13.3.1 THE QUR'ANIC CONCEPT OF THE GOLDEN MEAN

Four Qur’anic concepts relate to the golden mean: mizan, wasatiyah, tadhafu’u, and I’itidaal. Concept of mizan refers to balance. Concept of wasatiyyat refers to the center. Concept of tadafu’u refers to action and reaction. The concept of i’itidal refers to equilibrium. There is equilibrium between the internal and external environments. Homeostasis restores the normal state once it has been disturbed. Tauhid is related to homeostasis. Tauhid implies that the whole cosmos and what it contains have one deliberate creator. The contents must relate to one another in some harmonious way. It is unthinkable that the one creator could create systems that are contradictory to one another. The harmony must however be looked at in a dynamic way. Because there are constant changes, there must arise from time to time contradictions in the state of flux. There must therefore exist mechanisms for restoring the status quo after the changes have been accomplished. Thus tauhid and homeostasis are closely related. Feed-back may be positive or negative. Negative feed-back operates in homeostasis deviations from the norm are detected by specialized sensors and compensatory changes are triggered to restore the status quo. Positive feed-back is a very dangerous concept. If a change occurs, positive feed-back will reinforce it in a cyclic way that causes more of the same until all homeostasis is lost. The base-line is not constant. It changes with the environment and time. Variation can be within the range of normality or outside the range of normality. Change may be temporary or permanent. Sleep and fatigue are temporary. Lameness and blindness are permanent changes. The human body is in harmony with its internal and external milieu. The internal and milieu and the external milieu are themselves in harmony.

13.3.2 CARDIO-VASCULAR HOMEOSTATASIS:

The control centers are in the spine, medulla oblongata, the cortex, or the chemoreceptors. The input is from baro-receptors, chemo-receptors, cerebellum, and cerebrum. The output is through the autonomic nervous system to the heart and blood vessels. The hormonal factors involved are autocoids, adrenal medulla catecholamines, adrenal cortical hormones, and vasopressin. Oxygen and carbon dioxide have a direct effect on the smooth muscles of the pre-capillary sphincters of arterioles. Kidney auto-regulation also keeps blood flow at a constant rate. The integrated control of cardiac output depends: sympathetics, catecholamines, and increased venous return.

13.3.3 RENAL EXCRETORY HOMEOSTATASIS:

The kidney maintains plasma osmolality by ultra filtration followed by selective tubular reabsorption.

13.3.4 RESPIRATORY HOMEOSTASIS

Neural and chemical mediators are involved in respiratory control. The respiratory rate is controlled by the respiratory center, stretch receptors in the lungs, peripheral chemoreceptors, and central chemo-receptors. The diaphragm and the intercostals are responsible for respiratory movements.

13.3.5 GIT HOMEOSTASIS

There is balance of glucose, lipids, and nitrogen. Glucose is the final pathway of carbohydrate metabolism. The level of glucose in the blood is finely controlled. Glucose balance depends on dietary intake, rate of entry into cells, and the homeostatic activity of the liver. There is a balance among glycolysis, gluconeogenesis, and glycogenolysis. The level of free plasma fatty acids is finely controlled. It is increased by lipolysis. It is decreased by incorporation into lipoproteins, binding to albumin, and deposit as triglycerides. Plasma cholesterol is also kept in balance. It is increased by dietary intake, liver synthesis through a negative feed-back control, and breakdown of lipid stores. It is removed through feces and bile salts. Intake of nitrogen is dietary. The output is by excretion is in the form of excretion as urea and ammonia; about 80% of the ingested nitrogen is excreted as urea.