• Homeostasis keeps the internal environment within set ranges.

• Temperature

• Water

• Blood pressure

• Acid/base (pH)

• Calcium

• Glucose

• Oxygen & carbon dioxide (CO2)

• Wastes

• Bacteria/viruses

• Negative feedback is similar to a thermostat:

• 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

• CountryStateCountyCity

USAMichiganKentGrand Rapids

OrganismOrgan SystemsOrgansTissuesCells

HumanRespiratory

SystemLungsLung tissueLung cellsORGANS

ORGAN SYSTEM

ORGANISM

• 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

• Ex: Organ systems work together to control body temperature

BrainBrain

Spinal cordSpinal cord

Nerves (bundles Nerves (bundles of neurons)of neurons)

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!

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

Voluntary Reactions

AKA: Behavioral

You DO control this

Ex: walking, stretching, drinking, smiling, scratching,

flexing muscles

* CONTROLLED BY:

cerebrum

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

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)

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.

Stimulus Loud Crash

Cold Temperature

Familiar Face

Tap on Shoulder

Stub Toe

Dropped brick on foot

Smell of dinner cooking

Many more!!

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

Spinal Cord

All sensory nerves must travel to the spinal cord.

The spinal cord takes the messages to the brain.

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

Effector

The muscle or gland that has received a signal from the brain, telling it what to do

Ex: contract muscle to move leg

Response Move your hand away!

Pull foot away!

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

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

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

Reflexes

• Special type of nervous system reaction

• Very fast• Can anyone think of a reflex

example?

Reflex Examples

• Knee-jerk • Gag reflex• Pupil reflex• Blinking• Infant grasping• Scratching• Withdrawal reflex

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

Reflex Video

• http://www.youtube.com/watch?v=Y5nj3ZfeYDQ

Axon

Dendrites Synapse

Cell Body

Nucleus

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

• 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

Reflex Example 11. Stimulus

4. EFfector

3. Spinal Cord

5. Response (move your hand)

2. Sensor

Reflex Example 2

1. Stimulus

2. Sensor

3. Spinal Cord

4. Effector

5. Response

SYMPATHETIC & PARASYMPATHETIC

Both branches of involuntary nervous system

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

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

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)

Other Systems

Digestive – Breaks down food to release nutrients

Excretory – Eliminates waste and balances water, maintains blood pressure

Immune – protects from diseasesEndocrine – releases hormones

We have 11 of these systems in our bodies!