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Z YEAR 1 BRS Endocrinology > The pituitary gland > Flashcards

The pituitary gland Flashcards

1
Q

What is a hormone?

A

Hormone is a messenger: Carried from the organ where they are produced to the organ which they affect by means of the blood stream

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2
Q

Where are peptide hormones synthesised?

A

Synthesised as prohormones requiring further processing (e.g. cleavage) to activate

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3
Q

Where are peptide hormones stored?

A

Stored in vesicles (regulatory secretion)

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4
Q

What are the peptide hormones receptors?

A

Bind receptors on cell membrane and transduce signal using 2nd messenger systems

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5
Q

Where are synthesis hormones synthesised?

A

Synthesised in a series of reactions from cholesterol

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6
Q

Where are steroid hormones stored?

A

Released immediately (constitutive secretion

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7
Q

Where are the steroid hormone receptors?

A

Bind to intracellular receptors to change gene expression directly

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8
Q

Label the pituitary gland

A

ADD

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9
Q

What do hypothalamic parvocellular neurones regulate?

A

regulate anterior pituitary function

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10
Q

Describe the structure of hypothalamic parvocellular neurons

A

terminate on median eminence

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11
Q

What do hypothalamic parvocellular neurone release? How are they carried?

A
  • hypothalamic releasing/inhibitory factors into capillary plexus in median eminence
  • These hypothalamic regulatory factors carried by portal circulation to anterior pituitary
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12
Q

What are the two types of hormones?

A

Peptide and steroid

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13
Q

How is the anterior pituitary differ from the hypothalamus?

A

Anatomically distinct doom hypothalamus

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14
Q

What is the anterior pituitary made up of?

A 
-Endocrine cells
•Somatotrophs
•Lactotrophs
•Corticotrophs
•Thyrotrophs
•Gonadotrophs
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15
Q

What is the anterior pituitary regulated by?

A

Regulated by hypothalamic releasing/inhibiting factors via hypophyseal-pituitary portal system

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16
Q

What is the process of hypothalmo-pituitary system?

A
  1. Axon terminals of hypothalamic neurosecretory cells release hormones (RHs and IHs) into the
    hypothalamo-pituitary portal system
  2. The RHs and IHs travel in the portal system to the anterior pituitary
  3. The RHs and IHs stimulate or inhibit the release of hormones (black dots) from anterior pituitary cells
  4. Anterior pituitary hormones leave the gland via the blood
  5. These blood vessels constitute the hypothalamo-pituitary portal system
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17
Q

How is the hyoid hormone production regulated?

A
  1. Axon terminals of hypothalamic neurosecretory cells release Thyrotrophin Releasing Hormone (TRH) into
    hypothalamo-hypophysial portal system
  2. TRH travels in the portal system to the anterior pituitary
  3. TRH stimulates the release of Thyroid Stimulating Hormone (Thyrotrophin) from anterior pituitary thyrotrophs
  4. TSH leaves the gland via the blood to travel to the thyroid gland to stimulate thyroid hormone release (thyroxine)
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18
Q

What do somatotrophs produce? What are they regulated by?

A
  • Growth hormone (somatotrophin)
    1. Growth hormone relating hormone (witches on)
    2. Somastostatin (switches off)
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19
Q

What to lactrophs produce? What are they regulated by?

A

Prolactin (regulation is inhibitory)

1. Dopamine (inhibiting)

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20
Q

What to thyrotrophs produce? What are they regulated by?

A

TSH (thyoidtrophin)

1. Thyrotrophin realising hormone (stimulating)

21
Q

What do gonadotrophs produce? What are they regulated by?

A

LH and FSH

1. Gonadotrophin relasing hormone (stimulating)

22
Q

What do coricotrophs produce? What are they regulated by?

A

Adrenocortictrophic hormone ACTH, corticotrophin

1. Corticotrophin-relasing hormone (stimulating)

23
Q

Where are growth hormone receptors?

A

General body tissues (particularly liver)

24
Q

Where are prolactin receptors?

A

Breasts (lactating women)

25
Q

Where are thyrotrophin hormones?

A

Thyroid

26
Q

Where are gonadotrophins (LH and FSH) receptors?

A

Testes (males) Ovaries (females_

27
Q

Where are corticotrophin receptors?

A

Adrenal cortex

28
Q

What is bitemporal hemianopia?

A
  • Squishing optical chiasma
  • Lost peripheral vision
  • Sometimes patient unaware
  • Temporal field gone
29
Q

Why does bitemporal hemianopia happen?

