Anatomy & Physiology
Anatomy & Physiology
In this assignment the concept of homeostasis will be explained and the probable homeostatic responses to changes in the internal environment during exercise will be discussed. Homeostasis is simply how the body keeps conditions inside the same. It is described as the maintenance of a constant internal environment. Generally, the body is in homeostasis when its needs are met and it’s functioning properly. Every organ in the body contributes to homeostasis. A complex set of chemical, thermal, and neural factors interact in complex ways, both helping the body while it works to maintain homeostasis. In homeostasis there is the concept of Negative feedback which ensures that, in any control system, changes are reversed and returned back to the set level. There are four different homeostatic mechanisms for regulation these four are the heart rate, breathing rate, body temperature and blood glucose levels.
Negative feedback system is made out of receptors to detect change, a control centre to receive the information and process the response and effectors to reverse the change and re-establish the original state. (Anatomy & Physiology, 2013) The autonomic nervous system controls the heart and has two branches; the sympathetic nervous system and the parasympathetic nervous system. When the body is undergoing muscular work, fear or stress the sympathetic nervous system will be active. When the sympathetic nervous system is active it will cause every heartbeat to increase in strength and heart rate. During resting, peace and contentment the parasympathetic nervous system is active and it calms the heart output. During periods of fright, flight and fight the sympathetic nervous system is boosted by the hormone; adrenaline. The nerves of the adrenaline are the cardiac nerves. A special cluster of excitable cells are supplied by the sympathetic and parasympathetic nervous system in the upper part of the right atrium. We call this ‘the peacemaker’ in general terms.
A connection of impulses from the sympathetic and parasympathetic nerves acting on the sino-atrial (‘the pacemaker’) regulates the activity of the heart to suit situations from minute to minute, hour to hour and day to day. The sino-atrial node sends out a cluster of nerve impulses every few seconds around the branching network of atrial muscle fibres to cause contraction. The impulses are caught by a different group of cells forming the atrioventricular node and relayed to a band of leading tissue made of big, modified muscle cells called Purkinje fibres. In the atrioventricular node the transmission of impulses is delayed slightly to enable the atria to complete their contractions and the atrioventricular valves to start to close. The location of heart valves is on a fibrous figure-of-eight between the atrial and ventricular muscle masses.(Aldworth and Billingham, 2010) The lowest part of the brain is the medulla and is located above the spinal cord and is often known as the ‘brain stem’.
The two important centres for control of the heart rate are located in the brain stem. These are called the cardiac centres. The sympathetic fibres descend through the spinal cord from the vasomotor centre while the cardio-inhibitory centre is in charge of the origins of the parasympathetic fibres of the vagus nerve reaching the sino-atrial node. (Aldworth and Billingham, 2010) Baroreceptors are found in the walls of the aorta and they detect changes in blood pressure. If in the arteries a small upward change in blood pressure happens it often indicates that extra blood has been pumped out by the ventricles as result of the extra blood that enters the heart on the venous or right side. When the baroreceptors detect the change they relay the information in nerve impulses to the cardiac centres. Movement in the vagus nerve slows the heart rate down and reduces the high blood pressure to normal.
Thermo receptors are receptors that are sensitive to temperature and they are present in the skin and deep inside the body. Also they relay information through nerve impulses to the hypothalamus; this is a part of the brain which activates appropriate feedback systems. During fear, stress and exertion, the adrenal gland releases a hormone called circulating adrenaline. Circulating adrenaline stimulates the sino-atrial node to work faster, therefore boosting the effect of the sympathetic nervous system. The hypothalamus activates the sympathetic nervous system when thermo receptors indicate a rise in body temperature to the brain. When the sympathetic nervous system is activated it causes the heart rate to increase. Our rate of ventilation is mainly on ‘automatic pilot’ and do not notice little variations that are the result of homeostatic regulations. We are only voluntarily controlling our breathing when taking deep breaths, speaking or holding a breath.
Breathing rate increase slightly when metabolism produces extra carbon dioxide until this surplus is ‘blown off’ in expiration. Also a period of forced ventilation will decrease the carbon dioxide levels in the body and homeostatic mechanisms will slow or stop breathing until levels return to normal. A period of forced ventilation can be for example gasping.(Aldworth and Billingham, 2010) Internal receptors relay nervous impulses to the brain about the status of ventilation from the degree of stretch of muscles and other tissues when they function as stretch receptors in muscles and tissues. Changes in chemical stimuli are detected by chemoreceptors and they supply the brain with the information. There are to chemoreceptors; the central and peripheral. The central chemoreceptors are located in the medulla of the brain and monitors H+ ion concentration. When H+ ion concentration is increased it causes increase in ventilation rate. Peripheral chemoreceptor’s increase ventilation when oxygen levels decrease. Peripheral monitors changes in oxygen. (Aldworth and Billingham, 2010) The respiratory system has a dual autonomic supply.
