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Physiology exam 5 (shelby) > Lecture 67 > Flashcards

Lecture 67 Flashcards

1
Q

_______ two hormones does the thyroid gland produce?

A

T3 and T4

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2
Q

Overall function of T3 and T4: Increase rate of basal oxygen use, _______, and rate of heat production

A

Basal metabolism

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3
Q

Overall function of T3 and T4: Modulate delivery of substrates and oxygen by

A

cardiovascular and respiratory systems to sustain metabolic rate

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4
Q

_______ does thyroid hormone levels change based on?

A

Energy need, calorie supply and environmental temperature

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5
Q

_______ do you need for hormone thyroid synthesis?

A

2 tyrosines and iodine

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6
Q

_______ is the major thyroid hormone produced?

A

3, 5, 3’, 5’ Tetraiodothyronine (thyroxine, T4)

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7
Q

Thyroxine functions as a circulating _______

A

prohormone

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8
Q

_______ is the thyroid hormone that is secreted in lesser quanitity

A

3,5,3’- triiodothyronine (T3)

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9
Q

_______ is the biologically active hormone?

A

T3

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10
Q

_______ is the T4 hormone?

A

3, 5, 3’, 5’ - Tetraiodothyronine

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11
Q

_______ is the T3 hormone?

A

3,5,3’- triiodothyronine

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12
Q

T3 provides all thyroid hormone activity in

A

target cells

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13
Q

_______ converts T4 to T3

A

5’-deiodinase enzyme

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14
Q

alternative product of T4 (inactive form of T3)

A

Reverse T3

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15
Q

when is reverse T3 produced?

A

when less thyroid hormone action needed

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16
Q

Thyroid gland structure: single layered circular follicles comprised of _______ surrounded by a basement membrane

A

Cuboidal endocrine cells

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17
Q

Thyroid gland structure: Lumen of follicle contains _______?

A

Colloid material

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18
Q

Colloid material is newly synthesized, stored hormones which are attached to _______?

A

thyroglobulin

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19
Q

under stimulation, colloidal thyroid hormones are absorbed into?

A

follicular cells

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20
Q

Parafollicular cells (C cells) secrete _______?

A

Calcitonin

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21
Q

how is iodine supplied for thyroid synthesis?

A

by the diet

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22
Q

Synthesis of hormones is partially

A

intracellular and extracellular

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23
Q

Where are hormones stored?

A

Extracellularly in follicular lumen until stimulated to secrete

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24
Q

T4 is _______ but T3 is biologically active

A

hormone secreted

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25
Q

Step 1 in thyroid synthesis: Need to synthesize protein molecule called?

A

Thyroglobulin

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26
Q

_______ is needed to synthesize thyroglobulin

A

tyrosine

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27
Q

where is thyroglobulin synthesized?

A

on rough ER and golgi of follicular cells and put into follicular lumen

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28
Q

Step 2 in synthesis of thyroid hormones: Iodide transported from blood into follicular epithelial cells via?

A

2 Na/ 1 I symporter

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29
Q

Iodide transported from blood into follicular epithelial cells via 2 Na/ 1 I symporter and the activity is regulated by?

A

iodine levels in diet ( Decrease in levels stimulate)

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30
Q

step 3 of thyroid synthesis: Iodide (I) transported across apical membrane into colloid follicle via _______ and oxidized to iodine

A

Pendrin

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31
Q

step 3 of thyroid synthesis: Iodide (I) transported across apical membrane into colloid follicle via pendrin and oxidized to iodine via?

A

thyroid peroxidase

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32
Q

step 4 of thyroid synthesis: Iodide incorporated into tyrosines at specific sites in

A

thyroglobulin via thyroid peroxidase

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33
Q

step 5 of thyroid synthesis: coupling reaction results in?

A

MIT (monoiodotyrosine) and DIT (diiodotyrosine)

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34
Q

step 5 of thyroid synthesis: MIT and DIT remain attached to thyroglobulin until?

A

stimulus for secretion

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35
Q

Two DIT molecules (T3/T4)

A

T4

36
Q

is the synthesis of T3 or T4 faster?

A

T4 so most is T4

37
Q

One DIT and one MIT (T3/T4)

A

T3 (slower)

38
Q

ration of T4: T3 within gland is

A

10:1

39
Q

Transient reduction in thyroid hormone levels caused by ingestion of a large amount of iodine- last about 10 days

A

Wolff- Chaikoff effect

40
Q

Wolff- Chaikoff effect causes a large/small amount of iodine

A

LARGE

41
Q

Wolff- Chaikoff effect: Excessively high levels of dietary iodide will suppress activity of ?

A

2 Na/ 1 I pump

42
Q

_______ can you give short term to hyperthyroid cats?

A

Iodine short term

43
Q

_______ inhibits formation of hormones and release

A

autoregulatory

44
Q

wolff-chaikoff effect: Thryroid begins to resume normal function, iodine inside cells decrease and this stimulates synthesis to resume. _______ is this called?

