2. Kaveen
The symphathetic div. of the ANS
is also called the thoracolumbar
division bcoz d outflow of
symphathetic nerve impulses
comes 4m d thoracic & lumbar
segments of d spinal cord
D sympathetic preganglionic
neurons (SPN) hv their cell
bodies in d 12 thoracic & d 1st 2
lumbar segments of d spinal cord
D preganglionic axons
emerge 4m d spinal cord
thru d anterior root of a
spinal nerve along wit
axons of somatic motor
neurons
Afta exiting d cord, d sympathetic
preganglionic axons (SPA) extend to a
sympathetic ganglion.
Most postganglionic
axons emerging 4m STG
supply organs above d
diaphragm
STG lie in two vertical
rows, one on either side
of the vertebral column
In d sympathetic ganglia,
SPN synapse wt
postganglionic neurons
bcoz d sympathetic trunk
ganglia (STG) r near d
spinal cord, most
sympathetic
preganglionic axons r
short.
Other sympathetic
ganglia, d prevertebral
ganglia, lie anterior to d
vertebral column & close
to d large abdominal
arteries
These include d celiac
ganglion, d superior
mesenteric ganglion, &
d inferior mesenteric
ganglion
In
general, postga
nglionic axons
emerging 4m d
prevertebral
ganglia
innervate
organs below d
diaphragm
3. Kaveen
Once d axon of a preganglionic neuron of d sympathetic division enters a sympathetic trunk ganglion, it may follow 1
of 4 paths:
It may synapse wit
postganglionic
neurons in d
sympathetic trunk
ganglion it 1st
reaches
It may ascend /
descend to a higher /
lower sympathetic
trunk ganglion b4
synapsing wit
postganglionic
neurons
It may continue, without
synapsing, through the
sympathetic trunk ganglion to
end at a prevertebral ganglion
& synapse wit postganglionic
neurons thr
It may extend to
& terminate in d
adrenal medulla
A single sympathetic
preganglionic axon has
many branches & may
synapse with 20 / more
postganglionic neurons
Thus, nerve impulses tht arise in a single
preganglionic neuron may activate many
different postganglionic neurons that in
turn synapse with several autonomic
effectors
This process helps explain
why sympathetic responses
cn affect organs thruout d
body almst simultaneously
Mst postganglionic axons
leaving d cervical
sympathetic trunk ganglia
serve d head
They r distributed to sweat glands, smooth
muscles of d eye, blood vessels of d face,
nasal mucosa & salivary glands
A few postganglionic axons
4m d cervical sympathetic
trunk ganglia supply d
4. Kaveen
d inner part of d adrenal
gland, d adrenal medulla,
develops 4m d same
embryonic tissue s d
sympathetic ganglia, & its
cells r similar 2
sympathetic
postganglionic neurons
d sympathetic division of
d ANS aso includes part-
adrenal glands
Rather thn extending 2
anota
organ, howeva, these
cells release hormones
in2 d blood
Upon stimulation by sympathetic
preganglionic neurons, cells of d
adrenal medulla release a mixture of
hormones—abt 80% epinephrine &
20% norepinephrine
These hormones circulate
thruout d body &
intensify responses
elicited by sympathetic
postganglionic neurons
In d abdomen, axons of
postganglionic neurons
leaving the prevertebral
ganglia follow d course of
various arteries 2
abdominal & pelvic
autonomic effectors
Sum axons 4m thoracic
levels aso supply sweat
glands, blood vessels, and
smooth muscles of hair
follicles in d skin
In d thoracic region,
postganglionic axons
4m d sympathetic
trunk serve d
,lungs, & bronchi
