Internal & External Stimuli: Definition & Examples

Internal & External Stimuli: Definition & Examples
Coming up next: The Environmental Requirements for Growth, Reproduction & Dynamic Homeostasis

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:02 Homeostasis & Stimuli
  • 1:24 Internal vs External
  • 3:12 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Timeline
Autoplay
Autoplay
Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

What are internal and external stimuli? Learn how the body uses messages from outside and inside of you to maintain perfect balance and keep you healthy and safe.

Homeostasis & Stimuli

People often talk about the balance of nature and how everything has to stay in harmony. But your body is also part of nature, and it has its own balance. We're not talking about staying upright or balancing on a ledge. No, this is a different kind of balance. This kind of balance is called homeostasis.

Homeostasis is the property of biological systems where things are controlled to keep internal conditions stable and unchanging. For example, your body must maintain a temperature of 98.6°F, your blood's oxygen saturation needs to stay between 95% and 100%, and your blood has to sustain a pH between 7.35 and 7.45. If these things change even slightly, they can cause major problems inside the body. Even an increase in temperature of 1°F is considered elevated, and it only takes a temperature of 100.4°F to be considered a fever. Your body also needs to stay safe and protect itself to maintain homeostasis.

The body maintains homeostasis by responding to stimuli. These complex responses rapidly return the body to its usual state. If they didn't, we would be constantly getting fevers or otherwise feeling sick. Let's take a look at how the body responds to stimuli that might affect its homeostasis.

Internal vs External Stimuli

There are two types of stimuli that affect the body: external and internal. External stimuli are changes to conditions outside of the body, or in general, information from outside the body that our senses detect. For example, our bodies respond to changes in light and temperature and to sources of danger. Light affects our bodies' circadian rhythms, which cause us to feel sleepy or awake at the correct times. Temperature causes our bodies to rapidly find ways to heat up or cool down. It does this by sweating, shivering, increasing or decreasing the size of the blood vessels near the surface of the skin, and creating goosebumps to reposition hair. And danger causes a release of hormones, which create either a fight or flight response: to stay and fight the danger or to flee to safety.

To unlock this lesson you must be a Study.com Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create An Account
Support