Homeostasis is the maintenance of a constant internalenvironment within an organism or cell to maintain equilibrium, usually using asystem of feedback controls to stabilise health and proper functioning.Homeostasis can control steady water levels, blood sugar level and temperaturewhich are vital in survival as they can be changed depending on the externalenvironment, whether being in a cold or hot climate, the body will adaptinternally in order to keep itself functioning. The human body has receptors todetect stimuli, processing centres which receive information, a coordinator thatwill receive and control the information from the receptor and trigger theresponse that will correct the change and an effector that carries out theaction that will bring about the change. For example, the body’s overall temperature must always remainat 37 degrees Celsius as enzymes can only function properly at this temperature.
There are temperature receptors found within the skin which can detect change withinthe external environment and then this information is passed onto thehypothalamus as it is the brain’s processing centre and it also has receptorsthat can detect change in blood temperature. Whenever the internal or externaltemperature changes, the hypothalamus will be triggered and result in a changein the body’s effector (in this case sweat glands and muscles) to maintain thecorrect temperature. If it discovers that the body is too hot, glands withinthe skin will secrete sweat onto its surface which will increase heat loss byevaporation.
If the body is too cold, muscles in the skin contract, causing thehair on the arms to stand up straight which in turn traps a layer of warm airnext to the skin to prevent heat loss. This happens all over the body in manydifferent ways in order to maintain stability in the body or the body couldmalfunction. How the endocrine system is involved with homeostasisThe endocrine system has glands that secrete hormones, whichare chemical messenger molecules, into the bloodstream to be used in anotherpart of the body. The endocrine has an important role within homeostasisbecause it is the hormone’s job to regulate the activity of body cells whichcan be changed to achieve homeostasis. Release of hormones is controlled by astimulus which either increases or decreases the number of hormones secreted,depending on what is needed for a specific situation. The endocrine system is involved with certain homeostaticregulations such as osmoregulation, where antidiuretic hormones (ADH) arereleased from the pituitary glands in the kidneys. ADH balances theconcentration of urine by absorbing water, so too much water in the blood willincrease ADH release, while too little water will decrease ADH release. Theendocrine system is also involved in thermoregulation as the hypothalamus candetect change in blood temperature.
Examples of homeostasis within the bodyGlucose level within the bloodstream must be maintained inhomeostasis, so when this level changes, the body will react to correct it.When there is an increase in glucose levels in the blood, for example, eatingglucose rich food such as fruit and vegetable, the increase of the glucoselevel in the blood will be detected by the beta cells found in the pancreas.The pancreas then releases insulin into the bloodstream which helps the liverto take up the glucose and break it down into glycogen to be stored. Insulinincreases the rate of respiration within the body cells, therefore increasingthe glucose uptake which helps in the regulation of the glucose level in theblood. This is a negative feedback loop because the change detected was anincrease and this had to be reduced. 123 When there is a decrease in glucose level in the blood, forexample, not eating for an entire day, the alpha cells in the pancreas willdetect this change and glucagon will be released.
The glucagon will facilitatethe breakdown of glycogen stored to glucose within the liver and released intothe bloodstream, therefore increasing the glucose level in the blood. Hyperglycemiais when the glucose level is above the normal range (980mg – 100mg / 100ml),this can be a result of type 1 diabetes where the body cannot makeinsulin, or type 2 diabetes where the body cannot respond to insulin properly,so the glucose builds up in the blood. This can result in damaging the vesselsthat supply blood to vital organs, increasing risk of heart disease/stroke,kidney disease, vision problems and nerve problems for diabetic people.Hypoglycemia is the opposite, where the level of glucose in the blood is lowerthan the normal range which can be a result of not eating, or not takingdiabetic medicine and can result in confusion, seizures or death. The blood oxygen level is also maintained throughhomeostasis, as the kidneys constantly measure how much oxygen is in the blood,if they discover that there is a decreased red blood cell count, then there isa low blood oxygen carrying affinity, leading to decreased haemoglobin, meaningthat there is a decreased availability of oxygen. Erythropoietin (EPO, ahormone produced by a specialised cell in the kidney) is secreted by thekidneys which will then stimulate red bone marrow. Red blood cells are thenproduced by the red bone marrow as it is the effector which will in turnincrease the red blood cell count, meaning the oxygen level is increased,maintaining homeostasis.456 Carbondioxide is a waste product of respiration, in order to leave the body, ittravels in the blood streamfrom the cells to the lungs where it leaves the body during exhaling.
