The Senses of the Ear (audition & vestibular senses) and the Chemical Senses (olfaction & gustation)

This week we finish learning about our sensory systems by covering audition (hearing), vestibular senses (balance), olfaction (smell), and gustation (taste). It is a lot, but I also think it is fascinating.

In both of the senses of the ear, you will see that the sensory receptor cells are called "hair cells." These cells are covered with cilia (their "hairs") and are activated when the cilia are bent. In order to bend the cilia, either sound waves have to move the fluid around them or head movement has to occur; either way, a physical deformation of the hairs results, and the hair cells are activated. It is just that the steps that occur that lead to the bending of the cilia are a bit complicated, as is ear anatomy.

The stimulus for both olfaction and gustation is a chemical one. Smells and tastes are chemicals. Something is sweet, for example, if it has sugar in it, and sugar is a chemical. The receptor cells for olfaction and gustation must therefore be able to recognize chemicals in order to work.

For all of the senses for this week, we will progress through them in an orderly fashion, following this organizational scheme:

	the anatomy of the sensory organ
	the stimulus for the sense
	the way the sensory receptor cells work
	and then the way that the brain deals with this sensory information.

Many of the images I have used in this week's pages come from your textbook... however, they are from the previous edition of your textbook. You will notice that many of the images on the ear have been updated for the new edition, so that the figures here do not exactly match those in your book. I think that's not a bad thing, though, since it is always helpful to have many different images to view in order to get a better understanding of the topic.