regulation of blood glucose

Biochemistry for nurses

Regulation of Blood Glucose


Alternation between Anabolism and Catabolism

The human body alternates between Anabolic and Catabolic states:

Anabolism:• Synthesis of complexe molecules from smaller units (ex: from glucose

to glycogen)• Growth (body size increases)• Needs energy (powered by catabolism)

Catabolism: • Breaking down of large molecules into smaller units (ex: from starch to

glucose)• Synthesis of ATP molecules (cellular respiration)

Glucose Metabolism: The hormone Insulin supports Anabolic Activities.The hormone Glucagon supports catabolic Activities

ATP molecule is the source of

ENERGY!


Alternation between Anabolism and Catabolism


Glucose Metabolism (Anabolism + Catabolism)


The Brain requires Blood Glucose

The Brain requires a constant

supply of blood glucose

Glucose is the only energy source

for the brain (cannot use fats!)

Hypoglycemia (low blood glucose): Sometimes caused when

diabetic takes too much of insulin (Insulin shock).

Symptoms: Mental confusion, slurring of speech, coma and then

death

Treatment: Give glucose.


Blood Glucose is controlled mainly by the Liver

Immediately after meals, blood glucose comes

from meal.

Between meals (starvation), blood glucose

comes from the Liver and Kidneys.

During starvation, Liver provides 80% of blood

glucose and the Kidneys provide 20% of blood

glucose.


Blood Glucose is controlled mainly by the Liver

Liver makes glucose in 2 ways:1) Breaks down liver glycogen (glycogenolysis)2) Converts other types of small molecules into glucose (gluconeogenesis), many

small molecules can be converted to glucose: Lactate and Pyruvate: Mainly come from muscular activity. Glycerol: supplied by adipose tissue when triglycerides are broken down (Fats). Amino Acids: 20 of the 22 amino acids can be converted to glucose.


Blood Glucose is controlled mainly by the Liver Delivery of glucose to the

blood is controlled by Insulin and Glucagon.

Brain receives a constant 80 mg/min (does not change much in exercice)

Amount delivered of glucose to other tissues depends upon body state (rest or exercice)

At rest total glucose output to the blood is about 130 mg/min (80 to brain, 50 to other tissues)

During exercice total can increase to about 2500 mg/min


Insulin is the only hormone that can lower blood glucose

Muscle, adipose and liver tissues require Insulin to transport glucose into the cells: In these tissues, Insulin increases the number of glucose transporters in the cell membrane.

Brain does not require Insulin to transport Glucose into cells After a meal, blood sugar rises and this stimulates the release of

Insulin from the pancreas Insulin stimulates the synthesis of Glycogen (glycogenesis) for the

storage of glucose.

Average Blood Glucose level =

0.8 to 1.4 g/l


Glucagon can raise blood glucose

Between Meals, when blood glucose is low a large amount of Glucagon is secreted by the pancreas which rises blood sugar (glycogenolysis).

Other hormones can also raise blood glucose especialy during stress and

vigorous exercice. They are 3 major hormones:

1) Cortisol secreted by adrenal glands (situated above the kidneys) in response to

stress and low blood glucose

2) Adrenaline secreted by adrenal glands (brain and above kidneys) in response of

extrem stress

3) Growth hormone is also a stress hormone secreted by the Adenohypophysis

(Brain) which raises blood glucose and stimulates growth cell reproduction and

cell regeneration.

Glucagon raises Blood Glucose

Insulin lowers Blood Glucose


Diabetes Mellitus

Diabetes = excess production of urine

Mellitus = Sweet (refers to sugar in urine)

Diabetes Mellitus results when

Insulin is deficient or Ineffective

Type 1: (Insulin is deficient) Occurs early in life due to autoimmune destruction of pancreatic cells.

Low Insulin output

High blood glucose

Glucose in urine

Excess urine flow

Treated with Insulin injections, careful balance of diet and exercise is advised.

Diabetes Mellitus is of 2 types:


Type 2: (Insulin is Ineffective) Occurs later in life associated with Obesity.

Insulin is normal but is ineffective (Insulin

resistance)

Many of the symptoms are same but less severe

(high blood glucose, glucose in urine and excess

urine flow)

Cause is unknown, but may be insulin receptor

disease

May be reversed if weight is lost.

Diabetes Mellitus is of 2 types:

regulation of blood glucose

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