Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physiology and Pharmacology > Regulation of glucose > Flashcards

Regulation of glucose Flashcards

1
Q

what are the components of the endocrine pancreas?

A
  • endocrine tissue makes up 1-2% of pancreas and is richly perfused with blood

islet main secretory cells:

  • beta (65%)
  • alpha (20%)
  • delta (10%)

other single/grouped endocrine cells are scattered:

  • F cells
  • epsilon cells
  • enterochromaffin cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the secretions of the islets of beta cells?

A
  1. beta cells: insulin, proinsulin
    - C-peptide: cleaved from proinsulin
    - amylin (IAPP): regulatory polypeptide co-secreted with insulin to slow gastric emptying and inhibit glucagon release to lower blood glucose
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the secretions of alpha cells?

A

glucagon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the secretions of delta cells?

A

somatostatin to block secretion of insulin and glucagon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the secretions of F (PP) cells?

A

pancreatic polypeptide for exocrine secretion involved in digestion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what are the secretions of epsilon cells?

A

ghrelin to stimulate hunger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the secretions of enterochromaffin cells?

A

substance P involved in exocrine secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the humoral control of the pancreas?

A

blood-related:

  • small arteries distribute blood via fenestrated capillaries
  • vascular arrangement: venous blood bathes cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how does neuronal communication occur between pancreatic endocrine cells?

A

cell-cell via gap junctions:
- delta cells send dendrite-like processes to beta cells

islets are externally innervated by cholinergic, adrenergic and peptidergic neurons
- both sympathetic and parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what regulates insulin secretion?

A
  • secretion is mediated by beta cell receptors
  • high blood glucose stimulates synthesis and secretion, whereas low levels inhibit synthesis and secretion
  • humoral factors, GIP, amylin, somatostatin all affect stimulation and release of insulin
  • drugs e.g. sulphonylureas acting on K+/ATP channels increase secretion of insulin
  • neural control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

how does neural control affect insulin secretion?

A

islets are richly innervated:

  1. sympathetic
    - beta-adrenergic stimulation increases secretion
    - alpha-adrenergic stimulation inhibits secretion
  2. parasympathetic
    - stimulation via vagus nerve releases ACh to increase insulin release
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the process of insulin secretion from beta cells?

A
  1. glucose enters beta cells through GLUT2 via facilitated diffusion
  2. glucose is metabolised/oxidised to increase ATP
  3. this affects ATP/K+ channel, causing it to open and cause depolarisation by influx of K+
  4. this opens voltage-gated Ca2+ channels
  5. increase in intracellular Ca2+ triggers exocytosis of vesicles containing insulin
  6. CCK acts via metabotropic receptors and upregulates release of insulin
  7. beta-adrenergic agonists act on metabotropic receptors which upregulate cAMP and PKA which increase exocytosis of insulin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the inhibitory pathway of insulin secretion?

A

somatostatin downregulates adenylyl cyclase to stop exocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the structure of the insulin receptor?

A
  • insulin acts via receptor
  • 2 extracellular alpha chain
  • 2 membrane-spanning beta chains
  • intracellular tyrosine kinase domain: activation causes phosphorylation of insulin receptor substrates (IRS family) and itself
  • autophosphorylation downregulates the receptor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the downstream effects of the insulin receptor?

A
  • cell growth
  • proliferation
  • gene expression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what happens when the insulin receptor is activated?

A
  • receptor activated by insulin binding
  • causes autophosphorylation
  • phosphorylates proteins to activate/inhibit PKC, phosphatases, phospholipases and G-proteins
  • insulin-receptor complex is internalised via autophosphorylation: downregulated
  • insulin stimulates gene expression
17
Q

what kind of hormone is insulin?

A

hormone of abundance

  • when high availability of nutrients, insulin stores excess nutrients
  • insulin increases uptake of glucose by tissues
18
Q

what tissues does insulin target?

A
  • liver tissue
  • adipose tissue
  • muscle tissue
19
Q

what are the effects of insulin?

