Nerve Physiology - sciatic nerve and gastrocnemius

The sciatic nerve (also known as the ischiatic nerve) is a large nerve that starts in the lower back and runs through the buttock and down the lower limb. It is the longest and widest single nerve in the body.

The sciatic supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot.The nerve enters the lower limb by exiting the pelvis through the greater sciatic foramen, below the Piriformis muscle and above the superior gemellus muscle.

It descends midway between the greater trochanter of the femur and the tuberosity of the ischium, and along the back of the thigh to about its lower third, where it divides into two large branches, the tibial and common peroneal nerves. This division may take place at any point between the sacral plexus and the lower third of the thigh. When it occurs at the plexus, the common peroneal nerve usually pierces the Piriformis muscles.

Gastrocnemius muscle

Gastrocnemius muscle is a very powerful superficial muscle that is in the back part of the lower leg and also called the calf. It runs from its two heads just above the knee to the heel, and is involved in standing, walking, running and jumping. Along with the soleus muscle it forms the calf muscle.