The sympathetic causes the bronchial muscle to relax and the parasympathetic causes the bronchial muscle to contract. This causes narrowing in bronchi. Vagus means ‘a wanderer’ and the vagus nerves is so called because it wanders all over, supplying internal organs. Sympathetic nerves emerge from the places where nerves interconnect, to run to the bronchi, these places are called a chain of ganglia.(Aldworth and Billingham, 2010) The upper part of the brain is called cerebral cortex; this part of the brain is responsible for voluntary control of breathing. The respiratory centre, also called the involuntary centre is found in the medulla and the pons. Each centre receives information of internal receptors about the state of ventilation. The respiratory pacemaker and the respiratory centre are similar to each other. The inspiratory and expiratory centres are two groups of nerve cells. If one is active the other one is inhibited.
The inspiratory centre is actively sending nerve impulses to the nerve to the diaphragm, the phrenic nerve, and the thoracic nerves are sending impulses to the intercostal muscles which cause contraction and the contraction results in inspiration. Inspiration stops when the stretch receptors send bursts of impulses to the inspiratory centre. These bursts of impulses indicate that the chest and lungs are fully expanded, and the flow of impulses subsides, releasing the expiratory centre from inhibition. The expiratory centre then sends nerve impulses to the respiratory muscles which causes relaxation and expiration. The information that comes from the other internal receptors, for instance the chemoreceptors (which effects the homeostatic regulation) monitors and modifies the cycle.
The body predicts the changes before an individual starts the exercise, this is because the sympathetic nervous system is stimulated. Also adrenaline is released to rise cardiac output and stroke volume. When arterioles become narrow the blood pressure increases, whereas the arterioles in the muscle relax. The extra oxygen that is needed is received by an increase in blood flow and ventilation rate. (Aldworth and Billingham, 2010) The only animals that can survive in tropical and polar regions of the earth are human beings. This is because the efficient thermos-regulatory homeostatic processes and the use of intelligence (for shelter and clothing), which mean that body temperature changes only slightly. The importance is to keep all the organs and cells at a normal temperature while allowing the periphery to adapt to changing conditions of external temperature. When body temperature is too low the water component of the body will freeze and when body temperature is too high, enzymes and body proteins will be altered or denatured (form will alter).
It wouldn’t be possible to live in these conditions therefore homeostatic regulation of body temperature is vital. (Aldworth and Billingham, 2010) The skin plays an important role in regulation of body temperature. It covers the external surface of the body and it actually is the largest organ. The skin, protects the underlying tissues against friction damage, waterproofs the body, protects against ultra-violet radiation, protects deeper structures from invasion by micro-organisms, relays nerve impulses generated from the specialised skin sensory receptors for heat, cold, touch, pain and pressure, therefore informing the brain of changes in the environment and the skin synthesises vitamin D from sunlight acting on the adipose layer. When cells are shed from the surface layers, new cells will form to replace them and this happens continuously. The skin is an important part of our in-built or innate immunity. The skin forms a waterproof layer and a microbe-proof covering.
The skin has a major role in the homeostatic regulation of body temperature and is considered to be part of our nervous system; this is because of his sensitivity. Throughout the body the thickness of the skin will differ, for instance over the eyelids and lips and on the soles of the feet. The skin is divided into an outer thinner layer and a deeper layer. The outer thinner layer is called the epidermis and the deeper layer is called the dermis. The deeper layer covers adipose, areolar, striated muscle and some cartilage and bone. Hair follicles run down into the dermis and produce hairs made of keratin. Sebaceous glands that coat the surface in hairy parts are attached to the hairs that are made of keratin. The epidermis gets penetrated by sweat ducts as they emerge from the actual sweat gland in the dermis. The dermis is connective tissue, most likely areolar in which blood vessels, nerves, sweat glands, elastic and collagen fibres intermingle. In the basal layer we can find collections of pigment cells, also known as melanocytes and they produce skin colour.
