lab # 2
23/2/2011 Wednesday
Dr . Aaliyah
Review :
We know that the spinal nerves are 31 pairs:
8 cervical pair. 12 thoracic pair. 5 lumbar pair. 5 sacral
pair. 1 coccygeal pair.
And as we said before that the spinal nerve is originate
from the spinal cord by the union of :
 Anterior root {which is the motor root ,having its
cell bodies in the anterior horn of the gray matter of
the spinal cord }.
 Posterior root { which is the sensory root , having its
cell bodies in the dorsal root ganglia outside the
CNS}.
So, the spinal nerve is a mixed nerve; sensory & motor
nerve. And in some segments we have sympathetic or
parasympathetic nerve fibers (which come out with the
ant. Root).
Moreover, the gray matter which is an H-shaped area , is
divided into :
→anterior horns/motor.
→posterior horns/sensory.
Would have in some segments LATERAL HORNS ,in these
horns we would find sympathetic or parasympathetic
cell bodies – depending on the position *.
*All the thoracic (T1-T12) plus the first and second
lumbar (L1&L2) spinal nerves , have lateral horns
containing the cell bodies of sympathetic nerve fiber.
And the sacral spinal nerves (S1-S3(and sometimes
S4)),have lateral horns containing the cell bodies of the
parasympathetic nerve fibers.
BUT the parasympathetic nerve fibers don`t come out
exclusively from the lateral horns of (S1-S3),but also from
the cranial nerves as well.
Again we know that ant. & post. Horns give 2 roots which
unite creating the spinal nerve, after a short distance the
spinal nerve divides into:
anterior ramus
• more important ,
because it makes
plexuses that innervate
the anteriolateral parts
of the body ; the
abdomen, .
posterior
ramus
• innervates the skin &
muscles of the back.
**The axons of the sympathetic nerve fibers which come
out from the ant. Root , gather outside the CNS giving a
fiber called the preganglionic fibers that synapse inside
the sympathetic ganglia with the dendrites of another
cell and become postganglionic fiber.
Ganglia /ganglion:
Is an accumulation of cell bodies outside the CNS.
Remember! When the cell bodies accumulate inside the
CNS this is called nucleus.
There is 2 types of ganglia:
→Sensory ganglia.
we can differentiate between them histologically
→Autonomic ganglia.
Autonomic ganglia:
Associated with the ANS ;are 2 types sym. & parasym.(we
cannot differentiate between the under the microscope!)
The sympathetic autonomic ganglia:
Aren`t distributed randomly but they are present as
dilations around the vertebral column in 2 chain
ganglia©.
©bilaterally symmetrical sympathetic ganglia chains,
anteriolateral to the spinal cord on both sides of the
vertebral column from the cervical till the coccyx region ,
called the paravertebral ganglia due to there position.
Parasympathetic autonomic ganglia:
Present inside the organ which they innervate ;
Either inside the wall of that organ (we call it intramural
ganglia), or near the organ (called the terminal ganglia).
To differentiate between Autonomic and sensory ganglia:
Autonomic ganglia
Less
Glial(satellite)
Cells surrounding the
cell body
Nucleus of the cell body Not central
Shape of the cell body
Distribution of cell
bodies and fibers
Multipolar ; motor
function to the
blood
vessels,lungs,..
Even distribution
Sensory ganglia
More ; from all the
sides .
Central nucleus
Unipolar or
pseudounipolar ;
sensory function
Uneven distribution,
here we have zones
of neurons and
fibers*.
We cannot have a typical slide with all of these
differences obvious , try looking for a major one!!
*In the sensory ganglia there is an exception in that there
is NO synapse , cell bodies have only a tropic function:
(for the nutrition supplement ; proteins,ATP,etc of the
processes to transmit the nerve impulses). Because the
dendrites and axon that belong to the same cell carry the
information to CNS.
Again, the spinal cord is divided into:
White matter : the outer area, subdivided into lateral
,anterior & posterior columns.
Gray matter: the inner area ( the H-shaped area)
subdivided into: ❶anterior/motor horn.
❷posterior/sensory horn.
❸if present lateral horn/ANS.
❹gray commisure.
A scientist called Rexed , divided the gray matter into
lamina (=areas), depending on the presence of certain
types of cells and on their function. He found 10 areas
from the beginning of the post. Horn till the end of the
ant. Horn.
Each lamina has a specific nucleus.
Lamina I → postomarginal nucleus ;
in the posterior and marginal regions , doing a sensory
function (sensory axon).
Lamina II→substantia gelatinosa;
neurons with large cell bodies , present throughout the
whole length of the spinal cord. Receives nervous
information related to the pain, temperature, touch
&pressure.
Lamina III, IV→nucleus proprius ;
We call it proper because it occupies a large area of the
posterior horn. And it is an accumulation of cell bodies
which are related to the proprioception; the situation,
position,movements of the muscles, tendons or joints.
e.g. u can guess that ur triceps is now flexed for example.
Lamina V, VI→ nucleus dorsalis /Clarke`s column;
The last one in the posterior horn, the most anterior.
Present ONLY in (C8-L3/L4)®.
®we said L3/L4 roughly because the spinal cord is
exceptionally longer in children, so in adults it is till L1.
Lamina VII →intermediolateral& intermediomedial
nuclei;
The intermediate zone between the ant.&post. Horns
So , it has the lateral horns.
The intermediolateral have the sym. & parasym. Fibers
Lamina VIII →motor interneurons if present.
Lamina IX→ motor region of the anterior horn
Lamina X→gray commisure.
This was only an introduction to Rexed laminae and we`ll
take more details in the lecture.
*The laminae have other types of cells of unknow
function.
*The laminae exist throughout the whole length of the
spinal cord, BUT what differs is the presence of the
nuclei.
Finally, two types of cells are present inside the anterior
horn: (Lamina IX)
→Alpha cells α:
-large cells.
-multipolar / motor.
-supply the skeletal muscles.
→Gamma cells γ:
-small cells.
-supply the muscle spindles; which are small organs
inside the muscle ,its sensory part (giving information
about the muscle fatigue, contraction,…,etc).
*Done by : dalia ramadan