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Physiology exam 5 (shelby) > Lecture 68 > Flashcards

Lecture 68 Flashcards

1
Q

_______ controls thyroid hormone secretion?

A

Negative feedback

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2
Q

Negative feedback exerted predominantly at _______ to decrease TSH

A

anterior pituitary

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3
Q

_______ provides feedback

A

T3

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4
Q

TSh is tonically inhibited by _______ and _______ from hypothalamus

A

Dopamine and somatostatin

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5
Q

TSH can also be inhibited by?

A

cortisol and GH

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6
Q

Thyroid hormones decrease the sensitivity of the anterior pituitary to TRH thereby decreasing _______?

A

TSH secretion

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7
Q

Hypothalamic nuclei secrete TRH into

A

portal vessels

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8
Q

Negative feedback: Slightly pulsible TSH and fairly

A

steady T3 and T4

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9
Q

during fasting TSH response to TRH will

A

diminish and T3 falls (decrease metabolic rate)

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10
Q

TRH stimulates

A

TSH

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11
Q

Meal or cold exposure increases _______

A

T3 availability

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12
Q

T4 deiodinated equally to active T3 and rT3 within

A

tissues

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13
Q

if more thyroid hormone action needed, get more T3 relative to

A

rT3 and vise versa

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14
Q

_______ converts T4 to T3

A

5’ deiodinase

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15
Q

_______ converts T4 to rT3

A

5 deiodinase

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16
Q

starvation effects on conversion: inhibition of 5’ deiodinase

A

lower metabolism rate and O2 consumption

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17
Q

during starvation effects does the brain 5’ deiodinase get effected?

A

NO

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18
Q

during starvation effects the brain 5’ deiodinase does not get effected: more T3 if _______, less T3 if critically ill

A

cold

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19
Q

_______ are major sites of degradation of thyroid hormones

A

Liver, kidneys, skeletal muscle

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20
Q

some T4 excreted in

A

bile

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21
Q

How does T4 enter cells?

A

Facilitated diffusion

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22
Q

T4 is deiodinated to T3 where?

A

Inside cells

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23
Q

How is T4 deiodinated to T3 inside cells?

A

5’ deiodinase

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24
Q

T3 binds receptors within

A

nucleus of cell

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25
Q

T3- receptor complex binds to _______ on DNA to stimulate transcription of genes

A

Thyroid-regulatory element

26
Q

Translation and new synthesis of proteins tend to be tissue

A

specific depending on effect

27
Q

how can thyroid hormones enter cells?

A
  • Na/ K ATPase
  • Transport proteins
  • B1 adrenergic receptors
  • proteolytic enzymes
28
Q

Increased oxygen consumption and increased Na/ K ATPase is associated with

A

increased cell activity

29
Q

thyroid hormones increase cardiac output and pulse pressure (increased synthesis of

A

B-1 adrenergic receptors (Increase HR)

30
Q

effect of thyroid hormones on BMP: Increase

A

thermogenesis

31
Q

thyroid hormones increase supply of substrates for production of energy. Need substrates for oxidation. Increase _______?

A
  • Mobilize glucose
  • Gluconeogenesis
  • absorption of glucose from GIT
  • lipolysis
  • FFA oxidation
32
Q

how does thyroid hormones affect appetite, gut absorption and motility

A

Increases

33
Q

Thyroid hormones also increases mobilization of

A

carbs and fat

34
Q

Protein synthesis vs degradation dependent on thyroid hormone levels: If thyroid hormone levels are normal

A

protein synthesis predominates

35
Q

Protein synthesis vs degradation dependent on thyroid hormone levels: If thyroid hormone levels are high

A

protein degradation predominates AA for energy

36
Q

_______ is required for normal growth

A

Thyroid hormones

37
Q

Thyroid hormones act with GH and IGFs to promote?

A

Growth of bone, cartilage, teeth, epidermis and hair

38
Q

Thyroid hormones are essential for normal maturation of

A

CNS

39
Q

Thyroid hormones increase blood flow and glucose metabolism in the

A

brain

40
Q

Thyroid hormones enhance

A

peripheral nerve reflexes (activates skeletal muscles and deep tendon reflexes)

41
Q

Thyroid hormones interact with SNS to have similar effects on increasing

A

cardiac output and heat production etc.

42
Q

Thyroid hormones in the ANS activate

A

Smooth and cardiac muscle

43
Q

_______ is it when there is an overactive thyroid, excess thyroxine

A

Hyperthyroidism

44
Q

_______ are the clinical signs of hyperthyroidism

A

Increased metabolic rate, food intake, heat production, heart rate, weight loss, muscle weakness and atrophy

45
Q

Hyperthyroidism is common in?

A

Cats

46
Q

Hyperthyroidism is common in cats due to adenoma, adenocarcinoma and thyroid disruptors including

A

Flame retardants (thyroid disruptors)

47
Q

Hyperthyroidism is seen in horses and dogs usually do to?

A

Thyroid adenocarcinoma

48
Q

_______ is high in hyperthyroidism?

A

T3 and t4

49
Q

If hyper disorder is in thyroid gland, TSH is

A

LOW

50
Q

Over producing thyroid hormones lots of T3 for negative feedback so

A

TSH is inhibited

51
Q

If hyperthyroidism disorder is in hypothalamus or pituitary, TSH is

A

HIGH

52
Q

When hyper disorder in in hypothalamus or pituitary, TSH is high, over producing TSH constantly

A

stimulates thyroid hormones

53
Q

Typical blood for hyper tests show low _______ and high _______

A

TSH, T4

54
Q

underactive thyroid, low thyroid hormones

A

Hypothyroidism

55
Q

decrease metabolic rate, cardiac output, cold intolerance, decrease sweating, weight gain are signs of

A

Hypothyroidism

56
Q

Lacking enzymes to make thyroid hormones

A

Congenital cretinism - thyroid dwarf

57
Q

Acquired hypothyroidism is common id dogs, rare in cats or horses

A

Usually immune mediated or idiopathic ( destruction of gland or blocking hormone synthesis)

58
Q

T3 and T4 is _______ in hypothyroidism

A

low

59
Q

If issue is in hypothalamus or pituitary gland for central hypothyroidism (TSH is Low) Not producing TSH as normal so no stimulus for

A

T4/T3

60
Q

If issue is in thyroid gland, TSH is high (most common; overt primary hypothyroidism)

A

not producing thyroid hormones so pituitary constantly stimulating to produce TSH

61
Q

typical blood test for hypothyroidism shows

A

high TSH and low t4

62
Q

Only “healthy” animals should be tested for thyroid function, as overt illness can

A

alter circulating thyroid hormone concentration

Physiology exam 5 (shelby) (18 decks)

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