Lecture 4, 5, 6: Spinal cord/Brainstem

Question 1

Where would you see the 6 layer structure?

Answer 1

Grey matter of the Neocortex.

Question 2

What is the name of the thin structures that comes off once the spinal cord terminates?

Answer 2

Cauda Equina (Come out at around L1)

Question 3

What is the Cauda Equina?

Answer 3

The cauda equina (from Latin horse’s tail) is a bundle of spinal nerves and spinal nerve rootlets, Bathed in CSF

Question 4

What is the Filum Terminale?

Answer 4

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

Question 5

The ___________ is an extension of the pia mater

Answer 5

The filum terminale is an extension of the pia mater

Question 6

Is the Grey matter on the outside or inside of the SPINAL CORD?

Answer 6

Inside (Opposite to the brain)

Question 7

Name the 4 important landmarks in the spinal cord

Answer 7

1) Posterior Median Sulcus (back)
2) Ventral Median Fissure (front)- significant rift
3) Dorsal intermediate sulcus
4) Dorsolateral sulcus

Question 8

What are funiculi?

Answer 8

Funiculi in the spinal cord are portions of white matter.

Question 9

Describe the different pathways of the nerves into the spinal cord

Answer 9

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)

Question 10

What is the purpose of the nerve pathways that do not involve the brain?

Answer 10

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.

Question 11

How are the 8 and 9 nuclei organised int he spinal cord?

Answer 11

Flexor muscles more centrally

Extensors more laterally.

Question 12

Describe the neural processes when you touch something hot with your hands

Answer 12

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

Question 13

What are the 2 types of reflexes?

Answer 13

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.

Question 14

What is the motor column?

Answer 14

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.

Question 15

Name all of the parts of the Spinal Cord

Answer 15

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

Question 16

Name the general areas of the grey matter in the Spinal cord

Answer 16

Dorsal horn

Anterior/Ventral horn

Intermediate horn (in the middle)

General principle: motor fibres are carried forward, sensory fibres are carried at the back.

Question 17

How does the Spinal Cord change as you go from top to bottom?

Answer 17

The Size of the Cuneate is larger in the upper areas of the spinal level and the Gracile is larger in the lower areas of the spinal cord.

Question 18

What are cranial nerves?

Answer 18

Like spinal nerves but they exit via the brain stem.

These have an additional layer of complication.

Question 19

How is the motor and sensory areas mapped out in the brain stem?

Answer 19

Motor at the front, Sensory at the back.

Question 20

Name the 3 parts of the Tegmentum

Answer 20

1) Mesencephalic Tegmentum
2) Pontine Tegmentum
3) Medullary Tegmentum

Question 21

What is the purpose of the Tegmentum and how does it undergo its function?

Answer 21

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

Question 22

What is found anteriorly to the tegmentum?

Answer 22

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

Question 23

What is in the posterior part of the Tegmentum?

Answer 23

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.

Question 24

How do you tell between the different regions of the midbrain down a microscope?

Answer 24

Present of Substantia nigra- upper 3rd

Ponteine nuclei- middle 3rd

Inferior olives - lower 3rd

Question 25

What are the 4 regions of the upper 1/3 of the brainstem

Answer 25

Top: Tectum (superior and inferior colliculi) Mesencephalic tegmentum Substantia nigra Crus cerebri

Question 26

Describe the 3 layers of the Pons

Answer 26

Top: 3x cerebellar peduncles Middle: Pontine tegmentum Bottom: Pars Basilaris

Question 27

Describe the 2/3 layers of the bottom 1/3 of the brainstem

Answer 27

Top: Gracile/Cuneate or Inferior Olives Middle: Medullary tegmentum (?) Bottom: Medullary pyramids

Question 28

Describe the steps to which facial motor neurons activate the face.

Answer 28

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.

Question 29

Describe the steps to which leg motor neurons activate the leg.

Answer 29

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_)

Question 30

Name the different funiculi in the spinal cord

Answer 30

Dorsal (Gracile and Cuneate) Lateral Ventral

Question 31

Describe the neural pathways when someone touches your arm (C8)

Answer 31

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.

Question 32

Describe the neural pathways when someone touches your leg

Answer 32

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 - in the gracile fasciulus) . This axon is myelinated 3) Goes into the medulla. It goes into the **Gracile Nucleus** (behind the Medullary tegmentum) 4) The first nerve now synapses with the 2nd nerve (now called Medial Lemniscal Fibres) in the gracile 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 medial) 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 leg region). 9) More specifically the nerve goes into the 4th layer of the neocrotex.

Question 33

Describe the neural pathways for pain and temperature

Answer 33

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.

Question 34

What is another name for the Discriminative Sensation pathway?

Answer 34

Dorsal Column- Medial Leminiscal Pathway (dis. touch and pressure, conscious proprioception, vibration, stereognosis).

Question 35

What is another name for the Pain/Temperature pathway?

Answer 35

Lateral Spinothalamic Tract

Question 36

If you get told to take the baking out of the oven (verbal stimulus which leads to motor action and then is managed by the body and leads to a sensory outcome), what are the neurological processes that occur in your brain and in the spinal cord?

Answer 36

1) The tones that comes into the auditory nerve is sent to the thalamus (Medial Geniculate Body) and then to the Primary Auditory Cortex. 2) The PAC will break these down into individual tones and then send them to Wernike's area. 3) The Wernike's area talks via the arcuate fasiculus to the Broca's area. The BA needs to do some planning so the right muscles beome activated to speak. 4) The nerve goes into the VA/VL part of the thalamus and then back to the Broca's area. 5) The Broca's area will talk to the face to activate the large Betz cells. This activates the Cortico-bulbar pathway. 6) The face area in the PMC is activated and the face info goes down the corticobulbar pathway, and get to the pons 7) The pontine nuclei get activated by the corticobulbar pathways. 8) The corticobulbar pathway synapses onto the Trigeminal nerve 9) The Trigeminal nerve activate the muscles of the face (e.g. jaw) to articulate what you want to say 10) Then you hear what you say and the PAC is activated again. Note that your frontal cortex is also activated via the limbic system (to see if there's danger) Again the VA/VL is activated by the motor planning area to see which nerves need to be fibred to undergo the movement.