A

decreases blood glucose concentration
- increased glucose transport into target cells by insertion of GLUT4:

  1. once insulin is bound, receptor is activated and stimulates signal transduction cascade
  2. vesicle containing GLUT4 receptors fuse with membrane
  3. increased number of GLUT4 channels so there is increased glucose uptake from blood
20
Q

what processes does insulin trigger to remove glucose from blood?

A
  1. glycogenesis: promotes conversion of glucose to glycogen in liver and muscle
  2. lipogenesis: where glycogen stores are replenished, and excess glucose is converted into fat
21
Q

what is insulin action in the liver?

A
  1. glycogenesis: promotes formation of glycogen from glucose
    - insulin upregulates glucokinase and hexokinase
  2. inhibits glycogenolysis: stops breakdown of glycogen to glucose
  3. inhibits gluconeogenesis: stops production of glucose from non-carbohydrate substrates
22
Q

what are the 4 effects of insulin on hepatocytes?

A
  1. promotes glycogen synthesis from glucose by enhancing transcription of glucokinase
  2. promotes synthesis and storage of fats (lipogenesis) to form triglycerides
  3. promotes protein synthesis: movement from cellular amino acids into stored proteins
  4. promotes glucose metabolism and carbohydrate oxidation: respiration
23
Q

what is the action of insulin in muscle tissues?

A
  • increasing uptake of amino acids and protein
  • stimulation of protein synthesis and inhibition of degradation: anabolism
  • decreases blood amino acid concentration
  • promotes glucose uptake by recruiting GLUT4 and GLUT2 transporters to membrane
  • promotes hexokinase to enhance glycogenesis
  • promotes carbohydrate oxidation
24
Q

what is the action of insulin in adipose tissue?

A
  • increased GLUT4 transporter expression for rapid glucose uptake
  • glucose is converted into fatty acids by lipoprotein lipase and stored as triglycerides
  • lipolysis: insulin inhibits mobilisation of fat stores so decreases circulating levels of fatty acids and keto acids
25
Q

what are the molecular actions of insulin?

A
  • promotes K+ uptake into cells via increased activity of Na+/K+ ATPase
  • direct affect on hypothalamic satiety centre via increased feeling of being full
26
Q

what is diabetes mellitus?

A
  • high blood sugar over long periods
  • type 1: insulin-dependent - inadequate insulin secretion due to autoimmune destruction of beta cells
  • type 2: non-insulin-dependent - insulin resistance of target tissues
27
Q

what is Type 1 diabetes mellitus?

A
  • autoimmune response on islet: Beta cells secrete inadequate insulin
  • hyperglycaemia (high blood glucose) resulting from decreased glucose uptake into tissues
  • increased blood fatty acid and keto acid concentrations due to increased lipolysis
  • increased blood amino acid conc
  • osmotic diuresis due to change in components of blood which affects kidneys
  • polyuria, hypotension due to decreased BP hyperkalaemia due to K+ movement out of cells
28
Q

what are the symptoms of type 1 diabetes mellitus?

A
  • increased thirst and urination
  • hunger due to food not being passed into cells from lack of insulin
  • weight loss
  • fatigue
  • irritability
  • fruity smell on the breath
  • diabetic ketoacidosis
  • blurred vision
29
Q

how can type 1 diabetes mellitus be treated?

A

insulin replacement therapy

- insulin is injected straight into blood as ingestion would lead to its breakdown in the GI tract

30
Q

what is type 2 diabetes mellitus?

A
  • associated with obesity
  • exhibits some metabolic deviations of type 1
  • downregulation of insulin receptors in target tissues and insulin resistance
  • blood glucose is elevated after eating
31
Q

what are the symptoms of type 2 diabetes mellitus?

A
  • increased thirst and urination
  • increased hunger
  • weight loss
  • fatigue
  • blurred vision
  • headaches
32
Q

how can type 2 diabetes mellitus be treated?

A
  1. sulphonylurea drugs: tolbutamide
    - stimulates insulin secretion
  2. biguanide drugs: metformin
    - upregulate receptors on target tissues
  3. calorie restriction and weight loss
33
Q

.

A

Physiology and Pharmacology (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions