Descending tracts

Question 1

paralysis vs paresis

Answer 1

Paralysis - full loss of movement
Paresis - decrease in force of movement

Question 2

Define monoplegia, paraplegia and tetraplegia

Answer 2

Monoplegia - paralysis of one extremity
Paraplegia - paralysis of both inferior limbs
Tetraplegia - all 4 extremities are paralysed

Question 3

Types of movements transmitted by the cortico-spinal tract

Answer 3

Voluntary, isolated and specialised movements. It is an indirect parthway.

Question 4

Where does the cortico-spinal tract decussate?

Answer 4

At the bulb, but not every fibre. The 90% that do decussate continue as the lateral corticospinal tract
while the 10% that do not continue as the anterior corticospinal tract.

Question 5

Origins of the corticospinal tract?

Answer 5

1/3 - M1 (both the lateral and medial faces)

1/3 - AMS (Supplemental Motor cortex) - in the medial face and a small superior zone of the lateral face.

1/3 S1 + Parietal association cortex

Question 6

From the cortex, what is the trajectory of the Cortico-spinal tract?

Answer 6

1. Cortex
2. Corona radiata
3. Capsula Internal (posterior arm)
4. Mesencephalon (3/5 medial part of the pies of the peduncles)
5. Protuberancia (basilar portion)
6. Bulbo (decussation and seperation into anterior and lateral fibres)

Question 7

Where in the capsula interna does the cortico-spinal fibre pass ? Is there a somatopic representation? Explain your answer.

Answer 7

In the posterior arm, close to the rodilla(genu;knee genoll).

There is a somatotopic representation, fibres related to the face are found closer to the genu.

Question 8

Where in the mesencefal do the cortico-spinal fibres pass through?

Answer 8

Pies de los pedunculos, medial 3/5 , together with the Cortico-nuclear fibres.

Question 9

Where in the protuberancia do the cortico-spinal fibres pass through?

Answer 9

Basilar portion(anterior portion) of the pons

Question 10

Where is the decussation of the Cortico-spinal fibres?

Answer 10

Bulbo raquideo (decusacion piramidal). Forman el tracto c-e lateral y anterior.

Question 11

What are the 2 fibres that originate from the cortico-spinal fibre?

Answer 11

1. Lateral Corticospinal fibres in the cordon lateral
2. Anterior corticospinal fibres. They continue down the spine close to the ventral canal. The descussate before leaving by the anterior root of the spinal nerves.

Question 12

Where does the rubro-spinal tract originate from?

Answer 12

From the red nucleus, in the tegmen of the mesencefal. It is the continuation of the corticorubral tract.

Question 13

Where does the rubro-spinal tract descussate?

Answer 13

In the mesencefal(midbrain); called the decusación tegmental ventra.

Question 14

Where in the protuberancia does the rubro-spinal tract pass through?

Answer 14

Tegment

Question 15

Where in the bulb does the rubro-spinal tract pass through?

Answer 15

Behind the nucleo olivar

Question 16

Where in the spine does the rubro spinal tract pass through?

Answer 16

In the lateral column - cordon lateral. Just infront of the alteral corticospinal tract.
Ends in the anterior horn(asta) of the medula espinal.

Question 17

The tecto-spinal tract carries information regarding:

Answer 17

Vistual stimuli, related to movements of the head and neck.

Question 18

Where does the tectospinal tract originate from

Answer 18

From both the colliculi of the midbrain (mesencefal)

Question 19

Does the tectospinal tract decussate? If so where?

Answer 19

They decussate at the level of the midbrain, called the dorsal tegmental decussation.

Question 20

Where in the protuberancia is the tecto-spinal tract found?

Answer 20

tegmental portion (anterior)

Question 21

Where in the bulb is the tecto-spinal tract found?

Answer 21

behind the pyramids

Question 22

Where in the spine is the tecto-spinal tract found?

Answer 22

just lateral and anterior to the anterior corticospinal tract. But only reaches the cervical level since it’s only related to movements of the head.

Question 23

What are these 3 decussations:
1. dorsal tegmental
2. ventral tegmental
3. Pyramidal

Answer 23

1. dorsal tegmental - This is the decussation of the tecto-espinal tract at the level of the midbrain.
2. ventral tegmental - this is the decussation of the rubro-spinal tract at the level of the midbrain,
3. Pyramidal - this is decussation of the corticospinal tract at the level of the bulb. But this decussation is incompelete!