General Structure of the Nervous System

Central Nervous System (CNS)

Consists of the brain and spinal cord.

Peripheral Nervous System (PNS)

Consists of cranial nerves, spinal nerves, plexuses, and peripheral nerves.

Cranial nerves

Carry impulses between the brain and the head/neck.

Vagus nerve

10th cranial nerve that carries messages to and from the neck, chest, and abdomen.

Spinal nerves

Carry messages between the spinal cord and the chest, abdomen, and extremities.

Plexus

Large network of nerves in the peripheral nervous system.

Plexuses

Examples include cervical plexus, brachial plexus, and lumbosacral plexus.

Brachi/o

Combining form meaning arm.

Lymphatic plexus

Network of lymph vessels.

Rectal plexus

Plexus of veins in the rectal region.

Vertebral plexus

Plexus of veins near the backbone.

Sensory (afferent) nerves

Carry messages toward the brain and spinal cord.

Sensory nerves

Related to sight, hearing, smell, and touch.

Motor (efferent) nerves

Carry messages from the CNS to muscles.

Hot stove example

Pain and temperature receptors are stimulated when touching a hot stove.

Afferent nerves

Carry the message to the CNS in the hot stove example.

Efferent nerves

Carry the response message from the CNS to muscles.

Muscles

Pull the hand away from the stove.

Sympathetic nerves

Part of the autonomic nervous system active during stress or crisis.

Sympathetic nervous system effects

Increase heart rate, blood pressure, and airway dilation.

Adrenal glands

Release epinephrine (adrenaline).

Sympathetic nervous system

Slow digestion during stress response.

Parasympathetic nerves

Balance the sympathetic nervous system.

Parasympathetic nervous system effects

Slow heart rate and lower blood pressure.

Parasympathetic nervous system

Stimulate intestinal contractions and help clear the rectum.