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Endocrine physiology > The hypothalamus & pituitary gland > Flashcards

The hypothalamus & pituitary gland Flashcards

1
Q

Where is the hypothalamus arranged?

A

It is arranged** on both sides of the 3rd ventricle**

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2
Q

What are the different nuclei in the hypothalamus?

A
  • paraventricular (beside ventricle)
    * supraoptic (near optic nerve)
  • ventromedial
  • arcuate
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3
Q

what is a ‘nucleus’ in the CNS?

A

a cluster of neuronal cell bodies

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4
Q

Describe the** 2 types of hypothalmic neuroendocrine cells**?

A
  1. magnocellular - large cell bodies, long axons projecting down the posterior pituitary, release ADH and oxytocin, located at the paraventricular & supraoptic nuclei
  2. Parvocellular- small cell bodies, short axons projecting to the top of the pituitary stalk, secrete 6 hormones into the blood stream which are released into the hypophyseal portal circulation
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5
Q

What structure facilitates the connection between the hypothalamus and pituitary gland?

A

the pituitary stalk or infundibulum

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6
Q

what do peptidgeric neuroendocrine cells release?

A

peptide hormones

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7
Q

what is a ‘trophic’ hormone?

A
  • a hormone that **regulates the production of another hormone **
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8
Q

What are hypophysiotrophic hormones?

note hypophysis is another word for pituitary gland

A
  • they are hormones that regulate hormone production in the anterior lobe of the pituitary gland
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9
Q

What are the hypophysiotrophic hormones released by the hypothalamus?

A
  • GnRH - gonadotrophic releasing hormone
  • GHRH
  • somatostatin
  • CRH - corticotropin releasing hormone
  • dopamine
  • TRH - thyropin releasing hormone
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10
Q

what is Kallman’s syndrome?

what is it? what is it characterised by?

A
  • an inherited disorder of GnRH deficiency
  • KAL1 gene mutations interefere with normal migration of GnRH from hypothalamus during development
  • characterised by hypogonadotrophic hypogonadism (HH), infertility, absent/partial pubertal maturation, anosmia
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11
Q

Describe the functional histology of the neurohypophysis (ie the posterior pituitary lobe)

A
  • there are unmyelinated nerve axons whose cll bodies are located in the hypothalamus
  • there are** glial cells called pituicytes**
  • there are** herring bodies** (swellings along the axon) that contain ADH and oxytocin
  • high degree of vascularity - fenestrated capillaries (allowing easy movement of peptides in and out of the nuclei)
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12
Q

what 2 different receptors does ADH act on?

A
  • V1 receptors - vascular smooth muscle cells, activation leads to contraction
  • V2 receptors - renal tubule epithelial cells - the activation of these receptors leads to increased renal H20 reabsorption
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13
Q

How does plasma osmolality relate to ADH?

A
  • As the plasma osmolality increasee above 280mOsm/Kg, it is becoming more concentrated and ADH is secreted
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14
Q

what 3 stimuli control ADH release?

A
  1. a plasma osmolality above 280mOsm/kg
  2. hypovolemia (reduced blood volume) - activates strial stretch receptors
  3. hypotension (low BP) - activation carotid & aortic baroreceptors
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15
Q

Describe the **mechanism of ADH **on renal tubule epithelial cells

A
  • vasopressin binds to the membrane receptor (V2) on basolateral membrane
  • receptor then activates cAMP second messanger system
  • cell inserts** AQP2 water pores **into the apical membrane
  • water is absorbed via osmosis into the blood
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16
Q

What is an example of a disease that involves an ADH deficiency & what are the 2 types of the disease??

A
  • Diabetes Insipidus
    there are 2 types
    1. **neural **- no production of ADH - may be due to hypothalamus lesion
    2. nephrogenic - resistance to ADH - either by mutations in V2 receptor (inherited) or aquired- drug induced
17
Q

what is an example of a drug that can cause ADH defiency?

A

amphotericin B

18
Q

What** value of urine osmolality **indicates diabetes insipidus after a water deprivation test?

A
  • if after water deprivation test, the urine osmolality is greater than 600mOsm/Kg, DI is excluded
  • if urine osmolality is under 400mOsm/Kg after water deprivation test, this indicates DI
19
Q

What is the syndrome of inappropiate antidiuretic hormone secretion (SIADH)

A
  • a disease that involves excessive secretion of ADH despite a normal or increased plasma volume
  • it can be associated with GIT or lung tumours (that are also secreting ADH)
20
Q

what are the consequences of SIADH?

A
  • increased water reabsorption
  • increased urine osmolality
  • hyponatremia (conc of Na+ is low)
  • plasma hypo-osmolality
21
Q

what are the** physiological roles of oxytocin**?

A
  • child birth
  • lactation
  • social/mating
  • emotional behaviour
22
Q

How does oxytocin cause lactation (briefly explain)

A
  • oxytocin stimulates** myoepithelial contractions **to expel milk from the mammary alveoli into ducts/ collecting chamber
  • called the milk let down reflex
23
Q

What is oxytocin’s role in child birth?

A
  • stimulates the** uterus to contract**
  • may be used to induce labour
  • positive feedback mechanism (furgerson reflex) - ie oxytocin triggers more oxytocin production
24
Q

what other roles does oxytocin have (other than lactation & birth)

A
  • involved in maternal nurturing behaviour postpartum
  • reduces fear and anxiety
  • promotes trust & empathy
25
Q

what is a primary endocrine disorder?

A
  • disorders of the peipheral endocrine gland itself eg thyroid / adrenal
26
Q

what is a secondary endocrine disorder?

A

disorders of the pituitary or hypothalamus causing under or over stimulation of peripheral endocrine glands

27
Q

what kind of symptoms are presented with a hypothalamus/ pituitary gland disorder?

A
  • symptoms of a **deficiency or excess **of one or more of the hormone they produce
    *** neurological symptoms **eg headaches or visual disturbances from tumours of these glands
28
Q

what could be concluded if the the hormone is stimulated but levels dont rise?

A

there must be a problem with the production of that hormone

29
Q

what steps can be taken if a tumour is suspected?

A

*** usually MRI imaging **is used to detect / determine the location of the tumour
* this also determines if the tumour is suitable for surgery

30
Q

what are the different types of treatment used for** pituitary/hypothalamus disorders**?

A
  1. replacement hormones eg for deficiency problems
  2. surgery or radiotherapy for tumours
  3. drugs that inhibit hormone production - when surgery isnt suitable

Endocrine physiology (19 decks)

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