Blood Glucose Level

Higher Human Biology

Regulation of Blood Glucose Level

• All living cells in human body require

a continuous supply of energy

• This comes from the breakdown of

glucose during respiration

• The body only obtains glucose when

food is eaten

• Negative feedback control regulates

how much glucose is available to

cells

Blood Glucose levelnormal

Glucose content of the blood HIGH

Glucose content of the blood LOW Meal eaten

Between meals

Pancreas producesGLUCAGON

Liver breaks down GLYCOGEN

Pancreas producesINSULIN

Liver stores glucoseAs GLYCOGEN

Glucagon travels to Liver

Insulin travels to Liver

• About 100g glucose is stored as

GLYCOGEN in the liver

• This can be added to or removed

depending on demand by the body

Insulin

• Rise in blood glucose (after meal)

• Detected by receptor cells in pancreas

• Cells produce insulin

• Insulin carried in bloodstream to liver

• Excess glucose absorbed by liver cells

• Enzyme is activated

• Glucose Glycogen

• Decrease in blood glucose

Glucagon• Blood glucose levels drop (between meals or during

the night)

• Receptor cells in pancreas detect this

• Cells release GLUCAGON

• Transported to the liver in the bloodstream

• Activates an enzyme

• Glycogen Glucose

• Glucose released from liver cells

• Blood glucose increases

Antagonistic

• Insulin and Glucagon act

antagonistically

• They counteract each other/ act

against each other

Epinephrine

• During exercise or ‘fight or flight’ the body requires

additional supplies of glucose to provide energy quickly

• Adrenal glands secrete epinephrine (adrenaline)

• Overrides normal homeostatic control

• Inhibits secretion of insulin

• Promotes glycogen glucose

• Once the crisis is over epinephrine is reduced to a

minimum and negative feedback control returns blood

glucose to normal level

Diabetes

• Condition in which sufferers are unable

to control blood glucose level

• Normal blood glucose = 5mmol/l

• Untreated diabetes can rise to 10-30

mmol/l

• 2 types – refer to table 13.6 (page 189)

• Both types of diabetes, if untreated result in

a rapid increase of blood glucose after a

meal.

• Much of the glucose in an untreated diabetic

is not reabsorbed in the kidneys

– Passes out in urine

• Urine tests can be used as an indicator of

diabetes

Blood glucose levels and vascular disease

• Normally blood plasma has 5 mmol/l

glucose

• Diabetes sufferers have elevated

levels (sometimes up to 30 mmol/l)

• Endothelial cells absorb more

glucose than normal

• Leads to damage to blood vessels

and may in turn lead to

• Peripheral Vascular Disease, CVD or

stroke

Microvascular (small vessels) disease

• Arterioles/ Venules

• When they take in more glucose than normal

• Basement membrane becomes thicker but

weaker

• Affected blood vessel becomes thicker but

more likely to burst and bleed into

surrounding tissue

• A tissue can be affected by either;

– being flooded with leaked blood OR

– Not receiving an adequate oxygen supply

• Retina – affecting vision

• Kidney – causing renal failure

• Nerves – peripheral nerve dysfunction

Glucose Tolerance Tests

• Glucose tolerance

• How well the body deals with ingested

glucose

• Depends on adequate production of

insulin

• Clinical test used to diagnose diabetes

• Fast for 8 hours

• Blood glucose measured

• Consume a known mass of glucose

(glucose load)

• Blood glucose monitored over 2 ½

hours and results plotted

• Refer to Fig 13.15 (page 190)

• Curve 1: Glucose rises to a max after 30 mins then

quickly drops back to normal = normal insulin production

• Curve 2: Continues to rise for around 60 minutes before

slowly returning to normal = mild type 2 diabetes

• Curve 3: After fasting, blood glucose still very high.

Continues to rise after ingestion of glucose and fails to

drop to initial level even after 2 ½ hours = Diabetes

(probably type 1)

• Complete your blank negative feedback

control blood glucose level sheets

• Complete blood glucose table activity sheet

• Little AYK book – Page 45, Q7.

Do these activities before you make any

notes please!