Homeostasis is the state in which the body systems are in perfect harmony and balance. It is a dynamic concept rather than a static one. There are always disturbances to the homeostatic order but the body has corrective mechanisms that return it to the previous state almost instantly. This corrective ability declines gradually with age. The term homeostenosis is used to describe the declining ability to maintain the homeostatic order as compensatory mechanisms become impaired.

Geriatric medicine is a rapidly growing discipline due to the increasing longevity. A balance must be established between what is considered the normal physiology of aging (requiring no intervention) and pathology in old age (requiring intervention).  The physician must make a judgment on whether diagnostic and therapeutic measures planned will not make the prognosis worse. Care must be taken in prescriptions. The elderly are on several medications because of their multiple pathologies and drug interactions are common. Adverse drug reactions may be more severe in the elderly. The elderly have altered pharmacokinetics (absorption, metabolism, excretion). Care for the elderly: Routine screening of the elderly is very useful to discover problems early and deal with them. Rehabilitation is a multi-disciplinary effort involving physicians, nurses, physiotherapists, social workers, and psychologists. Members of the family must be an integral part of the team that cares for the elderly. There is a debate between home care vs institutionalization. Home care would be the best because it gives the elderly more feeling of dignity and personal worth.

2.0 MUSCULO-SKELETAL MOTOR DYSFUNCTION

The Qur'an describes old age as the age of weak bones[1]. The elderly have various degrees of immobility due to muscular, joint and bone degeneration. Their limited mobility is also associated with instability. The elderly are prone to falling and other accidents because of blurred vision and loss of balance (poor propioception, vestibular lesions).

The elderly, like the sick, are exempted from fulfilling all the acts and conditions of the physical acts of ibadat, salat, saum, and hajj. The elderly can pray sitting down[2]. If the sitting down posture is difficult they can pray lying on the side[3]. Abdullah Ibn Omar did not complete some acts of prayer because of a disability in his foot[4]. In sickness permission is given to omit circumbulation of the kaaba[5]. Circumbulation can be performed on another persons's back or a vehicle like a wheel chair. The prophet did circumbulate on an animal[6]. It is offensive, makruh, to circumbulate on an animal for no valid excuse[7].

3.0 NEUROLOGICAL DYSFUNCTION

Functional impairments in many organs occur due to imbalances in the autonomic nervous system. The elderly may suffer from urinary or fecal incontinence. They may also suffer from urinary or fecal retention. Postural hypotension occurs limiting their ability to stand up for prolonged periods or to walk. Impaired thermoregulation makes them very vulnerable to sudden changes in environmental temperature. Urinary incontinence and fecal incontinence may make it difficult for the elderly to maintain a state of ritual purity, wudhu, for long enough to complete the prayers. They are allowed to wear a diaper or urinary retainer, make wudhu, and pray immediately. They do not have to repeat the prayer because of any incontinence that they may experience.

4.0 PSYCHOSOCIAL DYSFUNCTION

The sleep patterns are altered with insomnia being common. The elderly cannot sleep in the early hours of the morning probably due to depression.

The elderly may suffer from various types and degrees of intellectual impairment. Alzheimer's disease is the commonest cause of intellectual decline. This manifests as cognitive impairment, memory loss, and reduced or distorted environmental sensory input. The cognitive impairment is due to decline of speed of information processing. This reduces fluid intelligence, the ability to solve new problems.

Memory loss is more pronounced for recent than for long-term memory. The experience and accumulated knowledge of the elderly sometimes more than compensates for the cognitive decline. Many elderly are functioning very well intellectually well into their 90s.

Ibadat: The elderly may not be able to fulfill all the conditions of prayer on account of their mental impairments.

Munakahaat: In extremes of age the pronouncements of the elderly on marriage contracts and divorce may be due to mental confusion.

Muamalaat: restriction on the elderly in transactions.

Jinayaat: reliability of evidence of the elderly. Reduced criminal liability for actions due to incapacity.

Psychosocial: Old age is a period of psychological stress because of the dependency status it engenders. Previously active and self-directed individuals feel loss of independence keenly. There is loss of self-esteem. Socially the elders suffer from the stress of reduced social interaction and loss of income. In many communities the elderly live in poverty. On the other hand there are a few elderly who enjoy their last years of life. These are generally in good health or have accepted their physical impairments. They usually feel they have accomplished their mission in life. In a stage of actualization, they have no more ambitions or challenges to face and there do not feel the frustrations and stresses of the young. 

Sexual function: Old age is looked at for both males and females as a period of declining reproductive ability[8]. Their sexual function is reduced due to anatomical changes or autonomic dysfunction. Reduction of sexual function may not be accompanied by reduction of sexual desire. In old age males may suffer from impotence due to erectile difficulties. Vaginitis in females due to deficient estrogens making sexual intercourse painful.

5.0 OTHERS

Eye accommodation is impaired leading to presbyopia. This is due to decreasing elasticity of the lens capsule and the thickening of the lens. Decline in the ears results in loss of high frequency hearing (presbyacusis). Bone loss starts from the age of 35 years and osteoporosis increases with age. Nutrition: Elderly malnutrition is common. The nutritional intake is lower because of poverty, inability to prepare and consume food or just loss of appetite. Nutritional deficiencies are also common due to unbalanced diets. An elderly person is exempted from fasting if it will hurt good health[9].