Module 1 Lesson 5 - 3 (Lab)
Completion requirements
Lesson 5 — The Basic Units of the Nervous System: The Neuron and the Reflex Arc
Lab #1 - Examining Neural Tissue
Introduction
In this lab, you will examine micrographs of neurons to identify various specialized neural structures.Procedure
Draw the neurons from the micrographs, and label key structural features.Analysis
Click the tabs to view the slides, and check your work below each slide.All images in this lab were developed by Dr. Peter Takizawa, Department of Cell Biology, Yale University.
Cross-Section of a Nerve Bundle
- Label a nerve bundle and a neuron.
Notice how a single nerve contains multiple bundles of individual neurons.
Cross-Section of Spinal Cord
- Label the grey and white matter.
- Label a sensory neuron, a motor neuron, and an interneuron.
Myelinated Axon
- Label the myelin sheath and a Schwann cell.
This is a cross section of a myelinated axon. You can see the myelin sheath (black) surrounding the axon.
Unmyelinated Axon
- Label the axon.
- Compare the unmyelinated axon to the myelinated axon.
This is a cross section of unmyelinated axons. Although there are Schwann cells surrounding the axons, there are no myelin sheaths.
Myelinated Axons
- Label a node of Ranvier.
Notice how neurons vary in size. Axons that conduct faster nerve transmissions are larger in diameter. The larger diameter decreases the resistance in nerve transmission and that is why rapidly conducting axons in all animals tend to be much larger than the slowly conducting axons.
Synapse
- Label the presynaptic neuron, the post-synaptic cell, synaptic vesicles, the synapse, and mitochondria.
Try This
To enlarge your understanding of the structures and their functions, complete the following table by selecting your response and dropping it into the correct space on the chart.
Self-Check Answers
Three Major Types of Neurons
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Sensory Neuron |
Interneuron |
Motor Neuron |
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Lab #2 – Reflex Responses
Introduction
A reflex response is an automatic, involuntary response to a stimulus. Often, reflex responses protect the body from external harm. Test the following three types of reflex responses and design a procedure to test a fourth reflex.Procedure
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Pupillary Reflex
- Dim the lights in the room for several minutes.
- While focusing on the pupils of your partner (use a mirror if you are doing this by yourself), turn on the lights.
- Check the size of the pupils.
- The pupils should have dilated in the darkened room. They should have contracted quickly when the lights were turned on.
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Blink Reflex
- Have your partner hold a clear plastic sheet in front of his or her face.
- Throw a light object, such as a cotton ball at your partner's face.
- Your partner likely will blink, demonstrating the blink reflex.
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Patellar Reflex
- Have your partner sit on a chair or a table so that at least one leg can swing freely from the knee.
- Tap below the knee very gently.
- The leg should kick out immediately.
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Design an experiment to test other reflexes of the body, such as plantar reflex, response time reflex.
Here is an example of an experiment to test response time.
Response time
Response time
- Hold a ruler vertically.
- Have another person put his or her hand on the bottom of the ruler without touching it, but instruct the person to be ready to grab it.
- Drop the ruler.
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Record the level at which the person catches the ruler.
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Convert he distance to reaction time to allow comparison with other persons' times.
Reaction time: 5 cm = 0.10 sec; 20 cm = 0.20 sec; 80 cm = 0.40 sec.