BI 231 - Human Physiology and Anatomy
Special Senses Study Guide

Compiled by Pat Bowne, Sherry Dollhopf,and Justin LaManna, 2007-11


The special senses include smell (olfaction), taste, sight, hearing, and balance. All five senses involve specialized sensory cells that detect changes in the environment and use neurotransmitters to pass this information to nerve tracts leading to sensory information centers in the brain.
Smell and taste are both senses that involve the detection of chemicals that are perceived as different smells and tastes. The sense of sight uses photosensitive proteins in the retina of the eye to detect bright light and light of different colors. Hearing and balance are both sensed in the ear with hair cells that are sensitive to sounds wave or movement.

Before class, make sure you:

Can explain action potential and cell firing

Can sketch and explain the structure and function of a synapse

Tutorials and reading assignment: Review the vision tutorials at:

Chapter 10, 274-288, 290-307

What you should know for the assessment:

1. READ and MAP OUT the processes of touch, taste, and smell. For each one, include:

A. What exactly is being measured?
B. What are the sensory cells that detect it? (there may be several different kinds)
C. HOW does the thing being measured make the sensory cells depolarize? (there may be several different mechanisms)
D. What is the pathway by which the nerve impulses reach the brain?
E. What area of the brain receives and processes the impulses?

Be able to DESCRIBE and DIAGRAM the pathway of light through the eye from the cornea to the retina.

Be able to EXPLAIN how the amount of light entering the eye is regulated and how focus of the image is achieved.

COMPARE and CONTRAST the function and structure of rod and cone cells in the eye, including where they are located in the retina, what kind of light they perceive and how they function in visual acuity, color vision, and dim light vision.

EXPLAIN visual phenomena such as the blind spot, adaptation to bright and dim light, and decreased visual acuity in peripheral vision.

DIAGRAM the path of sound waves through the structures of the ear, including how auditory hair cells fire and how sound waves of different frequencies are detected by the organ of corti

DESCRIBE how movement and orientation are detected in the ear.

PREDICT how degradation of particular sensory cells or structures will change perception of odors, tastes, light, sound, or motion.

Sensory terms to know - touch

Sensory terms to know - taste and smell (the chemical senses)

Sensory terms to know - sight and hearing
Practice Questions

WRITE complete answers to the following questions. Back up your answers with logical arguments based on physiological concepts.

A. You are trying to thread a needle and sew in very dim light. When someone else watches you trying to thread the needle, they notice that you are not actually looking directly at the needle, but a few inches to the side. Why would you do this? Why is it harder to see small things clearly in dim light?

B.How will each of the defects below affect eye function?

--a low number of ganglion cells in the retina
--a blocked canal of Schlemm
--decrease in blood flow to the choroid

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