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Chapter 1-6

BPK 205 Chapter Notes - Chapter 1-6: Blood Vessel, Homeostasis, Positive Feedback

2 pages33 viewsSummer 2009

Department
Biomedical Physio & Kines
Course Code
BPK 205
Professor
Parveen Bawa
Chapter
1-6

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Chapters 1-6 Practice Questions
1. How is the body temperature maintained at 37 deg C after you swallow a glass of very
cold water? Can the same mechanism maintain the body temperature when you are
dropped in the Arctic in December? [total one page with a figure; 15 minutes]
The body maintains its 37 deg C temperature by countering the loss of heat
instigated by the cold water. Nerves in the skin send signals to the hypothalamus in the
brain that senses the loss in body heat. This triggers the release of signals of both the
endocrine and nervous systems that start heat preserving actions. These actions may
include: reduced sweating, teeth chattering, shivering, blood flow distribution
concentrated more at the core of the body rather than skin. This system is called a
negative feedback system. There is a stimulus (the cold water), that causes a change in
temperature that is sensed by a sensor (nerves). This triggers an input signal that travels
to an integrating center (hypothalamus) via the afferent pathway. The integrating center
triggers multiple signals that travel via the efferent pathway to different targets/effectors
(blood vessels, sweat glands, muscles). The targets then initiate an appropriate response
(core blood vessel dilation, blood vessel constriction near skin surface, reduced sweat,
shivering).
Being dropped in the Arctic is a huge external change that would result in a great
internal body temperature change. This change would be too large for the body to
compensate for using this mechanism. The same mechanism would fail, and you would
die.
Stimulus Drinking cold water
Sensor/receptor Nerves
Afferent pathway
Integrating Center hypothalamus
Efferent Pathway
Target/effector blood vessels, sweat glands, muscles
Responses core blood vessel dilation, blood vessel constriction near skin surface,
reduced sweat, shivering
2.What is a negative feedback system? [Total one page, with a figure, No example; less
than 10 minutes]
Input/Desired Output Error Signal Control System Output
Feedback
This is a diagram of a closed loop system. A negative feedback system is a type of closed
loop system. In a negative feedback system, the difference between the desired output
and actual output is detected by the body, often through receptors or sensors. The body
will send out a response that will decrease this difference, most often in order to maintain
homeostasis. A negative feedback system opposes a stimulus, and opposes change. In a
way this can be perceived as correcting an error. Once this error is corrected the response
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