Bio 102 Lab 06: Nervous System And Sensory Reception

Bio 102 Lab 06 Nervous System And Sensory Reception

Complete all lab activities, answer the review questions, scan your lab pages using the AdobeScan app, and upload the PDF to Canvas.

Objectives: After completing this lab, you should be able to:

• Label and identify the parts of a typical neuron.
• Trace a reflex arc.
• Identify the form and function of white and gray matter in the brain and spinal cord.
• Label parts of the eye and ear.
• Describe the results of sensory tests performed in the lab.

The nervous system's basic conducting units are neurons, which transmit information via electrical impulses and chemical signals. Neurons have dendrites to receive signals and axons to send signals to other neurons, muscles, or glands. Nervous tissue also contains glial cells, such as Schwann cells, which produce the myelin sheath that wraps around axons, increasing conduction speed.

Labeling and Identification of Neuronal Parts

Exercise A: Motor Neuron

Identify and label these parts of a neuron: axon, dendrite, Schwann cell, nodes of Ranvier, cell body, nucleus, synaptic terminals.

Reflex Arc and Its Function

Exercise B: Simple Reflex

The patellar reflex involves stretching of the patellar ligament, triggering an impulse that travels through sensory neurons to the spinal cord and back via motor neurons, resulting in quadriceps contraction and leg extension.

Method: The procedure involves gently hitting the patellar ligament and observing the involuntary kick. This reflex is considered monosynaptic, occurring without cognitive processing in the brain, although sensory input is also transmitted to the brain for awareness.

Neural Structures in the Central Nervous System

Exercise C: White and Gray Matter

White matter appears white due to the high lipid content of the myelin sheath surrounding axons, facilitating rapid impulse transmission. In the spinal cord, white matter is on the outside, while gray matter is internal. In the brain, white matter is internally located, and gray matter forms the outer cortex.

Sensory Receptors and Touch Sensitivity

Exercise D: Touch Receptors

Touch receptors, such as Pacinian corpuscles, are located in the hypodermis or dermis, primarily inside the dermis. Pacinian corpuscles detect pressure and vibration, while Meissner corpuscles detect light touch.

The two-point discrimination test evaluates skin sensitivity. A smaller perceived distance indicates higher sensitivity and suggests a denser or more specialized receptor population.

Visual and Auditory Sensory Systems

Exercise E: Sensory Reception

The eye brings light to the retina, where photoreceptors (rods and cones) send signals via the optic nerve. Rods are sensitive to low light, enabling night vision, while cones detect color, primarily at the fovea. Photosensitive cells outside the cones contribute to circadian rhythms.

Identify parts of the eye such as cornea, iris, vitreous humor, pupil, sclera, fovea, retina, optic nerve, lens, ciliary body, suspensory ligaments, choroid, and blind spot.

Tests include near point measurement, blind spot detection, afterimages, and visual acuity assessments, including color vision and astigmatism tests.

The ear transmits sound vibrations from external ear through the middle ear bones (malleus, incus, stapes) to the cochlear fluid, where sensory receptors convert vibrations into neural signals.

Taste and Olfactory Interactions

The tongue detects salty and sweet tastes in specific regions, while the interaction of taste and smell influences flavor perception. Test involves applying sugar and salt solutions to different tongue areas and tasting fruit-flavored candies with nose closed and open to observe the influence of smell on taste perception.

Review Questions Summary

1. Schwann cells speed nerve impulses by forming the myelin sheath.

2. Axons convey impulses away from neurons.

3. Nerve tracts appear white due to myelin.

4. Pacinian corpuscles detect pressure and vibration.

5. Touch sensitivity is higher in areas with a dense concentration of touch receptors.

6. Astigmatism is a distortion of the eye's shape, corrected with glasses or contact lenses.

7. The blind spot lacks receptors due to the optic nerve exiting the retina, so images hitting this area are not processed.

8. Negative afterimages occur from cone and rod fatigue, with colors appearing inverted or unusual.

9. Ear bone sequence: tympanic membrane, malleus, incus, stapes, cochlear fluid, receptor cells.

10. Loss of smell can affect taste since olfactory input enhances flavor perception.

References

• Campbell, N. A., & Reece, J. B. (2014). Biology (10th ed.). Pearson.
• Marieb, E. N., & Hoehn, K. (2018). Human Anatomy & Physiology (11th ed.). Pearson.
• Sherwood, L. (2012). Human Physiology: From Cells to Systems. Cengage Learning.
• Ross, R. E. (2010). Anatomy and Physiology for Dummies. Wiley.
• Guyton, A. C., & Hall, J. E. (2015). Textbook of Medical Physiology (13th ed.). Elsevier.
• Fitzgerald, M. (2018). Sensory Systems. In J. W. Bear, B. M. Connors, & M. A. Paradiso (Eds.), Neuroscience: Exploring the Brain (4th ed.). Oxford University Press.
• Kandel, E. R., Schwartz, J. H., & Jessell, T. M. (2013). Principles of Neural Science (5th ed.). McGraw-Hill.
• Purves, D., et al. (2018). Neuroscience (6th ed.). Sinauer Associates.
• Kolb, B., & Whishaw, I. Q. (2015). Fundamentals of Human Neuropsychology. Worth Publishers.
• Tortora, G. J., & Derrickson, B. (2017). Principles of Anatomy and Physiology (15th ed.). Wiley.