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Metabolism > Endocrinology > Flashcards

Endocrinology Flashcards

0
Q

What are the two main forms of communication for a control system?

A
  • Hormones

- Nervous system

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1
Q

What are the 4 features of a control system?

A
  • Communication
  • Control centre
  • Receptor
  • Effector
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2
Q

What are the two pathways within a control system?

A
  • Afferent (receptor-> control)

- Efferent (control-> effector

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3
Q

What is the result of negative feedback?

A

-The response opposes the stimulus

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4
Q

What is the result for positive feedback?

A

-The response enhances the effect, often leading to major changes

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5
Q

Give two examples of positive feedback

A
  • Labour

- Ovulation

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6
Q

What is a circadian rhythm?

A

-Levels higher on a morning and low on an evening

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7
Q

How is melatonin released controlled?

A
  • Light/dark cycle

- Light to the retina inhibits melatonin production

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8
Q

The menstrual cycle is an example of a…

A

-Biological rhythm

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9
Q

What controls biological rhythms?

A

-Superchiasmatic nucleus in the hypothalamus

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10
Q

Define hormone

A

-Chemical signals produced in endocrine glands or tissues that travel in the bloodstream to cause an effect on other tissues

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11
Q

What are the 4 general categories of hormones?

A
  • Peptide
  • Glycoprotein
  • a’a derivatives
  • Steroid
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12
Q

Give an example of a peptide hormone

A
  • GH
  • Insulin
  • Thyrotropin releasing hormone
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13
Q

Give an example of glycprotein hormones

A
  • LH
  • TSH
  • FSH
  • human Chorionic Gonadotrophin (hCG)
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14
Q

Give an example of a’a derivative hormones

A
  • Tyrosine-> adrenaline and T3+T4

- Histidine-> Histamine

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15
Q

What are the 3 classes of steroid hormones?

A
  • Glucocorticoids
  • Mineralocorticoids
  • Sex hormones
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16
Q

What are steroid hormones derived from?

A

-Cholesterol

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17
Q

Which classes of hormones are water-soluble?

A

-Peptide and some a’a derivatives

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18
Q

Which hormones are lipid soluble?

A
  • Steroid hormones

- Thyroid hormones

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19
Q

How are water-soluble proteins transported?

A

-Dissolved in the blood at low concentrations

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20
Q

How are lipid-soluble hormones transported?

A

-Bound to a protein carrier in the blood

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21
Q

What effects do protein carriers have on hormones?

A
  • Increase solubility
  • Increase half-life
  • Act as a readily available reserve
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22
Q

What proteins bind to steroid and thyroid hormones for transport?

A
  • Steroid-> steroid binding globulin

- Thyroid-> thyroxine binding globulin

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23
Q

Which is the biologically active form of hormone bound or unbound?

A

-Unbound

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24
Q

Is there an equilibrium between bound and unbound forms of hormone?

A

-Yes

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25
Q

Describe the action of water-soluble hormones

A
  • Travel in the bloodstream to target tissue
  • Bind with receptor
  • Activates a second messenger, causing a signal cascade within the cell
  • Biological response generated
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26
Q

What does the magnitude of a response to hormone binding depend on?

A
  • The conc of hormone present at active tissue
  • Receptor number
  • Receptor affinity for substrate
  • Degree of signal amplification
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27
Q

How do lipid-soluble hormones (ie, steroids) cause a response?

A

-Cross pm
-Bind to receptor, bound to a hsp for stability, located in cytosol
-Receptor:hormone complex translocated to the nucleus
OR
-Hormone passes into nucleus and binds to a nucleus-located receptor
-Receptor:hormone complex binds to DNA, either increasing/decreasing transcription
-Thus controlling protein synthesis

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28
Q

What is the general structure of a feedback system?

A
  • Hypothalmus releases releasing factors into hypothalamic pituitary axis portal
  • Anterior pituitary produces a response and releases trophic hormones into main circulation
  • Signal recieved by endocrone glands which release hormone
  • Hormone levels regulate the hypothalamic release of releasing factors and also pituitary release of trophic hormones
29
Q

What controls negative feedback?

A
  • Change in parameter which the hormone regulates

- Change in hormone levels itself or a hormone which regulates it

30
Q

What type of gland is the pancreas?

A

-Both endocrine and exocrine

31
Q

Which part of the pancreas is endocrine?

A

-The islets of langerhans which are scattered throughout the pancreas

32
Q

What type of cells are in the islets of langerhans and what do they secrete?

