Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology Exam 3 > Lecture 61-Thyroid Hormones 1 > Flashcards

Lecture 61-Thyroid Hormones 1 Flashcards

1
Q

What are the two hormones the thyroid produces?

A

Thyroxine (T4)
Triiodothyronine (T3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do thyroid hormone levels change based on?

A

-energy need
-calorie supply
-environmental temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the overall functions of T3 and T4?

A

-increase rate of basal oxygen use, basal metabolism, and rate of head production
-modulate deliver of substrates and oxygen by cardiovascular and respiratory systems to sustain metabolic rate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do you need for thyroid hormone synthesis?

A

2 tyrosines
Iodine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the MAJOR thyroid hormone produced?

A

3,5,3’,5’-tetraiodothyronine

Thyroxine , T4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Which thyroid hormone is produced in lesser quantity?

A

3, 5, 3’ triiodothyronine (T3)

Biologically active hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which hormone is produced when less thyroid hormone action is needed? What is this an alternative product of?

A

Referees T3

this is an alternative product of T4 (inactive form of T3)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the thyroid gland structure?

A

-Single-layered circular follicles

-lumen of follicles = newly synthesized, stored hormones are attached to thyroglobulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Under stimulation what happens to colloidal thyroid hormone?

A

Absorbed into follicular cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do parafollicular cells (C cells) secrete?

A

Calcitonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

____ is major hormone secreted, but _____ is biologically active thyroid hormone.

A

T4

T3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where are hormones stored?

A

Stored extracellularly in follicular lumen until stimulated to secrete

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Synthesis of hormones is partially _______ and partially _______.

A

Intracellulär and extracellular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

For thyroid hormone synthesis to occur you need large amounts of?

A

Iodine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the steps in synthesis of thyroid hormones?

A
  1. Need to synthesize protein—Thyroglobulin
  2. Iodine transported from blood into follicular epithelial cells via 2 Na+/1 I- symporter
  3. Iodine transported across apical membrane into colloid of follicle via pendrin and oxidized to iodine
  4. Iodine incorporated into tyrosines at specific sites in thyroglobin via thyroid peroxidase
  5. Coupling reaction—results in MIT (monoiodotryosine) and DIT (diiodotryosine)
  6. Two DIT molecules = T4
  7. One DIT + one MIT = T3
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the ratio of T4:T3 within the thyroid gland?

A

10:1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where is thyroglobulin synthesized?

A

Rough ER and golgi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What regulated the 2 Na/1 I- symporter?

A

Dietary iodide

**low levels stimulate more activity!

19
Q

What enzyme oxidizes iodide to iodine?

A

Thyroid peroxidase

20
Q

One DIT + one MIT = T3

Faster or slower than …

Two DIT molecules = T4

A

T4 is the fastest reaction

21
Q

What are T3 and T4 catalyzed by?

A

Thyroid paroxidase

22
Q

(TRUE/FALSE) Not all MIT and DIT make hormones—leftover stays attached to thyroglobulin

A

True

23
Q

What will high levels of dietary iodine suppress activity of?

A

2 Na/1 I- pump

24
Q

What is the Wolff-Chaikoff effect?

A

Amount of hormone produced and released increases intimacy with increase iodide in diet -> intracellular iodide reaches a critical level -> hormone synthesis stops

25
Q

What is the escape phenomenon?

A

The thyroid begins to resume to normal function when the iodine levels decrease inside cells to down regulation of transporter, and resume synthesis

26
Q

Where is thyroglobulin stored?

A

Stored in follicles as colloid until stimulation for release of thyroid hormones

27
Q

How is thyroglobulin retrieved from the follicle lumen into the endocrine cell?

A

Endocytosis

Engulf a pocket of colloid, pinched off cell membrane

28
Q

When lysosomes fuse with colloid droplets, what do they release?

A

T3, T4 and free MIT and free DIT

29
Q

When a stimulus is received for the release of thyroid hormones, what happens to MIT and DIT?

A

Gets released rapidly and deodinated by deiondinase enzyme to recycle iodine

30
Q

____ circulating pool size of T4, and _____ half-life

____ circulating pool size of T3, and _____ half-life

A

Large, long

Small, short

31
Q

What are the (4) circulate bound to proteins?

A
  1. Thyroxine-binding globulin (TBG) -> THIS ONE IS IMPORTANT BC 70% OF HORMONE IS BOUND TO THIS
  2. Transthyretin
  3. Albumin
  4. Proteins help to buffer against acute changes in thyroid gland function
32
Q

What effect does hepatic failure have on circulating thyroid hormone?

A

Decrease hepatic protein synthesis -> less TGB -> transient increase in circulating hormones -> transient decrease in hormone synthesis

33
Q

What is sick euthyroid syndrome?

A

circulating levels of T3 and T4 abnormal, but thyroid glands doesn’t appear abnormal

34
Q

In sick euthyroid syndrome why is the T3 and T4 low, but rT3 high?

A

downregulation of 5’ deiodinase

35
Q

Where is the thyroid-stimulating hormone (TSH) released from?

A

Anterior pituitary

36
Q

Where is the thyroptin-releasing hormone (TRH) released from?

A

Hypothalamus

37
Q

Where is T3 and T4 released from ?

A

Thyroid gland

38
Q

Where does the negative feedback of T4 and T3 go to?

A

Anterior pituitary and hypothalamus

39
Q

What are the four steps of thyroid gland regulation?

A
  1. TRH is released from hypothalamus
  2. Causes release of TSH from anterior pituitary gland
  3. Causes release of T4 and T3 from thyroid gland
  4. Negative feedback of T4 and T3 to anterior pituitary and hypothalamus
40
Q

What type of hormone is TRH? What does it stimulate?

A

TRH is a tripeptide hormone

Stimulate transcription of TSH

41
Q

What are the two subunits of TSH?

A

Alpha subunit - non specific part of LH and FSH as well

Beta subunit - biologically active site

42
Q

What are the trophies effects of TSH?

A

Increase synthesis and secretion of thyroid hormone

Increase blood flow to glands

43
Q

What happens if there is an absence of TSH

A

The gland atrophies

44
Q

What occurs if there is sustained exposure of thyroid gland to TSH?

A

Hyperplasia and hypertrophy of follicular cells

Increase growth, increase size, increase of everything !

Physiology Exam 3 (17 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions