Skip Navigation

5.1: Planning

Difficulty Level: At Grade Created by: CK-12
Turn In

Key Ideas

  • A reflex is the simplest circuit in the nervous system.
  • Once triggered by a stimulus, a reflex goes to completion and causes a response, such as a muscle reaction. Some reflexes are easier to control than others.
  • The five parts of a reflex arc are the sensor, sensory neuron, control center, motor neuron, and muscle.


In the previous sections students learned about components of the nervous system. In this section they investigate a nerve circuit. They learn that reflexes are simple circuits in the nervous system that result in a response. Students identify reflexes, which are an important part of behavior and serve as protection from harm.



\begin{align*}\checkmark\end{align*} demonstrate and explain the five-part sequence of a reflex arc.

\begin{align*}\checkmark\end{align*} distinguish between a motor neuron and a sensory neuron.

\begin{align*}\checkmark\end{align*} explain the role of an inhibitory interneuron in a reflex.


reflex, stimulus

Student Materials

Activity 4-1: How Fast Is Your Reaction Time?

  • Activity Report
  • \begin{align*}20 \ cm\end{align*} metric ruler

Teacher Materials

Activity 4-1: How Fast Is Your Reaction Time?

  • Activity Report Answer Key

Advance Preparation

See Activity 4-1 in the Student Edition

Activity 4-1: How Fast Is Your Reaction Time

  • Gather \begin{align*}20 \ cm\end{align*} rulers.

Interdisciplinary Connections

Math Use strings of holiday minilights set to sequence mode to illustrate the nerve impulse traveling down the axon.

Notes/Highlights Having trouble? Report an issue.

Color Highlighted Text Notes
Show More

Image Attributions

Show Hide Details
6 , 7 , 8
Date Created:
Feb 23, 2012
Last Modified:
Apr 29, 2014
Save or share your relevant files like activites, homework and worksheet.
To add resources, you must be the owner of the section. Click Customize to make your own copy.
Please wait...
Please wait...
Image Detail
Sizes: Medium | Original