A
  • a-glucagon

- b-insulin

33
Q

How do the cells in the islets of langerhans store their hormones?

A

-Intracellularly in membrane bound vesicles (storage granules)

34
Q

How many storage vesicles can each cell contain?

A

-Upto 13000

35
Q

How are b-cells adapted to insulin synthesis?

A
  • Extensive rough endoplasmic reticulum
  • Well define golgi apparatus
  • Many mitochondria
36
Q

What is the structure of insulin?

A

-Two polypeptide chains covalently linked by 3 DSB

37
Q

What is insulin synthesised as?

A

-Preproinsulin

38
Q

What is the “pre” part of immature insulin?

A

-A signal peptide which ensures the newly synthesised protein enters the cisternal space of the ER

39
Q

When is the signal peptide of preproinsulin cleaved?

A

-Once preproinsulin has entered the ER

40
Q

What happens to proinsulin once in the ER?

A

-Folds to ensure correct DSB formation

41
Q

What happens to proinsulin once it has folded?

A

-Transported to the trans golgi

42
Q

How is proinsulin packaged in the trans golgi?

A

-Into secretory vesicles

43
Q

What happens to proinsulin once it has been packaged into secretory vesicles?

A

-Protelysis removing C peptide, creating two peptides held together by DSB, i.e. mature insulin

44
Q

What can C peptide be used for?

A

-A marker for endogenous insulin production as it will be in equimolar amounts to insulin

45
Q

How is insulin secreted?

A

-Through the regulatory secretory pathway

46
Q

How is insulin transported around the body?

A

-As free hormone in plasma

47
Q

What are the major target tissue for insulin?

A
  • Liver
  • Skeletal Muscle
  • Adipose tissue
48
Q

In what form is glucagon synthesised?

A

-Preproglucagon

49
Q

How is mature glucagon formed?

A

-Post-translational modification

50
Q

What happens when glucagon binds to receptor?

A

-Lacks DSB so has flexible 3D structure that takes up active conformation upon binding to receptor on target surface

51
Q

Which substrate metabolism does insulin have an effect on?

A
  • Carbohydrate
  • Lipid
  • Amino acid
52
Q

Is insulin anabolic or catabolic?

A

-Largely anabolic

53
Q

How are changes brought about in response to high insulin concentration in the circulation?

A

-Rapid response using pre-existing proteins (enzymes and transporters)

54
Q

What effects does insulin have on glucose transport?

A

-Increases uptake into adipose tissue and skeletal muscle

55
Q

What effect does insulin have on glycogen metabolism?

A

-Increases glycogenesis and decreases glycogenolysis in adipose tissue and skeletal muscle

56
Q

What effect does insulin have on gluconeogenesis?

A

-Inhibits gluconeogenesis in the liver

57
Q

What effect does insulin have on glycolysis?

A

-Increases glycolysis in the liver and skeletal muscle

58
Q

What effect does insulin have on lipolysis?

A

-Decreases lipolysis in adipose tissue

59
Q

What effect does insulin have on ketogenesis?

A

-Decreases ketogenesis in the liver through inhibiting lyase and activating HMG-CoA reductase so cholesterol is produced instead

60
Q

What effect does insulin have on lipoprotein lipase activity?

A

-Increases

61
Q

What effect does insulin have on protein synthesis?

A

-Increases a’a uptake and protein synthesis in the liver, skeletal muscle and adipose tissue

62
Q

What effect does insulin have on proteolysis?

A

-Decreases proteolysis in the liver, skeletal muscle and adipose tissue

63
Q

What controls insulin secretion?

A

-Levels of metabolites in the blood (glucose,FAs, a’a), levels of GI tract hormones (gastrin, secretin) and neurotransmitters (noradrenaline and acetylcholine)

64
Q

What effect does adrenaline have on insulin?

A

-Decreases secretion

65
Q

What effect does glucagon have on glycogenolysis?

A

-Increases in liver and skeletal muscle

66
Q

What effect does glucagon have on glycogenesis?

A

-Decreases in the liver

67
Q

What effect does glucagon have on gluconeogenesis?

A

-Increases in the liver

68
Q

What effect does glucagon have on ketogenesis?

A

-Increases in the liver

69
Q

What effect does glucagon have on lipolysis?

A

-Increases in the liver, skeletal muscle and adipose tissue

70
Q

What is the major factor which stimulates glucagon secretion?

A

-Low glucose concentrations in the blood

Metabolism (14 decks)

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