Quiz 6 guide + isotonic lab preview + grades
I appreciate sincere and honest evaluations that few of you gave to me. Those who did not hand in yet can do so as it helps me know how comfortable you are with this lab and what more can I do for you? I shall be elaborating everything as I was asked to do. Those who hate to read long things, forgive me/get use to it.
Also read comments posted by Matthew and Allison last time. Do you have any more inputs to what they have to say?
QUIZ TIPS
Muscle microanatomy
Should be able to identify any labeled region on EM of skeletal muscle or on slide (the same that you did on your worksheet)
Isometric muscle contraction
- Definitions of contraction, tension, load and what is isometric contraction.
- It is important to understand the length tension curve as shown in figure 2 in lab manual that demonstrates under what circumstances of muscle length you will see either increase or decrease in tension. Also important is the role of cross-bridge formation by actin and myosin filaments that results in tension.
- Plantar flexion and dorsi flexion (once again I apologize for this).
- Should remember how you dissected the muscle (gastrocnemius), where did you tied the knot (at Achilles tendon) & what bone did you cut (tibiofibula). Also remember how you went for hanging this muscle on the clamp and force transducer (This is trivial right now, however during final exams there will be few questions where someone might actually put an experimental setup and ask you to identify the error in experimental set up)
- What is recruitment, maximal stimulus and frequency modulation?
- The general trend (graph, figure 7 in lab manual) of muscle response to increasing stimulus frequency. You are expected to remember and label (if asked to) the threshold stimulus, recruitment, maximal stimulus, frequency modulation & tetany.
- Keep all three graphs that you generated with you. If you have handed me one graph for a group feel free to print the saved graph from computer. This one’s a useful data.
Isotonic muscle contraction lab preview
- Try to correlate differences between Isometric and Isotonic muscle contraction.
- How Isotonic muscle contraction works?
- Again you have three different graphs
- Procedure for muscle preparation remains to be the same. I will give you frog’s leg. First measure the plantar flexion and dorsi flexion and dissect the same way.
- Notice the difference in the experimental set up as compared to isometric. I would like to know from you why do we have this difference.
- In another experiment, we shall be playing with isolated muscle fibers and try to see how calcium and ATP effects the physiological length. Again for this we have a simple theory that calcium and ATP is required for actin and myosin to form cross bridges helps them slide.
GRADES
More to come....
class average of last quiz & worksheet
posted by Gaurav Joshi @ 3:12 AM
4 Comments:
For the plantar flexion and dorsiflexion do we just have to know what each does in regards to the leg of the frog or do we have to know the length of each?
I would imagine its different for every different leg, so it would not make sense to ask specific values. However, what they are and which one the gastrocnemius performs are probably going to be important.
I have my own quesion on the same topic, actually. Since the gastrocnemius does planar flexion, wouldn't it make more sense if the muscle were positioned so that its maximum physiological length was associated with this function rather than dorsiflexion? Since, assuming the normal physiological lengths do not allow overstretching (do they?), increasing the length of the muscle will increase its tension, wouldn't it make more sense if the maximum physiological length occured during planar flexion rather than dorsiflexion?
Emily, what Matthew says is correct.
Matt & Emily,
Refer to p. 330 of your Martini text for the explanation of gastrocnemius contraction and Fig. 11-2, which shows the contraction. When the gastrocnemius is contracted (i.e. shortened), the ankle is extended, which is plantar flexion. Dorsiflexion flexes the ankle, which extends (i.e. lengthens) the gastrocnemius. Do not confuse the action of the gastrocnemius "extension [plantar flexion] at ankle" as a lengthening of the gastroc. This action is upon the ankle.
Post a Comment
<< Home