Carbondioxide forms an acidic solutionwhen it dissolves in water, so the carbon dioxide levels must be controlled toprevent the blood frombecoming too acidic or too alkaline. If carbon dioxide levels get too high, thepH of the blood can be affected,resulting in blood proteins and enzymes being affected too which can result inblood clotting. During afeedback loop, the CO2 level increases, decreasing the pH and oxygenlevels in the blooddecrease aswell as cerebrospinal fluid. The reflex response has the chemoreceptors being stimulated,resulting inthe respiratory response where the medulla oblongata (Lowest part of thebrainstems thatcontrols theheart and lungs) is stimulated, increasing the respiratory rate, thereforerestoring homeostasiswith the CO2level decreasing, pH increasing, oxygen levels in the blood and CSFincreasing.
7 8910 How each key organ system works together and contributesto overall functioning of the human bodyAll of the major organsystems in the human body work together in at least way in order to keep thebody functioning. The cardiovascular system, which is responsible for bloodcirculation around the body, transports oxygen, carbon dioxide, nutrients andhormones to keep the body functioning. The cardiovascular system works with theendocrine system as the hormones released by glands within the endocrinesystem, use the bloodstream to transport hormones around the body to where theyare required. The cardiovascular system also works with the digestive system,as the digestive system processes food, nutrients and water are absorbed intothe bloodstream which can then be transported to where they are required aroundthe body. The cardiovascular system and excretory system coordinate because thekidneys filter out waste and fluid from the bloodstream to produce urine whichis micturated from the bladder, this keeps the blood as clean as possible. Thenervous system can prepare the body for the ‘fight or flight’ mechanism withthe sympathetic and parasympathetic systems, which can raise the heart rate asthere is more adrenaline or inhibit it.
The endocrine system workswith the digestive system as the pancreas can produce insulin, which is used toregulate glucose levels in the blood, which helps in maintaining homeostasis.The excretory system is regulated by the endocrine system, because thehypothalamus can detect when the body is dehydrated so antidiuretic hormonesare created and released from the pituitary gland, then circulates to thekidneys where it causes them to increase their rate of reabsorption of wateruntil homeostasis is restored. The endocrine and nervous systems are bothcommunication systems within the body and are connected by the hypothalamus,which controls the autonomic system, and this is responsible for bodilyfunctions not controlled consciously.
The hypothalamus is also responsible forsecreting many different hormones for where the nervous system detects thatthey are required. The nervous system also works with the digestive system asit can control the digestive tract’s size and tone to maximise its use. The digestive system helpsall other systems in the body as it provides nutrients, which provide energy,allowing everything to grow and function as it should. The excretory systemalso helps all of the other organ systems as it expels the waste products outof the bloodstream, which reaches all organ systems. Compareand contrast how the endocrine system and nervous system help control our bodyfunctionsThe endocrineand nervous systems have both similarities and differences, the largestdifference is that thenervoussystem uses chemical impulses through a continuous network of neurons to relaymessages inboth chemicaland electrical forms and are much quicker but shorter lasting. The endocrinesystem uses chemical messengerscalled hormones which are transported through the cardiovascular system usingtheblood streamtowards their target cells and while this signal transmission is slow, thefunctions are longer lasting. Thereare countless different types of hormones in the endocrine system, whereas inthe nervous system, thereare only three different types of neurons: sensory neurons which carryinformation from the sensoryreceptors, motor neurons, which transmit information from the brain to themuscles of the body and interneuronswhich communicate between different neurons within the body. Both systemsregulate bodily functions, however the nervous system mainly transmitsinformationregardingexternal stimuli, meanwhile the endocrine system transmits informationaffecting the interior and wellbeing ofthe interior of the body.
They are both connected via the pituitary glandswhich is connected tothehypothalamus which allows the nervous system to send and receive informationfrom the endocrinesystem, whichin turn, regulates reactions going on around the body. The nervous system candetect changes inthe environment which can activate a response from the endocrine system inorder to carry outa change.1 AdvancedBiology for You 2nd Edition by Gareth Williams published 2015 pp331-332.
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