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HUBS 191 > The hypothalamus, pituitary and growth hormone > Flashcards

The hypothalamus, pituitary and growth hormone Flashcards

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1
Q

where is the pituitary gland located and how big is it

A
  • about 1cm in diameter
  • located in the fossa of the Sella turcica of the sphenoid bone at the base of the brain
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2
Q

what important roles do the hypothalamus and pituitary gland play together

A
  1. in most aspects of growth
  2. development
  3. metabolism
  4. homeostasis
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3
Q

what are the 3 sections of the pituitary gland

A
  1. anterior pituitary (adenohypophysis)
  2. posterior pituitary (neurohypophysis)
  3. pars intermedius (intermediate lobe)
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4
Q

what is the anterior pituitary derived from

A

derived from epithelial tissue and accounts for around 75% of the pituitary gland

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5
Q

what are the 2 parts of the anterior pituitary

A
  1. pars distalis (the larger part)
  2. pars tuberalis which wraps around infundibulum superiorly
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6
Q

what is the posterior pituitary derived from

A

derived from neuroectoderm

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7
Q

what type of glial cells are posterior pituitary

A

pituicytes

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8
Q

what are the 2 parts of the posterior pituitary

A
  1. pars nervosa (larger bulbar portion)
  2. infundibulum (connecting with the hypothalamus of brain)
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9
Q

where is the pars intermedius

A

lies between the anterior and posterior lobes

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10
Q

what is the function of the pars intermedius

A

may produce melanocyre stimulating hormone (MSH) but mostly inactive in adult life

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11
Q

what are the 2 hormones that are synthesized by the hypothalamic neurons

A
  1. antidiuretic hormone (ADH)
  2. oxytocin (OXT)
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12
Q

where are the 2 hormones, antidiuretic hormone (ADH) and oxytocin (OXT), that are synthesized by the hypothalamic neurons

A

they are transported along axons within the infundibulum to the posterior lobe of the pituitary gland

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13
Q

what type of hormones are secreted by the hypothalamus

A

regulatory hormones

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14
Q

what is the function of regulatory hormones

A

control the secretory activities of endocrine cells in the anterior lobe of the pituitary gland

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15
Q

what is the function of the hormones that are secreted the anterior lobe of the pituitary gland

A

control the activities of endocrine cells in the thyroid gland, adrenal cortex and reproductive organs

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16
Q

what is does automatic center in the hypothalamus do

A

exert direct neural control over the endocrine cells of the adrenal medulla

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17
Q

what happens when the sympathetic division in the hypothalamus is activated

A

the adrenal medulla is stimulated directly and immediately
- the medulla of each adrenal gland secretes epinephrine and norepinephrine into the bloodstream

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18
Q

what are the components of the hypophyseal portal system

A
  1. capillary networks supplied by the superior hypophyseal artery
  2. portal vessels
  3. second capillary network
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19
Q

what hormones are released from the hypothalamic neurosecretory cell in the hypothalamic-hypophyseal portal system

A

releasing hormones and/or release inhibiting hormones are secreted from hypothalamic neurons in region of median eminence at base of hypothalamus

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20
Q

where do the RH OR RIH diffuse to in the hypothalamic-hypophyseal portal system

A

the primary capillary network (plexus) which is supplied by superior hypophyseal artery - branch of internal carotid

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21
Q

the _____ veins carry RH/RIH to where in the hypothalamic-hypophyseal portal system

A

the portal veins then carry RH/RIH to secondary capillary network in anterior pituitary

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22
Q

what does the RH/RIH do once it diffuses out of the secondary capillary system

A

they diffuse out of the plexus and stimulate or inhibit secretion of hormone from anterior pituitary cells

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23
Q

what happens to the hormones once it has been stimulated by RH/RIH diffused from secondary capillary system

A

the blood containing the hormone then drains into anterior hypophyseal veins to enter system circulation

