Reflex Activity (adapted from PH-Biology)



Introduction

The nervous system is a series of conducting tissues that carries impulses to all parts of the body. Your nervous system initiates many types of reflex actions. When you touch a hot object, you immediately

pull your hand away. You might be aware of this reflex action occurring, but you are unable to stop or control it. How do reflex actions occur? When your hand touches a hot object, for example, heat receptors in the skin send an impulse to the muscles of the arm to contract. The impulse travels along the sensory neurons, to the spinal cord, across a synapse, and stimulates a motor neuron. The impulse leaves the spinal cord, passes back to the same nerve, and back to the arm muscles, causing them to contract and pull your hand away. This pathway is called the reflex arc. Because the reflex arc involves only the spinal cord and not the brain, a reflex action occurs in a matter of a fraction of a second. you are not able to control a reflex—it happens automatically.

In a nonreflex response, an impulse must travel to the brain. The brain interprets the stimulus and initiates an appropriate response. In this case, the time it takes to respond is measurably longer than

the time required for a reflex arc. A person’s reaction time can be measured by how quickly he or she can perceive a stimulus and then react to it. Driving a car and playing tennis are examples of activities

in which reaction time is very important. In this investigation, you will observe one of two reflex actions and measure your reaction time. You will also make a brief video (don't forget your camera phone) visually showing evidence of your reflex.


Answer the following questions in your lab group:

  1. What is another name for an involuntary or automatic response to a stimulus?

  2. Which specialized cells are involved in an involuntary or automatic response to a stimulus?

  3. What is the difference between a sensory neuron and a motor neuron?

  4. Where are inter-neurons found in the human body?


Materials:

Meter stick (must wear goggles for activity 2)

iPad with Educreations (Educreations https://www.educreations.com/ will work on a computer also). Your group must register for the class, the class id will be provided in class).

Educreations allows you to take pictures from the iPad or web and then narrate over the presentation. Don't forget your references.

Use to “+” symbol to add pictures. Use the microphone button to record. If you don't record voice over the pictures, the picture will disappear.


Procedure:

Note: each lab group will do ONE or the other activities.

Activity One: Reflex




4.Repeat steps 1 to 3. This time, try to stop your knee from jerking. Record your observations.

5. Reverse roles and repeat steps 1 to 4.

6. Video your attempts AND also video (using one of the small white boards or poster paper to illustrate) your answers to the questions below:


  1. Is the activity you just completed a voluntary response or an involuntary response?

  2. How do you know which type of response was demonstrated in the activity (state or illustrate your evidence)?

  3. Using the small white board or poster paper, illustrate the pathway used in your nervous system. Be sure to label/identify the cellular and organ participants. Consider including the following words in your video/drawing presentation: synapse, neuromuscular junction, acetylcholine, calicium, actin, myosin, sensory neuron, interneuron, and motor neuron.

  4. Introduce your lab team and describe their role in this activity.

  5. Make sure you have saved your presentation. (NOTE: if it is still a draft you can edit, once you finalize, that's it).

Activity Two: Reaction Time



2. Have a group member hold a meter stick in the air, with the 0-cm line between the thumb and index finger of your extended hand.

3. Have the group member drop the meter stick without advance notice. Try to catch it between your thumb and index finger as quickly as possible.

4. In Data Table 2, record in centimeters the position of your thumb and index finger. This is the distance the meter stick fell before you caught it.

5. Repeat steps 2 to 4 three times. Record your values and calculate your mean average in cm.

6. Video your attempts AND also video (using one of the small white boards or poster paper to illustrate) your answers to the questions below:



  1. Is the activity you just completed a voluntary response or an involuntary response?

  2. How do you know which type of response was demonstrated in the activity (state or illustrate your evidence)?

  3. Using the small white board or poster paper, illustrate the pathway used in your nervous system and show how the nervous system works together with the muscles to see the movement you observed. Be sure to label/identify the cellular and organ participants. Consider using the following words in your video/drawing presentation: synapse, neuromuscular junction, acetylcholine, calicium, actin, myosin, sensory neuron, interneuron, and motor neuron.

  4. Introduce your video with a title and date, your lab team, and describe their role in this activity. Safety and procedures must be followed. Include any references used.

  5. Make sure you have saved your presentation. (NOTE: if it is still a draft you can edit, once you finalize, that's it).

Evaluation will be done by your peers in class using a rubric looking for the required elements.