Principles of Health Science 2012 Nervous System

Complex, highly organized system Coordinates all of the many activities of the body Allows body to respond and adapt to changes that occur both inside and outside the body What is the Nervous System?

Also known as nerve cell Basic structural unit of the nervous system Neuron: Parts of neuron Cell body Nucleus inside cell body Nerve fibers

Dendrites – carry impulses toward cell body Axon – single nerve fiber that carries impulses away from the cell body Covered with lipid (fat) covering called a myelin sheath Increases rate of transmission of an impulse Insulates and maintains the axon Nerve fibers continued:

Axon of a neuron lies close to the dendrites of many other neurons Space between them is known as synapse

Impulses coming from an axon “jump” the synapse to get to the dendrite of a neuron that will carry the impulse in the right direction Special chemicals called neurotransmitters located at end of each axon allow nerve impulses to pass from one neuron to another Impulses may follow many different routes.

Combination of many nerve fibers Located outside brain and spinal cord Nerves

Afferent or sensory nerves carry messages from all parts of the body to the brain and spinal cord Efferent or motor nerves carry messages from the brain and spinal cord to muscles and glands Nerves cont.

Associative or internuncial nerves carry both sensory and motor messages