Specialised receptors for temperature changes, pain, touch and pressure are formed by nerve endings. (Aldworth and Billingham, 2010) The metabolic processes that take place in the body generate heat. Energy is released during chemical reaction for muscle contraction but some of this energy is released as heat. The body gains some heat from hot foods and drinks and sometimes from the sun’s rays. Most heat is gained of chemical reactions that take place in the liver, the liver is a massive generator of heat but it doesn’t feel hot because the blood distributes this heat around the body.(Aldworth and Billingham, 2010) The receptor for heat temperature and cold temperature can be found in the peripheral skin and around the internal organs. These receptors are specially adapted cells with nerve fibres that run up the spinal cord to the temperature control centre in the hypothalamus of the brain.
Nerve impulses get send by the hypothalamus to muscles, sweat glands and skin blood vessels. This causes changes that counteract the external changes. (Aldworth and Billingham, 2010) The parasympathetic nervous system helps the unstriated muscle coats of the skin arterioles to relax, but has no significant role in thermo-regulation. The sympathetic nervous system’s function is to control sweat glands and the calibre of the arterioles. While thermoreceptors tell the hypothalamus in the brain that the temperature is rising, arterioles are expanded to let extra heat reach the surface of the skin and sweat glands get activated by the sympathetic nerves at the same time. When arterioles expand it will increase heat loss by radiation and disappearance of sweat. When the essential temperature is decreasing (cooling down), the sympathetic is active causing contraction of the arterioles but there is no sweat ‘‘it’s turned off’’. This makes the skin colder to touch and reduces heat loss and therefore it preserves the essential temperature.
Essential temperature dominates the peripheral skin thermoreceptors when conflicting information is received is the reason of the colder skin and reduced heat loss. (Aldworth and Billingham, 2010) An increase in glucose will stimulate the production of the hormone insulin from the beta cells in the islets of Langerhans in the pancreas. Glucose is produced by digestive enzymes when carbohydrates are broken down. The functions of insulin are to regulate the concentration of glucose in the blood and to increase the passage of glucose into actively respiring body cells by active absorption. Very little glucose is able to pass through cell membranes without insulin expect of liver cells, and so the plasma level of glucose rises. Individuals who have diabetes mellitus, which is caused by a lack of insulin, that are not treated will have high plasma glucose levels and this can lead to other biochemical disturbances. Glucose hardly varies at all in healthy people this is because the liver cells that are controlled by insulin convert glucose into liver glycogen for storage.
Another hormone, glucagon, from the alpha cells in the islets of Langerhans, is secreted when blood glucose starts to fall as a result of fasting or being used up by respiring cells. The secreted hormone converts liver glycogen back into glucose for release into the bloodstream. These two hormones control the amount of glucose in the blood plasma by negative feedback mechanisms and they both have receptors attached to their islet cells to recognize increase and decrease in plasma glucose levels. Also the conversion of glucose into fat is promoted by insulin and insulin delays the conversion of amino acids into energy. It is important to identify the role of another hormone, adrenaline, in the homeostasis of glucose. Adrenal glands release adrenaline when the sympathetic nervous system is active under stressful conditions, adrenaline acts aggressively to insulin and it dominates it, to adapt glycogen in the liver to glucose.
This provides energy for muscles to become active under emergency conditions. After the emergency, insulin will once more become active and store any surplus as before. (Aldworth and Billingham, 2010) In conclusion, the concept of homeostasis is explained and the probable homeostatic responses to changes in the internal environment during exercise are discussed. In this assignment I will be explaining why homeostasis occurs during exercise and how the body responses to homeostasis during exercise. There are two types of exercise; aerobic and anaerobic. Anaerobic exercise builds muscle, power and strength. When you do anaerobic exercise, your muscles are exercising at high intensity in a short time. This short time is usually not more than about two minutes. Aerobic exercise is done at moderate level of intensity for longer periods (at least 20 minutes). Aerobic is to improve the body’s consumption of oxygen and involves mainly the large muscle groups.
Homeostasis is the process by which the internal environment of the body relatively stable even with changes in the external environment. Homeostasis makes it able for the body to adapt to several conditions, for example an average human body temperature is 37 degrees. This varies slightly from individual to individual. When the temperature outside decreases your body will maintain the same temperature. This proves your body has the ability to regulate its own temperature. This is not only with body temperature but there are many other ways in which your body regulates itself, particularly during exercise.In order to maintain its normal state the body must account for and adjust functions inside the body, whenever your body feels a change on the outside. Most of the time people sweat without even thinking of why your body is suddenly dripping in moisture. During exercise, there will be a wide range of effects on the systems within the body. Each system strives to help create enough energy to continue exercising, also to help the body recover after exercise.
