Gas Regulation
Breathing rate mainly depends on the amount of carbon dioxide in the blood
(not oxygen as you would probably think!).
INCREASE
When carbon dioxide levels increase, the blood becomes more acidic.
Chemoreceptors in the brain and major arteries coming out of the heart (aorta
and carotid artery) sense this change. The brain sends signals to the
diaphragm and rib cage muscles to work harder (increases respiration rate) to
get rid of the extra carbon dioxide.
DECREASE
If CO2 levels are low chemoreceptors in the brain and major arteries coming
out of the heart (aorta and carotid artery) sense this change. The brain sends
different signals to the diaphragm and rib cage muscles to slow down
(decreases respiration rate).
CONTROL CENTER:
What sends out a
signal?
EFFECTOR:
What changes? What’s
the effect?
SENSOR:
What changes?
What senses it?
SET POINT
SENSOR:
What changes?
What senses it?
EFFECTOR:
What changes? What’s
the effect?
NOTE: In general, carbon dioxide (CO2) and oxygen levels in the blood are
opposites. Oxygen is being continually used by cells so its concentration in the
blood decreases naturally. In contrast to carbon dioxide, oxygen
concentration needs to fall significantly before any increase in breathing rate
results. The body mainly uses carbon dioxide levels to control breathing rate.
CONTROL CENTER:
What sends out a
signal?
EFFECTOR:
Thermoregulation (Temperature)
CONTROL CENTER:
The process of maintaining a steady body temperature under a variety of
conditions is known as thermoregulation. The hypothalamus protects the
body’s internal organs by monitoring temperature.
activates the
INCREASE
When thermoreceptors in the hypothalamus receive information that the
temperature of the blood is rising, it sends a signal to the sweat glands causing
them to release sweat to help cool the body. In addition, the hypothalamus
activates the adrenal glands. The adrenal glands release a signal telling the
blood vessels to relax and dilate bringing more hot blood to the surface so
heat can escape. The same signal also goes to the heart and lungs causing an
increase in heart and breathing rates. All of these activities carry heat away
from the center of the body to the surface, where excess heat can escape.
EFFECTOR:
EFFECTOR:
SENSOR:
SET POINT
SENSOR:
DECREASE
When the temperature of the blood falls too low, thermoreceptors in the
hypothalamus receive the information. A signal from the hypothalamus
causes the skeletal muscles to perform small, rapid contractions (shivering).
Then, the hypothalamus activates the adrenal glands. The adrenal glands
release a signal telling the blood vessels in the skin to constrict, reducing
blood flow to prevent loss of heat. The hypothalamus also activates the
pituitary to send hormone signals to the thyroid to increase production of
thyroxine hormone which speeds up metabolism. When metabolism speeds
up, more heat is generated. These activities reduce the loss of heat to the
environment and increase body heat.
CONTROL CENTER:
activates the
and the
EFFECTOR:
EFFECTOR:
EFFECTOR:
Osmoregulation (Water)
EFFECTOR:
CONTROL CENTER:
Osmoregulation is the regulation of water concentration in the bloodstream.
Water follows salt so salt regulation contributes to water regulation.
SENSOR:
INCREASE
When water levels rise above the normal range, osmoreceptors in the
hypothalamus in the brain sense increased water concentration and
decreased solute concentration (meaning there’s not much salt in the blood).
The hypothalamus stops making a hormone. Without this hormone, kidneys
reabsorb less water and more urine is produced to get rid of the extra water.
At the same time, stretch receptors in the heart sense increased blood volume
(blood has lots of water). Heart muscle cells send a signal to the kidney telling
it to excrete sodium. Water follows salt, so water leaves with the salt
lowering water levels in the body.
DECREASE
When water levels drop below normal range (by sweating), the
osmoreceptors in the hypothalamus in the brain detect higher concentration
of salts in the blood (lower concentration of water). The hypothalamus
releases a hormone it made through the pituitary. This signal causes the
kidney to reabsorb more water (reducing the amount that becomes urine) and
creates a feeling of thirst. The person drinks water to return water levels to
normal. At the same time, stretch receptors in the heart sense that there is
low blood volume. They tell the adrenal glands to release a signal to the
kidney. This signal causes the kidney to actively reabsorb sodium. Since water
follows salt, more water is returned to the body rather than excreted in urine.
CONTROL CENTER:
EFFECTOR:
SENSOR:
SET POINT
SENSOR:
SENSOR
EFFECTOR:
CONTROL CENTER:
EFFECTOR:
CONTROL CENTER:
This shows how water is
reabsorbed into the body
rather than released as urine.
EFFECTOR: