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Introduction

Saira Iram Shaukat Unit 5- Senzenni Assignment 4 Homeostasis-P5 P5) Describe the concept of homeostasis and the homeostatic mechanisms that regulate heart rate, breathing rate, body temperature and blood glucose levels. Definition of Homeostasis The actual word homeostasis means "steady state". Homeostasis describes how the body regulates its process to keep its internal conditions as stable as possible. Homeostasis is necessary because human cells are efficient but very demanding. The phrase "steady state" is a bit confusing; the conditions inside our bodies are not constant but are kept within a narrow range. Some factors such as core temperature and blood pH change slightly while others such as blood glucose vary considerably throughout a normal day without producing any harmful effects. A very brief description of homeostasis is that it is the maintenance of a constant internal environment in response to a change in external environment. Internal environment The conditions that prevail within the body of an organism, particularly with respect to the composition of the tissue fluid. To function properly they need to be bathed in tissue fluid that can provide the optimum conditions. Nutrients and oxygen must be delivered and waste needs to be removed. To maintain the internal environment there are 3 things that need to be done: * Organisms keep conditions in their bodies fairly constant to live. * Metabolism in organisms is almost always constant. * Conditions include temperature, water levels and salt levels. Salt levels Salt is a chemical compound that combines sodium and chloride. ...read more.

Middle

B) Loss of heat by the body- Radiation, conduction, convection, evaporation: For anything to maintain a stable body temperature it is important that heat loss is equal to heat gain. Heat can be gained or lost in 4 different ways: Radiation: This is the energy that travels through air/space in the form of particles or waves. It is the loss of heat into the surroundings. Conduction: This involves the transfer of heat between two objects that in contact with each other. Heat is always conducted from a region of higher temperature to a region of lower temperature. Convection: This is when you warm up the layer of air next your skin and it moves upwards to be replaced by colder air from the ground. Evaporation: When liquid water is converted into water vapour it requires heat energy to do so. C) Role of the hypothalamus: The receptors for temperature both heat and cold are located in the peripheral skin and around internal organs. These are specially adapted cells with nerve fibres that run up the spinal cord to the temperature control centre in the hypothalamus of the brain. It sends nerve impulses to muscles, sweat glands and skin blood vessels to cause changes that counteract the external changes. C) Roles of the nervous system-sympathetic and parasympathetic: The parasympathetic has so important role in the thermoregulation although it helps the unstriated muscle coats of the skin arterioles to relax, but it controls both sweat glands and the calibre of the arterioles. D) ...read more.

Conclusion

4) Breathing rate: A) Role of internal receptors Internal receptors can be stretch receptors in muscles and tissues that relay nervous impulses to the brain about the status of ventilation from the degree of stretch of muscles and other tissue. The intercostal muscles are the site of many stretch receptors. B) Role of the autonomic nervous system- sympathetic and parasympathetic nerve supply: Most internal organs have a dual autonomic supply. Like I explained earlier sympathetic always causes contraction and parasympathetic causes relaxation of muscles. However it can be different in this situation. In the case of bronchial muscle it is opposite, the sympathetic nerve allows it to relax and parasympathetic causes contraction which makes the bronchi narrower. Most of these fibres run in the vague nerve in serving the heart. C) Role of the respiratory centre, diaphragm and intercostal muscles: In the upper part of the brain called cerebral cortex voluntary control for breathing takes place. The involuntary centre is known as the respiratory centre is in the medulla and the area just above is known as the pons, these are both at the base of the brain. The internal receptors send information to each of the centres regarding the state of ventilation. There are two groups of nerve cells known as the inspiratory and expiratory centres and when one is active the other one is deactivated. It clearly shows that the inspiratory centre is actively sending nerve impulses to the nerve to the diaphragm, the phrenit nerve and the thoracic nerves are sending impulses to the intercostal muscles to make contraction take place which results to ispiration. ...read more.

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