Concept of Homeostasis

P5 Explain the concept of homeostasis Introduction In this task, I will be explaining the concept of homeostasis and the general features of homeostatic systems which include heart rate, breathing rate, body temperature and blood glucose. Our body need to control the body temperature and water level and this process that helps maintain a constant internal environment. The body needs to keep the body temperature as 37°C and the amount of water that we have inside out body. The thermoregulatory centre in the brain monitors and controls the body temperature. The pancreas controls the blood glucose concentration and it produces insulin that helps reduce the blood glucose levels. Negative feedback is found in the homeostasis which is an important type of control where the body systems maintain their normal state. A negative feedback control system responds once conditions change from the ideal condition and returns back to the current point. For example, when the body becomes too hot, sweating immediately happens in order to cool down the body temperature. However, when the body is too cold, shivering helps the body to warm itself up by increasing the movement in the body. Negative feedback system needs: receptors in order to detect change in the body, a control centre to help receive information and to process response and effectors to take on action which will help the body return to its set point. There is an endless cycle of events in negative feedback. Heart rate ● Roles of internal receptor The role of internal receptors in the heart rate detects changes in blood pressure. For example, when exercising our heart rate increases. This change is easily detected by the receptors that send a message to the brain which activates the effectors to bring the heart rate to its normal state. They are found in the walls of the aorta and a section of the carotid arteries and delivering blood to the neck and head. ● Autonomic nervous system - parasympathetic and sympathetic branches The heart is controlled by the autonomic nervous system that includes two branches which is known as the parasympathetic and sympathetic branches. The sympathetic nervous system speeds up the heart and it contracts blood vessels and it is active when we exercise. For example, when running, our pulse rate increases and the heartbeats strengthen. The parasympathetic nervous system decreases the speed of the heart and it dilates the blood vessels. It also calms down the heart output and it is active when resting. For example, after exercising and we rest, our heart beat slows down and is still active. The autonomic nervous system is in control of blood pressure, heart and breathing rates, body temperature, metabolism, digestion, balance of water and electrolytes, body fluids, urination, defecation and sexual response. There are many organs that are controlled by the sympathetic or the parasympathetic division. Both divisions can have opposite effects on the same organ. Overall, both divisions work together in order to ensure that the body is responding appropriately in different situations. ● Cardiac centre The cardiac centre is responsible for the regulation of the heart rate through the nervous and endocrine system. It is controlled by the autonomic nervous system and it is found in the medulla part of the brain. The medulla is located above the spinal cord which is known as the ‘brain stem’. There are two important centres to control the regulation of the heart that are located here. The cardio-inhibitory centre is responsible for the parasympathetic fibres of the vagus nerve which reaches towards the S-A node, while the sympathetic fibres are descending through the spinal cord from the vasomotor centre. ● Sinoatrial node The sinoatrial node is located in the upper wall of the right atrium and it is referred to the pacemaker of the heart. It’s function is to set out the rate of heart contractions. It contracts and generates nerve impulses which then travel in through the heart walls which results in both the atria to contract. Sympathetic and parasympathetic nerves acting on the sinoatrial node allow it to regulate the heart’s activity every minute. ● Effects of adrenaline on heart rate and increased body temperature When adrenaline is circulating around the body, a hormone is released from the adrenal gland due to fear, stress and excretion. It stimulates the S-A node making it work faster which results in boosting the effects of the sympathetic nervous system. Thermo receptors show an increase in body temperature to the brain which results the hypothalamus to activate the sympathetic nervous system, this then cause the heart rate to increase. Breathing rate ● Roles of internal receptors The roles of internal receptors in the breathing rate can be stretch receptors in the muscles and tissues of the body which pass on nervous impulses to the brain about the status of ventilation from the level of stretch of muscle and other tissues. Breathing includes actions which are both voluntary and involuntary. The respiration control centre is the centre of breathing which receives information from body parts and it coordinates the response automatically resulting organs and muscles to participate in respiration. ● Autonomic nervous system- parasympathetic and sympathetic branches Internal organs have dual autonomic supply which depends on they way they act, that also involves respiration. For example, for bronchial muscle, the sympathetic makes it relax and the parasympathetic causes it to cause contractions which results in the bronchial narrowing; for the bladder, the sympathetic cause the sphincter to contract and the parasympathetic causes it to relax. Overall, when an individual inhales oxygen and exhales oxygen it is then responsible to carry oxygen from the air and into the bloodstream and to remove carbon dioxide from the body as waste product. ● Respiratory centre The upper part of the brain known as the cerebral cortex is responsible for the voluntary control of respiration. The respiratory centre is also known as the involuntary centre which is located in the medulla and the pons which is located above the medulla. They are both located at the base of the brain and each centre receives information from the internal receptors in regards of the state of ventilation. The respiratory system is similar to a respiratory ‘pacemaker’. Nerve cells have two groups which are the inspiratory and expiratory centres; when one is activated, the other one inhibited. Clearly, the inspiratory centre sends nerve impulses to the nerve, the phrenic nerve and the thoracic nerve actively which are sending the impulses to the intercostal muscles in order to create contractions which then result in inspiration. Inspiration finishes when the stretch receptors pass on burst impulses to the inspiratory centre resulting the chest and lungs to be expanded, and the flow of the impulses decreases and releasing the expiratory centre from inhibition. Later, this centre sends nerves impulses to the respiratory muscles which causes relaxation and expiration. This cycle is monitored and modified by information which comes from other receptors such as chemoreceptors. ● Diaphragm and intercostal muscles The rib cage expands during inhalation and it deflated in exhalation. Our diaphragm also moves down to increase the space for the air to be sucked into the lungs. If they did not move, there would have not been no space for the air meaning that the lungs would have no been about to expand. When we exhale, our intercostal muscles and diaphragm relax. The diaphragm moves back up in order to decrease the amount of space for the air leading the air to be pushed out of the body. 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