Lesson OverviewLesson Overview ResponseResponse

Lesson OverviewLesson Overview28.1 Response Pt 128.1 Response Pt 1

QuickTime™ and a decompressor

are needed to see this picture.

Lesson OverviewLesson Overview ResponseResponse

How Animals RespondMost animals have evolved specialized nervous systems that enable them to respond to events around them.

Nervous systems are composed of specialized nerve cells, or neurons.

Neurons collect info from their surroundings, interpret, and “decide” what to do about it.

QuickTime™ and a decompressor

are needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

Lesson OverviewLesson Overview ResponseResponse

Detecting Stimuli Information in the environment that causes an organism to react is called a stimulus.

Animals’ ability to detect stimuli depends on specialized cells called sensory neurons.

Each type of sensory neuron responds to a particular stimulus such as light, heat, or chemicals.

Lesson OverviewLesson Overview ResponseResponse

Detecting Stimuli Many animals react to stimuli, including light, taste, odor, temperature, sound, water, gravity, and pressure.

But many animals have types of sensory cells that humans lack. That’s one reason why some animals respond to stimuli that humans cannot detect, such as very weak electric currents or Earth’s magnetic field.

Echolocation Sharks<3detect changes in the electromagnetic field

QuickTime™ and a decompressor

are needed to see this picture.

QuickTime™ and a decompressor

are needed to see this picture.

Lesson OverviewLesson Overview ResponseResponse

Processing Information When sensory neurons pass information about it to other nerve cells called interneurons.

Interneurons process information & determine responds.

The number of interneurons an animal has, determine how complex an animal’s behavior can be.

The more “intelligent” the animal the more interneurons, the more complex the response

Lesson OverviewLesson Overview ResponseResponse

Responding A specific reaction to a stimulus is called a response.

Responses to many stimuli are directed by the nervous system. However, those responses are usually carried out by cells or tissues that are not nerve cells.

For example, a lion’s decision to lunge at prey is carried out by muscle cells.

QuickTime™ and a decompressor

are needed to see this picture.

Lesson OverviewLesson Overview ResponseResponse

How Animals RespondHow do animals respond to events around them?

Lesson OverviewLesson Overview ResponseResponse

How Animals RespondHow do animals respond to events around them?

When an animal responds to a stimulus, body systems—including sensory neurons, the nervous system, and muscles—work together to generate a response.