7.3 Homeostasis

7/28/2019 7.3 Homeostasis

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7.3 Maintenance of thebody at rest, and in

activity


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Syllabus objectives

Discuss the concept of homeostasis and its importance

in maintaining the body in a state of dynamic

equilibrium during exercise, including the role of the

hypothalamus and the mechanisms of

thermoregulation.

Explain the principle of negative feedback in

maintaining systems within narrow limits.


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Understand that cardiac muscle is myogenic and describelectrical activity of the heart, including the roles of the s(SAN), the atrioventricular node (AVN) and the bundle of Hisuse of electrocardiograms (ECGs) can aid the diagnosis of

disease (CVD) and other heart conditions.

Explain how variations in ventilation and cardiac output enableof oxygen to tissues and the removal of carbon dioxide from thow the heart rate and ventilation rate are controlled and thcardiovascular control centre and the ventilation centre.


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Syllabus objectives Describe how to investigate the effects of exercise on

and breathing rate using data from spirometer traces.


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Definition the maintenance of a constant internal environment.


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How is homeostasis achieved?

Negative feedback mechanism


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Components of a negative feedback mech

The detectors are specialised cells either in the brain or in other organs, suc

The effectors are organs such as the skin, liver and kidneys. Informatio

detectors and effectors via

the nerves of the nervous system, or via hormones (the endocrine system), o

The outcome is an incredibly precisely regulated internal environment.


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Homeostasis in action control of body temp

Heat may be transferred between an animal and the envconvection, radiation and conduction, and the body losevaporation


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ThermoregulationThe regulation of body temperature, known as thermoregulation

consists of a heat loss centre

and a heat gain centre

temperature-sensitive nerve cells(neurones) are situated, anddetect changes in thetemperature of the blood flowingthrough the brain.

The thermoregulation centre ofthe hypothalamus also receivesinformation via sensory nervesfrom temperature-sensitivereceptors located in the skin andin many internal organs.


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How The hypothalamus communicates with tthe body

via the autonomic nervous system.

For example, when the body temperature is lower than normathe heat gain centre inhibits activity of the heat loss centre, ansends impulses

to the skin,

To hair erector muscles,

To sweat glands and elsewhere, that decrease heat loss (such as by causi

vasoconstriction of skin capillaries) and increase heat production (causing shivering, and enhanced brown fat respiration, f

example).


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The role of the skin in temperature regu

l f ill i i l i h


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role of capillaries in regulating heatloss through the skin


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role of the sweat glands in regulating hethrough the skin


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role of the hair in regulating heat lossthrough the skin

H t i i ti l ti f di


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Homeostasis in action regulation of cardia

The heart beats rhythmically throughout life, withoutfrom the momentary relaxation between beats.

The heart beat is myogenic in origin.

The heart beat originates in a structure in the muscle of thright atrium, called the sino-atrial node (SAN), also known apacemaker.

Muscle fibres radiating out from the SAN conduct impulses to t

both atria, triggering atrial systole (contraction).

Then a second node, the atrio-ventricular node, situated at thright atrium picks up the excitation and passes it to the vent

modified muscle fibres, called the Purkinje fibres.Ventricular systole is then triggered.


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7.3 Homeostasis

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