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Endocrine System > The Endocrine Pancreas > Flashcards

The Endocrine Pancreas Flashcards

1
Q

What parts of the hypothalamus determine the energy balance?

A

Feeding centre

Satiety centre

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2
Q

What controls the feeding and satiety centres?

A

Nutrients in plasma

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3
Q

What is the glucostatic theory

A

Food intake is determined by [BG]

As [BG] increases the drive to eat decreases

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4
Q

What is the lipostatic theory?

A

Food intake determined by fat stores

Leptin release by fat stores depresses feeding centre

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5
Q

What are the 3 elements of metabolism?

A
  1. Extracting nutrients from food
  2. Storing extracted energy
  3. Using the energy to do work
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6
Q

What are the 2 major types of metabolic pathway?

A

Anabolic

Catabolic

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7
Q

Describe anabolic?

A

Build up

Synthesises large molecules from smaller constituents

Stores

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8
Q

Describe catabolic?

A

Breaks down

Breaking down of larger molecules into smaller constituents

Uses stores

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9
Q

What is the absorptive state?

A

Follows after a meal

  • Ingested nutrients are used to supply energy demands
  • Excess energy is stored
  • Anabolic
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10
Q

What is the post absorptive stage?

A

Fasted state between meals and overnight

  • Body demands are reliant on stores
  • Catabolic
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11
Q

What is an obligatory glucose user and name one?

A

Tissue that can only utilise glucose as energy

The brain

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12
Q

What can the brain utilise in extreme starvation?

A

Ketones

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13
Q

What is normal [BG]?

A

4.2 - 6.3mM

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14
Q

How many Islets of Langerhans are there in the average pancreas?

A

1.2 million

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15
Q

What are the 4 types of cells in the islets of langerhans?

A

Alpha

Beta

Delta

F cells

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16
Q

What do alpha cells secrete?

A

Glucagon

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17
Q

What do beta cells secrete?

A

Insulin

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18
Q

What do delta cells secrete?

A

Somatostatin

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19
Q

What do F cells secrete?

A

Pancreatic Polypeptide

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20
Q

What is control of [BG] dependent on?

A

The insulin:glucagon balance

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21
Q

What is the only hormone that lowers [BG]?

A

Insulin

22
Q

How is insulin secreted from beta cells?

A
  • Have specific KATP ion channel
  • [BG] ^ causes glucose to enter the cells through a GLUT 2
  • Metabolism increases and the KATP channels are activated
  • K+ enters the cells
  • Cell depolarises
  • Ca2+ channels open and calcium enters
  • Calcium dependent exocytosis of insulin vesicles occurs
23
Q

What is the half life of insulin?

A

About 5 minutes

24
Q

What happens when [BG] is low to beta cells?

A

The cell hyperpolarises so calcium dependent exocytosis can’t occur

25
Q

What is the main role of insulin??

A

Stimulates glucose uptake by muscles and adipose tissue (insulin sensitive tissue)

26
Q

What is the process of glucose uptake by insulin sensitive tissue?

A
  • Insulin binds to tyrosine kinase receptors on the cell membrane
  • GLUT 4 transporters mobilised and migrated to the membrane
  • Allows glucose to enter the cell
  • When insulin release stops the tyrosine kinase receptor and the insulin molecule are endocytosed and destroyed
  • GLUT 4 transporters return to cytoplasmic pool
27
Q

What are the other non insulin dependent GLUT transporters?

A

GLUT 1 - Basal glucose in many tissue (brain, kidney, RBCs)

GLUT 2 - beta pancreatic cells and liver

GLUT 3 - same as GLUT 1

28
Q

What other pathways are promoted by insulin?

A

Glycogen synthesis

Increases amino acid uptake and therefore promotes protein synthesis

TAG synthesis

K+ entry via the sodium potassium pump

29
Q

What processes are inhibited by insulin?

A

Gluconeogenesis

Permissive effect on GH

30
Q

What stimuli increase insulin release?

A

High [BG]

High [AA]

Glucagon

Incretin hormones

Vagal nerve activity

31
Q

What incretin hormones stimulate insulin release?

A

Gastrin

CCK

GLP-1

GIP

32
Q

How does vagal nerve activity stimulate insulin release?

A
  • Stimulates release of major GI incretin hormones
33
Q

What stimuli inhibit insulin release?

A
  • Low [BG]
  • Somatostatin
  • Sympathetic A2 effects
  • Stress (e.g. hypoxia)
34
Q

GLUCAGON QUESTIONS

A
35
Q

What type of hormone is glucagon?

A

Peptide hormone

36
Q

What cells produce glucagon?

A

Alpha cells of islets

37
Q

What is the primary purpose of glucagon?

A

Maintain [BG] in the fasted state

  • Acts on the liver
38
Q

How does glucagon raise [BG] in the fasted state?

A

Involved in the glucose counter regulatory control system (along with cortisol and GH)

  • Binds to GPCRs liked to cAMP
  • Phosphorylates specific liver enzymes resulting in
    1. Increase glycogenolysis
    2. Increased gluconeogenesis
    3. Formation of ketones from FA’s
39
Q

When is glucagon secreted?

A

Relatively constantly

  • Increases when [BG] < 5.6mM
  • Ratio of glucagon:insulin most significant
40
Q

What other processes stimulate the release of glucagon?

A
  • High [AA]
  • Low [BG]
  • Sympathetic B2 innervation
  • Cortisol
  • Stress
41
Q

What inhibits glucagon release?

A
  • High [BG]
  • FFAs
  • Ketones
  • Insulin
  • Somatostatin
42
Q

How do amino acids regulate [BG] after a meal?

A

Release both insulin and glucagon to ensure that hypoglycaemia doesn’t occur

  • Also ensures that obligatory glucose utilisers get enough glucose
43
Q

What is the parasympathetic effect on islets?

A
  • Vagus
  • Increases insulin release
  • Increases glucagon release (to a lesser effect)
44
Q

During what phase does the vagus act?

A

Cephalic phase

45
Q

What is the effect of the sympathetic phase on islets?

A
  • Promotes glucose release
  • Increases glucagon
  • Increases epinephrine
46
Q
A
47
Q

What type of hormone is somatostatin?

A

Peptide hormone

48
Q

What cells secrete somatostatin?

A

D cells

Hypothalamus

49
Q

What are the functions of somatostatin?

A
  • Slow down GI tract (i.e. reduce absorption of nutrients to prevent plasma spikes)
  • Strongly suppresses the release of both insulin and glucagon
50
Q

What stimuli promote somatostatin release?

A
  • [BG] high
  • [AA] high
51
Q

What effect does insulin have during exercise?

A
  • Glucose enters muscle more in exercise even without insulin
  • Insulin sensitivity is increased so GLUT 4 mediated transport increases
  • This allows the muscle to get better energy supply
52
Q

What happens to adipose tissue during starvation?

A
  • Broken down into FFAs
  • These can be readily used by most tissue but brain requires Glc/Ketones
  • Brain adapts
  • This spares protein so muscle wasting doesn’t occur
  • Protein is used after fat stores are depleted

Endocrine System (90 decks)

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