Brainscape's Knowledge GenomeTM

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


See full index

Physiology > Thyroid Physiology > Flashcards

Thyroid Physiology Flashcards

1
Q

T3

A

Triiodothyronine

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

T4

A

Thyroxine

- more abundant

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

Thyroid hormones are composed of ____ and _____

A

Tyrosine; iodine

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

Functions of thyroid hormones

A
  • increased metabolic rate

- protein, lipid, CHO

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

Thyroid anatomy

A

Bi-lobed gland in cervical neck

  • vascular!
  • parathyroid glands (2 per lobe) = calcium metabolism
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the functional unit of the thyroid

A

Follicle

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

Follicular cells

A

Single layer of cuboidal columnar thyroid cells surrounding lumen
- lumen filled with colloid

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

Parafollicular cells

A

Secrete calcitonin

- calcium regulation

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

T3/T4 synthesis

A

Thyroglobulin synthesis

  • iodide trapping in follicular cell
  • iodide oxidation
  • organification: adding I to tyrosine resides on TG
  • coupling of iodinated tyrosine residues
  • release of hormone
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Thyroglobulin

A

Precursor protein

  • stored in colloid
  • synthesized in follicular cells
  • very large!!!
  • thyroid hormone synthesized on tyrosyl residues of TG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

_____ is required for T3/T4 synthesis

A

Iodide

  • absorbed from GIT
  • excreted by kidney
  • uptake by thyroid gland via iodide trapping and iodide pump (active)
  • uptake by salivary gland
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Organification of iodine to tyrosine residues

A

Iodine added to tyrosine

  • monoiodotyrosine (MIT)
  • diiodotyrosine (DIT)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Coupling of iodinated tyrosine residues

A
  • DIT + DIT = T4

- MIT + DIT = T3

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

Release of hormone

A
  • endocytosis of colloid
  • proteases break bonds between TG and T3/T4
  • released into cirulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Thyroid peroxidase

A
  • iodide oxidation
  • organification
  • coupling
  • hyperthyroidism drugs inhibit thyroid peroxidase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

___ is more active than ____

A

T3; T4

  • T3 enters cells more rapidly
  • T3 is more potent
17
Q

How much T3 is made in thyroid?

A

20%

  • rest from de-iodination of T4 in tissues
  • deiodinases present in many cell types (liver, kidney, muscle)
18
Q

Deiodinase

A
  • T4 is deiodinated to active T3 or inactive reverse T3

- rT3 formed during times of illness, starvation

19
Q

Protein-binding

A

Necessary for transport

  • 99% T3 and T4 are protein bound
  • binding affinity determines half life = more rapid degradation of unbound hormone
20
Q

Proteins

A
  • thyroxine-binding globulin

- albumin

21
Q

Only the ______ is active

A

Free hormone

- lipophilic, enters cell

22
Q

Drugs alter protein-binding

A

Usually do not alter free T4 concentrations

  • may bind to same proteins, lowering protein-bound fraction = decrease of total T4
  • increase binding protiens = increased TBG, increase overall T4, not free T4
23
Q

Thyroid hormones in circulation

A 
T4: 99% protein bound
- free form is biologically active
T3: 99% protein bound
- free form is biologically active
- reverse T3 has no biological activity
24
Q

Thyroid hormones do not affect which tissues?

A
  • lungs
  • testes/uterus
  • retinas
  • lymph nodes/spleen
25
Q

Metabolic effects of thyroid hormone

A
  • increases metabolic rate via oxidative phosphorylation in mitochondria
  • catabolic effects: lipolysis, protein, carb utilization, GI absorption
  • increased GI motility
26
Q

Cardiovascular effects of thyroid hormone

A
  • stimulation of cardiac beta adrenergic receptors = increased HR and cardiac output
  • increased GFR
  • stimulates erythropoiesis
27
Q

Neuromuscular effects of thyroid hormone

A
  • increased mental alertness

- necessary for normal growth and neuronal development

28
Q

Hypothalamus

A

Input from higher centers in brain, body

- thyrotropin releasing hormone = increased TSH release

29
Q

Pituitary gland

A

Thyroid stimulating hormone

  • binds TSH receptors in thyroid
  • stimulates synthesis of T3, T4
30
Q

Thyroid axis has _______

A

Negative feedback

  • free thyroid hormone inhibits TRH and TSH secretion
  • increased T4 leads to decreased TRH and TSH
31
Q

TSH promotes

A
  • iodine trapping
  • colloid endocytosis
  • thyroid cell hypertrophy
32
Q

Goiter

A

Decreased thyroid hormone secretion –> decreased negative feedback –> increased TSH = thyroid cell hypertrophy
- rare in dogs, seen in cats

33
Q

If a normal cat is given a large amount of T3, what should happen to the TRH, TSH, and T4 concentrations?

A

Should decrease TRH, TSH, and T4

Physiology (33 decks)

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