Physiology of the spinal cord

At levels segments of the spinal cord closed arc unconditioned reflexes. For example, blow hammer on the tendon below the kneecap causes irritation of receptors tendons, then the nerve impulse on the rear roots goes back to the cells Rogov, then passed on a motor cells of the front horns and in the form of motor pulse front roots and motor fibers are directed to the muscle, causing it to decline, resulting in the extension of the leg. Reflex arc knee-jerk reactions passes through II - IV lumbar segments of the spinal cord, arc Achilles reflex-through I-II sacral segments. Reflex from the biceps tendon hands passes through V-VI cervical segments, reflex with the triceps tendon - through VI - VII cervical segments. Reflexosegmental apparatus spinal cord depends on the descending of the impulses coming from the bark on the pyramid way, subcortical structures, reticular formation and the cerebellum. These impulses are provided with voluntary movements and the level of excitability of segmental apparatus of the spinal cord.
In addition fibers conducting descending impulses in the spinal cord are the fibers that carry ascending (sensitive or afferent impulses. These impulses arise as a result of stimulation of skin receptors (surface kinds of sensitivity - pain, temperature), tendons, muscles and joints surfaces (joint and muscle deep, or proprioceptive, sensitivity).
Proprioceptive impulses are on the rear and lateral spinal cord, pain and temperature pulse - by-side. Connection of peripheral receptors with cortical cells in the analyzer via trejdingovuju cross chain of neurons, and this is the intersection for proprioceptive conductors at the level of the medulla oblongata, and pain and temperature at the level of the spinal cord. In the back the horns begins the second neuron that carries pain and temperature sensitivity. He goes to the other side of the spinal cord.
In performing any act participates complex innervation system of the spinal cord. So, for example, to smoothly happened flexion of the hand flexors should be reduced, and the extensor to some extent to relax.