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MD4001 Week 8 > 4. The hypothalamus-pituitary axis > Flashcards

4. The hypothalamus-pituitary axis Flashcards

1
Q

Ducts of endocrine gland?

A

There are none

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2
Q

Different types of secretion for endocrine glands?

A
  • Some hormones diffuse directly into capillaries to act on distant target organs (endocrine secretion)
  • Others are secreted and act more locally (paracrine secretion)
  • Still others act on themselves (autocrine secretion)
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3
Q

Discrete endocrine organs?

A

Thyroid
Pituitary
Adrenals

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4
Q

Endocrine organ associated with other tissues?

A

Pancreas

Mostly an exocrine organ, but does have some endocrine pockets

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5
Q

Endocrine glands are very vascular via…

A

fenestrated capillaries

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6
Q

Others endocrine glands are scattered within complex organs e.g.??

A

Ovary, kidney, gut

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7
Q

Major endocrine glands

A

Pineal gland
Pituitary glands
Adrenal: Made up of cortex and medulla
Thyroid gland
Thymus
Pancreas: Insulin and glucagon release as part of endocrine funciton
Ovary and testis: Produce sex steroids e.g. oestrogens, testosterone

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8
Q

Humoral control of endocrine secretion

A

Humoral: Response of glands to component of blood e.g. electrolyte/metabolite, which control hormone release.
E.g. Low Ca2+ in blood the thyroid gland receptors bind calcium and send signal to parathyroid gland. PTH secreted.
E.g. Diabetes

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9
Q

Neuronal signalling in endocrine secretion control

A

Neuronal signalling

Release of catecolamines from adrenal medulla due to ACh release from sympathetic nerve

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10
Q

Hormonal control of endocrine secretion?

A

The hypothalamus secretes hormones that…..
stimulate the ant pituitary gland to secrete hormones that …..
stimulate other endocrine gland to secrete hormones

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11
Q 
What are the hormones of the following endocrine glands:
•  HYPOTHALAMUS-PITUITARY AXIS 
•  ADRENAL CORTEX / MEDULLA
•  THYROID 
•  PARATHYROIDS 
•  PANCREAS
A
  • HYPOTHALAMUS-PITUITARY AXIS (>20 different endocrine and neuroendocrine hormones)
  • ADRENAL CORTEX / MEDULLA (glucocorMcoids, mineralocorticoids, catecholamines)
  • THYROID (thyroid hormones, calcitonin)
  • PARATHYROIDS (parathyroid hormone, PTH)
  • PANCREAS (insulin, glucagon, pancreaticpolypeptide, somatostatin)
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12
Q 
What are the hormones of the following endocrine glands:
GIT
Pineal galnd
Thymus
Gonads
A

GIT(CCK, GIP, GLP1&2, glicenMn, gastrin, bombesin, secretin, VIP, subs. P, guanylins)

Pineal (melatonin)

Thymus (thymopoietin)

Gonads (sex steroids, inhibins, activins)

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13
Q 
What are the hormones of the following endocrine glands:
Heart
Liver
Kidney
Adipose tissue
A

heart (natriuretic peptides, ANP, BNP)

Liver (insulin-like growth factors, leptin, angiotensinogen)

Kidney (erythropoietin, renin)

Adipose tissue (leptin)

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14
Q

Pituitary gland:
Enclosure?
Related to..
Lies posterior to..

A

Enclosed by the bony
sella turcica of the sphenoid

Related to cavernous sinus and optic chiasmsa

Lies immediately posterior to the optic chiasma and sphenoid sinus

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15
Q

Other name of pituitary gland.

A

Hypophysis

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16
Q

Two divisions of the pituitary gland?

A

Posterior pituitary

  • Posterior lobe
  • “Neurohypophysis”
  • Contains pituitary stalk

Anterior pituitary

  • Ant lobe
  • “adenohypophysis”
  • Made up of:
    1. Pars anterior (distalis)
    2. Pars tuberalis (PT)
    3. Pars intermedia
17
Q 
Pituitary Gland- pars intermedia:
Origin?
Position?
Contents?
Function?
A

Pars intermedia is derived from Rathke’s pouch
• is poorly developed in humans
• lies between and anterior and the posterior lobes of the
pituitary
• may contain colloid-filled, epithelial lined follicles
• function is obscure.
• numerous basophilic cells ….. there may be some
connection with the secretion of melanocyte stimulating hormone MSH??

