5. 3 Types of Muscle Tissue

10. In this photomicrograph, you should notice: the epimysium on the left, the multiple fascicles, the translucent perimysium partitioning them , and the multiple muscle fibers making up the fascicles.

13. Indirect attachments are typical. The muscle CT extends and forms either a cordlike structure (a tendon ) or a sheetlike structure ( aponeurosis ) which attaches to the periosteum or perichondrium. Muscle attachments may be direct or indirect . Direct attachments are less common. The epimysium is fused to a periosteum or a perichondrium.

21. Note the relationship between the thin and thick filaments

25. Here we have several different cross sections of a myofibril. Why are they different?

26. Here is a longitudinal section of skeletal muscle. See the multiple nuclei (N) pressed against the side of the muscle fibers. The light I bands and dark A bands are labeled for you. What do you think the F stands for?

30. Here is what happens as the filaments slide and the sarcomere and the muscle fiber shortens. In the process of contraction, what happens to the: 1. Distance btwn Z discs 2. Length of the A band 3. Length of the H zone 4. Length of the I band

31. Here are 2 electron micrographs of the same sarcomere. Do you see the Z discs, A band, H zone, M line, and I bands? How do the 2 pictures differ? What happened?

57. QUICK THOUGHT QUESTION: I n this sculpture, why are the lion’s back legs paralyzed even though they were not injured?

76. Here we have multiple twitches separated by ample time. Notice that the previous twitch has no effect on a new twitch and that these twitches are similar in size. This is why we can say that muscle contraction – at least on the level of a single fiber – is an all-or-none event . The black arrows signify stimulation

77. Here, we have an initial stimulation and resulting twitch all by itself. Then we have 2 stimuli in somewhat rapid succession. The 2 nd twitch has added on to the first. This is known as wave or temporal summation . It occurs because there is still calcium from the 1 st twitch in the sarcoplasm at the time of the 2 nd twitch.

79. Here, the stimuli are close enough to one another so that tetanus is complete and no relaxation occurs until fatigue sets in.

80. Here we have the phenomenon known as treppe (German for staircase). Notice that the subsequent contractions grow stronger. There 2 reasons for this: 1. Slight increase in sarcoplasmic [Ca2+] 2. Heat liberated by working muscle increases the rate and efficiency of enzyme function within the muscle fiber.

95. Thought questions: why do chickens have white breast meat and dark leg meat? What does this say about the activities of the associated muscles? Why do ducks have dark breast meat?

109. Smooth muscle relaxation: Calcium is pumped out of the cell, which decreases the amount of active calmodulin which decreases the amount of active MLCK which decreases the number of crossbridges. Relaxation can occur subsequent to contraction or at any time if anything causes a decrease in the calcium permeability of the smooth muscle cell. Why are calcium channel blockers given to people with hypertension?