Divisions of the Nervous SystemHB&H Chapter 7.2

Pages 196-202

• The Nervous System (NS) is divided into 2 parts:– Central NS: the brain and spinal cord– Peripheral NS: all the nerves outside

of the Central NS

Central Nervous System

• The Central NS is the control center of the body– The Brain controls most

functions in the body• Spinal Cord is a thick

column of nerve tissue that links the brain to the Peripheral NS.

The Brain

• Estimated to contain 100,000,000,000 Interneurons• Has 3 layers of connective tissue• Between the outermost and middle layer, there is

watery fluid for protection.

• Largest part of your brain• Three Functions:

1. Interprets input from senses2. Controls skeletal muscles3. Performs complex mental processes (Remembering,

learning, and making judgments)

Cerebrum

Cerebrum

• Divided into 2 halves or Hemispheres– Each half controls the opposite side of your body

• Right hemisphere is the “creative” side• Left hemisphere is the “logical” side

Cerebellum & Brain Stem

• The Cerebellum coordinates the actions of your muscles and helps you keep your balance

• The Brain Stem controls the involuntary muscle actions.

Exit Pass• What is the difference

between the Central and Peripheral Nervous systems?

Peripheral NSPage 200

• Where do nerve pairs originate from?• How are nerves like a road or highway?• What are the differences between Somatic and

Autonomic nerves?

Peripheral NSPage 200

• Where do nerve pairs originate from?• 12 pairs start in the brain, the other 31

begin in the spinal cord• How are nerves like a road or highway?• Impulses travel in two directions – to and

from the Central NS.

Peripheral NSPage 200

• What are the differences between Somatic and Autonomic nerves?• Voluntary actions are controlled by Somatic

nerves and involuntary actions are controlled by Autonomic nerves.

ReflexesPage 201

• Define a Reflex• Describe everything that happens when you

touch a sharp object.• Why is the difference in time between your

Reflex and the feeling of pain important?

ReflexesPage 200

• Define a ReflexAn automatic response that occurs without

conscious control.

ReflexesPage 200

• Describe the neuron actions that happens when you touch a sharp object.1. Sensory neurons send an impulse to interneurons in the

spinal cord

2. Motor neurons get the impulse and cause your hand to jerk away from the object.

ReflexesPage 200

• Why is the difference in time between your Reflex and the feeling of pain important?By removing yourself from harm before

your feel it, you prevent further or more serious injury.