Homeostasis keeps the internal environment within set ranges.

Temperature Water Blood pressure Acid/base (pH) Calcium Glucose Oxygen & carbon dioxide (CO 2 ) 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

Country State County City USA Michigan Kent Grand Rapids

Organism Organ Systems Organs Tissues Cells Human Respiratory System Lungs Lung tissue Lung cells ORGANS ORGAN SYSTEM ORGANISM

Organ systems must work together to keep the organism healthy.  Ex: Organ systems work together to produce Vitamin D 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

Brain Spinal cord Nerves (bundles of neurons)

The Brain Responsible 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 responses 1.Voluntary: Lets us react consciously to changes in our environment - Behavioral response - ex. Moving, eating, running, walking - controlled by cerebrum: largest part of the brain

Voluntary Reactions  AKA: Behavioral  You DO control this  Ex: walking, stretching, drinking, smiling, scratching, flexing muscles * CONTROLLED BY: cerebrum

2. Involuntary: Lets us react automatically to changes in our environment - Physiological response - ex. Blood pressure, heart rate, breathing - Maintains homeostasis - Controlled by brain stem: connects brain to 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

Effectors Voluntary 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 5nj3ZfeYDQ 5nj3ZfeYDQ

Axon Dendrites Synapse Cell Body Nucleus

Anatomy of a Neuron Each neuron contains: - Cell body with nucleus - Cell body with nucleus - Dendrites : fibers that receive messages from other neurons - Dendrites : fibers that receive messages from other neurons - Axons : fibers that send messages to other neurons - Axons : fibers that send messages to other neurons

Neurons do NOT touch; there is a gap between them called a synapse Neurons do NOT touch; there is a gap between them called a synapse Messages are sent across the synapses by special chemicals called neurotransmitters Messages are sent across the synapses by special chemicals called neurotransmitters

Reflex Example 1 1. 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/Parasympathetic Fight 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 diseases Endocrine – releases hormones

We have 11 of these systems in our bodies!