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BRS > The pituitary gland > Flashcards

The pituitary gland Flashcards

1
Q

What is a hormone?

A

A messenger
Carried from the organ which they’re produced in to target organ
2 types: peptide hormone and steroid hormone

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2
Q

How is a peptide hormone synthesised, where is it stored and what’s its receptor?

A

Synthesis: synthesised as pro hormones- need further processing to activate
Storage: Stored in vesicles (regulatory secretion)
Receptor: Bind on cell membrane and transduce signal using 2nd messenger systems

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3
Q

How is a steroid hormone synthesised, where is it stored and what’s its receptor?

A

Synthesis: synthesised in series of reactions from cholesterol
Storage: released immediately (constitutive secretion)
Receptor: Bind to intracellular receptors to change gene expression directly

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4
Q

What is the pituitary gland also known as?

A

The master gland

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5
Q

What structures make up the anterior pituitary?

A

Pars tubercles
Pars intermedia
Pars distalis

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6
Q

What structures make up the posterior pituitary?

A

Pars nervosa

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7
Q

What regulates anterior pituitary function?

A

Hypothalamic parvocellular neurones
They’re short- terminate on median eminence
Release hypothalamic releasing/ inhibitory hormones (RH/IH) into capillary plexus in median eminence

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8
Q

Where are hypothalamic regulatory factors (IH/ RH) carried to and how?

A

Carried by portal circulation to anterior pathways

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9
Q

What is the pituitary stalk also known as?

A

Infundibulum

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10
Q

What cells make up the anterior pituitary?

A 
Made up of endocrine cells: (GoTh CoLaS)
Gonadotrophs
Thyrotrophs
Corticotrophs
Lactotrophs
Somatotrophs
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11
Q

What is the hypothalamus- pituitary portal system?

A
  1. Axon terminals of hypothalamic neurosecretory cells release hormones (IHs and RHs) into hypothalamus- pituitary portal system
  2. The RHs and IHs travel in portal system to anterior pituitary
  3. RHs and IHs stimulate or inhibit the release of hormones from anterior pituitary cells
  4. Anterior pituitary hormones leave the gland via the blood
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12
Q

What do somatotrophs release and what stimulates them and what’s their target?

A

Release: Growth Hormone (somatotrophin)
Stimulated by: Growth hormone releasing hormone/ somatostatin (inhibits)
Target: Hepatocytes/Liver, bone, muscles

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13
Q

What do lactotrophs release and what stimulates them and what’s their target?

A

Release: Prolactin
Stimulated by: Dopamine (inhibits)
Target: Mammary glands

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14
Q

What do thyrotrophs release and what stimulates them and what’s their target and what’s their target?

A

Release: Thyroid Stimulating Hormone (thyrotrophin)
Stimulated by: Thyrotrophin releasing hormone
Target: Thyroid gland

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15
Q

What do gonadotrophs release and what stimulates them and what’s their target?

A

Release: Luitenising Hormone (LH) and Follicle Stimulating Hormone (FSH)
Stimulated by: gonadotrophin releasing hormone
Target: Gonads

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16
Q

What do corticotrophs release and what stimulates them and what’s their target?

A

Release: Adrenocorticotrophic hormone (ACTH, corticotrophin)
Stimulated by: Corticotrophin releasing hormone
Target: Adrenal cortex

17
Q

What does a pituitary tumour compressing the optic chiasm cause?

A

Bitemporal Hemianopia
Fibres from nasal retinae cross at optic chiasm
Compression of optic chasm by a pituitary tumour/ suprasellar tumour prevents transmission of sensory information from lateral visual fields to occipital lobes

18
Q

What is the neuroendocrine reflex arc (prolactin) and how does it cause milk production?

A
  1. mechanical stimulation of nipple and surrounding area activates afferent pathways
  2. Afferent signals integrated in the hypothalamus and inhibit dopamine release from dopaminergic neurones
  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
19
Q

What are mechanisms of growth hormone action?

A

2 mechanisms of growth:

  1. GH binds to GH receptors on bones and muscles
  2. … and binds to liver to form insulin-like growth factor (IGF-1 in post-natal growth) which stimulates growth
20
Q

What is acromegaly?

A

A disorder where theres excess growth hormone - too much somatotrophin
Does not result in increased height
Known as gigantism in children

21
Q

What are symptoms of acromegaly?

A 
Coarseing of facial features 
Macroglossia (big tongue)
Prominent nose
Large jaw- prognathism
Increased hand and feet size
Sweatiness
Headache
22
Q

What are the posterior pituitary gland hormones?

A 
Arginine Vasopressin (AVP) aka. anti-dietetic hormone
Oxytocin
23
Q

What are hypothalamic magnocellular neurones?

A

Long and originate in supraoptic (AVP) and paraventricular (Oxytocin) hypothalamic nuclei
Nuclei -> stalk -> pituitary

24
Q

How is the posterior pituitary regulated?

A
  1. Two sets of hypothalamic neurosecretory cells produce AVP and oxytocin and transport them to posterior pituitary
  2. Excitation of these hypothalamic magnocellular neurones stimulate release of AVP or oxytocin into the posterior pituitary where they diffuse into blood capillaries
  3. Then they leave the posterior pituitary via blood
25
Q

What are physiological actions of vasopressin?

A

Aka. anti-diuretic hormone (ADH)
Diuresis is the production of urine
ADH stimulates water resorption in collecting duct
This concentrates urine
Acts through V2 receptor in the kidney
Also a vasoconstrictor (via V1 receptor)
Stimulates ACTH release from anterior pituitary

26
Q

What is the action of oxytocin?

A

Acts on myometrial cells at the uterus (giving birth), causes contraction which allows delivery of baby
Acts on myoepithelial cells causing contraction of breast nipple and milk ejection

27
Q

What is the neuroendocrine reflex arc (oxytocin) and how does it cause milk production?

A
  1. mechanical stimulation of nipple and surrounding area activates afferent pathways
  2. Afferent signals integrated in the hypothalamus and stimulate oxytocin- releasing neurones activity
  3. APs travel down oxytocin neurones and oxytocin is secreted into bloodstream
  4. Increased plasma oxytocin increases milk ejection in mammary glands

BRS (60 decks)

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