Homeostasis.docx

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MONIQUE MAVRONICOLAS - HOMEOSTASIS

Homeostasis

Homeostasis is important for physiology and anatomy of the body, creating a stable

internal environment for our bodies to be able to live. The cells in our bodies require

nutrients, oxygen, water and a stable internal environment to survive. Changes to

our internal environment can be harmful to our bodies. Our bodies have the ability torespond to internal and external changes to maintain a balance within our cells and

organs.

Essentially all our organs and tissues within our bodies assist to maintain the internal

environment a process nown as homeostasis. !any physiological state of

homeostasis is controlled by the brain, as it taes control of the regulation without us

even nowing through automatic mechanisms. The hypothalamus and the pituitary

gland wor in con"unction and together they form the main control function in

homeostasis.

#hen thining of the homeostasis, one can thin of it as a very intricate balancingact. The following steps indicate a generalisation of how the body communicates tomaintain homeostasis$

Stimulus % creates a alteration to the element that is being regulatedReceptor % monitors the environment and senses the change by the stimulusand respondsInput % information from the receptor then travels along the afferent pathway&carry nerve impulses into the central nervous system' to the centre of controland decides a suitable response and corrective course of action.Output % the information that was sent with regards to the suitable response

now travels from the control centre down the efferent pathway &carry nerveimpulses away from the central nervous system' to the effector &muscles andglands'.Response % the response from the effector will now balance the originalstimulus out to achieve homeostasis again

The table below indicates some types of homeostatic regulation in the body

&http$((opencurriculum.org()*+)(homeostasisandregulationinthehumanbody('

Homeostatic Processes

Hormones

and OtherMessengers

Tissues, Organs

and OrganSystems Involved

Osmoregulation(also known asecretions!

Excess water, salts, andurea expelled from body

-ntidiuretichormone&-H',aldosterone,angiotensin //,carbon dioxide

0idneys, urinarybladder, ureters,urethra &urinarysystem', pituitarygland &endocrinesystem', lungs&respiratorysystem'

Thermoregulation 1weating, shivering,dilation(constriction of

2erve/mpulses

1eletal muscle&muscular system',

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blood vessels at sinsurface, insulation by

adipose tissue,breadown of adiposetissue to produce heat

nerves &nervoussystem', bloodvessels&cardiovascularsystem', sin and

adipose tissue&integumentarysystem',hypothalamus&endocrine system'

"hemicalRegulation(includingglucoregulation!

3elease of insulin andglucagon into the blood inresponse to rising andfalling blood glucoselevels, respectively4

increase in breathing ratein response to increasescarbon dioxide levels inthe blood, and release ofcarbon dioxide intoexhaled air from lungs,secretion oferythropoietin by idneysto stimulate formation ofred blood cells

/nsulin,glucagon,cortisol,carbondioxide, nerveimpulses,erythropoietin&E5O'

5ancreas&endocrinesystem', liver

&digestive system'4adrenal glands&endocrine system'lungs &respiratorysystem', brain&nervous system',idneys &urinarysystem'

6eedbac regulation loops is the pathway homeostasis relies on, a negative

feedbac mechanisms to assist the body in maintaining its conditions within specific

limits. /n order to do this, the body reacts by opposing a change that differs from the

norm. #hereas a positive feedbac mechanism is the precise opposite of a negative

feedbac mechanism. 2egative feedbac is when the output reduces the new effect

of the stimulus. #ithin a positive feedbac system, the output enhances the new

stimulus.

There is a dynamic equilibrium in homeostasis, suggesting that conditions are notidentical at all times, but fluctuate within an acceptable range. #hen we excise our

blood glucose levels might go down and when we eat our blood glucose level might

go up but the regulation mechanism ics in and eeps the parameter within the

acceptable range. 1ame with body temperature, when we exercise our body

temperature might go slightly and similar to when we go to sleep at night our body

temperature drops slightly but the fluctuation of this is still in an acceptable range

and that7s why we call homeostasis a dynamic equilibrium.

Temperature regulation

Humans are homoeothermic, being able to control our body temperature to a certainextent to around *8.) degrees centigrade despite temperature of our surroundings or

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from the heat we generate for ourselves through exercise and internal chemical

reactions. Our ability to thermoregulate temperature happens through our own

voluntary actions and through the automatic mechanisms of the body. Our sin

contains temperature senses that senses external temperature, either hot or cold

and this leads to the appropriate actions. #hen temperature rises, causing the rate

of the chemical reaction in our cells and could even threaten their structure by

destroying the proteins in the cell membrane.

#hen there is a rise in temperature &someone sitting in a steam room' the body

needs to protect its insides from becoming as hot as the outsides. The hypothalamus

is lie the body7s own thermostat, measuring the temperature of the blood flowing

through it. #hen temperature rises the hypothalamus responds with corrective

action, by sending a signal to the sweat glands to wor overtime by producing sweat,

which evaporates, cooling the sin and the blood flowing through it.

Other responses to temperature change is visible to the naed eye, an example is

shivering, when we shiver, the rapid contractions of our muscles generate heat. The

covering of hair over our bodies also assists with temperature control. #hen

piloerection occurs we get a visual result of cutis anserine &horripilation' and at the

same time, corrective processes tae place beneath the surface of the sin. #hen it

is cold outside the body responds by reducing heat loss through a process called

vasoconstriction, when the blood vessels in the dermis narrows.

