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Homeostasis
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The way the body keeps its internal
environment constant How the body “maintains a steady state”
What internal conditions need to be maintained? Temperature Blood pH Water levels Blood Glucose Levels
What is Homeostasis?
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General mechanism of nervous or
hormonal regulation in animals Triggered when the response to a
stimulus has an effect of some kind ( or ) on the original stimulus Type of response ( or ) determines
how we label feedback
Feedback Mechanisms
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Negative feedback : When a change in
the system occurs, a corrective measure occurs to bring system back towards the set point.
Positive feedback : When a change in the system occurs, a corrective measure occurs to amplify the system, moving it away from its set point
Feedback Mechanisms: How do we label?
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How does your body try to warm-
up when you feel cold? Hair’s stand on end Blood vessels near the surface
receive less blood Shivering Behavioral responses
Thermoregulation: Cold
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Hair stands on end so
air currents do not get to the skin, traps an insulating layer of still, warm air next to skin
Blood vessels near the skin constrict (vasoconstriction) so less blood passes through them. This means less heat is lost by radiation.
hair
Bloodvessel
Thermoregulation:Cold
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Shivering:
Your muscles contract involuntarily, generating heat
Behavior: Curl up, huddle, put on more
clothes, drink something warm
Thermoregulation: Cold
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How does your body try to warm-up
when you feel cold? Sweating Blood vessels near the surface receive
more blood Hairs lie flat Behavioral responses
Thermoregulation: Hot
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Sweat is produced by sweat glands. When this evaporates, it cools the skin.
Thermoregulation
Sweat gland
Hair lies flat so air currents get to the skin. Heat is lost by convection.
Blood vessels near the skin dilate (vasodilation) so more blood passes through them. This means more heat is lost by radiation.
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Normal body temperature is restored
Normal body
temperature
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VasodilationHairs lie flatBody sweats
Normal body temperature is restored
VasoconstrictionHairs stand on endBody doesn’t sweat
Shivering occurs
Normal body
temperature
The
hypothalamu
s detects a
fall in
temperature
Body
temperature
falls
Body
tem
pera
ture
rises
The
hypo
thal
am
us d
etec
ts a
rise
in
tem
pera
ture
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Heat Stroke: a condition marked by
fever and often by unconsciousness, caused by failure of the body's temperature-regulating mechanism when exposed to excessively high temperatures.
Mark’s Case
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Exit Ticket Think back about Mark’s Case and the video you
just watched on heat stroke and answer the following questions: Why is Mark weak, delirious, nauseous, and
disoriented (this is a straightforward answer!)? DESCRIBE how Mark’s body initially reacted to being in
extremely warm temperatures. Why couldn’t Mark produce anymore sweat once he had
been out in the sun for a long period of time? Why would his blood pressure drop and his heart rate increase?
Is thermoregulation an example of positive or negative feedback? WHY?
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