Nervous System pathways?

Question

List the order in which a somatic efferent impulse would travel between the big toe and the cerebrum of the brain. Include all the divisions and parts of the PNS and CNS through which it would have to pass.

Please can someone help me !!! I would really appreciate it

Answer 1

It is the pyramidal tract (also known as corticospinal tract) which carries efferent (motor) signals from cerebral cortex to all peripheral muscles (including those of big toe).

For diagram see, http://upload.wikimedia.org/wikipedia/co...

Anatomically, it is divided into 2 parts-

1. Upper motor neuron (CNS part)

2. Lower motor neuron (spinal cord onwards)

It originates at motor cortex (cerebrum), then passes through internal capsule. 80% fibers cross to opposite side in medulla oblongata.These crossed fibers form lateral corticospinal tract. 10% fibers remain uncrossed. Remaining 10% cross at spinal cord level to form anterior corticospinal tract. Neurons from cerebrum to spinal cord are called upper motor or 1st order neurons.

After entering the spinal cord, they (1st order neurons) synapse with ventral horn neurons in spinal cord. Thus, ventral horn neurons are 2nd order (or lower motor) neurons. They leave the spinal cord via anterior roots to form spinal nerves and provide motor innervation to voluntary muscles.