Tracts (Dustin, incomplete)

Question 1

What are the 6 long ascending spinal tracts?

Answer 1

1. Gracile Tract (Goll)
2. Cuneate Tract (Burdach)
3. Spinothalamic Tract (Edinger) - {with anterior and lateral branches that combine}
4. Spinoreticular Tract
5. Posterior Spinocerebellar Tract (Flechsig)
6. Anterior Spinocerebellar Tract (Gowers)

Question 2

What are the types of epicritic sensibility?

What receptors are associated with them?

Answer 2

• *Touch** - Meissner corpuscles
• *Vibration** – Paccinian corpuscles
• P*roprioception – muscle spindles, Golgi tendon organs, nerve endings in joint capsule and ligaments

Question 3

Which tract carries proprioception (epicritic) to the cerebellum for spinal segments C8-L2/L3?

Which neuron is it in sequence?

Where is the neuron cell body?

Is the path crossed or uncrossed?

Through which cerebellar peduncle does it travel?

Answer 3

Posterior Spinocerebellar Tract of Flechsig

2nd neuron

Neuron cell body is in Dorsal Column of Clarke (Clarke’s Nucleus)

Uncrossed Pathway

Travels through Inferior Cerebellar Peduncle

Question 4

Which tract carries proprioception (epicritic) to the cerebellum for spinal segments L4-S3?

Which neuron is it in sequence?

Where is the neuron cell body?

Is the path crossed or uncrossed?

Through which cerebellar peduncle does it travel?

Answer 4

Ventral Spinocerebellar Tract of Gowers

2nd neuron

Neuron cell body is in posterior column

Crossed pathway (for majority of fibers), crossing is at anterior white commissure

Travels through superior cerebellar peduncle

Question 5

Which tract carries proprioception (epicritic) to the cerebellum for spinal segments C1-C7 (upper body)?

Which neuron is it in sequence?

Where is the neuron cell body?

Is the path crossed or uncrossed?

Answer 5

Cuneocerebellar Tract

1st neuron

The neuron cell body is in the Dorsal Root Ganglion

Uncrossed pathway, travels to medulla and synapses with Accessory Cuneate Nucleus (2nd neuron) to travel through the cerebellum via the inferior cerebellar peduncle

Question 6

Which tract carries fine touch (epicritic) sensation to the lower medulla for the cervical fibers?

Which neuron is it in sequence? Where is the neuron cell body?

Is the path crossed or uncrossed?

Where does the pathway continue after?

Answer 6

Cuneate Fasciculus of Burdach

1st neuron, cell body in DRG

Uncrossed pathway to cuneate nucleus

however, the next neuron will cross at the medial lemniscus and then travel to the thalamus VPL, then Post-Central Gyrus (somatosensory area)

Question 7

Which tract carries fine touch (epictritic) sensation to the lower medulla for the lower body fibers?

Which neuron is it in sequence? Where is the neuron cell body?

Is the path crossed or uncrossed?

Where does the pathway continue after?

Answer 7

Gracile Fasciculus of Goll

1st neuron, cell body in DRG

Uncrossed pathway to gracile nucleus

however, the next neuron will cross at the medial lemniscus and then travel to the thalamus VPL, then Post-Central Gyrus (somatosensory area)

Question 8

Which spinal tract carries protopathic sensation for the body?

Which neuron is it in sequence? Where is the neuron cell body?

Is the path crossed or uncrossed?

Where does the pathway continue after?

Answer 8

Spinothalamic Tract (both anterior and lateral, then they meet) of Edinger

~2nd neuron. After the first neuron, it may have several interneurons so cannot say which it is in sequence

Neuron cell body is in Substantia Gelatinosa of Rolandi

Crossed pathway at anterior white commissure

Continues to Thalamus VPL then to postcentral gyrus / sensory cortex

Question 9

What is the difference between the anterior and lateral spinothalamic tracts in the information they convey?

Where do they meet to become the same tract?

Answer 9

The lateral spinothalamic tract transmits pain and temperature.

