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With reference to specific examples and mechanisms assess the significance of homeostasis to the human body.

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Introduction

WITH REFERENCE TO SPECIFIC EXAMPLES AND MECHANISMS ASSESS THE SIGNIFICANCE OF HOMEOSTASIS TO THE HUMAN BODY What is homeostasis? According to the 'Oxford Colour Medical Dictionary, Third Edition' homeostasis is the "the physiological process by which the internal systems of the body (e.g. blood pressure, body temperature, acid-base balance) are maintained at equilibrium, despite variations in the external conditions" Homeostasis is the maintenance of a stable internal environment within tolerance limits, this is the restricted range of conditions where cellular operations effectively work at a consistent rate and maintain life. These conditions include temperature, blood glucose levels, pupil diameter control and many more. Homeostasis actually means 'unchanging', but that is not a true description of biological systems. DYNAMIC EQUILIBRIUM is a more accurate description. (1) "An amoeba, a single celled organism, needs to be able to take in oxygen, food and nutrients and to excrete waste products. It needs a constant state of hydration and a controlled temperature for a happy life. Man is complex and multicellular but each cell has the same needs as the amoeba and we have developed complex mechanisms to provide each cell with all that it needs" (2) The human animal is a very complex multi-cellular organism in which the maintenance of life depends upon various physiological and biochemical activities.

Middle

It receives an input from the detector, and integrates the incoming information. An effector-when the incoming signal indicates that an adjustment is needed the effector responds and the input is changed (corrective response) e.g. this could be the release of a hormone that lowers blood glucose levels for example i.e. insulin. (5) Source: http://www.biology-online.org/4/1_physiological_homeostasis.ht This type of homeostatic mechanism is known as negative feedback where the body opposes the departure of a controlled variable from the normal range and restores the variable to its normal range. This is the most common type of regulation in the body. The outcome is to maintain a relatively constant or stable environment. An example could be in thermal homeostasis, which maintains normal cell function and normal metabolism where during cold stress (below body core temperature) which could potentially slow down chemical reactions and slow down neural signals, the body would engage in many activities to reduce this stress, these include: -Stimulation of skeletal muscles by the brain's hypothalamus (control centre) to contract and shiver to produce body heat -Stimulation of smooth muscle tissue (effectors) in blood vessels in skin by the brain (control centre) to contract to reduce blood flow to skin and slow down loss of heat by skin's surface (response). In heat stress (above normal core temperature), which disrupts structure of body proteins, the hypothalamus (control centre)

Conclusion

On the other hand if pupil constriction happened during dim light, insufficient light would go into the eye to activate the photosensitive pigments in the rods and cons, which stimulate nerve endings in the retina. The iris contains one layer of circular muscle and one layer of radiating smooth muscle fibres. Contraction of the circular fibres constricts the pupil, and contraction dilates it. The size of the pupil is regulated by the autonomic nervous system and it demonstrates an example of a nervous-control mechanism. Sympathetic stimulation causes dilation while parasympathetic stimulation causes constriction of the pupil. (9) Source: Marieb EN, 2003, Human Anatomy & Physiology, sixth edition, San Francisco, Pearson Benjamin Cummings, page 566 Significance of homeostasis Homeostasis is so important that most disease is regarded as a result of its disturbance, a condition called homeostatic imbalance. As we get older, the body's internal environment becomes progressively less stable. As a result we are more vulnerable to illnesses and they produce the changes we associate with ageing. Homeostatic imbalance takes place when the usual negative feedback mechanisms are overwhelmed and the destructive positive feedback mechanisms take over. An example of this phenomenon is heart failure. Illnesses such as hypertension, diabetes are all a result of failed homeostatic mechanisms, this demonstrates the importance of homeostasis to an individual. (10) Put simply, it is the difference between health and illness. Word count =1649 (excluding reference) Student Id Number:03235386 1

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