A
  1. Fibres from the nasal (medial) retinae cross at the optic chiasm
  2. Compression of the optic chiasm by a pituitary tumour/suprasellar tumour prevents transmission of sensory information from lateral visual fields to the occipital lobe
30
Q

Describe the neuroendocrine reflex arc for milk production

A

less dopamine means more prolactin

  1. Mechanical stimulation of nipple & surrounding area activates afferent pathways
  2. Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurons
  3. Less dopamine in the hypothalamic-pituitary portal system causes less inhibition of anterior pituitary lactotrophs
  4. Increased plasma prolactin increases milk secretion in mammary glands
31
Q

What are the mechanisms of growth hormone action?

A
  • Works 2 ways one via intermediate
  • Binds to directly growth hormone receptors on skeleton
  • Also binds to growth hormone rectpros on liver which causes production of IGF-1 and IGF 2 (insulin like growth hormone factor) mostly IGF -1
  • Skeleton expresses IGF 1 receptors and GH receptors
32
Q

What is it when there are too much growth hormone?

A

Acromegaly (adults) - can’t actually get taller but other features e.g. hand
Gigantism (child)

33
Q

What are the symptoms of acromegaly?

A
  • Coarsening of facial features
  • Macroglossia
  • Prominent nose
  • Large jaw - prognathism
  • Increased hand and feet size
  • Sweatiness
  • Headache
34
Q

What are the posterior pituitary gland hormones?

A
  • Arginine vasopressin (AVP) (also known as Anti-diuretic hormone)
  • Oxytocin
35
Q

What is the relation between posterior pituitary and hypothalamus?

A

Posterior pituitary is anatomically continuous with hypothalamus

36
Q

What are the hypothalamic magnocellular neurones?

A

Hypothalamic magnocellular neurons:
•Long, originate in supraoptic (AVP) and paraventricular (oxytocin) hypothalamic nuclei
•Nuclei → stalk →posterior pituitary

37
Q

What is the regulation of the posterior pituitary gland?

A
  1. Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to the posterior pituitary
  2. Excitation of these hypothalamic magnocellular neurons stimulates release of AVP or oxytocin into the posterior pituitary where they diffuse into blood capillaries…
  3. …then leave the posterior pituitary via the blood
38
Q

What is the physiological action of vasopressin?

A

Stimualtion of water reabsporption in renal collecting duct and this concentrates urine

39
Q

How does vasopressin act? What are its other actions?

A
  • Acts through the V2 receptor in the kidney
  • Also a vasoconstrictor (via V1 receptor)
  • Stimulates ACTH release from anterior pituitary
40
Q

What is ADH?

A

Diuresis is production of urine

41
Q

How does vasopressin concentrate urine?

A
  1. AVP binds to receptor V2 in collecting duct
  2. This stimulates intracellular cascade which promotes movement of aqauporin-2 towards the membrane which is in contact with urine
  3. Water can flow from urine down concentration gradient into lumen cell and then water flows through Aquaporin-3 channels into plasma
42
Q

What are aquaporins?

A

-Water channels, allow passage of water through membrane

43
Q

What is the function of oxycotin in delivery of baby?

A
  1. Uterus at partition
  2. Myometrial cells
  3. Contraction
  4. Delivery of baby
44
Q

What is the function of oxycotin in milk ejection?

A
  1. Breast during lactation
  2. Myoepithelial cells
  3. Contraction
  4. Milk ejection
45
Q

Describe the neuroendocrine reface arc for milk ejection

A
  1. Mechanical stimulation of nipple & surrounding area activates afferent pathways
  2. Afferent signals integrated in the hypothalamus and stimulate oxytocin-releasing neuron activity
  3. Action potentials travel down oxytocin neurons and oxytocin is secreted into the bloodstream
  4. Increased plasma oxytocin increases milk ejection in mammary glands
    - Prolactin milk production, Oxycotin milk ejection
46
Q

What is the anterior pituitary gland referred to as?

A

Adenohypophysis

47
Q

What is the posterior pituitary gland referred to as?

A

Neurohypohysis

48
Q

What does the hypophyseal portal system do?

A

Connect hypothalamus and anterior pituitary

49
Q

What is secretion influenced by in anterior pituitary gland?

A

Secretion influenced by ‘releasing hormones’ and ‘inhibitory hormones’ released from hypothalamus

Z YEAR 1 BRS Endocrinology (8 decks)

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