Anatomy and Physiology

Part One

Initially , the senses focus on executing the activity specifically on the steps . The person looks at the steps , unconsciously controlling balance , estimating the height needed to lift the feet as well as the distances between each step . Afferent neurons send signals to the primary motor cortex of the brain

This in turn sends impulses to the efferent fibers towards the muscles of the lower extremities . Each nerve fiber terminates into two to a hundred skeletal muscle fibers where it reaches a physiologically functioning neuromuscular junction . The stimulus allows for

the release of the neurotranmitter acethylcholine (AcH , exciting the muscles in the process . Muscles in the posterior thigh flex while the muscles in the anterior thigh extend to pull at the knee primarily , moving the patella and then the tibia and fibula . Posterior thigh muscles include the biceps femoris , semitendinosus , semimembranosus and popliteus . The anterior muscles include the quadriceps femoris , rectus femoris and the three vasti . Muscles in the foot then support the weight that is being distributed into one side of the body . The other leg does the same thing

Part Two

Upon reaching the specific height , the primary motor cortex sends signals to the muscle fibers on the upper extremities to extend and reach above the head . Nerve impulses travel through the corticospinal tract , again reaching the neuromuscular junction . In a relaxed state the actin filaments barely overlap . When a stimulus is provided depolarization of the muscle occurs . This allows interaction between the actin and myosin filaments...