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NUT1005 > The Endocrine System > Flashcards

The Endocrine System Flashcards

1
Q

What is endocrine communication

A

Messages are trasmitted by circulating body fluids and specificity depends on receptors

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2
Q

What is the classical definition of the endocrine system

A

Endocrine cells within endocrine glands release hormones which are convent by the bloodstream and act on distant cells

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3
Q

Why has the classical definition of the endocrine system been updated

A

Hormones produced by many tissues can have local effects as well as distant effects

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4
Q

What is the updated definition of the endocrine system

A

Specialised cells release hormones which are converted by the bloodstream and act via receptors in target tissues

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5
Q

What are hormones

A

Chemical messengers synthesised by specialised cells that are secreted into the bloodstream in small amounts which act on specific receptors in target organs to regulate cellular function

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6
Q

What are the non classical endocrine tissues

A

Kidney, heart muscle, endothelium, platelets, adipocytes and white blood cells

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7
Q

What are the 3 main classes of hormones based on chemical structure

A

Steroids, peptides and amino acids

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8
Q

What are steroid hormones

A

Synthesised from cholesterol

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9
Q

What are peptide hormones

A

Synthesised from amino acids

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10
Q

What are amino acid hormones

A

Synthesised from tyrosine (or tryptophan for melatonin)

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11
Q

What are the features of steroid hormones

A
  • small and hydrophobic
  • released immediately following synthesis
  • circulate in bound form
  • slow long lasting effects
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12
Q

How do steroid hormones regulate gene transcription

A

Act on intracellular receptors which bind to DNA and regulate gene transcription

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13
Q

How do steroid hormones act on intracellular receptors

A

Bind to hormone binding site, which opens up the hinge region and disassociates the inhibitory protein complex from the DNA binding site, leaving the DNA binding site exposed

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14
Q

How are peptide hormones synthesised

A

Synthesised as preprohormones and stored prior to release

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15
Q

How do peptide hormones cause effects in target cells

A

Act on cell surface receptors then via 2nd messenger systems to cause an effect

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16
Q

How are amino acid hormones synthesised

A

Mostly from tyrosine and stored for instant release

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17
Q

Describe how amino acid hormones cause an effects

A

Have different modes of action ( some act on intracellular receptors others on cell surfaces)

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18
Q

What mechanisms regulate hormone secretion

A

Feedback control

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19
Q

What is feedback control

A

Response to maintain homeostasis

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20
Q

Describe negative feedback control

A

Systematic effects are imputed to hypothalamus by other brain areas, hypothalamus releases releasing factors to anterior pituitary, anterior pituitary releases tropic hormone to endocrine tissue, endocrine tissue releases hormone have a systematic effect. All areas feedback changes to hypothalamus

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21
Q

What is the hypothalamus-pituitary axis

A

The site of interaction between the nervous and endrocrine systems that exerts control over several endocrine glands and physiological activities

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22
Q

What is the hypothalamus

A

The region of the brain that plays a key role of homeostasis

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23
Q

What is the pituitary gland

A

The hypophysis which consists of two lobes (posterior and anterior pituitary)

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24
Q

What is the posterior pituitary

A

The posterior lobe which is of neural origin (neurohypophysis) and consists id axons and nerve endings of neurones whose cell bodies reside in the hypothalamus

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25
Q

What is the anterior pituitary

A

The anterior lobe which originates from Rathke’s pouch and is known and the adenohypophysis and consists of endocrine tissue

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26
Q

Where are posterior pituitary hormones produced

A

The magnocellular neurones of the hypothalamus

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27
Q

What are the 2 posterior pituitary hormones

A

Oxytocin and ADH

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28
Q

What are hypothalamic hormones

A

Hypophysiotropic hormones that the hypothalamus releases into portal circulation to act upon the anterior pituitary

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29
Q

What are the 6 hypothalamic hormones

A

thyrotropin releasing hormone, Gonadotrophin releasing hormone, corticotrophin releasing hormone, growth hormone releasing hormone, growth hormone inhibiting hormone, dopamine

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30
Q

Which hypothalamic hormone targets thyrotroph tissue

A

Thyrotropin RH

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31
Q

Which hypothalamic hormone targets gonadotroph tissue

A

Gonadotrophin RH

32
Q

Which hypothalamic hormone targets corticotrophs tissue

A

Corticotrophin RH

33
Q

Which hypothalamic hormones targets somatotroph tissue

A

Growth hormone RH and growth hormone IH

34
Q

Which hypothalamic hormone targets lactotroph tissue

A

Dopamine

35
Q

What are anterior pituitary hormones

A

Hormones released into systematic circulation and controlled by hypothalamic hypophysiotropic hormones

36
Q

What are the 6 anterior pituitary hormones

A

Thyroid stimulating hormone, follicle stimulating hormone, lutenising hormone, adrenocorticotropic hormone, growth hormone and prolactin

