1. The Nervous System

2. Functions
Receives information about what is happening inside and outside your body.
Directs how body responds to information
Helps maintain stable internal conditions (homeostasis)

3. Stimulus vs. Response Stimulus = Signal Response = Reaction
Stimuli cause responses. Some internal stimuli and responses are controlled by nervous system (Ex. Heart rate)

4. Neurons
Neuron = nerve cell
Nerve Impulse = message neuron carries

5. Types of neurons
Sensory Neuron– pick up stimuli from environment and convert stimulus to impulse, found in sense organs
Interneuron – carries impulse from one neuron to another neuron, located in brain to interpret impulse
Motor Neuron – sends impulses to muscles to create a response
Remember S  I  M

6. Structure of Neuron
Dendrite
Axon Tip
Cell Body
Axon
Nucleus
Impulse

7. Neuron Vocabulary
Dendrites – receive nerve impulses and carry them to cell body
Axons – carry impulses away from cell body
Synapse – space between nerve cells
Impulse always travels dendrite  cell body  axon  through synapse  dendrite  cell body  axon (and so on)
To cross synapse, axon tips release neurotransmitters.

8. Divisions of Nervous System
Central Nervous System – Brain and spinal cord
Peripheral Nervous System – all nerves outside central nervous system
Autonomic Nervous System = involuntary actions
Somatic Nervous System = Voluntary Actions

9. Reflex Automatic response Occurs rapidly without conscious control
NOT controlled by brain
Stimuli are still involved

10. Injuries
Concussion – bruiselike injury of the brain (cerebrum tissue bumps the skull)
Paralysis – loss of movement in some part of the body (spinal cord injury – no impulses in that region)

11. Brain Protected by skull
Has 100 BILLION neurons (all are interneurons)
Cerebrum
Brainstem
Cerebellum

12. Parts of Brain Cerebrum Cerebellum Brainstem Cerebrum Brainstem

13. Brainstem Between cerebellum and spinal cord
Controls involuntary actions

14. Cerebrum largest part of brain Divided into halves (hemispheres)
Controls mental processes (thinking, remembering)

15. Cerebellum
Coordinates muscles
Controls balance