W5 BIOSCEINCE

Describe the spinal cord (SC)

Long, thin, delicate structure protected by the vertebral column

What are the 5 regions of the spinal cord?

What are mixed nerves?

Axons of sensory and motor neurone

Explain the difference between dorsal roots, dorsal root ganglion and ventral roots

**Dorsal roots:** axons of sensory neurons

**Dorsal root ganglion:** cell bodies of sensory nuerons

**Ventral root:** axons of motor neurone (somatic n autonomic)

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What is the cauda equina?

The collection of nerves

What structures protect the spinal cord, and how?

**Spinal meninges:** pia mater, arachnoid mater, dura mater

* enable lumbar puncture
* doesn’t damage spinal cord > around L4-L5 (spinal cord ends around L1-L2)
* draw CSF for testing (check pathogens)

**Vertebral column:** helps in bending and turning

**CSF:** nourishes neural tissues > remove wastes

Describe the internal anatomy of the spinal cord?

* neural tissue (neurons, neuroglia)
* divided into left and right sides (2 grooves) > ventral median fissure & dorsal median sulcus
* areas of grey (outer) & white (inner) matter

What is the difference in the structure between grey and white matter?

**Grey matter:** neuron cell bodies, unmyelinated axons and neuroglia

* grey comminsure: axons cross from 1 side to other

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**White matter:** superficial to grey matter > myelinated and unmyelinated axons

* anterior white comminsure

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What is the difference in the organisation of grey and white matter?

**Grey matter:** gray horns

* sensory nuclei: cell bodies of spinal cord interneurons
* somatic motor nuclei: cell bodies of lower motor neurons
* autonomic motor nuclei: cell bodies of preganglionic neurons (glands, cardiac, smooth muscles)

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**White matter:** white columns (bundles of axons)

* ascending tracts: sensory input > brain
* descending tracts: motor output > away

List the functions of the spinal cord

1. A two way conduction pathway to and from the brain
2. Spinal reflexes (gray matter) ; somatic reflex (skeletal muscle), autonomic reflex (smooth muscle)

Which ascending tract conducts crude touch, deep pressure, pain and temperature? Name the neurons, tract and location of tracts (white matter)

Spinothalamic pathway

* First, second and third- order neurons
* Anterior spinothalamic tract (crude touch, deep pressure)
* Lateral spinothalamic tract (pain, temp)
* Lateral and anterior white columns

Which ascending tract conducts fine touch, light pressure, vibration and proprioception (conscious)? Name the neurons, tracts and location of tracts (white matter) 

Posterior column pathway

* First, second, third-order neurons
* Fasciculus gracilis tract
* Fasiculus cuneatus tract
* Posterior white columns

Which ascending tract conducts proprioception (unconscious)? Name the neurons, tracts and location of tracts (white matter) 

Spinocerebellar pathway

* First and second-order neurons
* Anterior spinocerebellar tract
* Posterior spinocerebellar tract
* Lateral white column

Which descending tract conducts somatic motor output (skeletal muscle - limbs)? Name the neurons, tracts and location of tracts (white matter)

Lateral corticospinal pathway

* Upper and lower motor neurons
* Lateral corticospinal tract
* Lateral white column

Which descending tract conducts somatic motor output (skeletal muscle - axial skeleton)? Name the neurons, tracts and location of tracts (white matter)

Anterior corticospinal pathway

* Upper and lower motor neurons
* Anterior corticospinal tract
* Anterior white column

what is the spinal cord

long, thin, delicate tubular structure

what protects the spinal cord

vertebral column

what does spinal cord pass through

vertebral foramen of each vertebra

where does the spinal cord end in adults

between L1 and L2

where does the spinal cord end in infants

L4

what does the spinal cord terminate in

cone shaped structure called conus medullaris

what anchors the spinal cord to the coccyx

filum terminale

5 regions of the spinal cord

cervical, thoracic, lumbar, sacral, coccygeal

how many segments are there

31

how many segments in cervical region

8

how many segments in thoracic region

12

how many segments in lumbar region

5

how many segments in sacral region

5

how many segments in coccygeal region

1

what connects to each segment

a pair of spinal nerves

where do spinal nerves emerge from

vertebral column

what do spinal nerves branch to form

peripheral nerves that innervate all parts of the body (except the head)

what do spinal nerves contain

axons of sensory and motor (somatic and autonomic) neurons

how do spinal nerves connect to the spinal cord

by the dorsal and ventral nerve roots

what do dorsal roots contain

axons of sensory neurons

what does the dorsal root ganglion contain

cell bodies of sensory neurons

what do ventral roots contain

axons of motor neurons (somatic & autonomic)

the \_________, \___________ and \____________ nerve roots travel beyond the \_________ \______________ to reach the vertebral region from which the \________, \__________ and \_______________ spinal nerves emerge.

