Homeostasis Presentation

8/13/2019 Homeostasis Presentation

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Gerry Lennon

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Learning Outcomes1. Define homeostasis and explain its importance to

health

2. Identify the role of the nervous, endocrine andcirculatory systems in homeostasis

3. Describe the components of a feedback system

4. Compare positive and negative feedback loops andgive examples of each.

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Definition

Homeostasis is the bodys ability to maintain relatively stableinternal conditions even though the outside world iscontinuously changing

(Marieb, 2000)

The body is able to buffer fluctuations in the environmentwhich ensures cell functioning and ultimately survival.Changes include;

Nutrients eg.Glucose

Level of toxins/waste

Salinity (osmotic pressure)

WaterpHOxygenTemperature

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Why is homeostasis so important?

The body cells are extremely fussy about intracellularconditions (inside the cell) and it is the fluid outsidethe cell (extracellular/interstitial fluid) whichdetermines whether the inside of the cell is keptconstant. For continued health, chemical balance

must be maintained inside and outside of the cells

glucose carbondioxide

oxygen

ICF=Intracellular Fluid

cell

Extracellular

fluid (ECF)

ICF

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Maintenance of Homeostasis

Occurs via adaptive mechanisms under the control ofthe NERVOUS SYSTEM(neural responses) and theENDOCRINE SYSTEM(hormonal responses).

Neural and hormonal responses ensure that the

following are kept at optimum levels;

Body temperature

Blood pressure (BP)Balance of body salts (eg. NaCl)

Balance of O2 and CO2

Concentration of substance in blood eg. H2O

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Body Systems and Homeostasis

Practically everything that goes on in the body helpsmaintain homeostasis;

Kidneys removes a carefully regulated amount ofH2O and wastes

Lungs work with heart, blood vessels, blood todistribute O2and remove CO2

Digestive system- nutrients pass through the smallintestine into the blood and then to all body parts

Coordinated feedback mechanisms ensure thathomeostasis takes place and appropriate adaptationsby body made in response to changes or STRESSORS

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Imbalance

Most disease is seen as being due to the result ofhomeostasis being disturbed i.e. homeostaticimbalance

With increasing age the control systems are lessefficient and the stability of internal environment isweakened

Enabling Homeostasis to Occur

Need communication within the body: Nervous system - uses electrical & chemical

information that travels through nerves Endocrine system - uses hormones (chemicals

released from endocrine organs) which travel in thebloodstream to their target areas

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The Control SystemReceptor

Is a sensor that monitors the environment andresponds to the change (stimuli)

The control centre

Determines the set point i.e. the range or level at

which the variable has to be maintained Information is now analyzed and an appropriate

response

The effector

This provides the way that something can happen The results then get fed back to influence the stimulus

so that it is repressed/ reduced (negative feedback) orenhanced (positive feedback)

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Variables such astemperature, blood

sugar, and BP areregulated by the bodysresponse to deviationsaway from the norm

and which is calledHomeostasis.Changes in a variablewill stimulate a

receptor to sendmessages to the brainor control centre whichtriggers a response tobring it back to normal


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Negative Feedback

The variable changes in a direction OPPOSITE to thatof the initial change returning it to its ideal value

The output of the system shuts off the original

stimulus or reduces its intensity

The endocrine, cardiovascular and neurologicalsystem are all important for this process

One example is that of temperature control

Can you think of any others?

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Example of Negative Feedback

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Positive Feedback The result or response ENHANCES OR

EXAGGERATES the original stimulus so that theactivity (output) is accelerated

It is positive as the change that occurs is in the SAMEdirection as the initial disturbance and so the variable

deviates further and further from its original value orrange

They control infrequent events that do not needcontinuous adjustments

Amplifies something and usually triggers a cascadesystem

Example: clotting cascade and contractions whengiving birth

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Types of Stressors Affecting

Homeostasis Physical: heat, noise

Chemical: food, hormones

Microbiological: viruses, bacteria

Physiological: tumour

Developmental: age, genetic factors

Psychological: emotional and mental disturbances.

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Illness and DeathIf all systems are functioning adequately thenhomeostasis can be restored quickly via the feedbackmechanisms.

If a system breaks down then person may feel ill.When the body is unable to restore homeostasis thenexternal interventions may be required in order to avoidor delay death.

Can you suggest such interventions you may have seenin clinical practice?

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Group Work!

1. Split into groups of three and identify yourselves as A, B or C

2. Those who are As should explain the components includedin a homeostatic feedback system and how it works- trydrawing a diagram to help you.

3. Those who are Bs need to give an example of a negativefeedback mechanism in our body and describe how it works

including stating where the control centre is located.(choose a simple example!)

4. Finally, those of you who are the Cs need to give an exampleof a positive feedback mechanism, and explain why this isnot as common as negative feedback systems. (you do not

need to explain the detail of your example)

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Homeostasis Presentation

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