Control of Blood Glucose Level

7/28/2019 Control of Blood Glucose Level

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Homeotasis


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Concept of Homeotasis

Homeostasis is the maintenance of a constant

internal environment within a living organism.

Homeostatic mechanisms maintain optimal

physical and chemical conditions in the body

to allow normal enzymatic and other cellular

activities to be carried out.

In biological systems, homeostasis usually

achieved by negative feedback.


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inputReceptor(sensor)

Coordinator(control)

Effector(output)

Feedback loop


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(a) A stimulus is a change in the level of the factor(parameter) being regulated.This detectablechange is known as the input.

(b) The receptor (sensor ) detect a stimulus.

(c) A coordinator (control) receives and controlinformation from the receptor.It triggers the

action that will correct the change. (d) An effector (output) carries out the action

(corrective mechanism) that restore condition toits optimum.

(e) The feedback loop enables the sensor tomonitor any changes brought about the effector.


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Control of Blood Glucose Level


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When blood glucose concentration

rises above the set point, insulin issecreted by the beta cells of the

islets of Langerhans in the pancreas

The insulin molecules bind to

receptor on the cell membrane


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And bring about changes in both cell

surface membrane permeability and

enzyme activity which leads to the

following effects:

An increase in the uptake of glucoseand amino acids into cells

An increase in the rate of conversion of

glucose to fat in adipose cells


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An increase in the rate of

conversion of glucose to glycogen

in liver and muscle cells

(glycogenesis)

An increase in the rate of cellularrespiration (conversion of glucose

to O and HO)


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Insulin affects all the cells but

muscle, fat and liver cells are its main

targets

When blood glucose concentrationfalls below the set point, the alpha

cells of the islets of Langerhans in

the pancreas secrete glucagon


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DIABETES MELLITUS


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Diabetes mellitus is caused by the failure of

beta cells in the pancreas to produce insulin or

the failure/reduction of target cells to respondto insulin.


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The liver and other cells are unable to take up

and metabolise glucose. The blood glucose

level rises to above normal level(hyperglycaemia).

The patients feels thirsty as more water is

needed to dilute the blood and to lower theosmotic concentration of the blood.


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The kidney tubules are unable to reabsorb the

high level of glucose. Excess glucose is

removed in the urine (glycosuria).

Fats and proteins are used as respiratory

substrates resulting in the patient losing

weight.


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Diabetes Mellitus

Type 1 (insulindependent

diabetes mellitus)

Type 2 (non-

insulin dependentdiabetes mellitus)


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TYPE 2 DIABETES MELLITUS (non-

insulin dependent diabetes mellitus)

The remaining 80-90% of the patients has thistype of diabetes.

It is due to defiency in insulin secretion or the

failure of insulin receptor on the plasmamembrane of target cells to respond to insulin.

This is often associated with inherited geneticfactors, diet, obesity and increasing age.

Some patients control their blood glucose levelby regulating their diet and exercise. In severecase they still need daily insulin injections.


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Long term complications of diabetes

mellitus if not treated include kidney

disease, cataracts, blindness andcardiovascular disorders.

Reduced circulation can lead to gangrene

in the arm and legs. Excessive metabolism of fats lead to high

concentration of ketones in the blood,

acidosis (acidic metabolites accumulate in

the blood) and the lowering of blood pH

which can lead to coma and death


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Blood glucose levels can now be

monitored using dipsticks and electronic

biosensors. Human insulin used in treating diabetics

can now be produced on a large scale by

genetic engineering.

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Control of Blood Glucose Level