The Nervous SystemChapter 36

Basic Structure

• Neurons• Composed of 3 parts

• Cell body

• Dendrites

• Axon

DENDRITES• Branchlike extensions that receive impulses

and carry them to the cell body

AXON

• Single extension of neuron that carries impulses away from the cell body and toward other neurons, muscles, and glands

CELL BODY

• Contains nucleus of nerve cell

How are neurons connected?

• SYNAPSES!• Junction between neurons

• Impulses must cross synaptic space to reach the brain and other destinations

What’s the Matter?White and Gray Matter

• Axons are covered with a white substance called the MYELIN SHEATH

• This white covering gives this part of the brain its “white” appearance.

• The MYELIN SHEATH is formed from SCHWANN cells

• SCHWANN cells insulate the axon and increase the speed of the impulse

WHITE MATTER

GRAY MATTER

• Absence of myelin sheaths in neurons accounts for gray matter in the brain.

MOVEMENT OF A SIGNALThe “Electric Slide” in the body!• Neurons send electrical signals/impulses in

the body!

• Where is the signal going?• Sensory organs

• Brain

• Muscles

3 Types of Neurons• Sensory neurons

• carry signals from outside and inside the body to the brain and spinal cord

• Interneuron• found in brain and spinal cord

• process sensory impulses and send the message on the motor neuron

• Motor neurons• carry impulses away from the brain and spinal

cord

How do neurons work?

1. Reception-stimulus from outside is detected

2. Transmission-message is sent to brain3. Interpretation-brain interprets message

and formulates response4. Transmission-message is sent to muscle5. Response-muscle responds to stimulus

LOOK AT PICTURE ON NOTES

ANATOMY OF THE BRAIN• CEREBRUM - 2 hemispheres

• controls conscious activities, intelligence, memory, language, skeletal muscle movements, and senses

• gray matter

• surface area increased by folds (more surface area = greater intelligence)

ANATOMY OF THE BRAIN• CEREBELLUM-located at back of brain

• controls balance, posture, and coordination

ANATOMY OF THE BRAIN

• MEDULLA OBLONGATA - brain stem• controls involuntary activities (ex: breathing

and heart rate)

CENTRAL VS PERIPHERAL

• Brain and spinal cord

• Control center

• Nerves

• Outside informers

• Somatic system

• Autonomic system

• Sympathetic system

• Parasympathetic system

PERIPHERALSOMATIC SYSTEM -Relays info to and from skin,

skeletal muscles, and CNS

-Voluntary

-Exceptions: reflexes are involuntary p. 981

AUTONOMIC SYSTEM

-Sympathetic

-Parasympathetic

-Relays info to and from internal organs and CNS

-Involuntary

SYMPATHETIC -controls in times of stress

PARASYMPATHETIC -controls when body is at rest

REFLEX ARC