain produces neurohormones

Question 2

neuroendocrine systems

Answer 2

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

Question 3

neuroendocrine integration

Answer 3

process by which neuroendocrine signals register/transduce/interpret important signals/internal and external environment & direct adaptive changes in prevailing physiological and behavioural states

Question 4

what do NTs/neurohormones/hormones cause

Answer 4

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

Question 5

neurosecretion

Answer 5

production and secretion of neurohormones by neurons into the bloodstream
vesicles are larger (100-400um) longer AP duration = more Ca2+ influx per AP

Question 6

neurosecretory cells

Answer 6

posterior pituitary (cell bodies in SON/PVN)
similar structure to other neurons/dendrites/perikarya/axons
different morphology for specialised function

Question 7

peptidergic

Answer 7

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

Question 8

neuropeptide processing

Answer 8

neuropeptide - prepro - pro - hormone

Question 9

evidence for neuropeptide processing

Answer 9

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

Question 10

excitation/secretion coupling

Answer 10

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

Question 11

define homeostasis

Answer 11

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

Question 12

what is the circumventricular organ

Answer 12

present in many sites in the ventricular system
lacks the BBB - endothelial cells are fenestrated allowing diffusion
hormones out/circulating factors in (median eminence)

Question 13

types of nuclei in the hypothalamus

Answer 13

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

Question 14

what are the tissues which form the neurohypophysis and adenohypophysis

Answer 14

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)

Question 15

secretion of the anterior and posterior pituitary

Answer 15

anterior: LH/FSH/TSH/ACTH/PRL/GH
posterior: AVP/OT

Question 16

appetite hormones

Answer 16

leptin - secreted from adipose, decreases food intake
PYY3-36 - decreases food intake
GLP-1 - releases insulin
ghrelin - increases food intake

Question 17

hypothalamo-hypopysial portal system

Answer 17

anterior pituitary passes via long/short hypophyseal portal vessels
superior hypophyseal artery supplies the median eminence and stalk
inferior hypophyseal artery supplies the posterior lobe and anterior lobe via short portal vessels
both lobes drain into venous sinuses

Question 18

milk reflex

Answer 18

suckling activates the afferent nerves
activates efferent nerves in hypothalamus
neurosecretion of oxytocin
oxytocin mediated milk ejection

Question 19

nipple innervation

Answer 19

contains mechanosensory nerves and sends an AP
increased OT via posterior P milk ejection via contraction
increased prolactin decreased DA (negative feedback)

Question 20

neuronal reflex

Answer 20

similar to neuromuscular reflex
transient fixed pattern response to a stimulus
e.g. Posterior P OT milk ejection

Question 21

homeostatic control mechanisms

Answer 21

restrict physiological/behavioural variable around a set point
use negative feedback
hypo-pituitary-endocrine organ axis
food intake

Question 22

homeostatic neuroendocrine axis 3 Tier

Answer 22

HPT/HPA/HPG
hypothalamus to anterior pituitray via hypothalamus releasing/inhibiting factors
anterior pituitary to end organ by adenohypophysis hormone
end organ signals back to hypothalamus and pituitary
negative feedback via long/short loop feedback

Question 23

Homeostatic neuroendocrine axis 2 tier

Answer 23

GH/PRL release - acts at multiple target organs, feedback from pituitary more important
hormone secretion mainly under control of short feedback loop (from anterior pituitary)