Nail problems can also be caused by: 1  An injury to a nail. 2  Hangnails, which may lead to a minor infection next to your nails (paronychia), causing the skin around the nails to become swollen and tender. 3  Nail-biting, which can lead to fingertips that are red and sore and cuticles that bleed.
a reflected action or movement; the sum total of any particular automatic response mediated by the nervous system. A reflex is built into the nervous system and does not need the intervention of conscious thought to take effect.
Medical Definition of Peripheral nervous system Peripheral nervous system: The portion of the nervous system that is outside the brain and spinal cord. Abbreviated PNS. The nerves in the PNS connect the central nervous system (CNS) to sensory organs, such as the eye and ear, and to other organs of the body, muscles, blood vessels, and glands. The peripheral nerves include the 12 cranial nerves, the spinal nerves and roots, and the autonomic nerves.