18
Q

Embryonic development of the pituitary gland?

A

Ant pit:
An upgrowth of epithelium from the oral cavity (Rathke’s pouche)

Posterior pit:
Down-growth from the brain (infundibulum)

By week 3, section of the developing head shows development of Rathke’s pouch

By week 8, Rathke’s pouch loses contact with the oral cavity.

19
Q

Where do craniopharyngiomas develop?

A

Slow growing tumours may develop along the track of Rathke’s pouch

20
Q

What are the secretory cells found int he ant pit?

A

Chromophils:

  • Acidophils 65% GH and prolactin secretion
  • Basophils 35% secrete the others.

Chromophobes don’t take up stain

(Secretory cells classified based on how they take up stain)

21
Q

Different nuclei of the hypothalamus?

A 
Arcuate nucleus
Supraoptic n.
Infundibular n.
Vestiomedial n.
Suprachiasmix nucleus
Posterior nucleus
Dorsomedial nucleus
paraventricular
22
Q

Difference between large-boaded and small-bodied nuclei in the hypothalamo-pituitary axis?

A

Large-bodied neurones:
Make AVP and OT and transport these hormones down their axons to post pit for release.

Small bodied neurones:
Make releasing hormones, transport these down their axons and secrete them into the primary capillary plexuses

23
Q

What are the neurohormones released the control the anterior pit?

A

TRH: Thryotropin-releasing hormone

CRH: Corticotrophin-releasing hormone

GHRH: Growth hormone-releasing hormone (or SRH, somatotrophin releasing hormone)

GnRH: Gonadotropin-releasing hormone (or FSH or LH-RH)

PRF: Prolactin releasing factor aka TRH

PIF: Prolactin released Inhibiting Factor aka Dopamine

24
Q

What are the neurohormones released that control the posterior pit?

A

Vasopressin (VP) or ADH

Oxytocin (OT)

25
Q

What are the hormones that are released from the ant pit?

A
  1. Trophic hormones

2. Hormones acting on peripheral target cells

26
Q

Hormones released from the anterior pituitary?

A 
The anterior pituitary contains a number of secretory cells that release hormones, the main ones being:
adrenocorticotrophic hormone (ACTH)
thyroid stimulating hormone (TSH)
growth hormone (GH)
follicle stimulating hormone (FSH)
luteinising hormone (LH)
prolactin (PRL)
27
Q

What stimulates hormone release from anterior pituitary?

Eg’s

A

Peptide hormones secreted by nerve cells in they hypothalamus.
Travel via vessels in the pituitary stalk to pituitary secretory cells.
E.g.
1. Corticotrophin releasing hormone (CRH) + Vasopression –> ACTH release
2. Thyrotrophin releasing hormone (TRH) –> TSH release
3. GnRH –> FSH and LH release
4. Growth Hormone Releasing Hormone (GHRH) –> GH release
5. Thyrotrophin releasing hormone (TSH) –> Prolactin release

28
Q

What makes up the parvicellular system?

What is it?

A

The negative feedback exerted to hypothalamus parvicellular cells from the target cells of the ANTERIOR pituitary

Three main axes involving the hypothalamus and pituitary:

  1. Hypothalamo-pituitary-adrenal axis (HPA axis)
  2. Hypothalamo-pituitary-thyroid axis (HPT)
  3. Hypothalamo-pituitary-gonadal axis (HPG axis).
29
Q

What is the hypothalamo-pituitary axis for the posterior pituitary?

A

Nerves originating in the supraoptic nuclei and the paraventricular nuclei of the hypothalamus produce oxytocin and vasopressin. These hormones are transported down the nerve cells to the posterior pituitary where they are then released into the bloodstream to affect their target organs. This is known as the MAGNOCELLULAR system.

30
Q

Causes for vasopressin release?

A 
Stress
Trauma
Injury
Increase osmotic pressure of blood
Decreased BV
Decreased O2 in blood
Increase CO2 in blood
31
Q

Causes for oxytocin release?

A

Suckling stimulation

Vaginal stimulation

MD4001 Week 8 (7 decks)

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