The Nervous System

The nervous system has 3 types of neurons (nerve cells):

• Sensory Neurons-receive signals from the environment and send them to the brain.
• Interneurons- relay messages.
• Motor Neurons-cause muscles to act.

Organization of the Nervous System:

2 Major Divisions:

1. Central Nervous System (CNS) = brain and spinal cord.
2. Peripheral Nervous System (PNS) = paired cranial and spinal nerves.

The PNS is broken down into 2 functional divisions:

1. Sensory (afferent) division:

• Sensory afferent fibers (external).
• Visceral afferent fibers (internal).

2.  Motor (efferent) division:

• Autonomic Nervous System (ANS) = control of smooth muscle, cardiac muscle, and glands.
• Somatic Nervous System (SNS).

The ANS is broken down further still:

• Sympathetic Nervous System
• Parasympathetic Nervous System