Homeostasis keeps the internal environment within set ranges.
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Transcript of Homeostasis keeps the internal environment within set ranges.
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• Homeostasis keeps the internal environment within set ranges.
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• Temperature
• Water
• Blood pressure
• Acid/base (pH)
• Calcium
• Glucose
• Oxygen & carbon dioxide (CO2)
• Wastes
• Bacteria/viruses
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• Negative feedback is similar to a thermostat:
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• Compares current conditions to “set points”
– What is normal? Is it above or below normal?
• Negative feedback counteracts change.
Negative Feedback Loop
Holding breath, CO2 levels rise,
Control system forces exhale, inhale
O2 / CO2 level returns to normal
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• CountryStateCountyCity
USAMichiganKentGrand Rapids
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OrganismOrgan SystemsOrgansTissuesCells
HumanRespiratory
SystemLungsLung tissueLung cellsORGANS
ORGAN SYSTEM
ORGANISM
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• Organ systems must work together to keep the organism healthy.
Ex: Organ systems work together to produce Vitamin D.
1
2
3 4
Skin absorbs UV light
Liver produces inactive vitamin D
Kidneys produce active vitamin D Active vitamin D used in bones
UV light
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• Ex: Organ systems work together to control body temperature
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BrainBrain
Spinal cordSpinal cord
Nerves (bundles Nerves (bundles of neurons)of neurons)
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The BrainThe BrainResponsible for:1) Balance, breathing, posture,
moving, speaking…- Different parts control different functions
2) Higher-level functions such as: Thinking & learning– This requires connections
between neurons–When you remember
something, you are pulling info from different parts of your brain!
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2 main responses2 main responses
1.1. VoluntaryVoluntary: Lets us react : Lets us react consciouslyconsciously to changes in our to changes in our environmentenvironment
- Behavioral response - Behavioral response
- ex. Moving, eating, running, - ex. Moving, eating, running, walkingwalking
- controlled by cerebrum: - controlled by cerebrum:
largest part of the brainlargest part of the brain
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Voluntary Reactions
AKA: Behavioral
You DO control this
Ex: walking, stretching, drinking, smiling, scratching,
flexing muscles
* CONTROLLED BY:
cerebrum
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2. 2. InvoluntaryInvoluntary: Lets us : Lets us react react automaticallyautomatically to to changes in our changes in our environmentenvironment
- Physiological - Physiological responseresponse
- ex. Blood pressure, - ex. Blood pressure, heart rate, breathingheart rate, breathing
- Maintains - Maintains homeostasishomeostasis
- Controlled by brain - Controlled by brain stem: connects brain stem: connects brain to spinal cordto spinal cord
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How does your body send and receive signals?
• 1. Stimulus: A change (internal or external)• 2. Sensor: Nerve that detects the change and
sends information to brain**Brain interprets the message-
• 3. Effector: The glands, organs, or muscles that the brain sends a message to based on the stimulus
• 4. Response: Reaction/what changes because of the stimulus
• These responses can be VOLUNTARY or INVOLUNTARY(behavioral or physiological)
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HOW IT WORKS
Basically, a signal comes in from the outside world, the signal travels to the brain, and the brain sends a signal back out to the body to act.
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Stimulus Loud Crash
Cold Temperature
Familiar Face
Tap on Shoulder
Stub Toe
Dropped brick on foot
Smell of dinner cooking
Many more!!
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Sensors A sensor is an
organ or part that picks up a signal from the outside world.
Ex: Five Senses finger gets burned
Foot steps on a nail
Ear hears loud bang
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Spinal Cord
All sensory nerves must travel to the spinal cord.
The spinal cord takes the messages to the brain.
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Brain
Signals travel through the spine, to the brain.
The brain processes the signal and decides what to do.
Ex: move arm, run away, smile, shiver
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Effector
The muscle or gland that has received a signal from the brain, telling it what to do
Ex: contract muscle to move leg
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Response Move your hand away!
Pull foot away!
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Example• Stimulus = Someone throws a ball at you• Sensor = Your eyes see the ball and send
the information to your brain• Effector = Your arm muscles• Response = You move your arms to catch
the ball
• What kind of response is this? Voluntary/involuntary? Physiological/Behavioral?
• VOLUNTARY / BEHAVIORAL
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Example• Stimulus = There is a bear in the forest where you’re walking• Sensor = Your eyes see the bear and
send the information to your brain• Effector = Your blood vessels and heart• Response = Your blood vessels
constrict and your heart begins beating faster (fight or flight)
• What kind of response is this? • INVOLUNTARY / PHYSIOLOGICAL
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EffectorsVoluntary
• Skeletal Muscles (ones we can control)
• Makes a BEHAVIORAL response
• Examples: smiling, laughing, walking, talking, kicking a ball, eating, reading
Involuntary
• Smooth and cardiac muscles (ones we can’t control)
• Glands
• Makes a PHYSIOLOGICAL response
• Examples: increased blood pressure, breathing, blood flow, heart beat, digestion
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Reflexes
• Special type of nervous system reaction
• Very fast• Can anyone think of a reflex
example?
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Reflex Examples
• Knee-jerk • Gag reflex• Pupil reflex• Blinking• Infant grasping• Scratching• Withdrawal reflex
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How a reflex works
• Most reflexes are things that we could choose to do (bending knee, scratching, blinking) but a reflex is involuntary
• The Reflex Arc involves just a few neurons– Usually the neurons travel only to the
spinal cord, not all the way to the brain – very fast– The spinal cord “tells” the body what
to do
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Reflex Video
• http://www.youtube.com/watch?v=Y5nj3ZfeYDQ
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Axon
Dendrites Synapse
Cell Body
Nucleus
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Anatomy of a NeuronAnatomy of a Neuron
Each neuron Each neuron contains:contains:
- - Cell bodyCell body with with nucleusnucleus
- - DendritesDendrites : fibers : fibers that receive that receive messages from messages from other neuronsother neurons
- - AxonsAxons : fibers : fibers that send that send messages to messages to other neuronsother neurons
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• Neurons do NOT Neurons do NOT touch; there is a touch; there is a gap between them gap between them called a called a synapsesynapse
• Messages are sent Messages are sent across the across the synapses by synapses by special chemicals special chemicals called called neurotransmittersneurotransmitters
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Reflex Example 11. Stimulus
4. EFfector
3. Spinal Cord
5. Response (move your hand)
2. Sensor
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Reflex Example 2
1. Stimulus
2. Sensor
3. Spinal Cord
4. Effector
5. Response
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SYMPATHETIC & PARASYMPATHETIC
Both branches of involuntary nervous system
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SYMPATHETIC Nervous System
“Fight or flight” – prepares body
• Increases heart rate – oxygen to muscles
• Liver releases glucose – energy• Bronchioles dilate (get bigger) –
greater air flow• Increases adrenaline – stress
response• Pupils dilate – better vision
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PARASYMPATHETIC nervous system
“Rest and digest” – relaxes/ recovers body
• Decreases heart rate and blood pressure
• Liver stores glucose• Bronchioles constrict – less air• Pupils constrict – more normal size• Decreases adrenaline - relax• Digestion - Activity increases in
stomach
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Homeostasis & the nervous system
• Sympathetic/ParasympatheticFight or Flight vs. Rest and Digest
• Adjustments to breathing, blood pressure, etc. through negative feedback
• Keeps our body from hurting itself (reflexes)
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Other Systems
Digestive – Breaks down food to release nutrients
Excretory – Eliminates waste and balances water, maintains blood pressure
Immune – protects from diseasesEndocrine – releases hormones
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We have 11 of these systems in our bodies!