Motor systems Flashcards
In the cortex, explain the somatotopic organization. (arm, leg, and face)
- Leg medial
- Face lateral
- Hand in-b/w
What cells does Polio affect?
Kills anterior horn cells (CST)
What is Post-Polio Syndrome?
Gradual weakening–when Polio pts have nl loss of ant horn cells, it has more of a dramatic effect because there ant horn cells may be innervating several thousand m. fibers instead of just a few hundred (like a nl person)
What are the names of the 3 major types of motor units?
S-unit (slow) (is also fatigue-resistant)
FR-unit (fast fatigue-resistant)
FF-unit (fast fatigable)
Rank the 3 types of motor units from most force to least force.
FF, FR, S
Rank the 3 types of motor units from most to least mito/caps.
S, FR, FF
What types and color of m. fibers are involved in each of the 3 motor units?
S: I (red)
FR: IIa (white)
FF: IIb (white)
Rank the 3 types of motor units from fastest twitch speed to slowest twitch speed.
FF, FR, S
FF and FR both considered “fast,” S considered “slow”
Where would you find LMNs?
Brainstem and sc
In the sc, explain the LMN column somatotopic organization. Medial? Lateral? Dorsal? Ventral?
- Medial: Axial/trunk (proximal)
- Lateral: Distal limb
- Dorsal: flexors
- Ventral: extensors
What NT do LMNs typically use? Which receptors are sensitive to them?
- ACh
- Nicotinic receptors
What is a motor unit?
All m. fibers innervated by 1 anterior horn cell AKA 1 LMN
Explain the “size principle” of LMN recruitment.
LMNs are recruited in order of size and force (added, not replaced):
- S-units
- FR-units
- FF-units
What are examples of UMNs?
Corticospinal and corticobulbar neurons
Where would you look for the descending tract of the lateral CST in the sc?
Lateral funiculus
What are the 4 centers of motor control for LMNs?
- Reflex and pattern generators in the sc
- Descending pw’s
- Cortical centers
- Basal ganglia and cerebellum
What is the function of the vestibulospinal tract?
(descending pw)
- Postural adjustments/head movements
What is the function of the reticulospinal tract?
(descending pw)
- Locomotion and postural control
What is the function of the tectospinal tract?
(descending pw)
- Reflexive turning of head to visual/auditory stimuli
What is the function of the rubrospinal tract? (not important)
(descending pw)
- Unknown significance in humans