This use of energy has several effects on the body’s homeostasis including increased heart rate, breathing rate and sweat rate.(wiseGEEK, 2015) Homeostasis and exercise must work together within the human body to ensure that the pulmonary, heart and muscle system function properly. Two common forms of exercise are; lifting weights or jogging down the street, these two exercises produce a stress or strain on the body. During movements of the exercise the muscles must react fast, while blood flow and oxygen levels must be redirected to compensate for the extra energy use. If an individual is jogging his breathing rate has to be higher than a person who is resting. If the individual has a lack of oxygen to any vital body system it will result in cellular damage, or injury. The extra oxygen that enters the jogger’s lungs, which comes through the pulmonary system, helps to return balance to the body. Homeostasis refers to the human body’s balance among all vital life systems. When oxygen intake increases, the muscles will produce more adenosine triphosphate (ATP). Adenosine triphosphate is needed for continued muscular movement.
The heart is the main muscle that is affected by exercise and homeostasis. During exercise the heart must beat quicker to move oxygen-rich blood out to the skeletal muscles for motion. When the individual slows the exercise, the heart will respond to the change in homeostasis by reducing the pumping action. Until the individual is at rest, the body will continue to change its functions to maintain homeostasis.(wiseGEEK, 2015) The cardiovascular system has chemoreceptors which are located in two places; in the carotid arteries that run through the neck to the brain and in the aortic arch, which is an arterial feature near the heart. Some of the most essential chemoreceptors notice carbon dioxide. When the chemoreceptors sense high levels of carbon dioxide during exercise, the breathing rate and heart rate is going to increase to remove the waste product from the blood. The chemoreceptors work with the cardiovascular system and the respiratory system, since the cardiovascular system gets carbon dioxide to the lungs for elimination and the lungs need to work harder to exhale the carbon dioxide.
During exercise the blood flow supply routes change within the body. To enhance oxygen supply to the muscle cells, the stress placed across the muscular system requires more blood than normal. The body switches blood normally directed toward digestion or nervous system activities to the skeletal muscles, in response to the exercise and homeostasis requirements. Removing the stress on the muscles will result that the blood flow returns to its normal routes to achieve a resting homeostasis. In relation to exercise and homeostasis, body temperature is an important consideration. During exercise your body’s system for regulating works quicker and harder. Heat production by the body can cause your internal temperature to rise up to as high as 40 ͦC. This can possibly lead to fatal complications.
Homeostasis occurs during exercise by allowing the body to sweat. Homeostasis occurs by allowing the body to sweat. The lossof sweat from the skin cools the body down, which results in overall temperature balance to allow continued exercise without overheating. During exercise your metabolic rate increases. Heat is produced during metabolism. An increase in metabolic rate also increases heat production. The change in body temperature during exercise is produced by the action of large muscle groups contracting. The more heat that is produced means the higher the temperature during exercise. Muscles that have enough energy store fat for a short burst of activity, after thisthey rely on increased blood supply to deliver oxygen, blood sugar and other nutrients to produce more energy. The human body burns the sugar in the blood and calls for the liver to supply stored glucose to keep up with energy demands, which causes variation in the blood sugar when exercising. Your muscles start calling for nutrients, as you warm up, to produce energy. Energy supplies are; glucose that is carried in the blood and delivered to the muscles and free fatty acids, which is a type of lipid that is carried in the blood that provides energy when glucose is decreased.
Using energy during exercise assists in balancing high blood sugar and provides fuel at the same time. Energy supply increases at the same time as blood flow to the muscles increases. The muscle cells refer signals to start burning glucose, and more of it is delivered to the cells which lower the blood sugar levels. During exercise the amount of oxygen available in the bloodstream increases, but the body must get rid of carbon dioxide from the blood at the same rate. When the body cells make energy, carbon dioxide is produced as a waste product. The carbon dioxide goes back into the bloodstream and from there it will flow through the veins back to the lungs where the carbon dioxide will be exhaled out of the body. Your breathing rate must continue to stay at a high level, to maintain balance. Now the lungs can expel the extra carbon dioxide being produced by the muscle cells during exercise. When the individual stops exercising and the cells turn back to normal energy needs, there will be less carbon dioxide that is created. This allows the breathing rate to return to normal.
