UNIT 2: SENSITIVITY AND COORDINATION

1.      STIMULI AND RESPONSES

-STIMULI AND RESPONSES

The function of sensitivity is the ability to receive stimuli from the world around us and produce responses to them.

ü  A stimulus is anything that affects any of the body ś activities. A sound, an object that you see or touch, a smell or a taste are examples of stimuli. There are two types of stimuli: 

                 A)   Internal. They come  from inside our bodies, like the feelings of hunger  or thirst.

                  B) External. These come from outside the body, like the smell of a     cake or the texture of a cloth.

ü  A response is the body´s answer to a stimulus. We eat when we are hungry, we protect ourselves from the rain and heat, and we laugh when we hear something very funny. These are all responses to different stimuli. 

 

-STIMULI RECEPTORS

   The body has different receptors to receive different types of stimuli. There are two types of receptors:

·         Internal receptors. They receive the internal stimuli our bodies produce. They are all over the body. They perceive hunger, thirst, sleep or the pain of sore muscles.

·         External receptors. They receive external stimuli. They are in the sensory organs. Our eyes let us see a landscape. Our noses let us smell a flower. Our tongues let us taste what we eat. Our ears let us hear many sounds. The skin on our bodies lets us perceive cold, heat or the surface of an object.  

 

-     RESPONSES

 

     The body responds to any stimuli. There are two basic types of responses.

·         Muscular responses. These are movements the muscles make in response to a stimulus, like removing your hand when you touch something hot.

·         Glandular responses. These are when glands produce various substances in response to a stimulus, like when your sweat glands produce sweat in response to heat.

 

ACTIVITIES

 1.- What is an stimulus? Explain it.

 2.- Write an example of an internal stimulus and another one of external stimulus.

 

3.- What´s a response? Name the different types of responses and write examples.

4.- Fill the gap

 Stimuli receptors can be_______________ or _____________.

Internal receptors are _____     ______ the body.

External receptors are in the  _________    ____________.