37
Q

What is the function of thyroid stimulating hormone

A

Stimulates thyroid hormone release

38
Q

What is the function of follicle stimulating hormone

A

Stimulates sex steroid production

39
Q

What is the function of lutenising hormone

A

Stimulates sex steroid production

40
Q

What is the function of adrencorticotropic hormone

A

Stimulates cortisol release

41
Q

What is the function of growth hormone

A

Stimulates growth

42
Q

What is the function of prolactin

A

Stimulates milk production

43
Q

What hormones are secreted by thyrotrophs

A

Thyroid stimulating horome

44
Q

What hormones are secreted by Gonadotrophs

A

Follicle stimulating hormone and lutenising hormone

45
Q

What hormone is secreted by corticotrophs

A

Adrenocorticotrophic hormone

46
Q

What hormone is secreted by somatotrophs

A

Growth hormone

47
Q

What hormone is secreted by lactotrophs

A

Prolactin

48
Q

What is growth hormone (somatotropin)

A

Peptide hormones synthesised by somatotrophs in the anterior pituitary to stimulate growth and cell reproduction and regeneration that are released in response to GHRH from the hypothalamus and realises is inhibited by GHIH (somatostatin) from the hypothalamus

49
Q

What is an indirect function of growth hormone

A

Stimulates the production of insulin-like growth factor 1 (IGF-1)

50
Q

What are the acute metabolic actions of GH (direct)

A
  • fatty acid release from adipose tissue and conversion to acetyl coa (energy from fats)
  • reduced glucose metabolism and uptake into cells
  • increased gluconeogenesis in the liver
  • Increased production of insulin-like growth factor-1
51
Q

What are the long term effects of GH (indirect via IGF-1)

A

-growth promotion on bone, epiphyseal cartilage, soft tissue, gonads, viscera
- promotes amino acid uptake and protein synthesis
- insulin like effects on tissues

52
Q

What is the thyroid

A

2 lobes connecting isthmus which a rich blood supply and two pairs of parathyroids

53
Q

What are the functional units of thyroid

A

Follicles

54
Q

What are thyroid follicles

A

Functional unit of thyroid that consists of a pool of colloid surrounded by c cells

55
Q

What is the colloid in the thyroid

A

Pool where thyroid hormones are are stored and produced

56
Q

What are the c cells in the thyroid

A

Single layer of cells surrounding a pool of colloid that secrete calcitonin (involved in calcium homeostasis)

57
Q

What are the thyroid hormones

A

Thyroxine (T4) and Triiodothyronine (T3)

58
Q

What is the major thyroid product

A

T4

59
Q

What is the most active thyroid hormone

A

T3

60
Q

What are the physiological effects of the thyroid hormones

A

Increased cardiac output and systolic pressure
Increase BMR
Improved altertness, memory, reflexes and wakefulness (neurological)
Foetal neural development and bone growth after birth

61
Q

What are the three major thyroid transporting proteins

A

Thyroxine binding globulin, thyroxine binding prealbumin and albumin

62
Q

How is most plasma T3 derived

A

From peripheral metabolism of T4 by deiodination

63
Q

What are the three enzymes controlling local control of thyroid hormones

A

Type 1 deiodinase, type 2 deiodinase and type 3 deiodinase

64
Q

What does type 1 deiodinase result in

A

Active or inactive T3

65
Q

What does type 2 deiodinase result in

A

Active T3

66
Q

What does type 3 deiodinase result in

A

Inactive/reverse T3

67
Q

What are the 2 main components of the adrenals

A

Medulla and cortex

68
Q

What are the 3 distinct zones of the cortex of the adrenals

A

zona glomerulosa (outer), zona fasciulata (middle) and zona reticularis (inner)

69
Q

What hormones does the zona glomerulosa produce

A

Aldosterone

70
Q

What hormones does the zona fasciculata and zona reticularis produce

A

Cortisol and androgens

71
Q

What is the medulla

A

Highly specialised part of sympathetic nervous system that has a major product of epinephrine

72
Q

What is aldosterone

A

Major mineralocorticoid that is bound to albumin in plasma and acts on kidney, colon and salivary glands to maintain normal Na+ and extracellular fluid volume

73
Q

What does aldosterone upregulate in the kidney to

A

ENaC (Na+ channel), Na+/K+ pump and ATPase

74
Q

How does aldosterone cause an effect on the kidney

A

Binds to mineralocorticoid receptors within principle cells

75
Q

What is cortisol

A

The stress hormone that is a major glucocorticoid that effects virtually all tissues by controlling gene transcription and is mostly bound to plasma protein

76
Q

What are the effects of cortisol

A

Hepatic gluconeogenesis
Inhibits glucose uptake
Stimulates muscle catabolism
Inhibits bone formation
Leads to loss of collagen and connective tissue
Increases vascular sensitivity to epinephrine and norepinephrine
Modulate behaviour and cognitive function
Inhibits gonadal release of testosterone, oestrogen and progesterone
Inhibits cytokines production and T cell proliferation
Inhibits prostaglandin and leukotriene production

77
Q

What is Cushing’s syndrome

A

Excess cortisol

NUT1005 (18 decks)

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