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z basic sciences > control of plasma glucose > Flashcards

control of plasma glucose Flashcards

1
Q

which structures rely entirely on glucose and why?

A

CNS

retina

germinal epithelium

brain cannot synthesise of store more than a few minutes supply of glucose

requires a continuous supply from circulation

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2
Q

why do we take fasting blood glucose levels

A

huge variation in blood glucose spike after eating

eating different things

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3
Q

fasting blood glucose levels are :

A

70-100 mg glucose/100cm3 (dl) of blood

or

3.9 – 5.5 mmol-1

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4
Q

which organ is reponsible for responding to signals that indicate changes in blood glucose levels

A

liver is the predominant tissue

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5
Q

name and explain ways that glucose is used, synthesised and stored

A
  • Glycogenesis:
    • Liver causes:
    • Conversion of glucose to glycogen
    • Skeletal muscle & liver
    • Glycogen can be used as an energy source
  • Glycogenolysis:
    • Breakdown of glycogen to glucose
    • Liver (and kidney) can release glucose into circulation in response to low plasma glucose
  • Gluconeogenesis:
    • Glucose from non-carbohydrate precursors
    • Proteins (amino acids) & Lipids (glycerol)
    • Liver (& Kidney)
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6
Q

what happens when glycogen stores are fully saturated

A

Glucose converted to FFA and stored in adipocytes in the form of triglycerides

Glucose converted into fat

process does not usually happen in reverse

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7
Q

what will blood glucose levels below 3.9mmol/L lead to?

A

loss of consciousness (coma)

hypoglycaemia

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8
Q

what will blood glucose levels above 7mmol/L lead to?

A

glucose will appear in urine

pH of blood will fall

leads to coma - above 10mmol/L

hyperglycaemia

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9
Q

if there is inadequate amounts of glucose to catabolise, what is the action of the cells

what occurs during starvation

A
  • If cells have inadequate amounts of glucose to catabolize, the cells immediately shift to the catabolism of fats for energy.
  • In starvation, proteins are also used for energy after carbohydrate and fats are depleted.
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10
Q

short term regulators of blood glucose levels

A

insulin

glucagon

hormones released by gastrointestinal tract

fight or flight

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11
Q

long term regulators of blood glucose levels

A

Adrenaline,

glucocorticoids,

growth hormone

thyroid hormones

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12
Q

important structure of pancreas

A

islet of langerhans

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13
Q

what cells does the islet of langerhans contain and what do they secrete

A

alpha, beta and delta cells

secrete peptide hormones

  • a cells (20%) secrete glucagon
  • b cells (75%) secrete insulin
  • d cells (5%) secrete somatostatin
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14
Q

properties of insulin

summarised role of insulin

A
  • 5 minute half life (no carrier protein)
  • Released (& stored) by the islets of Langerhans β cells in the pancreas in response to high blood sugar levels
    • Blood perfuses islets
    • B cells sense
  • Raised plasma glucose: depolarisation of the beta cells (acts directly)
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15
Q

describe the events which lead to the secretion of insulin

A
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16
Q

explain actions of insulin

what is the outcome?

A
  • Key target tissues of insulin are liver, muscle & adipose tissue
  • Binds to insulin-dependent receptor and force fat and muscle cells to take up glucose from the blood through the glucose transporter (GLUT4)
  • Stimulates the liver to convert glucose into glycogen (glycogenesis)
  • Activates glycolysis & Inhibits gluconeogenesis
  • As a result, blood glucose levels drop
17
Q

how does glucose uptake in the CNS differ from the rest of the body??

A

glucose uptake is independant of insulin

18
Q

explain the actions of insulin if the glycogen stores are fully saturated

A
  • Stimulates excess glucose to be converted into fat: triglyceride synthesis
  • Increases uptake of amino acids and promotes protein synthesis
  • Increase the number of GLUT4 receptors on the cell surface –
    • increase capacity of the cell for glucose uptake
  • Prevents glycogenolysis and lipolysis
  • Lowers plasma glucose levels
  • As a result, blood glucose levels drop
19
Q

summary of insulins actions and effect on cell membrane transporters

A
  • Insulin binds to the alpha subunits of the insulin receptor,
    • which increases glucose and amino acid transport
20
Q

draw graph of insulin and glucose levels after a meal

A
21
Q

which gastrointestinal hormones have roles in lowering blood glucose levels

A

Glucagon-like peptide-1 (GLP-1)

gastric inhibitory peptide (GIP)