In this assignment I’m going to explain the importance of homeostatic within the body. Homeostasis is the control of internal situations: it maintains a constant internal environment by negative feedback. The human cells live and function in a certain temperature which means that they depend on the body environment. The body environment is kept under control by homeostasis and it keeps the condition accurate for cells to function and live. If the cells don’t get the accurate condition they won’t be able to function properly. Certain process such as osmosis and enzymes will not function correctly. Homeostasis maintains the body’s water and salt balance, if the water and salt balance are in a good condition it will maintain the process of diffusion and osmosis. Diffusion and osmosis is the transport of chemicals such as; oxygen, carbon dioxide and dissolved food .The living cells depend on the movement of these chemicals around the body. The cells in our body are kept alive by chemical reactions; the chemical reactions make the cells do their job.
Enzymes speed the chemical reactions up which keep the cell alive and also enzymes ensure that the job is done. Homeostasis is responsible for maintaining a constant body temperature and enzymes work best at particular temperatures which is maintained by homeostasis, therefore homeostasis is very important to cells. (Bbc.co.uk, 2015) Negative feedback makes sure that, in any control system, changes are reserved and returned back to normal state, for instance; keeping a constant body temperature even in a hot or cold environment. Shivering is a reflex which is controlled by the nervous system. Without homeostasis the human body would not be able to function in hot or cold temperature. Shivering is a way to warm the body up, because it generates heat. If an individual is cold, homeostasis occurs and sends signals to the body which causes the reflex of shivering. Sweating is the opposite of shivering. If the body has an absence of sweating, which is also defined as hyperhidrosis, it can affect small and large areas within the body.
Sweat is important for the human body because it keeps the human body cool, gets rid of excess body heat and protect from overheating. If an individual is not able to sweat it can be very dangerous, that’s why it is important to maintain homeostasis. Not sweating in whenever the body is hot can lead to serious damages and injuries, such as coma and death. It is important that the human body has homeostasis, because a failure in maintaining homeostasis can lead to death or diseases. For example heart failure can occur when negative feedback mechanisms become overwhelmed and unhelpful positive feedback mechanisms take over. Diseases that can occur from a failure in maintaining homeostasis are; diabetes, dehydration, hypoglycaemia, gout and any other diseases that are caused when toxin gets into the bloodstream. (wiseGEEK, 2015) A failure in maintaining energy balance can result in obesity and diabetes. Obesity is caused when a person overeats. The stomach releases a hormone which is called hormone ghrelin. This hormone goes to the brain and increases a person’s appetite. The answer will come from another hormone which is named Leptin; this hormone is produced by cells in the fat tissue.
Leptin goes to the brain and encourages a sense of satiety, or fullness. If the brain refuses to respond to ghrelin, an individual will keep feeling hungry. If the brain refuses to respond to the hormone Leptin, an individual will never be happy from a meal. Therefore a person will keep on eating and a person may overeat and this causes obesity. Homeostasis maintains energy balance. Without homeostasis an individual would overeat. (Biology-online.org, 2015) Homeostasis is also important in fighting viruses inside the body. For example if someone in your environment spread flu when he/she sneezed, your body will be affected. The body needs to fight off the entering virus, which likes living at normal body temperature. At 37ᵒ C the virus is able to breed and reproduce/multiply well, this will make the individual more prone to the illness as there is more bacteria to spread it. Although the body wants to maintain homeostasis and a normal temperature, but it would result that the virus takes over your entire body. Therefore the body temperature rises above the normal range.
When the body temperature rises it makes the body an uncomfortable place to live for the virus. In hotter temperature, the virus will slow down and you immune system will be able to attack the virus. Therefore homeostasis is very important, it helps fighting illnesses. If homeostasis would be disrupted an individual would become sick. A failure in homeostasis can result in dehydration. Maintaining water balance is important for good functioning of nerves. The kidney can detect blood pressure and the brain can detect the amount of water in the blood. The brain makes the body ‘thirsty’ when water levels in the body are low, while sending signals to the kidneys to retain more water. Dehydration occurs when there is too little water and it can cause kidney damage, heat cramps, shock, and coma and organ failure.
However, when an individual drinks too much water, it can cause hyper hydration. Hyper hydration can lead to weakness, confusion, seizures and irritation. The human body’s weight is more than the half percentage of water. Homeostasis maintains the correct balance of water. (Balance, 2015) Homeostasis has a survival value, because it allows the human body to adapt in a changing environment. It deals with the temperature difference that a human faces when they step out their front door. The body will try to maintain a norm, the desired level of a factor to achieve homeostasis. But it can only work within acceptable limits. In extreme condition the negative feedback mechanism can be disabled. In these circumstances, death can be caused unless there is medical treatment. (Biology-online.org, 2015)
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University/College: University of Chicago
Type of paper: Thesis/Dissertation Chapter
Date: 25 September 2016
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