Originate in the brainstem or lateral gray
matter of the S2-S4 spinal cord
segments
Have less than 4 branches
Long
Postganglionic Axons
Short
Ganglion
Terminal Ganglia
Close to target organ
Intramural Ganglia
Within walls of target organ
Sympathetic
Function
Fight or flight
Increase alertness and metabolic activity
Mass Activation
Supplies visceral organs and structures of superficial body regions
Increase heart rate, increase
blood pressure, increase depth of
respiration and breathing rate,
dilate pupils
Structure
Ganglia
Close to vertebral column
Sympathetic Trunk Ganglia
Sympathetic Trunk
White Rami Communicantes
carry preganglionic sympathetic axons
from T1-L2 spinal nerves to sympathetic
trunk
Gray Rami Communicantes
carry postganglionic sympathetic axons
from the sympathetic trunk to the spinal
nerves
Located on both sides of the vertebral column
Each sympathetic trunk ganglia is associated with each spinal nerve
house sympathetic ganglionic neuron cell bodies
Prevertebral Ganglia
Splanchnic nerves
composed of preganglionic sympathetic
axons that do not synapse in a
sympathetic trunk ganglion that extend
anteriorly to most of the viscera
Occur only in abdomen and pelvis
Lie anterior to the vertebral column
Main Ganglia of the Splanchnic nerves
Celiac Ganglion
innervate stomach, spleen, liver, gallbladder,
proximal part of duodenum, part of the pancreas
Superior mesenteric ganglion
distal half of duodenum, part of the
pancreas, remainder of small intestine,
proximal part of large intestine, kidneys,
and proximal parts of ureters
Inferior mesenteric ganglion
innervate distal colon, rectum, urinary bladder,
distal parts of ureters, most of reproductive organs
inferior hypogastric ganglia
Neurons
Preganglionic Axons
Short
20 Branches
Postganglionic Axons
Long, unmyelinated
All sympathetic preganglionic neurons originate in the
lateral gray horns of the T1-L2 segments of the spinal
cord
Pathways
Spinal nerve pathway
Postganglionic sympathetic nerve pathway
Splanchnic nerve pathway
Adrenal medulla pathway
receives preganglionic sympathetic axons
Major organ of the sympathetic nervous system
Constitutes largest sympathetic ganglia
The cells within the adrenal medulla that synapse
with the axons release hormones that circulate in
the blood stream to help prolong the “fight or flight”
response
Epinephrine and Norepinephrine
Autonomic Plexus
Collections of sympathetic postganglionic axons
and parasympathetic preganglionic axons as well
as some visceral sensory axons
Cardiac Plexus
Composed of postganglionic sympathetic axons that
extent from the cervical and thoracic sympathetic
trunk ganglia and preganglionic axons from the vagus
nerve
In Thoracic Cavity
Controls heart rate and blood pressure
Pulmonary Plexus
Composed of postganglionic sympathetic axons
from the thoracic sympathetic trunk ganglia and
preganglionic axons from the vagus nerve
Controls the diameter of the bronchi and
secretion from mucous glands of the
bronchial tree
Hypogastirc Plexus
Composed of a complex meshwork
of postganglionic sympathetic axons
and preganglopnic parasympathetic
axons from the pelvic splanchnic
nerve
Innervate viscera within the pelvic region
Esophageal plexus
Composed of preganglionic axons from the vagus nerve
Controls cardiac sphincter and swallowing reflex
Abdominal aortic plexus
Celiac plexus,
superior mesenteric
plexus, inferior
mesenteric plexus
Composed of postganglionic axons
projecting from the pre vertebral ganglia and
preganglionic axons from the vagus nerve
that enter the abdominopelvic cavity with the
esophagus
Neurotransmitters
a compound released at the synapse
Neurotransmitter only acts on receptors specific to that molecule
generally much faster than the endocrine transmission.
Acetylcholine (ACh)
Neurotransmitter in PNS and SNS
released by all preganglionic axons and binds to
specific receptors in the ganglionic plasma
membrane and has an excitatory effect on the
ganglionic cell
a nerve that releases ACh as its
neurotransmitter is called a cholinergic
nerve
Norepinerphrine (NE)
neurotransmitter unique to the SNS
can have an excitatory or inhibitory effect
on the effector, depending on the receptor
on the effector plasma membrane
made in, released from all
postganglionic sympathetic nerves when
the SNS is activated
a nerve that releases NE is called an adrenergic nerve
Epinephrine (EPI)
Hormone unique to SNS
Adrenaline
Made in, released from cells of the adrenal medulla
Dual Innervation
visceral effectors are innervated by
postganglionic axons from both ANS divisions
and the actions are antagonistic to each other
Autonomic Reflexes
smooth muscle contractions, cardiac muscle
contractions, or secretion by glands that are
mediated by autonomic reflex arcs in response
to a specific stimulus
CNS Control of ANS
Cerebrum
Conscious activities in the cerebrum affect
hypothalamus control of ANS
Hypothalmus
ntegration and command center for autonomic functions; involved in emotions
Amygdala
Main limbic center for emotions
Brain Stem
Contains major ANS reflex centers
Spinal Cord
Contains ANS reflex centers for defecation and urination