Nervous System

Nervous System

• Helps you observe and react to the world around you

• Neuron= cells of the nervous system

Neuron Structure

nucleus

dendrites

Myelin sheath

Cell body

axon

axon endings

Neuron Structure

• Dendrites = receive impulses (messages)• Axon = send messages away• Myelin sheath = insulates axon to speed

up the message

3 Neuron Types

• Sensory = carry messages from the senses to the brain/spinal cord

• Interneurons = in the brain and spinal cord, process the messages

• Motor = carry messages to muscles

Reflex Arc

• The nerve pathway that consists of a sensory neuron, interneuron, & motor neuron.

Nerve Impulse

• Electrical charge traveling down a neuron

**also called an ACTION POTENTIAL

http://library.thinkquest.org/25500/emotions/media/neuron.gif

Synapse

• Synapse = open space between neurons• Neurotransmitter = chemical messenger

released by the axon endings

Organization of the Nervous System

Chapter 33.2

Central Nervous System

• Brain & spinal cord• Coordinates all of

your bodies activities

3 Brain Divisions

1. Cerebrum

-Conscious activities, intelligence, memory, language, skeletal muscle movements, senses

3 Brain Divisions

2. Cerebellum

-back of brain

-balance, posture, coordination

3. Medulla Oblongata

-brain stem

-involuntary activities

Peripheral Nervous System

• Sensory and motor neurons

2 Divisions of the PNS

1. Somatic Nervous System = Relays information to and from the skin and skeletal muscles **voluntary**

2 Divisions of the PNS

2. Autonomic NS = Relays info to internal organs **involuntary**

a.) Sympathetic NS = in control when body is in stress (flight or fight)

b.) Parasympathetic NS = in control when body is at rest