BIOLOGY IN FOCUS
MAINTAINING A BALANCE
Chapter 1 Temperature regulation
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HSCCOURSE
Negative feedback mechanisms and temperature
regulation
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gather, process and analyse information from secondary
sources and use available evidence to develop a model of
a feedback mechanism
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Linked to
page 20
Relevant websites on negative feedback mechanisms and
temperature regulation
Use the websites below to develop a general model for a negative feedback mechanism.
www.seas.harvard.edu/courses/es96/spring1997/web_page/health/thermreg.htm
This website deals with how the body functions under changed temperature conditions.
www.innertchill.com/index.php?page=updates
This website has a flow chart and explanation of how a computer monitors its heat levels and
maintains a constant temperature, with software implementing a cooling system to reduce
overheating in the hardware. For this to occur, the software must be able to monitor the hardware
and control and react to changed situations.
http://fig.cox.miami.edu/~cmallery/150/physiol/sf38x17.jpg
Model of room temperature controllers.
http://fig.cox.miami.edu/~cmallery/150/physiol/c44x10thermo-reg.jpg
How the hypothalamus regulates body temperature; this has an excellent diagram representing
homeostatic feedback control of thermoregulation.
www.abcbodybuilding.com/magazine04/thermoregulation.htm
A very interesting website that looks at temperature regulation in the body while participating in
sport. It deals with both overheating in body builders and other athletes and with overcooling,
particularly for people taking part in water sports.
www.southtexascollege.edu/nilsson/4_GB_LectureNotes_f/4_GB_16_AnimS_Ho_J_
Spr2003.html
A simple outline of homeostasis, temperature regulation in the human body and negative feedback,
suitable to give a basic understanding to secondary school students.
1
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Questions on negative feedback model
1. Draw a flow chart of a general model of a negative feedback mechanism in the space provided
below.
2. Compare the model with negative feedback in temperature regulation in humans:
Model
Temperature regulation
stimuli
co-ordinating (control) centre
effectors
negative feedback loop
3.. Using the model of a negative feedback mechanism that you have developed or the generalised
one given to you by your teacher, use different-coloured pens to annotate the model with the
various stages of temperature regulation in humans.
4. To validate your model:
(a) Describe ways in which the application of your model to temperature control is an accurate
representation of a negative feedback mechanism.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
(b) Describe any limitations of this model for temperature control.
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________
2
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5. Complete the table below by naming the effectors and summarising the responses that occur in
each when body temperature increases in mammals:
Heat ________ centre of the hypothalamus sends nerve impulses to effector organs:
Effector
Response
6. Complete the table below by naming the effectors and summarising the responses that occur in
each when body temperature decreases in mammals:
Heat ________ centre of the hypothalamus sends nerve impulses to effector organs:
Effector
Response
7. Insert a suitable diagram (from a website or any other source) to represent the negative
feedback mechanism for thermoregulation in mammals, for example humans. Acknowledge your
source.
3
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
Answers
1. Draw a flow chart of a general model of a negative feedback mechanism in the space provided
below.
Negative feedback model
control centre
receives information
from sensor and
initiates a response
sensor:
detects change
effector:
reponds to
counteract change
increase in
variable
response:
decreases variable
external
change
decrease in
variable
response:
increases variable
sensor:
detects change
effector:
reponds to
counteract change
control centre
receives information
from sensor and
initiates a response
4
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
2. Compare
p
the model with negative
g
feedback in temperature
p
regulation
g
in humans:
Model
Temperature regulation
stimuli
heating up/cooling down
co-ordinating (control) centre
hypothalamus (thermostat)
effectors
arterioles of the skin, muscles, sweat glands, hairs, thyroid
glands
negative feedback loop
negative—the response decreases or counteracts the
stimulus
3.. Using the model of a negative feedback mechanism that you have developed or the generalised
teacher, use different-coloured pens to annotate the model with the
one given to you by your teacher
various stages of temperature regulation in humans.
Negative feedback model
e.g. central nervous system
co-ordinates input and
initiates a response
control centre
receives information
from sensor and
initiates a response
e.g. sensory
receptors in
hypothalamus
e.g thermostat
initiates a response
sensor:
detects change
e.g. oven probe
thermostat detects
change
body
overheats
increase in
variable
effector:
reponds to
counteract change
e.g. heating
element
switches off
e.g. oven
overheats
E
EG
EGs
SWEATGLANDS
produce sweat
sSKINCAPILLARIESDILATE
sDECREASEDMETABOLIC
rate
e.g. oven
cools down
response:
decreases variable
e.g body
e.g.
co down
cools
e oven
e.g.
o
overcools
e.g. oven
heats up
response:
increases variable
e.g.
e.g body
warms
up
wa
e.g. oven probe
e
in thermostat
detects change
d
e.g. heating
element
switches on
n
effector:
reponds to
counteract change
EGs
EG MUSCLESCONTRACT
and produce shivering
sSKINCAPILLARIESCONSTRICT
sHAIRSSTANDERECT
sSWEATINGISINHIBITED
external
change
body
overcools
e.g. sensory
receptors in
hypothalamus
decrease in
variable
sensor:
detects change
e.g thermostat
initiates a response
control centre
receives information
from sensor and
initiates a response
e.g.
e
g central nervous system
co-ordinates input and
initiates a response
5
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.
BIOLOGY IN FOCUS
4. To validate your model:
(a) Describe ways in which the application of your model to temperature control is an accurate
representation of a negative feedback mechanism.
It is accurate because it shows negative feedback where the response decreases
(counteracts) the original stimulus.
(b) Describe any limitations of this model for temperature control.
The model is a simplification of the process and only shows the negative feedback aspects
that we are interested in representing. For example, a thermostat responds to changes in the
external temperature only, but in thermoregulation both external and internal temperature
are monitored and affect the response.
5. Complete the table below by naming the effectors and summarising the responses that occur in
each when body temperature increases in mammals:
Heat loss centre of the hypothalamus sends nerve impulses to effector organs:
Effector
Response
skin—sweat glands
sweating
skin arterioles
dilate
thyroid gland
metabolic rate decreases
6. C
Complete
the ttable
below
by naming
the effectors
and
l t th
bl b
l
b
i th
ff t
d summarising
i i th
the responses th
thatt occur iin
each when body temperature decreases in mammals:
Heat promoting centre of the hypothalamus sends nerve impulses to effector organs:
Effector
Response
involuntary muscles
shivering
skin arterioles
constrict
erector muscles of hairs
contract, causing hairs to stand up
thyroid gland
metabolic rate increases
6
Copyright © 2008 McGraw-Hill Australia. Permission is granted to reproduce for classroom use.