Human Anatomy & Physiology and Renal Disorders

Our nervous system could be studied under two main headings for quick understanding: (1) The Central Nervous System (CNS) or Cerebrospinal Nervous System and (2) The Autonomic Nervous System. The autonomic nervous system includes the sympathetic nervous system and parasympathetic nervous system.

The central nervous system includes the brain and the spinal cord, and the nerves arising out from these. The nerves arising from the brain and the spinal cord are called peripheral nerves. The nervous tissue is one of the four elementary tissues of our body and commands the sensory and motor functions of our body in addition to intellect, emotions and memory functions. The nervous tissue is composed of nerve cells, dendrites, nerve fibres and nerve endings. The composite mass of nerve cells is called grey matter. The grey matter is found in the cortex of the brain, inner part of the spinal cord and cerebral ganglia. The role of the grey matter is the processing of the sensory and motor information, control of emotions, memory and intellect. The control of emotions, memory and intellect is associated with the growth and development of the brain. The nerve fibres and or axons constitute the white matter. The white color of the sheath of fatty matter called the myelin sheath covering the axons or nerve fibres is the reason behind the nomenclature as white matter. The white matter is the major component of the central portion of cerebral part of brain. The myelin sheath serves to protect, nourish and insulate the nerve fibres from each other. A nerve cell along with its dendrites, nerve fibre or axon and nerve endings is called a neuron as depicted in the figure-1 below:

Figure-1: Components of a Neuron

There are two types of neurons in our body. The neurons which carry impulses out from the brain to the tissues are called efferent neurons and the neurons which carry impulses to the brain from the tissues are called afferent neurons. Efferent neurons which supply impulses to the muscles and produce movement are called motor neurons and which supply impulses to the glands and produce secretion are called secretory neurons. Afferent neurons are also known as sensory neurons since these help us to assess a feeling of touch, pain and heat or cold.