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MEH > The Hypothalamic Pituitary Axis + Growth Hormone > Flashcards

The Hypothalamic Pituitary Axis + Growth Hormone Flashcards

(41 cards)

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1
Q

Location of the pituitary gland

A

Inferior to hypothalamus within the sella turcica of the sphenoid bone

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2
Q

What processes do the hypothalamus and pituitary gland modulate?

A

Body growth
Reproduction
Adrenal gland function
Water homeostasis
Milk secretion
Lactation
Thyroid gland function
Puberty

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3
Q

Why is the anterior part of the pituitary gland a gland but the posterior part isn’t?

A

Anterior - produces hormones it releases
Posterior - site of release

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4
Q

Embryological origin of anterior pituitary gland

A

Arises from evagination of oral ectoderm (primitive gut tissue)

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5
Q

Embryological origin of posterior pituitary

A

Originates from neuroectoderm (primitive brain tissue)

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6
Q

What connects the posterior pituitary to the hypothalamus?

A

Infundibulum

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7
Q

Outline the neurocrine function of the posterior pituitary

A
  • oxytocin and ADH are produced by neurosecretory cells in the supraoptic + paraventricular nuclei of the hypothalamus
  • hormones transported down the nerve cell axons to the posterior pituitary
  • stored + released to act on distant targets
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8
Q

Outline the synthesis, secretion, release and action of hormones acting on the anterior pituitary gland

A
  • hormones synthesised in hypothalamus
  • hormones transported down axons + stored in median eminence
  • released into hypophyseal portal system
  • hormones stimulate/inhibit target endocrine cells in anterior pituitary gland
  • effect distant cells - endocrine function
  • effect neighbouring cells - Paracrine function
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9
Q

What hormones are released from the posterior pituitary and what are their actions?

A

OT - oxytocin - milk let down + uterus contractions during birth
ADH - antidiuretic hormone/vasopressin - regulation of body water volume

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10
Q

What does it mean if a hormone is tropic?

A

Effects production and release of another hormone

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11
Q

What are the 6 tropic hormones produced in the hypothalamus

A

RH - releasing hormone
TRH - thyrotropin releasing hormone
CRH - corticotropin releasing horomone
GnRH - gonadotropin releasing hormone
GHRH - growth hormone releasing horomone

IH - inhibitory hormone
PIH - prolactin release-inhibiting hormone - dopamine
GHIH - growth hormone-inhibiting hormone/somatostatin

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12
Q

What hormones are produced by the anterior pituitary gland?

A

TSH - thyroid stimulating hormone
ACTH - adrenocorticotropic hormone
LH - luteinising hormone
FSH - follicle stimulating hormone
PRL - prolactin
GH - growth hormone

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13
Q

What is TRH and what does it act on?
What does this cause?

A
  • Thyrotropin releasing hormone
    .
  • Acts on thyroid stimulating hormone + (prolactin)
    .
  • Causes secretion of thyroid hormone (T3/4) from thyroid gland
  • (Causes mammary gland development and milk secretion (PRL))
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14
Q

What is CRH and what does it act on?
What does this cause?

A
  • Corticotropin releasing hormone
    .
  • Acts on adrenocorticotropic hormone (ACTH)
    .
  • Causes secretion of hormones e.g. cortisol from adrenal cortex
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15
Q

What is PIH and what does it act on?
What does this cause?

A
  • Prolactin release-inhibiting hormone - dopamine
    .
  • Acts on prolactin
    .
  • Causes a decrease in mammary gland development + milk secretion
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16
Q

What is GHRH and what does it act on?
What does this cause?

A
  • Growth hormone releasing hormone
    .
  • Acts on growth hormone
    .
  • Causes growth, energy metabolism + IGFs stimulation - insulin like growth factors
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17
Q

What is GHIH and what does it act on?
What does this cause?

