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Metabolism 2 > Hypothalamus and Pituitary > Flashcards

Hypothalamus and Pituitary Flashcards

1
Q

describe generally the HPA axis

A

Generally a stimulus will cause the Hypothalamus
to secrete a hormone

This will cause the pituitary to secrete a hormone

This will act on a target organ which may or may
not secrete another hormone

The final hormone produced will cause an effect

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2
Q

what is the pituitary gland composed of

A

anterior

posterior

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3
Q

what is the anterior lobe of the pituitary derived from

A

Anterior derived from the upward migration from the roof of the mouth called the Rathke’s pouch

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4
Q

what is the posterior lobe of the pituitary derived fro m

A

Posterior derived from the downward migration of the neuroectoderm from the diencephalon.

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5
Q

what lobe of the pituitary is directly connected to the hypothalamus

A

posterior via the infindubulum

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6
Q

what hormones does the anterior pituitary release

A

Thyroid Stimulating Hormone (TSH)

Prolactin (PRL)

Growth Hormone (GH)

Follicle Stimulating Hormone (FSH)

Luteinising Hormone (LH)

Adrenocorticotropic hormone (ACTH)

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7
Q

what hormones from the hypothalamus stimulate the hormones in the anterior pituitary

A

Thyroid Releasing Hormone (TRH) → TSH - this causes the adrenals to produce T4 and T3 ( I inhibited by SS)

Nipple suckling → PRL - this causes milk glands immunosystem (inhibited by dopamine)

Growth Hormone Releasing Hormone (GHRH) → GH (inhibited by SS)

Gonadotrophin Releasing Hormone (GnRH) and kisspeptin → FSH - this causes sex steroids, inhibin, ovulation, spermatogenesis

Gonadotrophin Releasing Hormone (GnRH) and kisspeptin → LH - this causes sex steroids, inhibin, ovulation, spermatogenesis

Corticotrophin Releasing Hormone (CRH) → ACTH - this produces cortisol in the adrenals

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8
Q

what does the posterior pituitary hormone release

A

ADH

oxytocin

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9
Q

where are the posterior pituitary hormones produced

A
  • they are produced in the hypothalamus
  • ADH in the supraoptic nuclei
  • oxytocin in the paraventricular nuclei
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10
Q

describe the blood supply to the pituitary

A
  • supplied by the superior hypophyseal artery

anterior pituitary

  • superior hypophyseal artery goes and forms a primary plexus
  • this goes down via hypophyseal portal veins
  • this goes into a secondary plexus where the hormones are secreted into the blood

posterior pituitary
- this is attached to the anterior pituitary via short blood vessels, therefore posterior pituitary can influence the anterior pituitary

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11
Q

what is negative feedback

A

Thyroid Releasing Hormone (TRH) → TSH

Nipple suckling → PRL

Growth Hormone Releasing Hormone (GHRH) → GH

Gonadotrophin Releasing Hormone (GnRH) → FSH

Gonadotrophin Releasing Hormone (GnRH) → LH

Corticotrophin Releasing Hormone (CRH) → ACTH

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12
Q

what happens if too much hormone is produced

A

If too much hormone is produce by the target
organ, this causes inhibition of pituitary and
hypothalamus hormone

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13
Q

what happens if too little hormone is produced

A

If too little hormone is produced by the target
organ, this stimulates the hypothalamus to
produce its hormone which in turn will stimulate
the pituitary and so on.

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14
Q

Describe how G protein works

A
  • on a G protein alpha subunit is attached to a gamma and beta subunit
  • when the ligament binds to the G protein this causes it to become phosphorylated so GDP is converted to GTP
  • this causes the alpha subunit to detach
  • alpha subunit then binds to adenyl cycle
  • this causes ATP to convert to cAMP
  • this increases the activity of PKA
  • this causes the cell response
  • after the ligand leaves GTP is converted back to GDP this causes alpha subunit to bind to the gamma and beta subunit again
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15
Q

what does ADH do

A
  • increase the number of aquaporins in the collecting duct s
  • this increases the amount of water reabsorption
  • works via a G protein
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16
Q

which artery do the hypophyseal arteries branch from

A

internal carotid artery

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17
Q

what inhibits prolactin

A

dopamine

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18
Q

what does prolactin inhibit

A

GnRH

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19
Q

what two hormones does somatostatin inhibit

A

GH

TSH

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20
Q

why is there an increase in TSH in hypothyrosdim

A
  • due to negative feedback

- there is low T3/T4 this stimulates the production of TSH

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21
Q

the stimulus of nipple sucking causes the production of which two hormones

A

oxytocin and prolactin

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22
Q

which hormone stimulate the production of GnRH

A

kisspeptin

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23
Q

what is the final hormone that is produced to stimulate growth

A

IGF-1

24
Q

how do the posterior pituitary organs cause their effect on their target organs

A

Neurones

25
Q

what does the hypothalamus regulate

A
  • Pituitary function
  • Feeding (appetite and satiety)
  • Stress response
  • Water balance
  • Sleep-wake cycle
  • Thermoregulation
  • Emotions
26
Q

Name some nuclei of the hypothalamus

A
  • paraventricular
  • anterior
  • Supraoptic
  • Dorsomedial
  • Ventromedial
  • Arcuate
  • Posterior
  • Mamillary body
27
Q

what does the pituitary gland sit in

A

sella turicia

28
Q

what happens when the pituitary has a tumour to the eyesight

A

can get a bitemporal hemianopia

29
Q

what is a bitemproal hemianopia

A

Bitemporal hemianopia = loss of vision in the outer halves of both eyes.

