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SEM1 BIOSCIENCE > Case 4 > Flashcards

Case 4 Flashcards

1
Q

What is the structure of the GH receptor?

A

Homodimer

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2
Q

Through what mechanism does the GH receptor signal?

A

JAK-STAT

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3
Q

Outline the JAK-STAT receptor mechanism

A

GH binding causes homodimerisation
JAK domains transphosphorylate
STAT recruited and phosphorylated
Phosphorylated STAT- transcription factor

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4
Q

How would you describe the tyrosine kinase activity in GHR?

A

Associated activity

Enzyme associated

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5
Q

How would you describe the tyrosine kinase activity in IGF-1R?

A

Inherent activity

Enzyme domain

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6
Q

LH, TSH and FSH receptors are all examples of…

A

G protein coupled receptors

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7
Q

What are the major steps in GPCR activation?

A

GTP replaces GDP
a and by subunits dissociate
G protein activates adenylate cyclase
Cyclic AMP produced

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8
Q

What intracellular signalling pathways are activated by GPCR stimulation?

A

MAP kinase and PI3K pathways

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9
Q

What are myeoid cells?

A

Smooth muscles in seminiferous tubules that help move sperm towards the epididymis

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10
Q

‘Female, short stature, delayed puberty’

A

Turners syndrome 45X

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11
Q

‘Male, tall but not in puberty, low IQ’

A

Klinefelters syndrome 47XY

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12
Q

‘hypogonadism, lack of smell’

A 
Kallmans syndrome
Olfactory and (collateral) GnRH neurone damage
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13
Q

‘Headaches, vomit, fatigue, thrist, lack of growth’ (unisex)

A

Craniopharyngeoma

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14
Q

‘Lack of growth with sufficient IGF1 levels’

A

Hypothyroidism

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15
Q

What is cellular hypertrophy?

A

Increase in cellular protein synthesis causing an increase in size and functional capacity
A cellular response to trophic hormones

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16
Q

What is hyperplasia?

A

The enlargement of tissues directly as a result of an increase in cell division

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17
Q

What type of receptor is the IGF-1 receptor?

A

RTK

Integral enzymatic domain

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18
Q

Through what downstream pathway does IGF-1R signal?

A

MAP and PI3K

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19
Q

From where is GH released?

A

Somatotrophs in anterior pituitary

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20
Q

How is GH released?

A

Pulsatile frequency, mainly at night

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21
Q

What type of hormone is IGF-1?

A

Peptide hormone

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22
Q

Where is IGF-1 produced?

A

Liver and bone

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23
Q

What is the function of GH at the liver?

A

IGF-1 production

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24
Q

What is the function of GH at the bone/cartilage?

A

Stimulation of chondrocytes @ zone of proliferation

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25
Q

What is the function of GH on adipose tissue?

A

Increases lipolysis

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26
Q

What is the function of GH on muscle?

A

Increases protein synthesis

Increase in amino acid uptake

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27
Q

What is the function of IGF-1 on muscles?

A

Increases protein synthesis

Increase in amino acid uptake

28
Q

What is the function of IGF-1 on bone?

A

Increase in osteoblast and osteoclast activity

Increase in collagen I synthesis

29
Q

What is the function of IGF-1 on cartilage?

A

Stimulation of chondrocytes @ zone of proliferation

30
Q

What is the effect of IGF-1 on peripheral glucose uptake?

A

Stimulates preipheral glucose uptake

31
Q

Where is the IGF-1 receptor expressed?

A

In every cell hence IGF-1’s global growth promoting effects

32
Q

In what manner is IGF-1 produced?

A

Non-pulsatile

33
Q

In addition to IGF-1, what other protein is released upon GH binding to the liver?

A

Somatomedin

34
Q

How is GH release regulated?

A

Tight -ve feedback control
Somatomedin binds somatotrophs in anterior pituitary
Somatostatin released from hypothalamus
Somatostatin inhibits GH release from somatotrophs

35
Q

What hormone controls appetite?

A

Ghrelin

36
Q

What hormone controls the release of thyroid stimulating hormone?

