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SGUL - Physiology 1 > Neuroendocrinology > Flashcards

Neuroendocrinology Flashcards

1
Q

What are neuroendocrine cells?

A

Neurosecretory cells that release hormones from synaptic terminals into the blood.

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2
Q

How are neuroendocrine cells controlled?

A

Synaptic transmission from presynaptic neurons.

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3
Q

Give three examples of neuroendocrine cells.

A
  • Chromaffin cells of the adrenal medulla
  • Hypothalamic magnocellular neurons
  • Hypothalamic parvocellular neurons
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4
Q

Describe the embryology of the pituitary gland.

A
  • Begins as two simultaneous invaginations, one downwards from the neural ectoderm and one upwards from the oral ectoderm.
  • Upward invagination is called Rathke’s Pouch, and it is pinched off, while the downward growth is aligned with it.
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5
Q

Describe the separate blood and hormone supplies of the two lobes of the pituitary. PART 1

A
  • Inferior hypophyseal artery supplies the posterior pituitary, divides into a capillary bed
  • Capillary bed contacted by axons of magnocellular neurosecretory cells in the hypothalamus.
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6
Q

Describe the separate blood and hormone supplies of the two lobes of the pituitary. PART 2

A
  • Cells can secrete hormones into capillary bed, and drain off by the inferior vein.
  • Hormones secreted by hypothalamus through posterior pituitary can enter systemic circulation.
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7
Q

Describe the separate blood and hormone supplies of the two lobes of the pituitary. PART 3

A
  • Anterior lobe is supplied by the superior hypophyseal artery indirectly.
  • Artery vascularises the median eminence
  • Artery divides into a capillary bed in the median eminence, and then this is drained off by the venules which become a portal system.
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8
Q

Describe the separate blood and hormone supplies of the two lobes of the pituitary. PART 4

A
  • Portal veins supply to the anterior pituitary, where they revascularise into a capillary bed in the anterior pituitary.
  • Secretions of anterior pituitary can be secreted into the bed, where it drains off via superior hypophyseal vein into systemic circulation.
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9
Q

Describe the separate blood and hormone supplies of the two lobes of the pituitary. PART 5

A
  • Parvocellular neurosecretory cells, via axonal terminals, release hormones into the capillary bed of median eminence
  • Signals are carried into capillary bed of the anterior lobe, where they act locally.
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10
Q

List the hormones that are released from the posterior lobe of the pituitary gland and where they act.

A
  • oxytocin: uterine muscles
  • ADH: kidney tubules
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11
Q

List the hormones that are released from the anterior lobe of the pituitary gland and where they act.

A
  • TSH: thyroid
  • ACTH: adrenal cortex
  • FSH and LH: testes or ovaries
  • Growth Hormone (GH): the entire body
  • Endorphins: pain receptors in the brain
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12
Q

Describe ADH as an example of a neuroendocrine reflex.

A
  • ADH’s main function is osmoregulation
  • If body water is low, ADH is released from neuroendocrine cells and stimulates water retention in the kidney.
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13
Q

What are some growth hormone functions?

A
  • role in growth and development
  • allows growth to occur in relation to nutritional status
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14
Q

How is growth hormone secretion controlled hormonally?

A
  • Ghrelin (endocrine cells of the stomach)
  • GH-Releasing hormone (hypothalamic neurosecretory cells)
  • Somatostatin/GHIH (hypothalamic neurosecretory cells)
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15
Q

How is growth hormone secretion controlled by negative feedback?

A
  • By the GH in the circulation
  • By IGF-1 (released by the liver in response to GH)
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16
Q

List some other factors that stimulate GH secretion.

A
  • GHRH
  • Ghrelin
  • Hypoglycemia
  • Fasting
  • Exercise
  • Stress
17
Q

List some other factors that inhibit GH secretion.

A
  • Somatostatin (GHIH)
  • GH (negative feedback)
  • Hyperglycemia
  • Increased fatty acids
  • IGF-1
18
Q

Describe GH action in the body. PART 1

A
  • Stimulates production of IGF-1
  • Increases lipolysis in adipose tissue: raises free fatty acids (FFA)
  • Increases gluconeogenesis
19
Q

Describe GH action in the body. PART 2

A
  • Increases amino acid uptake into muscle
  • Stimulates chondrocytes
  • Stimulates somatic growth: increased organ/tissue size
20
Q

What is acromegaly and what is it caused by?

A
  • Condition causing excess GH.
  • Commonly due to pituitary adenoma: an increase in GH-secreting somatrophs.
  • Or due to to GH-secreting tumors
21
Q

What does acromegaly cause?

A
  • Insulin resistance - impaired glucose tolerance and hyperinsulinemia.
  • Rapid bone growth in face, hands and feet.
22
Q

What are GH concentrations like during life?

A
  • Birth is low
  • Increases and stays constant at childhood
  • Increases dramatically during puberty
  • Decline during adult life and old age
23
Q

What does IGF from the liver promote?

A

→ Increase somatic cell growth
→ Increase chondrocyte function (cartilage in bones)
→ Increase bone modelling

24
Q

How does IGF get produced?

A

→ GH released from somatotropes
→ GH acts on liver and increases gluconeogenesis
→ Increases IGF

25
Q

What secretes GH?

A

Somatotropes

26
Q

When blood glucose concentration is low, where does the body get its glucose from?

A

Glycogen stores/gluconeogenesis

27
Q

What is the brain dependent on?

A

Glucose

28
Q

Describe the cascade of TRH

A

→ Hypothalamic hormone TRH changed into TSH in the anterior pituitary
→ stimulates thyroid gland
→ thyroid produces thyroid hormones

29
Q

How does ADH get regulated?

A

→ Sensory neurons in the hypothalamus detect changes in ECF osmolality
→ passed on to magnocellular neurons (supraoptic)
→ increase or decrease in firing of magnocellular neurons
→ higher/lower release of ADH into the posterior pituitary

30
Q

What kind of hormones do the parvocellular nuclei release?

A
  • Trophic hormones
31
Q

What is the pathway of ADH?

A

→ Synthesized in the magnocellular nuclei
→ packaged into vesicles and transported along the axons
→ stored in axon terminals
→ released into the hypophyseal capillaries

SGUL - Physiology 1 (68 decks)

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