Once stimulation from a nerve impulse stops, the muscle tissue will relax or the gland will stop secreting. It consists mainly of nerves that connect the brain and spinal cord to sensory receptors, muscles, and glands. Autonomic motor neurons control involuntary contractions of smooth muscle and cardiac muscle, as well as secretions of both exocrine and endocrine glands. Some examples of neuroglia include microglia, oligodendrocytes and Schwann cells. We will discuss the concept of the myelin sheath a little later.
Neurons are extremely long-lived.
As long as they are not damaged by disease or trauma, they can last a lifetime. Neurons have a high metabolic rate, requiring a continuous and abundant supply of oxygen and glucose. Neurons have limited powers of regeneration. If the cell body of a neuron is destroyed, that neuron can not be replaced. Mature neurons are incapable of cell division.