30
Q

what is the drug used to replace ADH

A

Desmopressin

31
Q

describe how the thyroid axis works

A
  • hypothalamus produces TRH
  • TRH activates the anterior pituitary gland to produce TSH
  • TSH causes the production of thyroxine in the adrenal gland
  • thyroxine(T4) casques liothyroonine(T3) to be produced
  • when thyroxine increases beyond a certain level this inhibits TRH and TSH
32
Q

what is primary under activity

A

this is when the target hormone doesn’t get produces so causes an increase in the hypothalamus stimulatory hormone and an increase in the pituitary hormone that is being produced

33
Q

what is secondary under activity

A

this is when the pituitary hormone does release its releasing hormone

  • this results in a decrease in the hormone being released by the target hormone
  • therefore resulting in a increase in hypothalamus stimulatory hormone
34
Q

what is primary overactivity

A
  • this is when there is a tumour at the target organ, this causes an increase in the target hormone
  • this would cause a decrease in the pituitary hormone and hypothalamus stimulating hormone
35
Q

what is secondary overactivity

A
  • this is when there is an tumour on the pituitary gland
  • causes increase in pituitary hormone which causes an increase in the target hormone
  • this causes a decrease in the hypothalamus stimulatory hormone
36
Q

describe how the GH axis works

A

 GH is stimulated by GHRH, and ghrelin.
 Ghrelin also stimulates GHRH.
- GH activates SS production
- when SS is too high it inhibits GH production
 GH stimulates IGF production in the liver.
 IGF inhibits GH and GHRH via negative feedback.
 IGF also stimulates SS to reduce GH levels by activating SS

37
Q

what is the role of GnRH

A
  • promote GH cell clusters for coordinated responses
  • increases GH cell number
  • increases GH synthesis
  • stimulates GH release
38
Q

what causes McCunae-Albright syndrome

A

 Caused by spontaneous mutation. ( R201 mutation)
– not inherited
= mosaic mutation - this means that not all the cells have the mutation
 Prevents downregulation of cAMP via GPCRs.

39
Q

what are the symptoms of McCunae-albright syndrome

A

hyper-functioning endocrine organs (goitre),

  • precocious puberty
  • hyperthyroid gotire
  • adrenal hyperplasia
  • somatotroph hyperplasia

bone deformities

Café-
au-lait skin pigmentation.

40
Q

describe how the adrenal axis works

A

 CRH and ADH stimulate ACTH.
 ACTH stimulates cortisol release from the adrenal glands.
 Cortisol inhibits CRH, ADH and ACTH all via negative feedback.

41
Q

describe how the HPA axis works

A
  • hypothalamus relates CRH and arginine vasopressin
  • CRH stimulates ACTH production
  • A little part of arginine-vasopressin causes ACTH production
  • ACTH is in the pituitary gland
  • ACTH causes production of cortisol in the adrenal gland
  • when cortisol rises too much it causes the inhibition of CRH, ACTH, Arginine vasopressin
42
Q

if there is
- too much cortisol
- too little cortisol
what is caused

A
  • Too much = Cushings

- too little = Addisons

43
Q

describe how the circadian rhythm is linked to cortisol

A

 Cortisol levels start to rise at about 3 am.
 Cortisol levels peak in the morning between 6-9 am.
 After this the levels start to decline throughout the whole day.

44
Q

what are the two types of Cushing syndrome

A
  • ACTH independent

- ACTH dependent

45
Q

describe ACTH independent cushings syndrome

A
  • ACTH levels are not being primarily impacted.
  • Issue with the axis lies downstream of the pituitary gland.
  • Adrenal tumour may be the cause or steroid use
  • Cortisol levels are raised.
46
Q

describe ACTH dependent Cushing syndrome

A
  • ACTH levels are being raised primarily.
  • Issue due to a pituitary defect, such as an adenoma.
  • Both ACTH and cortisol levels are increased.
47
Q

what are the symptoms of Cushing syndrome

A
  • Weight gain.
  • Muscle weakness.
  • Skin changes.
48
Q

describe how Addisons disease is caused

A

Decreased levels of cortisol,

lack of adrenal gland steroid production.

49
Q

describe the gonadal axis

A

 Kisspeptin stimulates GnRH in the hypothalamus.
 GnRH stimulates LH and FSH in the pituitary glands.
 Oestrogen and testosterone are then produced in the gonads.
 Oestrogen and testosterone inhibit kisspeptin and LH/FSH via negative feedback.
- they inhibit LH and FSH by inhibin

50
Q

what happens if there is continuous GnRH drive

A

Receptor desnsitisation – used therapeutically when gonadal axis needs to be inhibited
• Prostate cancer
• Breast cancer

51
Q

what is the function of oxytocin

A

• Social recognition
– “love hormone” • Pro-sociality
– For and maintain attachment bonds with others • Perceptual selectivity/social salience
– intranasal oxytocin increases gaze to the eye region

52
Q

what does absence of ADH cause

A 
- diabetes insipidus 
symtpoms 
- massive thirst 
- polyuria 
- nocutira 
- greater than 12 litres a day
53
Q

How does the prolactin axis works

A 
 Prolactin is stimulated
by nipple sucking and
also TRH.
 Dopamine inhibits PRL
release.
 Prolactin inhibits
GnRH to reduce
LH/FSH secretion.
 Prolactin matures
mammary glands and
helps produce milk.
54
Q

What is the transcription factor PUOF1 responsive for

A
  • development of TSH, GH, PRL
55
Q

what does a mutation in PUOF1 cause

A

severe dwarfism

Metabolism 2 (40 decks)

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