Transcript Body temperature regulation

Detecting
Temperature Change
• Internal (core) body
temperature is kept constant
within a narrow range of
about 37 - 38
• Changes to internal body
temperature are detected by
hot and cold receptors in the:
–
–
–
–
–
Skin
Hypothalamus
Spinal cord
Large veins
Parts of the digestive system
Receptors
are made
up of
sensory
neurons
also
called
affector
neurons
External
Internal
Detecting
Temperature Change
• Changes in the external temperature
cause changes in the temperature of
exposed skin
• These changes are detected by 2
different types of receptors located
just under the skin:
– Hot – these receptors detect heat by
increasing electrical impulses to the
hypothalamus
– Cold – these send more electrical
impulses when cold.
Detecting
Temperature Change
Causes of
temperature change
• To maintain a stable core
temperature:
Heat Production = Heat Loss
• This is controlled by the
hypothalamus
Heat Production
• The body constantly produces heat
through:
– Cellular respiration
• The body is able to increase body
(all of these
temperature by:
– Shivering
– Movement
– Increased metabolism
}
things increase
the rate of
cellular
respiration)
– Raising the hair on skin surface
• Piloerection - trapping warm air close to
the skin’s surface and reduces heat loss
– Reducing blood flow to skin
• Vasoconstriction
Heat Loss
Heat is transferred
from warmer objects to
colder objects (a bit
like diffusion)
• Heat is lost by the body through a
range of processes: When heat is lost in energy waves
– Radiation
When heat is lost to the air due to direct
(both of these
due to
contactoccur
with skin
– Conduction
the temperature difference
Movement of air which maintains the
(gradient)
between our warm
– Convection
temperature gradient
bodies and the air at the
– Evaporation Even
without
sweating, water is lost from skin
skin’s
surface
}
continually, causing a cooling effect
• The body is able to reduce body
temperature by:
– Increased sweating
– Increased blood flow to skin’s surface
• Vasodilation
– Decreased metabolism
Vasodilation
Urine
Radiation
behaviour
sweat
faeces
Conduction
Expired air
Heat loss
Panting
Convection
Conduction
Radiation
Convection
Heat gain
Metabolism
Vasoconstriction
Vasodilation - capillaries increase in
size to increase SA for heat to be lost
(usually causes skin to appear pink/red flushed)
Vasoconstriction - capillaries decrease
in size in decrease SA for heat to be lost
(usually causes skin to appear
purple/blue)
Sweating
Water evaporates. For liquid to change to a gas
state heat is needed. As sweat evaporates it uses
body heat to turn it into a gas.
Shivering
Uncontrolled muscle spasms. Muscle
contraction requires energy (ATP)
therefore cellular respiration will
increase - a reaction that produces
60% heat.
Piloerection
Hairs stand on end producing goose
bumps trapping a layer of heat around
the body.
Thyroxine
Hormone that increases or decrease the
metabolic rate. Pituitary gland stimulates the
thyroid gland to increase/decrease
production of thyroxine.
Insulation - fur, blubber feathers.
Decreasing SA - roll into ball
sleeping together in nests.
Behavioural - take clothing off,
seek shade jump around.
•Sweating panting
•Vasodilation
Body temperature
increases
•Decrease in Thyroxine
•decrease SA
•Burrow
Normal Body
Temperature 37°C
Normal Body
Temperature 37°C
•Shivering
Body temperature
decreases
•Vasoconstriction
•Increase in Thyroxine
•Increase SA
•Piloerection