Chapter 14 The Autonomic Nervous System

What are the two parts of the ANS?

The ANS consists of the parasympathetic and sympathetic divisions.

How is the ANS different from the somatic nervous system?

The ANS differs from the somatic nervous system in that it can stimulate or inhibit its effectors.

Compare the somatic and autonomic nervous systems relative to effectors.

The effectors of the somatic nervous system are skeletal muscles, while the ANS innervates cardiac and smooth muscles and glands.

How does the central nervous system control the ANS?

The hypothalamus oversees ANS activity

Compare the somatic and autonomic nervous systems relative to efferent pathways.

In the somatic nervous system, the cell bodies of the neurons are in the spinal cord and their axons extend to the skeletal muscles they innervate. The ANS consists of a two-neuron chain in which the cell body of the first neuron, the preganglionic neuron, resides in the spinal cord, and synapses with the second neruon, the postganglionic neuron, reside within an autonomic ganglion outside the CNS.

What neurotransmitters and receptors does the ANS use?

Acetylcholine and norepinephrine are the major ANS neurotransmitters.

Compare and contrast the functions of the parasympathetic and sympathetic divisions.

Both divisions usually serve the same visceral organs, but cause opposite effects. The parasympathetic division, the "rest and digest" system, keeps body energy uses as low as possible, and directs digestion, and elimination of feces and urine. The sympathetic division, the "fight or flight" system, enables the body to cope with potential threats to homeostasis, by promoting adjustments in the cardiovascular and respiratory systems, sweat production, pupil dilation, and glucose release from the liver, while inhibiting nonessential tasks, such as gastrointestinal motility. Sympathetic and parasympathetic divisions differ in the site of origin, relative length of fibers, and location of ganglia.

Compare the somatic and autonomic nervous systems relative to neurotransmitters released.

The neurotransmitter released by the somatic motor neurons is acetylcholine, which always has an excitatory effect; the neurotransmitters released by the ANS are epinephrine and acetylcholine, and both may have either an excitatory or an inhibitory effect.

How do the sympathetic and parasympathetic division interact?

The parasympathetic and sympathetic divisions usually produce opposite effects

Compare visceral reflexes to somatic reflexes.

Visceral reflex arcs differ from somatic motor reflex arcs, in that they have two consecutive neurons in their motor components, and afferent fibers are visceral sensory neurons. The visceral sensory neurons are the first link in autonomic reflexes, sending information concerning chemical changes, stretch, and irritation of the viscera.