Spinal Cord & Spinal Nerves Flashcards
What are the following subdivisions of the nervous system?
What is the difference between grey and white matter?
Grey matter:
- collection of nerve cell bodies
White matter:
- axons with glial sheath (myelin)
- myelin is a fatty substance that appears white
Where is grey matter located within the CNS and PNS?
CNS:
- in the cortex - the outer layer of the hemispheres
- in the nuclei deep in the cortex
PNS:
- within the ganglia
What occurs within the gray matter?
Synapses occur within the gray matter
What is the difference between white matter in the CNS and PNS?
CNS:
- it is located in a pathway
- e.g. Tracts, fascicles, bundles
PNS:
- peripheral nerves
What is the purpose of the vertebral column?
It contains and protects the spinal cord and beginning of the spinal nerves
What are the different types of vertebrae within the vertebral column?
- 7 cervical
- 12 thoracic
- 5 lumbar
- sacrum (5 fused)
- coccyx (3-4 fused)
What is significant about the spinal cord with respect to the vertebral column?
The spinal cord narrows at the end
It ends before the vertebral column ends
What are the roles of the spinal cord?
- Part of the CNS
- Reflex centre
- Conduction pathway between the brain and the body
Where does the spinal cord extend from and to?
It extends from the foramen magnum of the occipital bone
it is continuous with the medulla oblongata
it runs to the vertebral levels LI - LII, where it terminates as the conus medullaris
What happens when the spinal cord terminates as the conus medullaris?
Single nerves leave from the region of the conus medullaris as the cauda equina
this gives rise to spinal nerves (PNS)
Label the components of the spinal cord
What is the filum terminale?
A small extension of pia mater that attaches the spinal cord to the coccyx
this gives stability
What are the roles of the cervical and lumbosacral enlargements?
They are thicker, larger regions of the spinal cord
they give rise to nerves that innervate the upper and lower limbs
In order to see the spinal cord, which layer must be opened?
The dural sac
What is the composition of the spinal cord like from top to bottom?
- 8 cervical segments (C1 - C8)
- 12 thoracic segments (T1 - T12)
- 5 lumbar segments (S1 - S5)
- 1 coccygeal segment (Co1)
- conus medullaris
- cauda equina
- filum terminale
What is meant by a ‘segment’ of the spinal cord?
How many spinal nerve segments are they and what do they form?
A segment refers to a pair of spinal nerves
there are 31 spinal nerve segments, each giving rise to a pair of segmental spinal nerves
31 pairs of spinal nerves form the PNS
Which features of the spinal cord are shown here?
Lumbar cistern:
- expansion of subarachnoid space that surrounds the cauda equina
Dural sac:
- extends to the level of S1
Filum terminale:
- this is an extension of the pia
- it extends to attach to the coccyx
Where is the conus medullaris located?
This is the termination of the spinal cord
It is situated between L1 and L2
What nerves are found within the cervical enlargement?
The brachial plexus (C1 - C8)
this supplies the upper limb
What nerves are found within the lumbosacral enlargement?
The lumbosacral plexus (L1 - S4)
this supplies the lower limb
What nerves are found within the cauda equina?
Dorsal and ventral roots of lower lumbar, sacral and coccygeal spinal nerves
What is meant by the spinal nerve transition zone?
At vertebral levels C1 - C7, the spinal nerve leaves above the corresponding vertebra
C8 leaves below the corresponding vertebra
all nerves below this level leave below their respective vertebra
What is the difference in the way the cervical spinal nerves leave the spinal cord?
Spinal nerves C1 - C7:
- leave the vertebral column superior to their corresponding vertebra
- C1 from above CI, C2 from above CII….
C8 spinal nerve:
- leaves from above TI
- there are only 7 cervical vertebrae
How do spinal nerves T1 - C0 leave the spinal cord?
They leave from below their corresponding vertebra
ALL spinal nerves leave the spinal cord via the intervertebral foramina
Label the meninges and features of the spinal cord
What are the denticulate ligaments?
Extensions of pia that attach the spinal cord to the outer meningeal layers
this secures the spinal cord laterally
What are the subdural and subarachnoid spaces of the spinal cord?
Subdural space:
- this is a potential space between the dura and arachnoid mater
Subarachnoid space:
- this is a real space between the pia and arachnoid
- it is filled with CSF
What happens to the spinal nerves as they leave the vertebral canal?
As each spinal nerve leaves the vertebral canal it takes with it the meningeal coverings
these go on to form the epineurium
this is a protective outer sheath of connective tissue
What are the main differences between the spinal and cranial dura?
- Cranial dura has an inner meningeal layer and outer periosteal layer
- Spinal dura only has a meningeal layer
- the epidural space in the cranium is a potential space
- it can become a pathological space if there is bleeding
- the epidural space in the spinal cord is a real space
- it is filled with fat
Label the differences of the spinal and cranial dura
How does the spinal cord change in length during development?
Why?
During development, the dural sac grows along the vertebrae but not the spinal cord
the bones of the vertebral column grow faster than the spinal cord, leading to regression of the spinal cord
What is the consequence of changes in spinal cord length on spinal nerve roots?