There is a limit of how much heat variation our bodies can control, when the core

temperature of our body drops below *) degrees centigrade &hiers getting stuc in

an avalanche waiting for a rescue team', most of the chemical processes slows

down and the body starts the process of hypothermia. 1hould the body7s core dropbelow 9: degree centigrade the function of the automatic temperature regulation

through the hypothalamus is lost. 1hould this happen the body is no longer in

homeostasis and the body starts cooling down to match the external temperature.

1hould the body7s core drop below 9) degrees centigrade, death is liely to occur.

The diagram below indicates how body temperature by maintaining homeostasis.

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#lood sugar levels

Our cells need blood glucose to function correctly and for cell respiration. The ideal

ratio of blood glucose for the body is between +;mg % :;mg per ymesin the tissues, especially the liver and the muscles. /t converts the glycogen bac to

glucose, where the glucose passes out of the tissue and into the bloodstream.

The diagram below represents how the endocrine system controls the regulation of

blood sugar levels in our body to maintain homeostasis.

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Osmoregulation

This process taes place in the idneys and is controlled by an antidiuretic hormone&-H'. ?ie most homeostasis mechanisms, the maintenance of water balance

requires negative feedbac. #hen the body is short of water, the salt concentration

within the blood is high, osmoreceptor cells &found within the thalamus' detect the

high salt concentrations. The hypothalamus then responds in two ways, by

stimulating the thirst censors in the brain and then it stimulates the pituitary gland,

enabling the secretion of -H into the blood, which is carried to the idneys. The

idneys then filter the blood and regulates its water content.

Osmoregulation is basically eeping osmolality &concentration of substances such as

sodium, potassium, chloride, glucose and urea' in our blood the same. -lcohol has a

huge impact on this as it disturbs the homeostasis of water regulation. -lcohol is a

diuretic and is the opposite of antidiuretics that we require for homeostasis. #hen

we drin too much alcohol it maes us produce a lot more urine and due to the

diuretic the consequences are extremely concentrated blood.

The idney filters blood and regulates osmolality. -s blood enter the glomerulus and

the small little bits are filtered out and enters the filtrate, down the loop of Henley,

through the collecting ducts and eventually enters into the bladder. 1o basically

osmoregulation is the process in which the systems decides whether it has enough

water in the body, if so, it can let some of it go through urination, however, if we don7t

have enough water we are going to eep, 1o we can regulate how permeable this isto water and so we can osmoregulate.

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The diagram below indicates how the endocrine system controls our blood

osmolarity enabling homeostasis.

"alcuim homeostasis

Calcium homeostasis in extracellular and cellular fluids is essential to normal

function of a different processes within the body. Calcium homeostasis is theregulation of the number of calcium ions in the extracellular fluid. The importance of

calcium homeostasis lies within the amount of calcium that is absorbed by the gut.

#e lose some of our calcium through sweat, urine and fasces but at the same time

the gut compensates for those losses. 3eplacing the calcium lost through excretion,

we require a new source which is our bones. The resorption in our bones protect us

against the ma"ority of extracellular fluid calcium depletion. @ut taing calcium

continuously from the bones could lead to the degradation of the bone and

eventually lead to osteoporosis. -nother example might include people with

tuberculosis, which causes the level of vitamin within the body to increase. #ith

increased vitamin levels it enables more absorption within the body which allowsfor the increase in calcium in the blood. This will increase the extracellular fluid and

cause hypercalcemia and voltagegated ion channels donAt open as easily. This will

in turn cause a depressed nervous system which could lead to more imbalances.

The diagram below explains the complex process of calcium homeostasis.

The rise in calcium in the blood due to the greater absorption of calcium. The thyroidgland receives the information and releases a hormone calcitonin. This travels to theidneys to reduce the output of calcium and to the bones to stimulate calcium ionsdeposition in the bones. The response from the effector would have reduced the

calcium ions and the levels of calcium would have declined to a set point balancingthe original stimulus out to achieve homeostasis again. The opposite happens with

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the low intae ofcalcium as depicted inthe image andsuggested in theparagraph above.

Regulation o$

"ar%on &ioide in

the %lood

/n respiration &in

breathing and

gaseous exchange'

one has two

molecules involved,

oxygen and carbon

dioxide and the

relation between

these two molecules

are regulated in the

blood as a

homeostatic

mechanism through

negative feedbac.

#hen we breathe in,

the O9 vs CO9 ration

is more or less 9;$


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rapidly. This leads to the CO9 level dropping and homeostasis is once again

achieved.

The below image reflects the above description. &www.active learning.com'

Stress and Homeostasis

#hen we experience stress the responses threatens homeostasis that is facilitated

by the stress system. The dominant and peripheral effectors of this system regulates

the cognitive function within the brain affecting many systems that include4

• 3eward and fear systems

• 1leep and awae systems

• =rowth and 3eproductive systems

• /nfluences the gastrointestinal, metabolic and cardiorespiratory systems

•

/mmune system

#hen we there is constant imbalance in the systems above through the stress

system this might lead to various acute and chronic diseases. Bnfortunately our

behaviour and external environment is often very accommodating to stress and the

related disorders.

The diagram below indicates various possible effects on the body and how it

influences and responses in homeostasis.

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3eferences

!aintaining stable body conditions available at

http$((www.bbc.co.u(education(guides(>ncfg+(revision accessed on * Dune 9;


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Homeostasis and regulation in the human body available at

http$((opencurriculum.org()*+)(homeostasisandregulationinthehumanbody(

accessed on Dune 9;

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Homeostasis.docx