LEARNING AIM B: UNDERSTAND THE HOMEOSTATIC MECHANISMS USED BY THE HUMAN BODY
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Unit 9 - Human Regulation and Reproduction
Instelling
PEARSON (PEARSON)
B. P2 DESCRIBE HOW HOMEOSTATIC MECHANISMS MAINTAIN NORMAL FUNCTION.
B. M2 EXPLAIN THE ROLE OF HORMONES IN HOMEOSTATIC MECHANISMS
B. D2 ANALYSE THE IMPACT OF HOMEOSTATIC DYSFUNCTION ON THE HUMAN BODY
HAJRAH ALI – 40157986
UXBRIDGE COLLEGE
UNIT 9: HUMAN REGULATION AND REPRODUCTION
LEARNING AIM B: UNDERSTAND THE HOMEOSTATIC MECHANISMS USED BY THE HUMAN BODY
HOMEOSTATIC CONTROL OF BODY SYSTEMS
,B. P2 DESCRIBE HOW HOMEOSTATIC MECHANISMS MAINTAIN NORMAL FUNCTION.
B. M2 EXPLAIN THE ROLE OF HORMONES IN HOMEOSTATIC MECHANISMS
HOMEOSTASIS
Homeostasis is the maintenance of a constant internal environment within a living organism. The body has two systems
which require a maintain constant internal environment:
I. Nervous response (The Nervous System)
II. Hormonal response (The Endocrine System)
Homeostasis is important as it allows the survival of organisms to survive in a range of habitats and extend their
geographical range and it is responsible for:
Blood pH: optimum enzyme activity, maintaining shape of antibodies.
Core temperature: optimum enzyme activity
Blood glucose concentration: effective energy transfer and maintaining water potential of blood. Glucose is needed
for respiration.
Water potential of the blood: Maintain correct cellular water potential and structure and maintains osmotic balance
(osmoregulation) of tissue fluid so cells do not burst or shrink.
SET POINTS: Are required by the body to keep physiological features within a narrow range close to the set point. The
set point is the ideal physiological value around which the normal range fluctuates.
Blood glucose concentration: 4-7 mmol/L
pH of Blood: 7.35-7.45
Body temperature: 36˚C – 37.5 ˚C
HOMEOSTATIC MECHANISMS
Process in the body are controlled by feedback mechanisms or loops. Most biological process use negative feedback.
STIMULUS (Imbalance
detected): Muscle and glands
EFFECTOR (Responds to RECEPTOR (Input sent via
change) Responds to the afferent pathway): Detects
output sent from the control changes and sends a message
center. to the control center
(Output sent via efferent pathway) CONTROL
CENTRE (Brain and Spinal cord): Receives the
message and coordinates a response. Sends an
output message to an effector.
, NEGATIVE FEEDBACK
Negative feedback is when change is reversed and
brought back to normal optimum levels (set
point). It ensures the body’s condition remain
within tolerance range.
EXAMPLE: REGULATION OF BODY TEMPEARTURE
Hypothalamus Relaxation of hair erector
muscles.
Temperature Vasodilation
increase sweating
Thermoreceptors
37˚C 37˚C
Temperature Vasoconstriction
Decrease Shivering
Thermoreceptors
Contraction of hair erector muscles
Hypothalamus
The hypothalamus is situated in the brain and contains the thermoregulatory centre (coordinator). Monitors and
controls body temperature.
TEMPERATURE REGULATION (Poor system) TEMPERATURE REGULATION (Effective system)
The body requires an optimum temperature of 36˚C – The body requires an optimum temperature of 36˚C –
37.5 ˚C so that the enzymes involved in key bodily 37.5 ˚C so that the enzymes involved in key bodily
processes and reactions. If an increase in temperature is processes and reactions. If an increase in temperature is
detected by the thermoreceptors, the hypothalamus detected by the thermoreceptors, the hypothalamus
then communicates this with the effectors and these then communicates this with the effectors and these
structures respond by increasing the production of structures respond by increasing the production of
sweat and vasodilation. As a result, the body sweat and vasodilation. As a result, the body
temperature will decrease and return within the range temperature will decrease and return within the range
limits. However, if that was it the increased sweating limits. However, if that was it the increased sweating
and vasodilation would continue and the body and vasodilation would continue and the body
temperature would eventually go below the lower temperature would eventually go below the lower
range, which is just as dangerous. range, which is just as dangerous. To
return to within the range, the
receptors detect this, and the
hypothalamus instructs the effects to
reduce sweating and to stop vasodilation, so that the
temperature remains within limits.
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