Homeostasis, Co-ordination and Control and the Excretory system

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Homeostasis, Co-ordination and Control and the Excretory system.

Homeostasis is when a living being keeps control of the internal bodily conditions to keep the inside the “same”. It maintains things such as the bodies temperature at around 37 degrees, keeps the blood amount at around 5 liters and maintains water amount inside the body. All these can change due to different conditions, such as, the temperature outside or exercising causing the body to “sweat” which looses water. Inside the human body there are lots of, “Sensors” which monitor everything. They send signals to the brain when something is “different”, sensors in the brain will then monitor the changes and signal to effectors to make changes if necessary.


The human body temperature sits at 37 degrees, whatever the temperature externally the temperature within the body will always try to remain the same. This is controlled by what is known as the, “Negative feedback system”. There are receptors all over the bodies skin which detect and analyse all changes in temperature. All information passes from these receptors to the hypothalamus, which is the part of the brain that processes temperature regulation.

When the body gets to hot, blood vessels will dilate. This means the blood vessels will become larger allowing the blood flow to increase nearer to the surface of the skin allowing body heat to escape. As well as this, when hot, the body will also sweat. When we sweat water is removed from the body and evaporates onto the skin, this effect will cool the body down slightly. If the temperature gets to high it could cause the body to oversweat. If the person isnt able to get liquids in them they will become dehydrated. This is known as a heat stroke. When the body gets to cold, blood vessels will become smaller and will reduce blood flow around the surface of the skin, this will keep body heat within the body. This is known as Vasoconstriction. Quite often people will get what is called, “goosebumps” over their skin. This is when the hairs over the body become raised by the small muscles on the skin, the hairs will catch the air which helps to insulate our body. When the body temperature drops below 37degree's it will typically start to shiver, this is when the muscles inside the body start to shake involuntarily and produce extra heat. If the temperature of the body falls below 35degree's the body will suffer from hypothermia, typically the body will violently shiver which can lead to difficulty in moving. This can be treated by warming the person up. 316

Around 50-75% of the human body consists of water. In babies its higher at around 75% to 78% dropping as they get older. We must always be in-taking liquids to keep our water level up as we can excrete water though things such as sweating, urinating and breathing out water vapour. We take in water from food and drink. The human body NEEDS water to live. Cells within the body need water to pass through their membrane depositing needed partials inside them. Water helps to digest food, carry waste products, sends electrical messages amongst cells, regulates body temperature and lubricates joints. The water levels must be kept at the correct balance and this is done through the kidneys. The kidneys are one of the major organs of homoeostasis, the human body has two kidneys found in the abdominal cavity (below the ribcage).They regulate waterloss in the body, blood goes through the kidneys and is filtered. Kidneys produce urine, this is the waste of “filtered” molecules of water etc.. leaving the body. Around 180 litres of water is processed through the kidneys on a daily basis. The remains of what was filtered and not secreted from the body is then redistributed across the bodies circulatory system. Kidneys produce urine at different concentrations which maintain water balance. When the body is dehydrated and we intake more liquids the kidney will filter and keep the majority of liquid processing through it. Any urine that does exit the body will be more concentrated appearing darker in colour. Whereas if we are fully hydrated and drink more fluids than our body needs the kidney will process the liquids and filter out the majority, it will be very diluted and will be more in quantity than when your dehydrated. The kidneys water balance can change according to temperature, exercise, fluid intake and salt intake. 308 Within the body we require a certain volume of glucose (Sugar) in order to create Andesine triphosphate (ATP), energy within the body. ATP is important as it’s the only energy source used by cells in the brain and nervous system. ATP levels will always be changing; therefore the body must regulate its blood sugars through Sugar homoeostasis. Too much sugar could result in a high PH level in your blood, which breaks down sugars into energy without 02 making acids. This makes blood more acidic and disturbs the balance, thus insulin is needed. This homeostasis is regulated by two hormones, Insulin and Glucagon. Insulin and Glucogon are protein hormones with a half-life, they need to be rapidly produced to maintain a constant homoeostasis.

This all happens within the pancreas, inside the pancreas are lots of receptors which monitor sugar levels within the bloodstream. Insulin's main job is to decrease the blood sugar levels, insulin also synthesizes fatty acids and muscle tissue and transports (k+), which is responsible for causing the electric pulses in your nerve system that transmits signals to your brain and muscles. Insulin is produced by the beta cells of the pancreatic islets when there is a high blood sugar. When the levels of blood glucose drop the production of insulin will also lower. Whenever the blood glucose levels become elevated, for example when we have just eaten, the production of insulin will become higher again. This will occur because of Parasympathetic stimulation from the nervous system. During this phase insulin levels in the blood increase and sugar levels lower.

