Nervous System Responsible for coordinating the many activities performed inside and outside the body Every square inch of the human body is supplied with fine fibers known as nerves; there are over 100 billion nerve cells, known as neurons, in the body

Neurology The study of the nervous system and its disorders The nervous system is one of the most important systems of the body; controls and coordinates the function of all other systems, making them work harmoniously and efficiently

Divisions of Nervous System Principal parts are the brain, spinal cord and nerves

Cerebrospinal System Also known as the central nervous system Consists of the brain, spinal cord, spinal nerves & cranial nerves It controls consciousness and all mental activities, voluntary functions of the five senses Seeing, hearing, feeling, smelling & tasting Controls voluntary muscle actions, including all body movements and facial expressions

Peripheral Nervous System Made up of sensory and motor nerve fibers that connect the peripheral (outer) parts of the body to the central nervous system It has both sensory and motor nerves and carries messages to and from central nervous system

Autonomic Nervous System Controls the involuntary muscles Regulates the action of the smooth muscles, glands, blood vessels and heart

Brain Spinal Cord Brain is largest mass of tissue in the body Average weight is ounces Central power station of the body

Brain Spinal Cord Contains 12 pairs of cranial nerves All of which originate in the brain & reach various parts of the head, face & neck Spinal cord originates in the brain Enclosed & protected by spinal column 31 pairs of spinal nerves Extend from spinal cord to muscles & skin of trunk & limbs

Nerve Cell Structure & Function Neuron or nerve cell Primary structural unit of nervous system; composed of cell body & nucleus Dendrites Tree-like branching of nerve fibers extending from the nerve ell that receive impulses from other neurons

Nerve Cell Structure & Function Axon & Axon terminal Send impulses to other neurons, glands & muscles Nerves Long, whitish cords made up of bundles of fibers held together by connective tissue, through which impulses are transmitted

Types of Nerves Sensory nerves (afferent) Carry impulses or messages from sense organs to the brain, where sensations of touch, cold, heat, sight, hearing, taste, smell, pain & pressure are experienced Motor (efferent) nerves Carry impulses from brain to muscles; the transmitted impulses produce movement

Types of Nerves Mixed nerves Contain both sensory and motor fibers and have the ability to both send and receive messages Reflex Automatic response to a stimulus that involves movement of an impulse from a sensory receptor along an afferent nerve to the spinal cord, and a responsive impulse along an efferent neuron to a muscle causing a reaction Example: the quick removal of a hand from a hot object Reflexes do not have to be learned