Regulating the Body to Maintain Homeostasis

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HOMEOSTASIS

• Regulating the Body to Maintain Homeostasis

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As in all systems in nature,animal systems must
maintain balance. We call this
homeostasis.
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How do ecosystems maintain balance?
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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)

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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

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There are a lot of organ systems at work here.
How does the body monitor all of this?
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Your Brain Does the Monitoring

• How does this happen?
• Certain parts of your brain are responsible for
  completing specific tasks.

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The Brain is part of the Nervous System.

• Two parts of the nervous system
• Central Nervous System (CNS)
• Control center of the body
• Consists of the brain and spinal cord
• Functions to interpret and respond to information
  from the environment and from within the body
• Peripheral Nervous System
• Transmits signals between organs and CNS
• Sensory neurons-send information from sense
  organs to CNS.
• Motor neurons-send commands from CNS to muscles
  and other organs.

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The Brain
Which part of the brain do you think will be
involved in maintaining homeostasis in an animal
system?
THE BRAIN STEM
CEREBRUM Learning, Memory, Perception,
Intellectual Function
Regulates breathing and heart rate, feelings of
hunger and thirst, controls secretions of
hormones, regulates body temperature, sleep.
Regulates balance, posture, and movement
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The Brain Stem-divided into two areas

• The Upper Brain Stem
• Thalamus- central site for sensory processing
• Hypothalamus- regulates heart rate, breathing
  rate, feelings of hunger and thirst, controls the
  release of hormones

• The Lower Brain Stem
• Relays information throughout the CNS
• Medulla oblongata- Regulates heart rate,
  breathing rate, body temperature, and sleep

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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 bodys
  internal state and environmental conditions.

Structure of a Neuron
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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.

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We are going to start by looking at O2 CO2
levels.
Back to the brain regulating homeostasis by
monitoring what is in the bloodstream!
Review!
Which system is responsible for bringing O2 into
the body and releasing CO2? RESPIRATORY SYSTEM
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Respiratory System

• How does the structure of the alveoli relate to
  its function?

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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.
  

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How does the brain do it?

• Receptors in the brain continuously monitor the
  amount of CO2 in the blood.
• If there is too much CO2the 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?

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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.

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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.

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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!

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How do the kidneys filter blood?

• Within each kidney are about one million
  nephrons.
• Blood passes through the nephron where wastes
  (urea, excess water, salts) are filtered out.
• The cleansed blood goes back into the veins that
  carry the blood from the kidneys and back to the
  heart.

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The kidneys arent 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.

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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.

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Okay, so far weve regulated CO2/O2 levels and
wastes.

• What about body temperature?
• Not all animals have to maintain a constant body
  temperature.

• Cold-Blooded
• Adjust to the temperature of their surroundings.
• Do not use their metabolism to regulate body
  temperature.

• Warm-blooded
• Maintain a constant internal temperature using
  their metabolism.
• Called endothermy.

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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?

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Because of this, endotherms can stay active at
temperatures that would slow down the activity of
ectotherms.
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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.

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How is balance accomplished?

• Levels of oxygen/carbon dioxide
• Amount of water
• Levels of hormones
• Levels of waste
• Body temperature (warm-blooded animals)

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Maintaining Homeostasis

• How does the body adapt to change?

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Maintaining Homeostasis

• Two ways the body responds to change
• Negative Feedback
• Positive Feedback

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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?
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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?
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Real Life ExampleRegulation of Room Temperature

• A heater works to maintain the temperature of a
  room at the temperature it is set (72F for
  example)
• As the unit runs, the temperature will rise above
  72F. 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?