22
Q

what roles do gastrointestinal hormones have in lowering blood glucose levels

A
  • after detection of plasma glucose in lumen of the small intestine
  • Increase production of incretins
  • Enable cells to respond better to insulin

incretins used as diabetes medication

23
Q

properties of glucagon

summarised role of glucagon :

A
  • The most potent hyperglycaemic hormone
  • Actions directly oppose insulin
  • Synthesised by the alpha cells of the pancreatic islets
  • 6 minute half life
  • Released in response to lowered plasma glucose
  • Acts to raise glucose levels
  • Insulin inhibits glucagon secretion
24
Q

explain the actions of glucagon

A
  • blood glucose levels fall -> alpha cells of pancreas release glucagon
  • Exerts its effects on CHO, fat and protein metabolism
  • Converts glycogen into glucose (glycogenolysis)
  • Inhibits glycogen synthesis (glycogenesis)
  • Activates amino acid uptake and gluconeogenesis
  • Lipolytic effect (triglycerides broken down to fatty acids)
  • Provides a ready supply of metabolic substrates
    • Enables glucose to be spared for CNS
25
Q

role of somatostatin

A

inhibits both insulin and glucagon release

26
Q

draw diagram of regulation of blood glucose levels

A
27
Q

hormones involved in maintainance of long term blood glucose

and roles

A
  • Adrenal glucocorticoids,
  • Growth Hormone,
  • Catecholamines
  • Thyroid hormone
  • Maintenance of glycogen stores, stimulates gluconeogenesis and mobilisation of fatty acids and proteins.
  • Significant role during prolonged fasting
  • Conserve glucose for CNS
28
Q

symptoms of diabetes

A
  • frequent urination
  • always tired
  • sudden weight loss
  • wounds that dont heal
  • always thirsty
  • blurry vision
  • numb or tingling hands or feet
29
Q
A
30
Q

outline characteristics of type 1 diabetes

A
  • Organ specific autoimmune disorder
  • Destruction of pancreatic beta cells
  • Complete loss of insulin secretion
  • Triggers unclear
  • Not associated with diet/lifestyle
  • Cannot be prevented
31
Q

outline characteristics of type 2 diabetes

A
  • Genetic and environmental risk factors (& ethnicity)
  • Strongly linked to obesity
  • Reduction in pancreatic insulin or an increasing failure of tissues to respond to insulin
    • Insulin constantly being released
    • Receptors stop working
      • changes to expression/binding/intracellular cascade
  • Insulin resistance
  • Can be controlled with diet
32
Q

how does exercise affect diabetes risk?

A
  • increases number of insulin receptors
  • may enhance insulins binding to receptors on muscle fibre
  • Up-regulation (receptors) occurs with insulin after 4 weeks of exercise to increase its sensitivity (diabetic importance)
  • improved insulin mediated glucose metabolism - decreased insulin resistance
  • decreased risk of obesity and type 2 diabetes
33
Q

consequences of hyperglycaemia

common symptoms :

A

Polyphagia -

  • frequent hunger, especially pronounced hunger

Polydipsia -

  • frequent thirst, especially excessive thirst

Polyuria -

  • frequent urination, especially excessive urination
34
Q

how does hyperglycaemia cause polyuria and polydipsia ?

A
  • excessive glucose in kidney filtrate
    • acts as osmotic diuretic
    • inhibition of water reabsorption
    • therefore huge urine output and decreased blood volume
    • also leads to dehydration
      • dehydration stimulates hypothalamic thirst centres
35
Q

what is polyphagia and why does it occur

A
  • excessive hunger and food consumption
  • plenty of glucose is available but cannot be used so the cells begin to starve
  • cells cannot produce energy without fuel
    • leads to fatigue and weight loss
36
Q

what is the consequence of insulin deficiency or resistance

A
  • no detection of insulin -> leads to secretion of glucagon
  • Increase in glycogen breakdown
  • Increased rate of gluconeogenesis (weight loss)
  • Increased lipolysis (production of ketone bodies; ketoacidosis)

leads to chronic hyperglycaemia

37
Q

symptoms of excessive ketone

A

‘ketone breath’

38
Q

consequences of chronic hyperglycaemia :

A
  • Kidney damage
  • Neurological damage
  • Cardiovascular damage
  • Damage to the retina
39
Q

dental complications associated with diabetes:

A
  • Higher risk of gum disease
  • Early tooth loss
  • Gingivitis,
  • Periodontitis
  • Dental caries
  • Xerostomia,
  • Oral burning sensation
  • Taste disturbances
  • Fungal infection
  • Lichen planus
  • considered as major risk factor for periodontal diseases

z basic sciences (21 decks)

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