The anterior spinothalamic tract transmits crude touch

Meet in the medulla to form a single spinothalamic tract

Question 10

Which spinal tract is involved in the more complex sensation of pain?

Which neuron is it in sequence? Where is the neuron cell body?

Is the path crossed or uncrossed?

Where does the pathway continue after?

Answer 10

Spinoreticular tract (or spino-reticulo-thalmic)

2nd neuron, cell body in the posterior horn

Crossed pathway

Goes to Reticular Formation then Thalamus VPL then Primary Somatosensory Cortex

Also has some fibers travel via the anterior thalamic radiation to the frontal cortex

Involved in automatic/ emotional aspects of pain

Question 11

What (shorter) ascending spinal tract is responsible for visual/auditory reflexes?

Where do these nerve fibers travel to?

Answer 11

Spinotectal reflex (spinomesencephalic)

Travels to Superior Collicle (vision) or Inferior Collicle (auditory)

Question 12

What are the steps of the pathway carrying epicritic information to the head?

Where are its neurons?

Answer 12

Neuron cell body locations:

1. Trigeminal Ganglion (Gasser) in Meckel’s Cave
2. -> Principal/Pontine Trigeminal Nucleus (General Somatosensory)
   
   • from here, it decussates as it courses through the Dorsal Trigeminal Lemniscus
3. -> Thalamus VPM
4. -> Postcentral Gyrus (primary sensory area)

Question 13

What are the steps of the pathway carrying protopathic information to the head?

Where are its neurons?

Answer 13

Neuron Cell Body locations:

1. Trigeminal Ganglion
2. -> Spinal Trigeminal Nucleus (General Somatosensory)
   
   • Crosses and travels via the Trigemal Lemniscus (NOT dorsal!)
3. -> Thalamus VPM
4. Postcentral gyrus (primary somatosensory area)

Question 14

What are the major tracts of the pyramidal system?

What is the function of this system?

Answer 14

Corticospinal for body control,

and Corticonuclear (aka corticobulbar) tracts for head control

(Thieme includes Corticoreticular too)

Function: voluntary motor, fine movements

Question 15

What is the difference between upper motor neurons and lower motor neurons?

Answer 15

Upper motor neurons are pyramidal neurons within the CNS, which then form a synapse with the lower motor neurons that run outside the CNS to affect muscles.

Lower motor neurons are generally Aα fibers

Question 16

Where is the nucleus of the cell body (perikarya) of both the corticospinal and corticonuclear tracts?

Answer 16

In the motor cortex (precentral gyrus, Brodmann 4)

in Layer V (internal pyramidal layer) - large pymamidal neurons (Betz cells)

Also have beginnings in the premotor cortex and supplementary motor cortex

Question 17

What is the path of the corticospinal tract?

Answer 17

Corticospinal: from cortex through corona radiata then through internal capsule (posterior limb)

Down through midbrain, pons, then in medulla through the pyramids where 90% of fibers cross

(uncrossed fibers = direct aka anterior corticospinal

crossed fibers = cruciate aka lateral corticospinal)

Go through spinal cord in their respective corticospinal tracts, then enter the grey matter and synapsing with lower motor neurons and interneurons in the ventral horn + intermediate zone

Question 18

What is the path of the corticonuclear/ corticobulbar tract?

Answer 18

Corticonuclear: Cortex -> Corona Radiata -> Internal Capsule (genu)

In brainstem, they synapse with the lower motor neurons of cranial nerves (the non-occular ones)

Provides voluntary control of the face/head

Question 19

What is the general pattern of the motor homunculus?

Answer 19

Starting Supero-medially: small foot and leg, then moving to trunk and upper arm

Supero-laterally: huge space for hand and finger control

Laterally: large area for face, eyes, mouth

Infero-laterally: jaw, tongue, swallowing

Question 20

Where is the main motor speech area (Broca)?

Answer 20

Brodmann 44,

in frontal lobe, anterior to primary motor cortex

(Broca’s area is required for meaningful speech formation)