The spinal nerve roots show disparity between their segmental attachment to the cord and the corresponding vertebral levels
within the cervical region, the nerves close to the vertebrae leave close to their point of origin
nearer the end of the spinal cord, the nerves travel down to leave below their vertebra
these form the cauda equina
Label the diagram and the position of the needles for performing certain procedures
What is the role of the ligamentum flavum?
It connects the lamina of adjacent vertebrae
the needle for lumbar puncture passes between the vertebrae through the ligamentum flavum to reach the dural sac and obtain CSF
Where should the needle be inserted for lumbar puncture?
How should the patient be positioned?
The needle is inserted between LIV and LV
the needle is inserted into the lumbar cistern
due to the cauda equina, the nerve roots move out of the way when the needle is inserted
the patient should be hunched over or in the foetal position to stretch the space between the vertebrae
Where should the needle be inserted for epidural anaesthesia?
Within the lumbar region or sacral hiatus
the needle is only inserted into the epidural space
Label the sulci of the spinal cord
What structures pass through them?
Blood vessels travel in the posterior median sulcus and anterior median fissure
rootlets that form spinal nerves travel in the posterior lateral sulcus and anterior lateral sulcus
Label the arterial supply to the spinal cord
Where do the vessels originate from?
The anterior and posterior spinal arteries are branches of the vertebral artery
the segmental spinal artery arises from a branch of the aorta (depending on the location within the spinal cord)
The segmental spinal artery gives rise to the medullary artery
the medullaris artery give rise to the anterior & posterior radicular arteries which supply the roots of nerves
What are the different segmental spinal arteries depending on the location within the spinal cord?
- Vertebral artery
- deep cervical artery
- posterior intercostal artery
- lumbar arteries
- lateral sacral artery
What is the main difference in the grey and white matter in the CNS?
Brain:
- grey matter is found in the cortex and nuclei - the outside
- white matter is found on the inside
Spinal cord:
- grey matter is found on the inside
- white matter is found on the outside of the spinal cord
How is grey matter organised within the spinal cord?
It is organised into horns
- Dorsal horn
- Ventral horn
- Lateral horn - only present T1-L2 and S2-S4
What is significant about the lateral horn?
It only exists between T1 - L2 and S2 - S4
How is white matter organised within the spinal cord?
It is organised into columns
- Dorsal white column
- Ventral white column
- Lateral white column
- Ventral white commisure
What is the ventral white commisure?
An area of white matter that connects the left and right sides of the spinal cord
What horns/columns are represented in this transverse section of the spinal cord?
label the transverse section of the spinal cord
What are the 2 types of fibres within the peripheral nervous system?
The PNS is all the connections outside of the brain and spinal cord
sensory (afferent) fibres:
- these send information from the periphery towards the CNS
motor (efferent) fibres:
- these send information away from the CNS and towards the periphery
How is the spinal cord connected with the PNS?
Via nerve rootlets
each spinal level gives rise to 1 pair of spinal nerves
these spinal nerves are part of the PNS
Label the components of a spinal nerve
Where do the dorsal and ventral rootlets of the spinal cord leave from?
dorsal rootlets:
- leave from posterolateral sulcus
ventral rootlets:
- leave from anterolateral sulcus
Label the transverse section of the spinal cord and spinal nerve
Somatic and visceral sensory fibres travel through the dorsal root ganglion and dorsal root
somatic motor fibres travel through the ventral root
visceral motor fibres travels through the ventral horn and into the spinal nerve
What is the purpose of the reflex arc?
When there is no time to pass through the normal pathway
a sensory neurone connects directly to a motor neurone for a rapid response via an interneurone
How does the amount of white matter change as you go through the spinal cord?
The amount of white matter increases as you ascend the cord
i.e. there is more white matter in the cervical cord than the lumbar cord
What is significant about the size of the ventral grey horn in certain locations of the spinal cord?
The ventral grey horn is enlarged where motor fibres to limbs arise
these are the cervical and lumbosacral enlargements
they contain cell bodies from motor neurones innervating the upper and lower limbs
What are the dorsal columns of white matter present on either side of the midline in the spinal cord?
How do these change as you ascend the spinal cord?
Gracile fascicle:
- This is located medially
- it runs the entire length of the spinal cord
- it carries sensory information from the lower limb
Cuneate fascicle:
- this is located laterally
- it is only present above segment T6
- it carries sensory information from the upper limb
Label the sections of the spinal cord
What are the functions of the cuneate and gracile tubercles?
Tubercles contain cell bodies
The gracile and cuneate fascicles terminate as the gracile and cuneate tubercle
these are part of the dorsal column pathway
the cuneate tubercle carries sensory information from the upper limb
the gracile tubercle carries sensory information from the lower limb
Is this section from above or below T6?
How can you tell?
Above T6
this is a thoracic vertebral section as the lateral grey horn is present here
there is also a small ventral grey horn
How is spinal grey matter divided?
The grey matter is divided into regions called Rexed’s laminae
these are sites of sensory or motor nuclei
