Neuroendocrinology

Question 1

State an example of a neuroendocrine reflex?

Answer 1

Osmoregulation

Neuroendocrine reflex: A physical stimulus causes a nervous signal (recieved and integrated in the CNS), which triggers the release of hormones from the brain into the blood

Question 2

What is neuroendocrine signalling

Answer 2

Nerve cell has a nerve impulse
Causes release of neurohormone
Neurohormone travels through blood where it binds to neurotransmitter receptor on target cell

Question 3

State the 3 types of neural and humoral signalling

Answer 3

• Endocrine
• Neurocrine
• Neuroendocrine

Question 4

Describe function of parvocellular nuclei?

Answer 4

Neurosecretory cells release hormones to capillaries of median eminence (supplied by superior hypophysial artery)
- the goes enters the portal veins to anterior pituitary where they regulate endocrine secretion

Median eminence is where secretions of the hypothalamus collect before entering the portal system emptying into the general circulation.

Question 5

What are the metabolic consequences of acromegaly?

Answer 5

Excess GH leads to insulin resistance
Many patients will have impaired glucose tolerance and hyperinsulinemia
May also have dyslipidaemia

Question 6

State the 2 neuroendocrine cells of the hypothalamus?

Answer 6

Parvocellular nuclei
Magnocellular nuclei

Question 7

What is the neuroendocrine integration?

Answer 7

Signals are received and integrated in the CNS and the output is a change in hormone release

Question 8

What controls the release of the posterior pituitary hormones?

Answer 8

ADH + Oxytocin released under neural control into hypophysial capillaries supplied by inferior hypophysial vein

Question 9

State the stimulatory factors that control GH secretion?

Answer 9

GHRH
Ghrelin
Hypoglycemia
Decreased fatty acids
Fasting
Exercise, sleep
Stress

Question 10

What hormones are growth hormone secretion increased by?

Answer 10

• GH-releasing hormone (from hypothalamic parvocellular neuroendocrine cells)
• Ghrelin (‘hunger hormone’ secreted by endocrine cells of the stomach)

Question 11

State examples of neuroendocrine cells?

Answer 11

Magno and parvocellular neurons of the hypothalamus
Chromaffin cells of the adrenal medulla

Question 12

State the 6 actions of growth hormone?

Answer 12

Stimulates production of IGF-1 by liver
Increases lipolysis: raises free fatty acids (FFA)
Increases gluconeogenesis: raises blood sugar
Increases amino acid uptake into muscle, protein synthesis and lean body mass
Stimulates chondrocytes: linear growth
Stimulates somatic growth: increased organ/tissue size

Question 13

What hormones are growth hormone decreased by?

Answer 13

GH-inhibiting hormone (also known as somatostatin, from hypothalamic parvocellular neuroendocrine cells)

Question 14

How does growth hormone concentration differ throughout life?

Answer 14

Increases from childhood to puberty (highest here)
Decreases adult life onwards.
- Diurnal fluctuation is high in young adult and very low in older adult

Question 15

State the functions of growth hormone

Answer 15

• Growth and development (anabolic)
• Couples growth to nutritional status

Question 16

Describe function of magnocellular nuclei?

Answer 16

Project to posterior pituitary and release to capillaries supplied by inferior hypophysial artery

Question 17

What are neuroendocrine cells?

Answer 17

Neuroendocrine cells are neurosecretory cells that release signal molecules (hormones) from their synaptic terminals into the blood

Question 18

How are neuroendocrine cells controlled by?

Answer 18

Controlled via synaptic transmission from presynaptic neurons
- Occurs from neuroendocrine integration

Question 19

Describe the posterior pituitary?

Answer 19

PP is basically an extension of hypothalamus, with hormones stored in hypothalamic neuron terminals

Question 20

State the inhibitory factors that control GH secretion?

Answer 20

Somatostatin (GHIH)
GH
Hyperglycemia
Increased fatty acids
IGF-1

Question 21

What is neurocrine signalling?

Answer 21

Nerve cell has nerve impulse
Leads to release of neurotransmitter into synaptic cleft
Which binds to neurotransmitter receptor on neuron or effector cell locally found

Question 22

What is the less common way/secondary acromegaly occurs by?

Answer 22

Tumour elsewhere secretes GHRH

Question 23

What allows for control of negative feedback of growth hormone?

Answer 23

GH in circulation
IGF-1 in circulation (released by liver in response to GH)

As these conc. increases, negative feedback on hypothalamus and P increase

Question 24

State the 4 hormones which control anterior pituitary secretions?

Answer 24

TSH: thyroid stimulating hormone (thyrotropin)
TRH: thyrotropin releasing hormone
ACTH: adrenocorticotropic hormone (corticotropin)
CRH: corticotropin releasing hormone

Question 25

Describe the embryology of the pituitary gland (so how it arises)?

Answer 25

1) Evagination of floor of 3rd ventricle
- called neural ectoderm)
2) Evagination of oral ectoderm
- Forms Rathke’s pouch
3) Rathke’s pouch pinched off

Question 26

What is the most common way acromegaly occur?

Answer 26

Most commonly due to pituitary adenoma: increase in GH-secreting somatotrophs

Excess GH: acromegaly

Question 27

How can acromegaly be diagnosed?

Answer 27

Glucose tolerance test