Lecture 3 Central nervous system (spinal cord)

what does the spinal cord connect

brain and the peripheral nervous system

describe the structure of the spinal cord

elongated, cylindrical, suspended in the vertebral canal and protected by the vetebrae

the spinal cord is surrounded by what

meninges and cerebrospinal fluid

how long is the spinal cord in adult males

45cm

main function of the spinal cord

transmission of the neural signals between the brain and the rest of hte body

three main components of the vertebrae of the spinal skeleton

the vertebrae, the vertebral body, and the spinal canal

function neuroforamen

openings on the sides of the spine that allows the spinal nerve to pass through laterally

location and function of the intervertebral discs

between the vertebrae that acts as shock absorbers

how many vertebral bones are there in the vertebrae?

30

the structure that acts as shock absorber in the spinal cord

intervertebral discs

where does the spinal cord extend from and to

from foramen magnum to second lumbar vertebra

the spinal cord is continuous along which structure

medulla oblongata

what structure forms the tapered inferior end of the spinal cord

conus medullaris

in where does the actual spinal cord end

conus medullaris

what structure anchors the spinal cord to the coccyx from the conus medullaris

non-neuronal cord called film terminale

what is the bundle of nerve roots that surrounds filum terminale?

cauda equina

how many spinal nerves do the spinal cord give rise to?

31

how are the 31 spinal nerves segmented? (name the sections and how many bones there are in each section)

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

why are there 30 vertebrae bones but 31 spinal nerves

due to how the nerves exit above and below the bones

why is there an extra C8 spinal nerve but no C8 bone/vertebrae?

because the C7 nerve exits above the C7 vertebra and leaves an empty space below the C7 vertebra (and above the first thoracic vertebra, T1)

what are the two enlargements of the spinal cord

cervical enlargement and lumbosacral enlargement

function of the cervical enlargement in the spinal cord and the bones it connects

supplies upper limbs, C4 to T2

function of the lumbosacral enlargement in the spinal cord and the bones it connects

supplies lower limbs, L2 to S3

what is the periphery outer layer in the spinal cord?

white matter

what is the inner layer in the spinal cord?

grey matter

why is the white matter in the periphery layer in the spinal cord

because it contains myelinated axons that allows them to run vertically up and down the spinal cord directly to and from the brain without crisscrossing the central processing region

why is the grey matter in the inner layer in the spinal cord

because it contains neuronal cell bodies, dendrites, and synapses where local integration and reflex processing occur in the central core

the three components of the grey matter in the spinal cord and their relative position

dorasal horn (posterior), lateral horn, ventral horn (anterior)

what is the anterior fissure that runs down the spinal cord

ventral median fissure

the ventral median fissure is in the anterior or posterior side

anterior

what is the posterior fissure that runs down the spinal cord

dorsal median sulcus

the dorsal median sulcus is in the anterior or posterior side

posterior

where does the central canal continue along

continuation of the central aperture of 4th ventricle

what is the central canal lined by

ependyma

where does the central canal open into, superiorly and inferiorly respectively?

4th ventricle, and conus medullaris

what is a ganglion

a group of neurons (cell bodies) outside the CNS

the term for “a group of neurons (cell bodies) outside the CNS”

ganglion

what is a nucleus

a group of neurons (cell bodies) within the CNS

the term for “a group of neurons (cell bodies) within the CNS”

nucleus

what is a nerve

a group of nerve fibers (axons) outside the CNS

the term for “a group of nerve fibers (axons) outside the CNS”

nerve

what is a tract

a group of nerve fibers (axons) within the CNS

the term for “a group of nerve fibers (axons) within the CNS”

tract

axons in the white matter are wrapped in what

fatty myelin sheaths

how is the grey matter formed in the spinal cord

When an axon reaches its target spinal level, it leaves the outer white matter tract, turns inward, and enters the central butterfly-shaped grey matter. It then synapses onto a brand-new, resident cell body

what happens to the grey matter in the cerebrum and cerebrellum and how do they transition into white matter in the spinal cord

The cell bodies (somata) of upper motor neurons reside permanently inside the grey matter of the cerebral cortex and stop at the brainstem. The cell bodies in the cerebral cortex send long myelinated axons downward. As these axons pass through the interior of the brain and down into the brainstem, they form the white matter tracts surrounding the center.

where does the cell bodies in the anterior (ventral) horn of the spinal cord come from?

they are lower motor neurons that receive synapses from the descending white matter axons (upper motor neurons) coming down from the cerebral cortex.

function of the cell bodies in the posterior (dorsal) horn?

they process incoming sensory information from peripheral spinal nerves and relay it back up to the brain via ascending white matter tracts

how does the C1 to C7 nerves exit ?

above its corresponding numbered vertebrae

how does the C8 nerves exit the spinal canal?

below the C7 vertebrae

how does the thoracic nerves exit the spinal canal ?

below its corresponding numbered vertebrae

how does the lumbar nerves exit the spinal canal ?

below its corresponding numbered vertebrae

how does the sacral nerves exit the spinal canal ?

through sacral foramina

how does the coccygeal nerves exit the spinal canal ?

at the base of the coccyx