Glucagon is the opposite of insulin, it will increase blood sugar levels and is secreted from the pancreas when blood glucose gets low. It’s produced in the alpha cells of the pancreatic islets. In the Sympathetic stimulation of the nervous system glucagon will help to elevate the amounts of blood glucose in the blood stream.

There is normally around 70 – 99mg of glucose in our blood, 70-120mg after eating. Diabetes is a disorder some people can get when the glucose levels in the blood are too high and remain so. Treatment for this is an insulin shot. In type 2 diabetes the persons cells that detect certain parts of sugar, which will simulate the production of insulin will become damaged or destroyed hence they won’t be simply produced. So treatment for this is a lifestyle change by changing diet and exercising regularly, type 2 can be cured through this unlike type 1.


All responses to any stimulus come from the central nervous system (CNS). The central nervous system consists of the Brain and the spinal cord which react to information received from senses. The brain is quite often compared to the human's processor and memory of a computer. The front of the brain is responsible for receiving and processing information ie/ thinking and controlling motor functions (motor pathway). The midbrain is responsible for audio and visual responces whereas the hindbrain contains all the sensory infromation (Sensory pathway). This is responsible for controlling things such as breathing, heart rate and digestion and is attached to the spinal cord. The spinal cord is a group of nerve fibres connected together which lead up to the brain. They appear in a cylinder shape and run down the centre of the spinal column towards the lower back. The spinal cord transmits data from the body organs to the brain. The Peripheral Nervous system (PNS) consists of two types of cells. Sensory and motor nervous cells and is divided into Somatic and Autonomic nervou system. The Somatic nervous system controls the skeleton muscle whereas the Autonomic nervous system controls involuntary muscles. 194 Similarities and Differences between Endocrine system and Nervous system

Endocrine System

Nervous System


Both the Endocrine system and the Nervous system rely on the release of chemicals, such as Epinephrine, around the body to work. They are both regulated by the negative feedback system and both work to monitor and regulate activities inside cells, organs, tissues etc... they respond to external and internal environments to help maintain the perfect homoeostasis.


One of the main differences between the Endocrine and Nervous system is, the Endocrine system works on chemical stimuli to pass signals around the bodies cells and organs. It is made up of a set of glands which secrete hormones. Every glad is responsible for a different area of the body and they use the circulatory system to transmit signals around the body. Communication is transmitted slowly across long distance and their effect becomes longer lasting.

Whereas the nervous system relies on electrical pulses to pass the signals. Is made up of a collection of cells called Neurons which are split into two systems, the Central nervous system (CNS) and the Peripheral nervous system (PNS).The nervous system used these Neurons to transmit signals. Communication is transmitted fast and across shorter distances and are shorter in life.

193 The excretory system is the process of the body removing waste through excretion. It removes waste produced through the homoeostasis cycle and In doing so it maintains a constant homoeostasis. The majority of organs in the human body produce a metabolic waste and thrus the whole body relies on the excretion system to maintain a perfect equilibrium. The major parts of the body involved in this process are the; Kidneys, Ureters, Urethra, Bladder, Skin, Lungs, Large intestine and the Liver.

The urinary system is the major part of the excretory system. The kidneys are two bean shaped organs located below the ribcage, in the middle of the human back. They are processors which process through blood and filter out around 2liters of waste products and water every day. All the waste will become urine which is passed through the Ureter to be stored in the bladder. When you go to the toilet, urine exits the body through the urethra tube. The second major part of the urinary system is based in the liver, one of the largest organs in the human body. Its found on the right side of the body and is the chemical powerhouse within the body. Its purpose is to detoxify and breakdown any alien chemicals that might enter our bodies. The liver produces something called bile, which breaks down fats into waste and usable fats. Around 5ft in lengh, the large intestine sits inside our stomach and transports solid waste to be excreted. It can take up to 24 hours for food to travel through a persons large intestine. The lungs are responsible for respiration, cellular respiration produces carbon dioxide which is a waste product and is eliminated from the body through exhalation. Finally the skin, a crucial part of the excretory system eliminates sweat from the body, sweat contains salt and is a metabolic waste. 310

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