Peripheral Nervous Lab

We will embark on a journey to explore the intricate and captivating mechanisms behind our ability to see, hear, and smell. Our focus will be on the special sensory organs responsible for these remarkable functions: the eye, the ear, and the nose.

Throughout this laboratory session, you will have the opportunity to delve into the intricacies of these sensory organs, unraveling their mysteries one layer at a time. We will begin by studying the eye, an organ so intricately designed that it can capture the wonders of the visual world. You will identify and describe the various layers of the eye, including the protective outermost layer, the cornea, the colorful iris that regulates light, and the light-sensitive retina that captures images and sends them to the brain.

Moving on, we will delve into the auditory realm and explore the regions and parts of the ear. From the outer ear that collects sound waves, to the middle ear that amplifies and transmits them, to the inner ear that converts sound into electrical signals, you will gain a comprehensive understanding of the ear's complex anatomy and the role it plays in our ability to hear and perceive sound.

Then, we will turn our attention to the nose, the gateway to our olfactory experiences. You will become familiar with the different parts of the nose, such as the external structures that shape its appearance and the intricate nasal cavity lined with specialized cells that detect and interpret various scents. You will discover how the brain interprets these signals, allowing us to savor the fragrances that surround us.

To solidify your understanding of these sensory organs, we will conclude our laboratory with a bovine eye dissection. Through this hands-on experience, you will carefully separate each layer of the eye, observing the structural details and appreciating the delicate harmony that enables vision.

Objectives

·         To identify and describe the major structures and layers of the human eye, including the cornea, iris, lens, retina, and optic nerve.

·         To understand the functions of the various parts of the ear, such as the outer, middle, and inner ear, and their roles in hearing and balance.

·         To explore the anatomy of the nose and its importance in the sense of smell and respiratory function.

·         To develop dissection skills and techniques through a hands-on bovine eye dissection, carefully separating and examining each layer and part.

·         To apply knowledge of human special senses to real-life examples and appreciate the complexity of sensory perception.

Materials

·         Models of the eye, ear, and nose

·         Bovine eyes

·         Dissection trays

·         Dissection kits

·         PPE

Special Senses Identification

Eye Dissection

·         Observe the exterior of the eye, identifying the sclera (white part), cornea (clear front surface), and optic nerve (located at the back).

·         Remove the extraocular muscles and fat surrounding the eye.

·         Use scissors to make a careful incision around the equator of the eye (creating anterior and posterior halves), cutting through the sclera and choroid layers. Separate the two halves of the eye, revealing the interior structures.

o    Observe the black tissue connecting the two halves of the eye, this is the tapetum.  The inside of the tapetum is a metallic blue and used to reflect light, improving night vision.  Humans do not have a tapetum.  Cut though this tissue.

·         Remove the vitreous humor (clear, gel-like substance) filling the space.

·         Use the scalpel to make a shallow incision around the cornea's circumference, being careful not to cut too deeply.

o    Using forceps and scissors, gently lift and cut away the cornea, revealing the anterior chamber and the iris.

·         Observe the iris and the pupil (central opening).

·         Use forceps to gently remove the lens, a hard structure located behind the iris.

·         In front of the lens, behind the iris observe the ciliary body (ring-shaped structure) and the suspensory ligaments (thin strands) that hold the lens in place.

·         In the posterior half of the eye, locate the retina (thin, delicate layer) lining the interior surface.

·         Identify the optic nerve at the back of the eye, where it connects to the retina.

·         Carefully peel away the retina to reveal the underlying choroid layer, which contains blood vessels and pigmented cells.

·      Cleanup

Draw and label all of the parts of the eye intact in a sagittal plane. 

Review Questions

1.       Which division of the peripheral nervous system controls voluntary movements of skeletal muscles?
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2.       How do the sympathetic and parasympathetic nervous systems differ in their effects on the body?
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3.       Which cranial nerve is responsible for controlling eye movements? ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4.       What are the functions of the different layers of the eye, and how do they work together to facilitate vision?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

5.       How do disorders of the peripheral nervous system, such as peripheral neuropathy, affect a person's ability to move and sense their body?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

6.       How could you design an experiment to test the sensory abilities of different areas of the body, such as the fingertips and the back of the hand?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

7.       Which cranial nerve is responsible for transmitting taste sensations from the tongue to the brain?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

8.       How might damage to the olfactory nerve affect a person's sense of taste?
______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

9.       How do the different parts of the ear work together to facilitate hearing and balance?
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

10.    How do vision impairments, such as nearsightedness, farsightedness, and astigmatism, affect the ability of the eye to refract light and form clear images on the retina?
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________