lumbar, sacral, coccygeal, conus medullaris, lumbar, sacral, coccygeal

cauda equina

collection of spinal nerves below the end of the spinal cord (lumbar, sacral and coccygeal nerve roots)

how is the spinal cord protected

- vertebral column

- cerebrospinal fluid --\> also nourishes the neural tissue and removes waste products

- spinal meninges

spinal meninges are continuous with

the cranial meninges

spinal meninges extend beyond the spinal cord to

the second sacral vertebra (S2)

what is a lumbar puncture (spinal tap)

insertion of a needle into the subarachnoid space beyond L3

does lumbar puncture damage the spinal cord

no

what is lumbar puncture used for

- withdraw CSF fluid for diagnostic testing (e.g. meningitis) or reducing intracranial pressure.

- used to administer medications

what separates outer dura mater from vertebral column

epidural space - site of anaesthetic administration

What are denticulate ligaments?

extension of the pia mater

what do denticulate ligaments do

prevent lateral movements of the spinal cord

what grooves divide the neural tissue (neurons and neuroglia) of the spinal cord into left and right side?

- anterior (ventral) median fissure

- posterior (dorsal) median sulcus

what areas is neural tissue of spinal cord organised into

gray matter and white matter

what is gray matter composed of

neuron cell bodies (mainly), unmyelinated axons and neuroglia

what does gray matter vary in

size and shape down the length of the spinal cord

what does gray matter enclose

central canal --\> filled with cerebrospinal fluid

what is the gray commissure

site where axons cross from one side of the CNS to the other

what is gray matter subdivided into

gray horns (anterior, posterior, lateral)

what do gray horns contain

sensory or motor nuclei

function of posterior gray horns

sensory

function of anterior gray horns

somatic motor function

function of lateral gray horns

autonomic motor function

what do sensory nuclei of the posterior gray horns contain

cell bodies of spinal cord interneurons

what do cell bodies of interneurons do

receive and process incoming sensory input

what do somatic motor nuclei of the anterior gray horns contain

cell bodies of lower motor neurons

what do cell bodies of lower motor neurons do

receive outgoing somatic motor output

what do autonomic motor nuclei of the lateral gray horns contian

cell bodies of preganglionic neurons

what do cell bodies of preganglionic neurons do

receive outgoing autonomic motor output

site of integration for spinal reflexes

gray matter

what do reflex integration centres do

- receive and interpret incoming sensory input

- decide on and generate the motor output that causes the reflex response

what do the reflexes rapidly and involuntarily stimulate

- skeletal muscle contractions \= somatic reflex (e.g. patellar reflex)

- smooth muscle contractions of visceral organs (e.g. bladder) or gland secretions \= autonomic reflex

white matter location in relation to gray matter

superficial to gray matter

what is white matter composed of

myelinated (mainly) and unmyelinated axons

what is the anterior white commissure

site where axons cross from one side of the CNS to the other

what is white matter subdivided into

white columns

what do white columns contain

ascending and descending spinal cord tracts \= bundles of axons

what do spinal cord tracts of white matter do

conduct sensory or motor information between the spinal cord and brain

what do ascending tracts do

conduct sensory input to the brain

what do descending tracts do

conduct motor output away from the brain

ascending tracts (6)

fasciculus gracilis, fasciculus cuneatus, lateral spinothalamic, anterior spinocerebellar, posterior spinocerebellar, anterior spinothalamic

white column location of fasciculus gracilis

posterior white columns

white column location of fasciculus cuneatus

posterior white columns

sensory information conducted by fasciculus gracilis

fine touch, vibration

sensory information conducted by fasciculus cuneatus

light pressure, proprioception

white column location of lateral spinothalamic tract

lateral white columns

sensory information conducted by lateral spinothalamic tract

pain and temperature

white column location of anterior spinocerebellar tract

lateral white columns

white column location of posterior spinocerebellar tract

lateral white columns

sensory information conducted by spinocerebellar tracts

proprioception

white column location of anterior spinothalamic tract

anterior white columns

sensory information conducted by anterior spinothalamic tract

crude touch, deep pressure

ascending tracts (2)

lateral corticospinal, anterior corticospinal

white column location of lateral corticospinal tract

lateral white columns

motor output conducted by lateral corticospinal tract

somatic motor output that controls the skeletal muscles of the limbs.

L for Lateral \= L for limbs

white column location of anterior corticospinal tract

anterior white columns

motor output conducted by anterior corticospinal tract

somatic motor output that controls the skeletal muscles of the trunk (axial skeleton)