Objectives

Learners can:

• explain how neurons transmit messages through the body

• model a neuron

• cell

• nucleus

Prerequisite Vocab

• nerve

• neuron

New Vocab

Vocabulary

a bundle of neurons

Nerve

a cell that sends an electrical signal

Neuron

The cell is the smallest unit of structure and function of all living organisms. The human body is made of many different types of cells. However, all cells have certain parts in common. This includes parts such as:

• cytoplasm

• ribosomes

• DNA (located in the nucleus, when present)

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The Cell

A neuron is a cell that sends an electrical signal. This function is an important part of an organism's ability to perceive and respond to its environment.

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Neuron

​The central part of the neuron contains the nucleus.

Cell Body

​The nucleus contains the cell's genetic material, or DNA.

Nucleus

Dendrites receive communications from other cells.

Dendrites

Nerve signals travel along the axon away from the cell body.

Axon

The myelin sheath insulates the axon and allows nerve signals to travel faster and more efficiently.

Myelin Sheath

The axon terminal connects the neuron with other neurons to create a network throughout the body.

Axon Terminals

Sensory neurons carry nerve impulses from tissues and organs to the brain.

Sensory

Motor neurons carry nerve impulses from the brain to muscles and glands.

Motor

Relay neurons carry nerve impulses back and forth between sensory and motor neurons.

Relay

​Types of Neurons

Nerve Impulse

Individual neurons are often bundled together into nerves. It is along the nerves that the body sends signals in the form of electrical impulses. These impulses are called nerve impulses. Within the nerve, these electrical signals pass through each individual neuron to send communications throughout the body. The impulse passes through the axon of neurons in a similar way to how people form a "human wave."

The fastest nerve impulses travel at a speed of about 100 meters per second. However, some nerve impulses are much slower. For example, the impulses that carry messages about warmth, cold, and aches travel at about one meter per second.

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Nerve Impulses