Motor Units & Muscle Spindles

Question 1

Describe anatomy of somatic nervous system.

Answer 1

Upper motor neurons:

• arise from cerebral cortex
• use glutamate as neurotransmitter

Lower motor neurons:

• arise from spinal cord
• use acetylcholine as neurotransmitter

Question 2

Describe types of motor unit.

Answer 2

Fast fatiguing:

• high tension
• Large a-MN, high threshold
• type 11x fibres

Fatigue resistant:

• high tension
• slow fatiguing
• intermediate a-MN and threshold
• type 11a threshold

Slow:
- low tension
- fatigue resistant
- small a-MN, low threshold
Type I fibres