A

Escape phenomenon

45
Q

amount of hormone produced and release rises initially with

A

T iodide

46
Q

amount of hormone produced and release rises initially with T iodide, but then intracellular iodide reaches a critical level which causes

A

hormone synthesis to stop

47
Q

Thyroglobulin stored in _______ until stimulation for release of thyroid hormones

A

follicles as colloid

48
Q

_______ is the stimulus for release of thyroid hormones?

A

TSH

49
Q

TSH stimulates retrieval of thyroglobulin from follicle lumen into endocrine cells via?

A

Endocytosis

50
Q

How does thyroglobulin get retrieved from follicle lumen by endocytosis?

A

cell membrane forms pseudopods and engulf pocket of colloid

51
Q

_______ fuse with colloid droplet to release T3, T4, free MIT and free thyroglobulin

A

Lysosomes

52
Q

T3 and T4 enter _______ after lysosomes fuse

A

blood

53
Q

_______ happens to MIT and DIT when lysosomes fuse the colloid droplets?

A

rapidly deiodinated by deiodinase

54
Q

why is MIT and DIT rapidly deiodinated by deiodinase?

A

to conserve iodide for recycling

55
Q

T4 has a long circulating pool size but _______ about its half life?

A

LONG - 6 days

56
Q

T3 has a small pool but _______ about the half life?

A

short - 1 day

57
Q

do large or small breed dogs have more circulating T3 and t4?

A

Small breed

58
Q

Circulating T3 and T4 increase or decreases with age?

A

Decreases

59
Q

T3 and T4 are bound to _______ in circulation

A

protein

60
Q

One of these can bind one T4 or one T3

A

Thyroxine- binding globulin (TBG)

61
Q

Thyroxine- binding globulin (TBG) accounts for _______ of circulating T4 and T3 bound to it

A

70 percent

62
Q

_______ has a lower affinity for T4 and readily gives up T4 to tissues?

A

Transthyretin

63
Q

T3 and T4 can also bind to _______ to circulate

A

Albumin

64
Q

Proteins help to buffer against _______ in thyroid gland function

A

acute changes

65
Q

Increase or decrease in thyroid hormone output can be compensated for

A

binding or releasing from proteins

66
Q

Binding proteins can vary in?

A

Species

67
Q

A decrease in liver protein synthesis (hepatic failure) causes a decrease in?

A

TBG increasing circulating thyroid hormone and decrease hormone synthesis

68
Q

Circulating levels of T3 and T4 abnormal but thyroid gland appears okay. _______ is this?

A

Sick euthyroid syndrome

69
Q

T/F: Thyroid is functioning normally in sick euthyroid syndrome

A

T

70
Q

Sick euthyroid syndrome is due to a dysregulation of ?

A

Thyrotropic functioning feedback control

71
Q

T3 and T4 is (low/high) and rT3 is (low/high) in sick euthyroid syndrome

A

low, high

72
Q

_______ profile is common in severe disease down regulation of 5’ deiodinase

A

low T3 and t4, high rT3

73
Q

set point of thyroid _______ is changed in disease, illness and medication (alter binding protein)

A

homeostasis

74
Q

_______ can cause sick euthyroid syndrome?

A

Fasting/ starvation, stress (cortisol), catabolic disease (cancer), hepatic and renal disease

75
Q

Regulation of thyroid gland: Thyrotropin releasing hormone (TRH) is release from ?

A

hypothalamus

76
Q

Regulation of thyroid gland: when TRH is released from hypothalamus this causes release of TSH from?

A

Anterior pituitary

77
Q

regulation of thyroid gland: Once TSH is releases this causes release of T4 and t3 from?

A

Thyroid gland

78
Q

regulation of thyroid gland: Once T4 and T3 is released the _______ of T4 and T3 to anterior pituitary and hypothalamus

A

Negative feedback

79
Q

TRH is a _______ hormone

A

Tripeptide

80
Q

TSH is a _______ hormone with 2 subunits

A

Glycoprotein

81
Q

TSH has a _______ and _______ subunit

A

Alpha and beta

82
Q

TSH a-subunit is

A

non specific (part of LH and FSH)

83
Q

TSH B-subunit is

A

biologically active site

84
Q

TSH stimulated iodine transport, endocytosis of colloid, release of T3 and t4 from?

A

Thyroid gland

85
Q

a sustained exposure of TSH to the thyroid gland can cause

A

hyperplasia/ hypertrophy to follicular cells

86
Q

Gland atrophies have _______

A

Absence of TSH

87
Q

Stimulate iodine uptake increase thyroid hormone and blood flow

A

Trophic effects of TSH

Physiology exam 5 (shelby) (18 decks)

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