Experiment 2: The Neuromuscular Junction
Each skeletal muscle is connected to the nervous system be motor end units. When the neurotransmitter acetylcholine is release at this site, the muscle fiber depolarizes. Calcium ions are released from stores in the sarcoplasmic reticulum. The presence of Ca2+ triggers the ratcheting of actin and myosin filaments and the contraction of the myofiber as all of the myofibrils contract simultaneously.
| MaterialsNeuromuscular Junction Digital Slide Images Neuromuscular Junction (Longitudinal Section) Digital Slide Images |
Procedure
1. Examine the digital slide images of the neuromuscular junction.
| Neuromuscular junction 100X. |
| Neuromuscular Junction (Longitudinal Section) 1000X. |
Post-Lab Questions
1. Identify the axon, terminal branches, and muscle fibers in the slide image below. If possible, trace the fiber to its terminus.
2. Are there few or many nuclei at the end plate?
3. What is a motor unit?
4. How is a greater force generated (in terms or motor unit recruitment)?
5. What types of sensors are present within the muscle to identify how much force is generated?
Experiment 3: Muscle Fatigue
Muscle contractions are essential for muscles to function properly. The inability of a muscle to maintain tension is muscle fatigue. Failure to contract may occur because of the accumulation of lactic acid, a lack of ATP, or decreased blood flow. In this exercise, you will investigate the correlation between repeated movements and muscle fatigue.
| MaterialsRubber Band | Stopwatch |
Note: If you suffer from a medical condition that does not permit you to perform this activity, please ask a partner to volunteer for you.
Procedure
1. Hypothesize how many times you can stretch a rubber band between your thumb and pinky finger in 20 seconds. Record your predictions in the table below.
2. Using your dominant hand, count the number of times you can completely stretch a rubber band between the thumb and pinky finger in 20 seconds. Be sure to stretch the rubber band as far as possible each time and do not take a break in between trials.
3. Record your count for each trial in Table 1.
| Table 1: Experimental Counts |
