Muscular System
 
 

Short Answer

1. Grady is examining a portion of a muscle cell under the microscope. He counts 14 nuclei in the cell fragment and observes alternating light and dark stripes across the cell. What type of muscle cell/tissue is he looking at?
2. Define Motor Unit. Do all muscle types have motor units? Indicate which ones do.
3. What is myoglobin? What is its role in determining if a fiber is a ‘fast twitch’ or a ‘slow twitch’ variety? Name the types of slow and fast twitch muscle fibers and indicate their predominance in the average adult.
4. Which muscle is most commonly biopsied in research?

Case Study A

Jessie is a bicyclist, training for her first criterion. During a practice, she experienced deep cramping of her left gastrocnemius muscle. Her coach instructed her to quickly get off the bike, and proceeded to massage her leg.

Q1: why does massage usually give immediate relief of skeletal muscle cramps?

Q2: what might be possible causes of muscle cramping?

After her coach finished massaging her leg, she had Jessie get back on her bike, and slowly work back to her training level. After practice, Jessie was instructed to stretch her legs diligently immediately after practice, and again before she went to sleep that evening. Jessie was also advised to visit a sports nutritionist. The nutritionist was most concerned about electrolyte balance.

Q3: what are electrolytes?

Q4: Which ones would be most appropriate to consider with muscle cramps – and why?

Case Study B

Aaron was ‘daydreaming’ in class one day [certainly not an anatomy class!] when the teacher asked him a question. Embarrassed, Aaron lowered his head, looked at the floor, and shrugged his shoulders to indicate he didn’t know the answer.

Q1: what muscle did he use to lower his head and look down?

Q2: what muscle did he use to shrug his shoulder?

The teacher continued with the lecture, and Aaron looked at the person sitting next to him, trying to see what page in the book the teacher was referring to. Aaron didn’t realize it, but he was squinting as he strained to see the page number.

Q3: what facial muscles did he use as he squinted?

Case Study C

Chris was practicing a ‘kick flip’ on his skateboard when he mislanded. Getting up, he noticed pain in his lower leg. After walking around a few minutes, he was relieved that he was able to move around, but was still very sore, and his lower lateral leg was starting to swell and throb.

Q1: Indicate the structures that might be injured – working superficially to deep. [omit skin and start with the fascia]

As Chris hobbles home, his leg continues to swell and he wonders if he should go to the ER. When he gets home, his roommate says to wait an hour first and then if his leg is still really bad, he will take him to the ER.

Q2: what routine first aid should Chris begin immediately?

Two hours later Chris is waiting in the ER to be seen. The doctor proceeds with an examination, and is trying to determine the extent of the damage – as the leg is still swollen, and beginning to show bruising. The injury is confined to the area in the lower half of the lateral leg.

Q3: What diagnostics should be used to differentially diagnose Chris’ injury?

After determining that the leg is not broken, but there is muscle and tendon damage, Chris is splinted and given instruction to use crutches for the next few weeks.

Q4: What is the difference between a strain and a sprain?