Receives information about environment and what happens inside your body Directs how body responds to information Maintains homeostasis

Stimulus –Any change or signal in the environment that can make an organism react Response –What your body does in reaction to a stimulus –Some responses are voluntary and some involuntary

Neurons –Cells that carry information through your nervous system (or nerve cells) Nerve impulse –Message carried by neuron

Large cell body containing nucleus Nerve fibers –Dendrites Thread like extensions Carry impulses toward neuron’s cell body Neuron can have many dendrites –Axon Carries impulses away from the cell body Neuron has one axon nerve: a bundle of nerve fibers

Sensory neurons –Pick up stimuli from the internal or external environment –Converts stimulus into a nerve impulse Interneurons –Carry nerve impulses from one neuron to another Motor neurons –Send an impulse to a muscle or gland which reacts in response

Begins in the dendrites of a neuron Moves toward cell body Then down axon to axon tip Moves in form of electrical and chemical signals Speed: up to 120 meters per second

The junction where one neuron can transfer an impulse to another structure Nerve impulse reaches the axon tip –Can pass to dendrite of another neuron –Can pass to muscle or cell in another organ It must cross the gap between the axon and the next structure (muscle, cell, or dendrite). The axon tips release chemicals that carry the impulse across the gap.

Central Nervous System –Consists of the brain and spinal cord –Control center of body Peripheral Nervous System –Network of nerves that branch out from central nervous system –Connect to rest of body

Controls most functions in body Directs responses Contains 100 billion interneurons Three main regions of brain –Cerebrum –Cerebellum –Brain stem

Largest part of brain Interprets input from the senses Controls movement Carries out complex mental processes (i.e. learning or remembering) Divided into right and left half RightLeft sends impulses to skeletal muscles on left side of body Associated with creative/artistic ability Sends impulses to skeletal muscles on right side of body Associated with Mathematical skills and logical thinking

Second largest part of brain Coordinates the actions of your muscles Helps you balance Gives muscular coordination

Lies between the cerebellum and spinal cord Controls body’s involuntary actions –breathing –Or heartbeat

Thick column of nervous tissue The link between your brain and the peripheral nervous system Protected by vertebral column

43 pairs of nerves –12 originate in brain –31 originate in spinal cord One of each pair goes to right side of body and other to left Impulses travel in two directions –Sensory neurons: carry impulses from body to central nervous system –Motor neurons: carry impulses from central nervous system to body

Somatic –Control voluntary actions Automatic –Control involuntary actions

Automatic response that occurs very rapidly without conscious control Some muscle contractions occur with spinal cord involvement not the brain Other impulses travel to brain which is interpreted as pain Pain impulses take longer to interpret than the reflex