Biology 211Anatomy & Physiology I

Autonomic Nervous System

Autonomic Nervous System

The efferent (motor) component of the peripheral nervous system includes two types of neurons:

Somatic Neurons regulate voluntary movement (contraction of skeletal myocytes)

Autonomic Neurons regulate involuntary functions (rate & force of of cardiac myocyte contraction) (contraction of smooth myocytes) (secretion of glands)

Both types of efferent neurons run through the same cranial or spinal nerves

Comparison: Somatic vs Autonomic efferent neurons

Somatic

Autonomic

Voluntary Involuntary Effectors: Skeletal M. Effectors: Cardiac M. Smooth M Glands

Neurons extend from CNS to effectors without synapsing.

Two neurons to get from CNS to effectors; therefore one synapse."Two neuron chain"

Autonomic Nervous System

Two divisions based on: a) Where the cell body of the first neuron is located (Brain; Specific region of spinal cord) b) Where the axon of the first neuron synapses with the dendrites of the second neuron (Far away from effector cells; Near effector cells)

First cell = Second cell =

of Autonomic Nervous System Preganglionic neuron starts in thoracic or lumbar levels of spinal cord. Preganglionic neuron synapses with postganglionic neuron relatively far from effectors

of Autonomic Nervous System Preganglionic neuron starts in brain or sacral level of spinal cord. Preganglionic neuron synapses with postganglionic neuron very near the effector cells

Sympathetic Division Synapse between preganglionic neuron and postganglionic neuron can occur in either of two sets of ganglia

1) "Chain" of ganglia along spinal column, next to vertebrae

2) Near major arteries of abdomen: Celiac ganglion Superior mesenteric ganglion Inferior mesenteric ganglion

Note: A sympathetic synapse can occur in either set of ganglia, but not both

Parasympathetic Division Synapse between preganglionic and postganglionic neurons occurs in ganglia very close to the target cells:

1. Above neck: Larger ganglia located near target organs (posterior to eye). (posterior to maxilla) (near angle of mandible) (inferior to foramen ovale)

Parasympathetic Division Synapse between preganglionic and postganglionic neurons occurs in ganglia very close to the target cells:

2. Below neck: Microscopic ganglia located within walls of target organs such as intestines

Parasympathetic Division Synapse between preganglionic and postganglionic neurons occurs in ganglia very close to the target cells:

2. Below neck: Microscopic ganglia located within walls of target organs such as heart

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

Sympathetic:

F

F

F

F

Parasympathetic:

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

For example:

Heart: Sympathetic increases heart rate & force of contraction Parasympathetic decreases heart rate & force of contraction

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

For example:

(Heart: Sympathetic increases rate & force Parasympathetic decreases rate & force )

Lungs: Sympathetic dilates air passages Parasynpathetic constricts air passages

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

For example:

(Heart: Sympathetic increases rate & force Parasympathetic decreases rate & force )(Lungs: Sympathetic dilates air passages Parasynpathetic constricts air passages)

Digestive System: Sympathetic decreases activity; constricts anal sphincter Parasympathetic increases activity; relaxes anal sphincter

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

For example:

(Heart: Sympathetic increases rate & force Parasympathetic decreases rate & force )(Lungs: Sympathetic dilates air passages Parasynpathetic constricts air passages)(Digestive System: Sympathetic decreases activity Parasympathetic increases activity)

Urinary System: Sympathetic inhibits urination Parasympathetic promotes urination

Most organs have both sympathetic and parasympathetic innervation, each of which acts in opposition to the other.

For example:

(Heart: Sympathetic increases rate & force Parasympathetic decreases rate & force )

(Lungs: Sympathetic dilates air passages Parasynpathetic constricts air passages)

(Digestive System: Sympathetic decreases activity Parasympathetic increases activity)

(Urinary System: Sympathetic inhibits urination Parasympathetic promotes urination)