Physiology Flashcards
Muscles that work together to bring about a common movement are known as?
Synergists
Muscles that oppose each other’s movements are known as?
Antagonists
Where within the spinal cord do you find greater numbers of motor neurones?
Cervical enlargement (C3-T1) - supplies arm Lumbar enlargement (L1-L3) - supplies leg
What is a motor unit?
The a-MN and all of the skeletal muscle fibres that it innervates
What is the smallest functional component of the motor system?
Motor unit
What is a motor pool?
The collection of a-MNs that innervate a single muscle
By which two mechanisms are force of muscle contractions graded?
Frequency of AP discharge of a-MN
Recruitment of additional, synergistic, motor units
What is the somatotrophic distribution of LMN cell bodies in the ventral horn?
Axial muscles = medial
Distal muscles = lateral
Flexors = dorsal
Extensors = ventral
What are the three regulatory inputs to an a-MN?
Central terminals of DRG whose axons innervate muscle spindles
UMNs in motor cortex and brain stem
Spinal interneurones
What are the major skeletal muscle fibre types?
Slow (Type I)
Fast (Type II)
What is the function of slow (type I) skeletal muscle fibres?
Slow contraction and relaxation
Fatigue resistant
Red fibres, high myoglobin
What are the functions of fast (type II) fibres?
Type IIa
Fast contraction and relaxation
Fatigue resistant
Red, reasonably well vascularised
Type IIb/x
Fast contraction
Not fatigue resistant
Pale, poorly vascularised
What is the composition of fast fatiguing motor units?
Very high tension
Fast fatiguing
Large a-MN, high threshold
Type IIb/x fibres
What is the composition of fatigue resistant motor units?
High tension
Slow fatiguing
Intermediate a-MN and threshold
Type IIa fibres
What is the composition of slow motor units?
Low tension
Fatigue resistant
Small a-MN, low threshold
Type I fibres
