Muscle fibers

Question 1

Movement

Answer 1

Only option for the ZNS to respond to environment

Question 2

Spinal motor neuron types and their associated muscle fibers

Answer 2

αS(slow)>type1 (slow twitch)
αFR (fatique resistant) >
type 2a (fast oxidative)
αFI (fatique intermediate) >
type 2x (fast adaptive)
αFF (fast fatiqueable) >
type 2b (fast glycolytic)
γ (gamma) > intrafusal fibers

Question 3

The motor Unit

Answer 3

smallest controllable segment of the neuromusculatur.
A single motor neuron and all innervated muscle fibers.
Each muscle fiber is only innervated by 1 motor neuron

Question 4

Formation & Regeneration of muscles

Answer 4

formed by fusion of myoblasts
For regeneration: inactive satellite cells get activated and differentiated into myoblasts.

Question 5

Metabolic properties of muscle fibers

Answer 5

high endurance (Type 1) ß-oxidation
high force output (Type 2b) Glycolysis
Type 1: get energy from fatty acids & lipids, have high Myoglobin content, lot of Mitochondria
Type 2b: energy from glucose/Glycogen, low myoglobin content, low Mitochondria

Question 6

Formation of neuronal progenitor domains in the ventral spiral cord

Answer 6

based on exogenous signals like shh gradients

Question 7

Columnar organisation of spinal motor neurons

Answer 7

Motor neurons innervating distinc regions are organised in motor columns
Medial motor column-innervates axial musculature
Lumbar motor column-innervates limbs
Hypaxial motor column-innervates body wall

Question 8

Morphological differences between Motor neuron types

Answer 8

Slow motor neurons have smaller cell soma and thinner axons
Slow motor neurons have lower capacitance, higher resistance and lower conductivity
This results in different electrical properties

Question 9

Electrophysiological differences of motor neuron types

Answer 9

Slow mn: low Rheobase, tonic firing
longer AHP half decay time
Fast mn: high Rheobase, phasic firing, shorter AHP, lower bistability

Question 10

Which type of motor neurons die first in disease

Answer 10

Fast motor neurons

Question 11

Name a motor neuron disease

Answer 11

ALS, Spinal muscular atrophy