Spinal cord II - Lec10

Question 1

Pyramidal system

Answer 1

Tracts that pass through the medullary pyramids

Composed of corticospinal tract and corticobulbar tract

Upper motor neurons: in lateral corticospinal tracts dessucation is in the pyramids. In anterior corticospinal tracts dessucate near the synapse with lower motor neurons

Question 2

Upper motor neurons of the pyramidal system

Answer 2

Classification is based on where they synapse in the ventral horn

• medial activation system
• lateral activation system
• nonspecific activating system

Question 3

Media activation system (UMN of the Pyrimydal system)

Answer 3

Innervates postural and girdle muscles

Contains:
-lateral vestibulospinal tract, tectospinal tract, medial reticularspinal tract, medial vestibulospinal tract and medial corticospinal tract

Question 4

Lateral activating system (UMN of pyramidal system)

Answer 4

Associated with distally located musces used for fine movements

Question 5

Nonspecific activating system (UMN from the pyramidal system)

Answer 5

Facilitate local refles arcs

Contains - ceruleospinal tract and raphespinal tract

Question 6

Corticospinal tract

Answer 6

Aka pyramidal tract

Origin: primary motor cortex, premotor cortex, somatosensory area

Pathway: origin -> internal capsule -> medullary pyramids -> cross in lower medulla then lateral column of spinal cord (lateral corticospinal tract.

If cross in lower then ventral (anterior) corticospinal tract.

Question 7

Lateral corticospinal tract vs Anterior spinal tracts and what they suppley.

General functions of cortico tract

Answer 7

Lateral - Crosses in the medulla
Lateral - Supplies all levels of spinal cord

Anterior - cross near synapse, supplies neck and upper limbs

Functions: adds speed and agility to conscious movement (hand) and high degree motor control, fingrs.

Question 8

Corticobulbar tract

Answer 8

Confined to the brainstem, innervates the head with most fibers terminating in the reticular fomraitaon

Association neurons leave the reticular formaitaon and synpase inthe nerve nuclei where they synapse with lower motor neuron

Question 9

Red nucleus

Answer 9

From primary motor cortex - corticorubral pathway - branches from the corticospinal tract in magnocellular portion of red nucleus

Magnocellular neurons give rise to rubrospinal tract (corsses in lower brain stem)
-Somatotropic representation of all muscles in the body

Stimulation results in stimulation of flexors and inhibition of extensors (antigravity muscles)

Question 10

Extrapyramidal system

Answer 10

Systems that contribute to motor control but are not part of the corticospinal tract (tracts that do not pass through medullary pryamids or corticobulbar tracts)

Rubrospinal tracts

Vestibulospinal tracts

Reticulospinal tracts

Question 11

Rubrospinal tract

Answer 11

Origin: red nucleus

Crosses in midbrain

Decends in lateral funiculus

Related to cerebellar function

Lesions: impairment of distal arms and hand movemnts and intention tremors

Question 12

Vestibulospinal tract

Answer 12

Origin: vestibular nuclei with input from CN VIII (vestibulocochlear nerve)

Anterior funiculus

Involved in maintences of upright posture

Question 13

Reticulospinal tract

Answer 13

Origin: reticular formation

Anterior portion of lateral funiculus

Mediate larger movemnts of trunk and limbs that do not require balance or fine movements

Question 14

Reticular Nuclei

Answer 14

Pontine reticular nuclei - make up the pontine reticulospinal tract with a stimulatory effect on extensors and flexors, with emphasis on extensors

Medullary reticular nuclei - fibers make up the medullary reticulospinal tract with an inhibitory effect on both extenosrs and flexors

Question 15

Compenent of the vestibular apparatus

Answer 15

Utricle
-macula located on horozontal plane and plays. A role in determining orientation of head when head is upright

Saccule
-macula in verticall plane and signals head orientation when person in laying down

Semicircular canals

Question 16

Macula

Answer 16

Covered with gelatinous layer with crystal structures callen statoconia

With hair cell projecting cilia into it

Weight of statoconia ends ciliain direction of graviational pull

Longest cilia is kinocillium

Question 17

How is a hair cell in the macula depolarized or hyperpolarized?

Answer 17

Bending of sterocilia towards kinocilulm -> depolarization

Bending in opposite direction -> hyperpolarization

Question 18

How does fluid in the semicircular canals move with the head?

Answer 18

Not, at first. Then after the head stops moving internal inertia keeps it going for a few seconds bending resident haircells in the opposite direction of the movement

Capula in ampulla of the semicircular tubes

Semicircular canals move with the head, it’s the fluid that moves independently

3 planes of movement detected by lateral ducts, anterior ducts and posterior ducts

Question 19

Vestibular nerve pathway

Answer 19

vestibular nerve into vestibular nucleus which connects to the fastigial nucleus to control the red nucleus in the reticular substance by both feedback and through the dentate nucleus