Nerves leading from the spinal cord and brain. The ganglia There are 31 pairs of spinal nerves in humans. There are 12 pairs of cranial nerves which connect directly with the brain. Some cranial nerves have only sensory dendrites, others have both sensory and motor axons or dendrites. It is covered by 3 layers of tissue called the meninges.
Gray matter has cell bodies and dendrites involved with reflexes.
The CNS is bathed in a fluid called cerebrospinal fluid. Nerves that carry sensory input to the CNS are called afferent Nerves that carry motor output away from the CNS are called efferent . The effect on glands and muscles depends upon the sum of the opposing signal. Both systems can send out excitatory or inhibitory signals. It is controlled by the hypothalamus.