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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
What is the anterior pituitary
The anterior lobe which originates from Rathke’s pouch and is known and the adenohypophysis and consists of endocrine tissue
26
Where are posterior pituitary hormones produced
The magnocellular neurones of the hypothalamus
27
What are the 2 posterior pituitary hormones
Oxytocin and ADH
28
What are hypothalamic hormones
Hypophysiotropic hormones that the hypothalamus releases into portal circulation to act upon the anterior pituitary
29
What are the 6 hypothalamic hormones
thyrotropin releasing hormone, Gonadotrophin releasing hormone, corticotrophin releasing hormone, growth hormone releasing hormone, growth hormone inhibiting hormone, dopamine
30
Which hypothalamic hormone targets thyrotroph tissue
Thyrotropin RH
31
Which hypothalamic hormone targets gonadotroph tissue
Gonadotrophin RH
32
Which hypothalamic hormone targets corticotrophs tissue
Corticotrophin RH
33
Which hypothalamic hormones targets somatotroph tissue
Growth hormone RH and growth hormone IH
34
Which hypothalamic hormone targets lactotroph tissue
Dopamine
35
What are anterior pituitary hormones
Hormones released into systematic circulation and controlled by hypothalamic hypophysiotropic hormones
36
What are the 6 anterior pituitary hormones
Thyroid stimulating hormone, follicle stimulating hormone, lutenising hormone, adrenocorticotropic hormone, growth hormone and prolactin
37
What is the function of thyroid stimulating hormone
Stimulates thyroid hormone release
38
What is the function of follicle stimulating hormone
Stimulates sex steroid production
39
What is the function of lutenising hormone
Stimulates sex steroid production
40
What is the function of adrencorticotropic hormone
Stimulates cortisol release
41
What is the function of growth hormone
Stimulates growth
42
What is the function of prolactin
Stimulates milk production
43
What hormones are secreted by thyrotrophs
Thyroid stimulating horome
44
What hormones are secreted by Gonadotrophs
Follicle stimulating hormone and lutenising hormone
45
What hormone is secreted by corticotrophs
Adrenocorticotrophic hormone
46
What hormone is secreted by somatotrophs
Growth hormone
47
What hormone is secreted by lactotrophs
Prolactin
48
What is growth hormone (somatotropin)
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
What is an indirect function of growth hormone
Stimulates the production of insulin-like growth factor 1 (IGF-1)
50
What are the acute metabolic actions of GH (direct)
- 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
What are the long term effects of GH (indirect via IGF-1)
-growth promotion on bone, epiphyseal cartilage, soft tissue, gonads, viscera - promotes amino acid uptake and protein synthesis - insulin like effects on tissues
52
What is the thyroid
2 lobes with connecting isthmus, a rich blood supply and two pairs of parathyroids
53
What are the functional units of thyroid
Follicles
54
What are thyroid follicles
Functional unit of thyroid that consists of a pool of colloid surrounded by c cells
55
What is the colloid in the thyroid
Pool where thyroid hormones are are stored and produced
56
What are the c cells in the thyroid
Single layer of cells surrounding a pool of colloid that secrete calcitonin (involved in calcium homeostasis)
57
What are the thyroid hormones
Thyroxine (T4) and Triiodothyronine (T3)
58
What is the major thyroid product
T4
59
What is the most active thyroid hormone
T3
60
What are the physiological effects of the thyroid hormones
Increased cardiac output and systolic pressure Increase BMR Improved altertness, memory, reflexes and wakefulness (neurological) Foetal neural development and bone growth after birth
61
What are the three major thyroid transporting proteins
Thyroxine binding globulin, thyroxine binding prealbumin and albumin
62
How is most plasma T3 derived
From peripheral metabolism of T4 by deiodination
63
What are the three enzymes controlling local control of thyroid hormones
Type 1 deiodinase, type 2 deiodinase and type 3 deiodinase
64
What does type 1 deiodinase result in
Active or inactive T3
65
What does type 2 deiodinase result in
Active T3
66
What does type 3 deiodinase result in
Inactive/reverse T3
67
What are the 2 main components of the adrenals
Medulla and cortex
68
What are the 3 distinct zones of the cortex of the adrenals
zona glomerulosa (outer), zona fasciulata (middle) and zona reticularis (inner)
69
What hormones does the zona glomerulosa produce
Aldosterone
70
What hormones does the zona fasciculata and zona reticularis produce
Cortisol and androgens
71
What is the medulla
Highly specialised part of sympathetic nervous system that has a major product of epinephrine
72
What is aldosterone
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
What does aldosterone upregulate in the kidney to
ENaC (Na+ channel), Na+/K+ pump and ATPase
74
How does aldosterone cause an effect on the kidney
Binds to mineralocorticoid receptors within principle cells
75
What is cortisol
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
What are the effects of cortisol
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
What is Cushing’s syndrome
Excess cortisol

NUT1005 (17 decks)

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