A close-up view of a spider web? Some sort of exotic bacteria? What do you think this is?
This is actually a nerve cell, the cell of the nervous system. This cell sends electrical “sparks” that transmit signals throughout your body.
The Nervous System
A small child darts in front of your bike as you race down the street. You see the child and immediately react. You put on the brakes, steer away from the child, and yell out a warning, all in just a split second. How do you respond so quickly? Such rapid responses are controlled by your nervous system. The
is a complex network of nervous tissue that carries electrical messages throughout the body. It includes the brain and spinal cord, the
central nervous system
, and nerves that run throughout the body, the
peripheral nervous system
). To understand how nervous messages can travel so quickly, you need to know more about nerve cells.
The human nervous system includes the brain and spinal cord (central nervous system) and nerves that run throughout the body (peripheral nervous system).
Although the nervous system is very complex, nervous tissue consists of just two basic types of nerve cells: neurons and glial cells.
are the structural and functional units of the nervous system. They transmit electrical signals, called
provide support for neurons. For example, they provide neurons with nutrients and other materials.
As shown in
, a neuron consists of three basic parts: the cell body, dendrites, and axon. You can watch an animation of the parts of a neuron at this link:
contains the nucleus and other cell organelles.
extend from the cell body and receive nerve impulses from other neurons.
is a long extension of the cell body that transmits nerve impulses to other cells. The axon branches at the end, forming
. These are the points where the neuron communicates with other cells.
The structure of a neuron allows it to rapidly transmit nerve impulses to other cells.
The neuron is discussed at
The axon of many neurons has an outer layer called a
is a lipid produced by a type of a glial cell known as a
. The myelin sheath acts like a layer of insulation, similar to the plastic that encases an electrical cord. Regularly spaced nodes, or gaps, in the myelin sheath allow nerve impulses to skip along the axon very rapidly.
Types of Neurons
Neurons are classified based on the direction in which they carry nerve impulses.
carry nerve impulses from tissues and organs to the spinal cord and brain.
carry nerve impulses from the brain and spinal cord to muscles and glands (see
carry nerve impulses back and forth between sensory and motor neurons.
This axon is part of a motor neuron. It transmits nerve impulses to a skeletal muscle, causing the muscle to contract.
Neurons are the structural and functional units of the nervous system. They consist of a cell body, dendrites, and axon.
Neurons transmit nerve impulses to other cells.
Types of neurons include sensory neurons, motor neurons, and interneurons.
Use this resource to answer the questions that follow.
Describe the three parts of a neuron.
What are accessory cells?
What is myelin?
What is a synapse?
1. List and describe the parts of a neuron.
2. What do motor neurons do?