CHAPTER 20

AUTONOMICS OF THE HEAD AND NECK

Overview of the Autonomic Nervous System

Sympathetics of the Head and Neck

Parasympathetic Pathways of the Head and Neck

Clinical Correlate

Questions

Overview of the Autonomic Nervous System

GENERAL INFORMATION

The autonomic nervous system (ANS) has control over the function of many organ systems and tissues

Provides innervation to:

• Cardiac muscle

• Smooth muscle

• Glands

Also provides innervation to the organs of the immune system and metabolic organs (mainly through the sympathetics)

The hypothalamus exerts control over the ANS and helps the body maintain homeostasis

The ANS uses a 2-neuron chain system:

• Preganglionic neurons–the cell bodies are located in the central nervous system (CNS) (i.e., the brain and spinal cord), and their myelinated axons pass out to the autonomic ganglia

• Postganglionic neurons–the cell bodies are located in the autonomic ganglia, which are outside of the CNS, and their unmyelinated axons travel to the effector organ

The ANS is divided into 2 parts:

• Parasympathetic–the portion responsible for preserving and restoring energy

• Sympathetic–the portion responsible for preparing the body for emergency situations

Organs typically receive dual innervation, which has an antagonistic action, although there are some notable exceptions, such as the arrector pili muscles (which are sympathetic only) and the male sexual re/>

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