An Educational Model for Understanding Acute Deep Tissue Injury of Motor Units: Common Lab Exercises with a New Twist

a common occurrence with DTIs. As an exercise for this student-lead research project, one can assume a relative large mass of tissue is injured (i.e., skeletal muscle) by either blunt force trauma of external object and/or with pressure injury from the internal skeleton. The testable hypothesis is that damaged muscle can cause an altered function of healthy muscle and neurons. In addition, intracellular constituents (i.e., K+ and amino acids) from injured muscle may also play a role in the spread of tissue dysfunction. Thus, a treatment to obtain a normal extracellular environment can help promote a faster recovery from the initial DTI insult. Students can develop variations to the experimental preparations presented in these laboratory exercises. The preparations presented consist of two types of muscle fibers (slow and fast). These preparations are well-known for student neurophysiology experimentation but novel for the use of investigating an injury topic on muscle and nerve function. Crayfish preparations are commonly used in undergraduate and graduate classes to teach basic neurophysiological measures (Johnson et al., 2014). The crayfish abdominal extensor muscle preparation is used to demonstrate effects on resting membrane potential with ion substitution in saline and is a good preparation for demonstrating synaptic responses for different types of motor units. Some muscles in crustaceans are selectively innervated by either a phasic or a tonic motor neuron, although some single fibers can be innervated by both phasic and tonic excitatory motor neurons, such as for extensor muscle in the crayfish walking legs (Atwood, 1976; see movie explanation in Wu and Cooper, 2010) and most other limb muscles (Wiersma, 1961a). By selectively An Educational Model for Understanding Acute Deep Tissue Injury of Motor Units: Common Lab Exercises with a New Twist