Muscle contraction & Motor pathways

Corticospinal tract

- Efferent motor neuron pathway

- 2 Neuron pathway

- Decussates at the medulla

- Movement execution

Dorsal column-medial lemniscal pathway

- Afferent somatsensory pathway

- 3 Neuron pathway

- Decussates at medulla

- Touch, vibration, two-point discrimination, proprioception

Spinothalamic pathway

- Afferent somatosensory pathway

- 3 Neuron pathway

- Decussates at spinal column

- Pain, temperature, some touch

a-motor neurons

contract the muscle

y-motor neurons

maintain tension and tone

1a sensory neuron

- encodes muscle length

- facilitates contraction (depolarization)

1b sensory neuron

- encodes muscle tension

- facilitates relaxation (depolarization)

Golgi tendon organs

Transmit information about tension to the spinal chord via 1b sensory neurons.

Knee-Jerk Reflex

Muscle spindle stretch → 1a sensory neuron → alpha motor neuron → quadriceps muscle contraction