Spinal cord, spinal nerve roots, and spinal nerves

spinal cord receives:

sensory information

what is integrated into the spinal cord?

motor commands from higher centers with sensory input

what does the spinal cord output to?

skeletal muscles

• somatic motoneurons

visceral organs

• autonomic nervous system

what communication happens in the spinal cord?

communication between motor & sensory related neurons

where does th spinal cord project to?

higher centers

• primarily sensory

where does reception to the spinal cord come from?

motor commands

sensory modulation

where does the spinal cord go from?

extends from foramen magnum to L2 in adult

terminates as conus medullaris

what makes up the upper extremity nerves?

axons from spinal nerves C5-T1 and forms the brachial plexus

what makes up the lower extremity nerves?

axons from spinal nerves from L1-S4 and forms the lumbosacral plexus

what enlargements does gray matter have?

cervical enlargements

lumbosacral enlargements

what is the ventral median fissure?

sulcal branch of anterior spinal

artery runs down through this space to supply arterial blood

what is dorsal median sulcus?

septum of pia matter

no space- sulcus

what is the ventral lateral sulcus?

exit of motor axons

forms ventral root

what is the dorsal lateral sulcus?

entrance of sensory axons

from Dorsal root

what is the dorsal intermediate sulcus?

only above T6

separates:

• fasciculus gracilis

  • take info from LE

• fasciculus cuneatrus

  • take info from UE

communication to the periphery- dorsal root

sensory

general somatic afferent

GV (general visceral afferent)

if you cut nerve root you will lose sensation

what is the dorsal root ganglion?

a cluster of nerve cell bodies in the peripheral along the dorsal root

what is a receptor?

a specialized ending at the end of an axon

what is general somatic afferent

sensation coming from out of the body allowing you to feel heat or cold

ex: hot cold and pain

what is general visceral afferent

sensation coming from the abdominal region.

describe the lateral division of the dorsal root

smaller fiber

unmyelinated or lightly myelinated

nociceptive (transduction of pain in the periphery) & thermal (GSA)

visceral sensory (GVA)

light touch

describe the medial division of the dorsal root

larger fibers

moderately and heavily myelinated

enter SC more medially

touch, vibration, proprioception (muscle, tendons, and joints )

(GSA)

discriminative touch

what are neurotransmitters and neuromodulators in the dorsal nerve roots ?

glutamate

substance P

calcitonin gene related protein (CGRP)

synapse- they give a spot where we can modify sensations

describe ventral nerve roots

motor

axons from motoneurons (GSE)

axons from autonomic preganglionic neurons (GVE)

acetylcholine- for bother at ending

spinal nerve roots contain what?

hundreds of axons

vernal roots are primarily what and exit where?

primarily axons of motoneurons

exit at anterior lateral sulcus

spinal nerves have what kind of axons?

motor and sensory axons

where does the spinal nerve exit?

intervertebral foramina

what branches does the spinal nerve have?

meningeal branches

communicating rami

each spinal nerve bifurcates to form:

anterior primary ramus

posterior primary ramus

what are the different plexuses?

cervical:

• C1- C4

brachial

• C5-T1

lumbosacral

• T12-S

coccygeal

• S4- Co1 nerve

peripheral nerves

where does C1-C7 spinal nerves exit?

above the named vertebrae

where does C8 exit?

below the C7 vertebrae

where does T1 and below exit?

below the named vertebrae

what makes up gray matter?

neuronal cell bodies and dendrites and initial parts of axons

axon terminals

what makes up white matter?

axons (myelinated and unnmyelinated)

what areas do both the white and gray matter have?

glial cells

what is the proportion of white to gray matter?

varies by the level of the spinal cord

describe Gray matter

horns

• ventral (motor neurons)

• dorsal ( sensory neurons)

• intermediate region (more seen in thoracic)

arranged in cell columns or layer with similar function

named nuclei ( collections of neurons)

what are interneurons?

have sensory functions

• receive sensory input from both GSA and GVA

recieve input from higher center to process/ modulate sensory input

some interneurons transmit sensory information via ascending tracts

also part of reflex arcs

it takes how many neurons to convey sensory information to cerebral cortex?

3

spinal cord → medulla → thalamus

what is a tract

a bundle of axons that sub surds the same actions

what is substance gelatinosa

II

has a opioid like substance

important for pain control

what is nucleus proprius

III, IV

principle sensory nucleus

LI-LIV of the dorsal horn merge with what?

the trigeminal nucleus in the brain stem

small diameter DRG fibers (lateral entry)

predominately thermal and noxious

terminate largely in LI, II, V

lare diameter DRG fibers ( medial entry)

mechanical (ie. touch, vibration, some proprioception)

collaterals to posterior horn

what is the function of the dorsal horns

recieve and process sensory input:

• some descending tracts terminate on dorsal horn cells

• site of origin of some ascending tracts

describe the ventral horn

primarily motor related functions

motoneurons- LIX (GSE-skeletal)

interneurons (L VIII and IX)