A

Thyrotropin releasing hormone

37
Q

From where is TSH released?

A

Anterior pituitary

Thyrotrophs

38
Q

Outline the mechanism involved in the production of T3 and T4

A

Dietary iodide absorbed
Converted to Iodine
Thyroglobulin donates Tyrosine to form mono/diiodotyrosine in colloid cells

39
Q

What is the name of the protein that is transported in complex with Thyroxine hormones?

A

Thyroid binding globulin

40
Q

What is the difference between T3 and T4?

A

T4 - inactive

t3 - active

41
Q

What is the function of thyroid stimulating hormone?

A

Binds follicular cells

Stimulates production of T4 which is then converted into T3 to increase basal metabolic rate

42
Q

What type of receptor is the thyroid hormone receptor?

A

Intracellular

43
Q

To which region of the epiphyseal plate does t3 bind?

A

Region of hypertrophy

44
Q

What are the additional affects of t3?

A

Increased sensitivity to adrenaline (fight or flight response)

45
Q

How do testosterone and estrogen effect thyroxine production?

A

Increases the production of t3 and t4 by stimulating TSH release from anterior pituitary

46
Q

How do testosterone and estrogen effect GH and IGF-1 levels?

A

Stimulate GH production from somatotrophs (and hence IGF-1)

47
Q

What protein is necessary for GnRH protein production? What does this explain?

A

Leptin

Earlier puberty in high BMI children

48
Q

What are the effects of testosterone during puberty?

A

Penis, scrotum and testicular enlargement
Hair development on chest/axilla/genitals
Hypertrophy of laryngeal mucosa
Increased skin thickness

49
Q

LH stimulates what cell to produce testosterone?

A

Leydig

50
Q

What cells are responsive to FSH?

A

Sertoli

Causes SC’s to aid spermatogenesis

51
Q

What are the functions of the sertoli cells?

A

Nourishment of developing spermatocytes
Secretory functions
Phagocytosis of cytoplasm
Blood testes barrier

52
Q

What are the different stages of spermatogenesis?

A

Germline epithelia —spermatogonia – (mitosis) – primary spermatocyte – (meiosis I) – secondary spermatocyte – (meiosis II) – spermatid – (differentiation) – sperm cells

53
Q

From what cell type is estrogen secreted in males?

A

Sertoli

54
Q

What is thought to initiate puberty?

A

Kisspeptin

55
Q

How is a childs predicted adult height calculated?

A

(height of mother + height of father +/- 13cm for boy or girl) / 2

56
Q

What is the most accurate measurement of whether a child is growing well?

A

Calculate mid parental centile
Plot on target centile range graph
If more than 2 centiles away from mean, then child has abnormal growth pattern

57
Q

What cell types generate osteoblasts?

A

Osteoprogenitor cells (from mesenchymal stem cells)

58
Q

What are volkmanns canals?

A

Signalling channels in compact bone that run perpendicular to osteons

59
Q

What are the 3 types of cartilage?

A

Hyaline (precursor to bone)
Fibro (eg. vertebral discs)
Elastic (eg. epiglottis)

60
Q

What is articular cartilage?

A

A type of hyaline cartilage that lines the moving surfaces of a joint

61
Q

What collagen fibres are found in hyaline cartilage?

A

Type II collagen

62
Q

What are the five zones of the epiphyseal plate?

A

Reserve, proliferative, hypertrophy, calcification, newly formed bone

63
Q

Give two other names for spongy bone

A

Trabecullar

Cancellous

64
Q

What is appositional bone growth?

A

Bone growth in diameter due to bone formation beneath the periosteum

65
Q

What are the 6 steps involved in embryonic long bone development?

A

i. cartilage body development
ii. Bony collar formation (diaphysis)
iii. Chondrocyte hypertrophy and calcification
iv. Chondrocyte death and medullary cavity formation
v. Primary ossification centre formed
vi. Blood supply exploration (secondary ossification centre formation)

SEM1 BIOSCIENCE (9 decks)

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