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A
  • Growth hormone-inhibiting hormone - somatostain
    .
    Acts on growth hormone
    .
    Causes a decrease in growth + energy metabolism + IGF stimulation
18
Q

What is GnRH and what does it act on?
What does this cause?

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A
  • Gonadotropin releasing hormone
    .
  • Acts on luteinising hormone + follicle stimulating hormone
    .
  • Causes ovulation + secretion of sex hormones (LH)
  • Causes development of eggs + sperm (FSH)
19
Q

What is TSH and what is its action?
What is it produced by?

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A

Thyroid stimulating hormones

Causes secretion of T3+T4 from thyroid gland

Produced by anterior pituitary gland

20
Q

What is ACTH and what is its action?
What is it produced by?

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A

Adrenocorticotropic hormone

Causes secretion of hormones from adrenal cortex

Produced by anterior pituitary gland

21
Q

What is LH what is its action?
What is it produced by?

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A

Luteinising hormone

Causes ovulation and secretion of sex hormones

Produced by anterior pituitary gland

22
Q

What is FSH what is its action?
What is it produced by?

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A

Follicle stimulating hormone

Causes development of eggs an sperm

Produced by anterior pituitary gland

23
Q

What is PRL what is its action?
What is it produced by?

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A

Prolactin

Causes mammary gland development + milk secretion

Produced by anterior pituitary gland

24
Q

What is GH what is its action?
What is it produced by?

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A

Growth hormone

Causes growth, energy metabolism + IGF stimulation

Produced by anterior pituitary gland

25
What factors influence growth?
Hormones - growth hormone Environment Nutrition Genetics
26
Outline the HPA axis using cortisol as an example of a negative feedback loop
Stress > hypothalamus > CRH > anterior pituitary > ACTH > adrenal cortex > cortisol > target cells - High levels of cortisol will have negative feedback on anterior pituitary + hypothalamus to lower their production of ACTH + CRH to lower cortisol levels
27
What stimulates and inhibits growth hormone release?
Stimulated by GHRH Inhibited by somatostatin/GHIH
28
How do growth hormones exert their effects?
- indirectly via insulin like growth factors - in response to GH cells of the liver and skeletal muscle produce + secrete IGFs
29
Explain the role of GH + IGFs in bone development during childhood
- **GH**: stimulates long bone growth - **IGFs**: stimulate bone + cartilage growth
30
Explain the role of GH + IGFs in bone development during adulthood
- Help maintain muscle + bone mass - Promote healing + tissue repair - Modulating metabolism + body composition
31
How is GH secretion regulation by long loop negative feedback?
Mediated by **IGFs** - **inhibit release of GHRH** from hypothalamus - **stimulates the release of somatostatin/GHIH** from hypothalamus - **inhibit release of GH** from anterior pituitary
32
How is GH secretion regulation by long loop negative feedback?
Mediated by GH itself via stimulation of somatostatin/GHIH release
33
What does growth hormone deficiency result in?
**Pituitary dwarfism** - proportionate type of dwarfism due to partial or complete deficiency
34
What does excess growth hormone in childrenhood cause?
Gigantism
35
What does excess growth hormone in childrenhood cause in adulthood?
Acromegaly Large extremities: hands, feet + lower jaw
36
How does GH exert its effects on cells?
**GH receptors activate Janus kinases** JAKs - GH binds to GHR - JAK activated - cross phosphorylation of JAK - phosphorylation of GHR - activates signalling pathway > IGR production
37
Actions of the 2 growth factors in mammals
IGF1- main growth factor in adults IGF2- mainly involved in fetal growth
38
What are the three ways IGFs communicate?
Paracrine Autocrine Endocrine
39
IGFs act through IGF receptors to modulate what?
- hypertrophy - hyperplasia - increase in the rate of protein synthesis - increase in the rate of lipolysis in adipose tissue
40
What other hormones influence growth?
Insulin Thyroid hormones Androgens Estrogens Glucocorticoids
41
What organ produces IGFs?
Liver

MEH (23 decks)

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