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TV2001 > Endocrine Physiology - Part 2 > Flashcards

Endocrine Physiology - Part 2 Flashcards

1
Q

What is the Thyroid gland?

A
  • A small gland located in the upper third of the neck, anterior to the trachea and just below the larynx in mammals
  • 2 lobes connected by a narrow isthmus
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2
Q

What hormones are secreted by the thyroid?

A
  1. Thyroxine (T4)

2. Tri-iodothyronine (T3)

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3
Q

Describe the basic histology of the thyroid?

A
  • 2 types of endocrine cells: thyroid hormone secreting cells and clear cells/C cells/para-follicular cells.
  • follicles filled with colloid store thyroid hormones
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4
Q

What is required for the synthesis of Thyroid hormones?

A

iodine and tyrosine.

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5
Q

What can enhance all aspects of thyroid hormone synthesis?

A

TSH

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6
Q

How are thyroid hormones transported?

A
  • 99% is bound with plasma proteins (released slowly to tissue cells by proteins)
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7
Q

What % of hormones released from the thyroid are T3 and what % are T4?

A 
93% = T4 
7% = T3
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8
Q

What tissues are effected by thyroid hormones?

A

almost all

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9
Q

Which thyroid hormones (T3 or T4) is more active than the other?

A

T3 is more active.

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10
Q

What happens to most of the T4 that is secreted?

A

converted to T3 in peripheral tissues by de-iodination

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11
Q

How do thyroid hormones work?

A
  • activate nuclear transcription of a large number of genes resulting in the synthesis of many proteins
  • this affects nearly all the cells in the body, which increases the functional activity of the whole body
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12
Q

What is the function of thyroid hormones?

A
  • increases cellular metabolic activity
  • increases O2 consumption in most tissues
  • produces heat (calorigenic effect)
  • maintains level of metabolism in the body
  • increases number and activity of mitochondria
  • increases activity of Na+-K+ATPase throughout the body
  • enhances cardiac output
  • increases rate of utilisation of food
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13
Q

What is the major factor that defines the body’s BMR?

A

plasma conc. of thyroid hormones

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14
Q

Describe thyroid levels in endotherms compared to ectotherms

A

generally elevated in endotherms, but in ectotherms it is selectively elevated during periods of metabolically demanding activity

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15
Q

What is the role of thyroid hormones in relation to body growth and the nervous system?

A
  • increases GH secretion
  • needed for development of CNS in foetus and after birth
  • needed for normal CNS activity in adults
  • needed for normal gonadal functions
  • required for metamorphosis in frogs
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16
Q

How are thyroid hormones regulated?

A
  • by the hypothalamo-pituitary-thyroid axis
  • cold exposure enhances secretion
  • starvation reduces seretion
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17
Q

What does euthyroid mean?

A

normal thyroid function

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18
Q

What is hyperthyroidism?

A

excess thyroid activity

19
Q

What is the most common disorders in animals?

A

thyroid disporders

20
Q

What is hypothyroidism?

A

deficient thyroid activity

21
Q

What is one of the most common endocrine disorders in cats?

A

hyperthyroidism

22
Q

What is the function of the adrenal medulla?

A
  • produces catecholamines: adrenaline and noradrenaline (aka epinephrine and norepinephrine)
23
Q

What stimulates the adrenal medulla?

A
  • sympathetic nervous system, fight or flight response
  • hypoglycaemia
  • decreased BP
  • cold exposure
24
Q

What is the target of adrenaline and noradrenaline?

A

heart, smooth muscle, pancreas, eyes

25
Q

What is Pheochromocytoma?

A

tumour of the adrenal medulla causing excessive secretion of catecholamines

26
Q

What is the function of the adrenal cortex?

A

secretion of steroid hormones

27
Q

What are the three layers of the adrenal cortex? (outside to inside)

A
  1. zona glomerulosa
  2. zona fasciculata
  3. zona reticularis
28
Q

What is secreted by the zona glomerulosa?

A

mineralcorticoids

29
Q

What is secreted by the zona faciculata?

A

glucocorticoids

30
Q

What is secreted by the zona reticularis?

A

sex steroids (androgens)

31
Q

What is the main glucocorticoid in mammals?

A

cortisol

32
Q

What are the metabolic effects of glucocorticoids?

A
  • increases blood sugar (needed during starvation)
  • enhances protein catabolism and lipid lipolysis
  • inhibits growth
  • adapts body to long term stress
  • anti-inflammatory and immunosuppressive effects
33
Q

What is the clinical use for glucocorticoids?

A
  • used to suppress inflammatory response (inhibits production of substances that promote inflammation)
  • inhibit allergic reactions
34
Q

How are glucocorticoids regulated?

A
  • by hypothalmic-pituitary-adrenal axis

- influenced by stress and circadian rhythm

35
Q

When are glucocorticoid levels highest in a normal animal?

A
  • in diurnal animals: highest in the morning

- reverse in nocturnal animals

36
Q

What is the main mineralocorticoid?

A

aldostrone

37
Q

how are mineralocorticoids regulated/ stimulated?

A
  • angiotensin II
  • elevated ECF K+ conc.
  • reduction of ECF Na+ conc.
  • renin
38
Q

What is the target tissue of mineralocorticoids?

A

renal tubules

39
Q

What is the effect of mineralocorticoids?

A
  • stimulates Na+ reabsorption and excretion of K+ and H+ at the kidneys.
  • major role in regulating ECF volume and therefore BP
40
Q

What happens if there is no aldosterone?

A
  • ECF K+ rises
  • sodium and chloride lost
  • ECF vol falls
  • cardiac output decreases
  • shock
  • death
41
Q

What is hyper-adrenocorticism (cushing’s syndrome)?

A
  • over secretion of CRH/ ACTH

- leads to excessive glucose (adrenal diabetes), protein shortage, fat deposition in abdomen

42
Q

What is primary adrenocortical insufficiency (addison’s disease)?

A
  • low BP, brady, weak pulse, prolonged CRT
  • lerthargy
  • lack of appetite, diarrhoea
  • syncope
  • hypoglycaemia
  • hyponatremia
  • hypokalemia
43
Q

What is hyperaldosteronism (Conn’s disease)?

A

caused by eithr an adrenal tumour hypersecreting aldosterone, or bilateral adrenal hyperplasia

44
Q

What are the two main causes of Cushing’s syndrome?

A
  1. pituitary gland tumour

1. adrenal gland tumour

TV2001 (21 decks)

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