Lecture 4, 5, 6: Spinal cord/Brainstem Flashcards
Where would you see the 6 layer structure?
Grey matter of the Neocortex.
What is the name of the thin structures that comes off once the spinal cord terminates?
Cauda Equina (Come out at around L1)
What is the Cauda Equina?
The cauda equina (from Latin horse’s tail) is a bundle of spinal nerves and spinal nerve rootlets, Bathed in CSF
What is the Filum Terminale?
The filum terminale is an extension of the pia mater that is attached to the coccygeal segments, whose function is to suspend the cord in the CSF
The ___________ is an extension of the pia mater
The filum terminale is an extension of the pia mater
Is the Grey matter on the outside or inside of the SPINAL CORD?
Inside (Opposite to the brain)
Name the 4 important landmarks in the spinal cord
1) Posterior Median Sulcus (back)
2) Ventral Median Fissure (front)- significant rift
3) Dorsal intermediate sulcus
4) Dorsolateral sulcus
What are funiculi?
Funiculi in the spinal cord are portions of white matter.
Describe the different pathways of the nerves into the spinal cord
1) Posteromarginal nucleus.
PMN and the white tract above it is related to info from pain and temperature fibres
The free nerve endings from the skin come in. These are unmyelinated and slow conducting.
It is hard to modulate pain from the fibres that end up in lamina 1 (e.g. burning sensation)
2) Substantia gelatinosa
There are lots of opioid receptors on the nerves that end up here. This is easy to modulate. (e.g. cut)
3 and 4) Nucleus Proprius
Assist in understanding limb position, discriminative info, touch sensation information etc.
5) Cuneate (upper) and Gracile (lower) fasiculi
Purpose is to get good discriminative information and a fast way to get info through the SC and into the brain.
Has a homuculi representation
Some necessary info and sent from the Nucleus Propius to the Cuneate/Gracile fasiculi.
6) Mainly related to visceral/organ input
7) 3 regions : Main one is: Dorsal Nucleus of Clark (Intermediate Zone)
Fibres that arise in the periphery to the DNC will eventually go into the cerebellum. These discriminative pathways telling the cerebellum will help with balance, posture etc.
8 and 9)
Where lower motor neurons are housed. (Pyramindal cells)
These go out the ventral root and innervate muscle.
Organised with nerves that innervate the flexor muscles centrallyand extensor muscles laterally
The purpose of this pathway (as it does not involve the brain), is to quickly activate muscle in response to action of another muscle (Myoactic Reflex)
What is the purpose of the nerve pathways that do not involve the brain?
Myotactic reflex
Move one muscle very quickly in response to movement of another muscle. (e.g. walking- left and right leg).
Only after the movement occurs, the brain gets told by the posterior part.
How are the 8 and 9 nuclei organised int he spinal cord?
Flexor muscles more centrally
Extensors more laterally.
Describe the neural processes when you touch something hot with your hands
1) Free nerve endings synapses with a nerve in the posteromarginal nucleus or the substantia gelantinosa
2a) It then synapses with a nerve fibre that goes out, cuts across and ends up in a large area of white matter called ______ and then this infomration is taken up to the brain
2b) Nerve fibres also activate lower motor neurons, which activates muscles to withdraw your hand.
=Withdrawal reflex or the Polysnaptic reflex
What are the 2 types of reflexes?
1) Myotactic reflex (e.g. walking).
This is very fast, it is when your muscles move in response to the movement of other muscles
2) Withdrawal reflex or the Polysnaptic reflex
Movement of your body limb due to a hot sensation.
What is the motor column?
Where all of the upper motor info will come down from the cortex into the Spinal cord, It will then tell the lower motor neurons waht to do.
Name all of the parts of the Spinal Cord
1) Posterior Median Sulcus
2) Ventral medial Fissure
3) Dorsal funiculus
4) Gracile Funiculus
5) Cunneate Funiculus
6) Postereomarginal nucleus
7) Substantia gelatinosa
8) Nucleus Proprius
9) Dorsal nucleus of Clark
10) Motor columns
Name the general areas of the grey matter in the Spinal cord
Dorsal horn
Anterior/Ventral horn
Intermediate horn (in the middle)
General principle: motor fibres are carried forward, sensory fibres are carried at the back.
Name the 3 parts of the Tegmentum
1) Mesencephalic Tegmentum
2) Pontine Tegmentum
3) Medullary Tegmentum
What is the purpose of the Tegmentum and how does it undergo its function?
Primary purpose is to convey sensory info from the spinal cord to the brain.
