Transcript The Autonomic Nervous System

Biology 211
Anatomy & Physiology I
Dr. Thompson
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 neurons run through the same nerves.
For example, the vagus nerve (cranial nerve #10) contains
some somatic neurons which control contraction of skeletal
myocytes in muscles of the pharynx during swallowing AND
some autonomic neurons controlling contraction of cardiac
myocytes and of smooth myocytes in the digestive sstem
Comparison: Somatic vs Autonomic efferent neurons
Somatic
Autonomic
Voluntary
Effectors: Skeletal M.
Involuntary
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 two criteria:
a) Where the cell body of the first neuron is located
(Brain or 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; or Near effector cells)
First cell = Preganglionic; Second cell = Postganglionic
Sympathetic Division of Autonomic Nervous System
Preganglionic neuron starts in thoracic or lumbar
levels of spinal cord.
Preganglionic neuron synapses with postganglionic
neuron relatively far from effector cells
Parasympathetic Division 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
Let’s Start Out With The Sympathetic Division
of the autonomic nervous system
Preganglionic neurons start in the
thoracic or lumbar levels of the
spinal cord
and
They synapse with postganglionic
neurons relatively far from the
target cells (smooth myocytes,
cardiac myocytes,
gland cells)
Sympathetic Division of the autonomic nervous system
That synapse between
preganglionic neurons and
postganglionic neurons can
occur in either of two sets of
ganglia:
Paravertebral Ganglia
Prevertebral Ganglia
Note: A sympathetic synapse can occur in
either set of ganglia, but not both
Sympathetic Division of the autonomic nervous system
1) Preganglionic sympathetic neurons can synapse with
postganglionic sympathetic neurons in paravertebral
ganglia which form a “chain” next to the vertebrae
(Sympathetic Division)
Note that the chain of
paravertebral ganglia
extends up into the neck
to supply sympathetic
innervation to structures
in the head, neck, and
upper thorax
Sympathetic Division of the autonomic nervous system
2) Preganglionic sympathetic neurons can synapse with
postganglionic sympathetic neurons in prevertebral
ganglia which are located near major arteries of
the abdomen.
There are three of these prevertebral ganglia:
Celiac ganglion
Superior mesenteric ganglion
Inferior mesenteric ganglion
The other part of the autonomic nervous system is its
Parasympathetic Division
Preganglionic parasympathetic
neurons start in the brain or in
sacral levels of the spinal cord
and
They synapse with postganglionic
parasympathetic neurons
relatively near the target cells:
(smooth myocytes,
cardiac myocytes,
gland cells)
The other part of the autonomic nervous system is its
Parasympathetic Division
1. In the head, there are four
larger parasympathetic ganglia
located near the target cells
Ciliary ganglion
(posterior to eye in orbit)
Pterygopalatine ganglion
(posterior to maxilla)
Submandibular ganglion
(near angle of mandible)
Otic ganglion
(inferior to foramen ovale)
The other part of the autonomic nervous system is its
Parasympathetic Division
2. Below the head: small
parasympathetic ganglia are
located within the
walls of target organs
such as intestines, heart,
uterus, etc.
Parasympathetic Autonomic Ganglia
Usually very small,
often only a few dozen
neuron cell bodies
Most organs have both sympathetic and
parasympathetic innervation, each of which acts in
opposition to the other.
Sympathetic:
Fear
Fight
Flight
F
Parasympathetic:
"Rest, Digest, and
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