29.3 The Senses KEY CONCEPT The senses detect the internal and external environments.

29.3 The Senses
KEY CONCEPT
The senses detect the internal and external
environments.
29.3 The Senses
The senses help to maintain homeostasis.
• Senses gather stimuli, and send
it to the nervous system.
• Nervous system responds to
stimuli.
– Pupils shrink when too much
light enters the eyes.
– Goose bumps when cold air
touches skin.
29.3 The Senses
The senses detect physical and chemical stimuli.
• The eye contributes to vision.
– Photoreceptors sense light.
– Two photoreceptors work
together: rod cells and cone
cells.
29.3 The Senses
• The ear contributes to hearing.
– mechanoreceptors called hair cells
– bend in response to vibrations
29.3 The Senses
• Taste and smell use chemoreceptors.
– Taste uses tongue, and smell uses nose.
– Chemoreceptors detect chemicals dissolved in fluid.
29.3 The Senses
• The skin senses touch.
– Mechanoreceptors detect pressure.
– Pain receptors detect damaged tissue.
– Thermoreceptors detect temperature.
pain receptor
light pressure receptor
hair follicle
heavy pressure receptor