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TRANSCRIPT
Regulating the Body to Maintain Homeostasis
HOMEOSTASIS
As in all systems in nature,
animal systems must
maintain balance.
We call this homeostasis.
How do ecosystems maintain balance?
In animal systems, what must be balanced?
Levels of oxygen/carbon dioxide
Amount of water
Levels of hormones
Levels of waste
Body temperature (warm-blooded animals)
Organ systems work together to
maintain balance Levels of oxygen/carbon dioxide
Taken in and released by the respiratory system
Transported around the body by the circulatory system
Amount of water
Absorbed through the digestive tract
Removed by the excretory system as urine.
Levels of hormones
Produced in endocrine glands
Delivered to their target cells by the circulatory system
Levels of waste
Filtered out of the blood when it passes through the kidneys, organs of the excretory system.
Body temperature
Sensed and maintained by the integumentary system
There are a lot of organ systems at
work here.
How does the body monitor all of this?
Your Brain Does the Monitoring
How does this happen?
Certain parts of your brain are responsible for
completing specific tasks.
How does the brain relay messages to
the rest of the body?
Specialized cells called
neurons.
Networks of neurons
constantly gather,
interpret, and respond
to information about
the body’s internal
state and
environmental
conditions.
Structure of a
Neuron
How does the brain relay messages to
the rest of the body?
Neurons do not touch end
to end. So how do they
pass on messages?
There is a gap between two
neurons called a synapse.
The neuron must use
chemical messengers called
neurotransmitters to
pass the message across the
synapse.
We are going to start by
looking at O2 & CO2 levels.
Which system is responsible for bringing O2 into the
body and releasing CO2?
RESPIRATORY SYSTEM
Back to the brain regulating homeostasis by monitoring what is in the bloodstream!
Respiratory System
How does the structure of the alveoli relate to its
function?
The RESPIRATORY SYSTEM is responsible for the
exchange of gases, BUT the breathing rate is not
controlled here.
The central controlling area for breathing, called the
respiratory center, is in the lower part of the brain stem,
in the medulla oblongata.
How does the brain do it?
Receptors in the brain continuously monitor the
amount of CO2 in the blood.
If there is too much CO2—the brain sends a signal to
increase breathing rates!
Why would this happen?
If there is too little CO2– the brain sends a signal to
decrease breathing rates!
Why would this happen?
What about waste in the bloodstream?
As cells carry out their daily activities they produce wastes
called metabolic waste.
The wastes leave the cell by crossing the cell
membrane and travels in the bloodstream.
These wastes are highly toxic and will poison the organism if
not removed.
What about wastes in the bloodstream?
The brain monitors the amount of waste
in the bloodstream.
How do you get rid of wastes?
As your blood is flowing through your
body, it passes through the kidneys.
The kidneys act as filters, removing
wastes from your blood.
Wastes & the Excretory System What wastes are filtered?
Excess water
Metabolic wastes
Ammonia (urea)
They combine to form urine
which is stored in the bladder
until it is ready to be excreted
when you urinate.
Every day the kidneys send
about 6 cups of urine to
the bladder!
The kidneys aren’t the only part of the
human body that performs excretion
(removal of wastes).
Your skin excretes salts, water,
small amounts of nitrogen wastes,
and other substances as sweat.
Your lungs excrete carbon
dioxide (a waste!) and water
vapor in exhaled air.
Excretion of Wastes in Animals
Simple aquatic invertebrates and some fishes excrete
ammonia into the water through their skin or gills by
diffusion.
Other animals, especially terrestrial animals, need to
minimize water loss.
To do so, they convert ammonia to nontoxic urea and it is
eliminated by urination.
The urine is concentrated or diluted based on how much water
is available.
In this way, eliminating metabolic wastes is linked to
maintaining water balance.
Okay, so far we’ve regulated CO2/O2
levels and wastes.
What about body temperature?
Not all animals have to maintain a constant body
temperature.
Warm-blooded
Maintain a constant internal
temperature using their
metabolism.
Called endothermy.
Cold-Blooded
Adjust to the temperature of
their surroundings.
Do not use their metabolism to
regulate body temperature.
How do endotherms regulate their
internal temperature?
Your body maintains a constant temperature due to the flow
of blood through the blood vessels just under the skin.
To release heat to the air, blood flow is increased to the
vessels.
To retain heat, blood is shunted away from the skin.
How does your body know what temperature it is?
Because of this, endotherms can stay
active at temperatures that would slow
down the activity of ectotherms.
REVIEW WHAT WE HAVE LEARNED SO
FAR:
We rely on our bloodstream to :
deliver nutrients & oxygen
carry wastes to be filtered out in the kidneys
to assist in maintaining body temperature
The brain helps monitor the substances in the bloodstream
& body temperature.
It sends signals to the body via neurons to respond to
changes in the levels of the substances.
How is balance accomplished?
Levels of oxygen/carbon dioxide
Amount of water
Levels of hormones
Levels of waste
Body temperature (warm-blooded animals)
How does the body adapt to change?
Maintaining Homeostasis
Maintaining Homeostasis
Two ways the body responds to change
Negative Feedback
Positive Feedback
Maintaining Homeostasis
Two ways the body responds to change
Negative Feedback
Change occurs and the body responds by reversing the direction of the
change
For example, a car trying to maintain a speed of 55 mph, suddenly
realizes they are going 80 mph
What does the driver do?
The driver applies the brakes.
What happens to the speed of the car?
Maintaining Homeostasis
Two ways the body responds to change
Positive Feedback
Change occurs and the body responds by pushing forward in the same
direction
For example, a car trying to maintain a speed of 55 mph, suddenly
realizes they are going 20 mph
What does the driver do?
The driver accelerates.
What happens to the speed of the car?
Real Life Example
Regulation of Room Temperature
A heater works to maintain the temperature of a room at the temperature it is set (72˚F for example)
As the unit runs, the temperature will rise above 72˚F. A thermostat detects this increase and shuts off the heater.
As the room cools, the thermostat detects the decrease in temperature and signals the heating element to turn on.
What would occur if a window was opened so that so that cold air was allowed to come into the room?