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24
Q

what is the connection between hypothalamus and neurohypophysis

A
  • neurosecretory cells are located in supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus
  • they produce hormones ADH and oxytocin
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25
what happens to the ADH and oxytocin once it has been produced in the hypothalamus
it is packaged into secretory vesicles and transported along axons to terminals in posterior pituitary where they are stored
26
how are hormones released and where do they enter the hypothalamic-hypophyseal portal system
hormones are released by exocytosis when action potentials arrive at terminals and diffuse into capillary plexus of posterior pituitary
27
from where are the hormones for hypothalamic-hypophyseal portal system supplied
supplied by inferior hypophyseal arteries
28
from where are the hormones for hypothalamic-hypophyseal portal system drained
drained by posterior hypophyseal veins
29
what type of hormone is oxytocin
a peptide hormone
30
where is oxytocin synthesised
mostly in neurons of paraventricular nuclei
31
where is oxytocin stored
in nerve terminals in posterior pituitary
32
what stimulates oxytocin to release
1. stretching pf the cervix of the uterus during childbirth 2. infant suckling during breastfeeding
33
what muscles contract during childbirth
contraction of uterine smooth muscle
34
what cells are stimulated to produce milk while breastfeeding
myoepithelial cells in mammary glands
35
what type of hormone is antidiuretic hormone (ADH)
a peptide hormone - differs from oxytocin by 2 amino acids
36
where is ADH synthesised
synthesised mostly in neurons of SON
37
what stimulates the release of ADH
secreted in response to increased ECF osmolarity
38
what receptors triggers the release of the AP to release ADH
osmoreceptors
39
where does ADH travel to through the blood
the kidney
40
what function does ADH cause in the kidney once it binds to receptors on duct cells
increases water reabsorption
41
what does higher doses of ADH cause
constrict arterioles in the body and increases arterial pressure - hence vasopressin name
42
what is diabetes insipidus
a disease in which the secretion of or response to the pituitary hormone vasopressin is impaired, resulting in the production of very large quantities of dilute urine, often with dehydration and insatiable thirst.
43
what are 2 types of diabetes insipidus
1. neurogenic 2. nephrogenic
44
what is neurogenic diabetes insipidus
when an insufficient amount of ADH is secreted therefore large volumes of dilute urine is produced due to reduced water reabsorption by collecting ducts of nephrons in kidneys = DEHYDRATION
45
what could be the cause of neurogenic diabetes insipidus
may occur following trauma, injury or infection in region of hypothalamus and posterior pituitary
46
what is nephrogenic diabetes insipidus
- when the kidneys do not respond to the ADH being secreted - This leads to the production of large amounts of dilute urine and excessive thirst, potentially causing dehydration. - secondary to renal disease - genetic
47
what is SIADH
syndrome of inappropriate ADH secretion, when too much ADH is produced despite normal or increased blood volume when drinking lots of water and hyperthermia this can lead to hyperthermia
48
what is hemodilution
a medical procedure where some of a patient's blood is removed and replaced with a solution, typically a water-based solution, to dilute the blood and reduce the concentration of red blood cells.
49
what effect does thyrotropin-releasing hormone (TRH) have on the anterior pituitary
release of thyroid stimulating hormone (TSH)
50
what effect does corticotropin-releasing hormone (CRH) have on the anterior pituitary
release of adrenocorticotropin (ACTH)
51
what effect does growth hormone-releasing hormone (GHRH) have on the anterior pituitary
release of growth hormone (GH)
52
what effect does growth hormone inhibiting hormone (GHIH) have on the anterior pituitary
inhibition of growth hormone (GH) release
53
what effect does Gonadotropin releasing hormone (GnRH) have on the anterior pituitary
release of luteinizing hormone (LH) and follicle stimulating hormone (FSH)
54
what effect does prolactin releasing hormone have on the anterior pituitary
release of prolactin
55
what effect does prolactin inhibiting hormone (PIH) / dopamine have on the anterior pituitary
inhibition of prolactin (PRL) release
56
what type of hormone is human growth hormone (hGH)
protein hormone
57
where is the hGH produced
secreted by somatotrophs of the anterior pituitary in response to GHRH
58
what is the function of the hGH
promotes increased size of cells, number of cells, particularly muscle, bone and cartilage
59
what effect does hGH have during childhood and teenage years
increases growth rate of skeleton and muscles
60
what effect does hGH have during adulthood
helps to maintain mass of muscle and bones, and promote healing of injuries and tissue repair
61
what does hGH cause the liver to do
causes the liver to form proteins called somatomedins which mediate growth hormones effecrs
62
what is the most important somatomedin/Insulin-like growth factors (IGFs)
somatomedin c / insulin growth growth factor 1 (IGF-1) as most of the growth effects of GH are thought to result from it
63
what are the 3 metabolic effects of GH
1. promotes growth and protein synthesis when nutrition state is favorable 2. switches cell metabolism toward use of lipids as an energy source 3. GH attenuates (weaken) some of insulins actions
64
how does GH promote growth and protein synthesis when nutrition state is favorable
- increases amino acid transport in cells and promotes protein synthesis - increases cartilage, muscle and bone growth - increases cell size and number in many other tissues too
65
how does GH switch cell metabolism toward use of lipids as an energy source
- increases mobilization of fatty acids from adipose tissue (fasted state) - increased use of fatty acids as energy source for cells - glucose in blood available for cells that are more dependent on it as energy source
66
how does GH attenuate (weaken) some of insulins actions
- less glucose taken up from blood by muscles and adipose tissue - increased glucose released into blood by liver
67
how is GH secreted (pattern)
secreted in pulsatile manner with bursts every few hours, experiencing dual control via releasing and inhibiting factors
68
what factors does GHRH stimulate GH release as a response
- deep sleep - low blood glucose (hypoglycemia) - strenuous exercise - fasting or starvation - trauma or stress - testosterone or estrogen
69
what factors does GHIH reduce GH secretion as a response
- increased blood glucose - increased fatty acids in blood - increased somatomedins in blood - aging
70
what is dwarfism
GH disorder due to lack of GH during childhood
71
what is gigantism
GH disorder due to excess GH prior to closure of epiphyseal plates
72
what is Acromegaly
GH disorder due to excess GH secretion after epiphyseal
73
what are some acromegaly features
- increased muscle, bone and internal organ mass - large spade like hands - thickened frontal bone - kyphosis (humpback) - large tongue - large mandible - arthritis due to skeletal overgrowth - carpal tunnel syndrome - enlarged heart and high bp - hyperglycemia - visual disturbances (if due to tumor of pituitary)

HUBS 191 (34 decks)

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