It uses 2 Nuclei in the posterior part of the tegmentum called the gracile and the cuneate nucleus
What is found anteriorly to the tegmentum?
1) Crus Cerebri
(carry motor info from the pyramidal tract)
The crus cerebri has an area that represents the facce (bulbar) and the body. The face area is more central.
This is the bridge between the cortex and the brainstem.
2) Pars Basilaris
Much bigger than the crus cerebri. In the Pars basilaris, there are lots of lots of grey matter/cell bodies called Pontine Nuclei.
These allow info from the cerebral cortex down the crus cerebri and then exit and innervate the face.
(mainly motor for the face)
3) Medullary Pyramids
Here the fibres cross over and into the lateral part of the spinal cords (motor columns) all the way down to the exiting spinal levels. (So the right brain controls the left of the body etc.)
-Also- medial to the crus cerebri there is the substantia nigra
What is in the posterior part of the Tegmentum?
3x Cerebellar Peduncles
-(Where all of the info goes to and from cerebellum.)
Tectum/ Corpora Quadrigenia (body, four, bundle of)
- Superior and Inferior Colliculus.
- Superior is involved in reflex orientation of your eyes towards a visual stimulus (e.g. blind people may be able to say something happened on one side)
- Inferior is involved in reflex orientation of auditory stimuli.
How do you tell between the different regions of the midbrain down a microscope?
Present of Substantia nigra- upper 3rd
Ponteine nuclei- middle 3rd
Inferior olives - lower 3rd
What are the 4 regions of the upper 1/3 of the brainstem
Top: Tectum (superior and inferior colliculi)
Mesencephalic tegmentum
Substantia nigra
Crus cerebri
Describe the 2/3 layers of the bottom 1/3 of the brainstem
Top: Gracile/Cuneate or Inferior Olives
Middle: Medullary tegmentum (?)
Bottom: Medullary pyramids
Describe the steps to which facial motor neurons activate the face.
Face region (pyramidal cells) become activated (in the primary motor)
Internal capsule (between the thalamus and the lens)
Crus cerebri- Corticobulbar region (cortex- face)
Cortical fibre ends and innervate the Trigeminal nerve
Goes and innervates the face.
Describe the steps to which leg motor neurons activate the leg.
1) Nerve in the leg region of the primary motor cortex is activated
2) AP down the axon through the IC (laterally- near the lens)
3) Corticospinal fibres
4) Via pons
5) Medialisation
6) In the pyramids 85% crosses over (decussate) to the other side (form the Lateral corticospinal tract)
7) They stay in this until they innervate the musscle at their spinal level.
6b) 15% keep going down then decussate and then leave the spinal cord. (Ventral corticospinal tract)
Name the different funiculi in the spinal cord
Dorsal (Gracile and Cuneate)
Lateral
Ventral
Describe the neural pathways when someone touches your arm (C8)
1) The Nerve that’s in the periphery will be activated
2) AP goes down the axon which goes into the dorsal root (where the cell body is) and into the Dorsal Funiculus (for C8- in the cuneate fasciulus) . This axon is myelinated
3) Goes into the medulla. It goes into the Cunneate Nucleus
(behind the Medullary tegmentum)
4) The first nerve now synapses with the 2nd nerve (now called Medial Lemniscal Fibres) in the cunneate nucleus.
5) The medial leminiscal fibres deccusate (Internal Arcuate FIbres) then form the Medial lemniscus.
6) The ML travels into the Medullary tegmentum to the Pontine Tegmentum to the Mesencephalic Tegmentum.
7) The fibres then reach the thalamus (Ventro-postero lateral) and synapse with a third nerve.
8) The nerve travels in the Internal Capsule (in the medial part) and up into the Primary Sensory cortex (in the arm aspect).
9) More specifically the nerve goes into the 4th layer of the neocrotex.
Describe the neural pathways for pain and temperature
1) Fibre that begins in the skin (free nerve ending) is a slow conducting fibre. It has its dorsal root ganglion.
2) The first nerve will either drive a reflex arc or synapse with another nerve which decussates at the spinothalamic level: Anterior White Commisure
3) This second nerve will form Lateral Spinothalamic Tract (green part lateral and anterior in the spinal cord)
4) The fibre goes up through the medulla and joins the Medial Leminisucs in the pons (from discriminative touch pathway)
5) The fibres then go up the tegmentum into the VP of the thalamus
6) A new fibre then goes from the VP, into the internal capsule and out to the arm area in the primary sensory cortex.
7) These fibres will go into layer 4 of the neocortex.
