To regulate smooth muscle, cardiac muscle and glands

• Cannot consciously control ANS

• Is a completely motor system

• Is composed of visceral efferent neurons

• Regulated by cortex, hypothalamus and medulla

Examples of visceral effectors:

• Cardiac muscle

• Smooth muscle

• Glandular epithelium

ANS divided into 2 divisions

Each organ is innervated by both, called dual innervation.

1. Sympathetic

2. Parasympathetic divisions

Somatic efferent pathway

1 neuron leads from CNS to the effector (skeletal muscle)

Autonomic Visceral Efferent Pathways

• Consist of 2 neurons

• 1 neuron from CNS to ganglion - preganglionic neuron

• 1 neuron from ganglion to effector - postganglionic neuron

preganglionic neuron

1 neuron from CNS to ganglion

postganglionic neuron

1 neuron from ganglion to effector

3 Groups of Autonomic Ganglia

Vertebral chain ganglia

Prevertebral or colateral ganglia

Terminal ganglia

Vertebral chain ganglia

• Lies in vertical row on either side of spinal cord
• Contains 22 ganglia per chain
• Only receives preganglionic fibers from sympathetic division of ANS

Prevertebral or colateral ganglia

Terminal ganglia

• Located at end of visceral efferent pathway close to visceral effectors or within walls of visceral effectors
• Only receives preganglionic fibers from parasympathetic division

Preganglionic neuron

• Cell body located in either brain or spinal cord.
• The myelinated axon passes out as part of cranial or spinal nerve.
• Preganglionic axon synapses with cell body or dendrite of postganglionic neuron in the ganglia.

Postganglionic neuron

Difference Between Autonomic Ganglia and Dorsal Root Ganglia

• Synapse between the preganglionic and postganglionic neurons occurs in the autonomic ganglia.
• No synapse occurs in dorsal root ganglia.

Sympathetic Division

• Called thoracolumbar outflow because preganglionic nerve cell bodies are located in the lateral gray horns of 12 thoracic segments and the first 2 lumbar segments of spinal cord.
• Most sympathetic responses have wide spread effects on body.

Parasympathetic Division

• Called craniosacral outflow.
• Cell bodies are located in nuclei of cranial nerves III, VII, IX, and X in brain stem and in lateral gray horns of second through fourth sacral segments.
• Most parasympathetic responses have more localized effects on body.

Where are cell bodies located?  

in nuclei of cranial nerves III, VII, IX, and X in

brain stem and in lateral gray horns of second through fourth sacral segments.

What responses have more localized effects on body.

parasympathetic

Neuroeffector Junction

Junction between neuron and effector

How are neuroeffector junctions classified?

on basis of the type of transmitter substance produced

What are the neuroeffector transmitter substances that are produced?

Cholinergic

Adrenergic

Cholinergic

release acetylcholine

• All sympathetic and parasympathetic preganglionic axons
• All parasympathetic postganglionic axons
• Some sympathetic postganglionic axons. Ex., sweat glands, blood vessels in skeletal muscles, skin and external genitalia.

Adrenergic

releases norepinephrine and includes most sympathetic postganglionic axons

Visceral Autonomic Reflex

• Receptor

• Afferent neuron

• Association neuron

• Visceral efferent preganglionic neuron

• Visceral efferent postganglionic neuron

• Visceral effector

Examples of Visceral Sensation that Give Rise to Conscious Recognition

• Hunger

• Nausea

• Fullness of bladder

• Fullness of rectum

Autonomic plexus

postganglionic axons arranged in a branching network

White rami communicants

the short connections between the spinal nerves and the sympathetic chain ganglia, through which the preganglionic axons pass

Splanchnic nerves

preganglionic axons which pass through the vertebral chain ganglia and synapse in

the colateral ganglia.

Comparison of Structural Differences Between the Parasympathetic and Sympathetic Divisions

The ratio of preganglionic to postganglionic neurons is greater for the sympathetic than the

parasympathetic division

Preganglionic axons are longer for the

postganglionic axons are longer for the

longer for the sympathetic division

The sympathetic division has a  ________ outflow

thoracolumbar outflow

the parasympathetic division has a _________outflow

craniosacral outflow

1. Functional Generalization about the ANS.

Usually each division produces an opposite effect on a given organ

2. Functional Generalization about the ANS.

Each division can produce inhibitory or excitatory effects.

3. Functional Generalization about the ANS.

Sympathetic activity generally prepares the body for physical activity, whereas parasympathetic

activity is more important for vegetative functions