Anatomy and Physiology 241 Objectives
MUSCLES
At the completion of this unit the student should:
1. Know the functions of skeletal muscle.
2. Describe the shape and size of skeletal muscle cells. Know sarcolemma, sarcoplasmic reticulum
and sarcoplasm.
3. Describe the connective tissues within and around a muscle: endomysium, perimysium,
epimysium. Know what connective tissue is composed of.
4. Explain the continuity of collagenous fibers from endomysium to tendon or aponeurosis to
periosteum
5. What is an aponeurosis? Describe its histology.
6. Know that skeletal muscle cells are multinucleated, and why. Where in the cell are they located?
7. What is a myofibril? Describe the shape and the position within the muscle cell. How many
myofibrils may be in a muscle cell?
8. What is a myofilament? What is its relation to a myofibril?
9. What is a sarcomere? What is its relation to a myofibril? What is a Z disc (line)? Describe the
arrangement of thick and thin filaments in a sarcomere. What is the “region of overlap” in a
sarcomere? Describe and be able to locate the A band, I band, M line and H zone.
10. Describe the 3-dimensional arrangement of thick and thin filaments in a sarcomere.
11. Have a good understanding of the 3-dimensional structure of a myofibril as a whole, with its series
of sarcomeres. Understand the relationships between Z discs and thin filaments, and between thin
filaments and thick filaments. Know that a muscle cell contracts when all of the sarcomeres in all of
its myofibrils shorten.
12. Know the location and role of titin.
13. Describe the structure of a thick filament. Be able to find an M line, H zone and the zone of
overlap. What is myosin? What is a myosin head? What is a cross bridge? What is a myosin tail?
Describe the arrangement of myosin heads on a thick filament. Know that myosin is an enzyme and
may be called myosinATPase
14. Know the terms A band and I band.
15. Describe the structure of a thin filament. Know F-actin & G-actin. Describe the structure of an
actin molecule, and explain how the actin molecules are arranged in a thin filament. What and where
is an actin active site? Where are the tropomyosin molecules, and what do they do? Where are the
troponin molecules, and what do they do?
16. What are transverse tubules and triads? Describe their structure and location. Where are they in
relation to myofibrils? What is their function?
17. What is the sarcoplasmic reticulum? Describe its structure and location. Where is it in relation to
myofibrils? What is a terminal cisterna? Know the function of the Ca++ pumps?
18. Why do muscle cells have so many mitochondria? Where in the cell are they? Why is it so
important that they be right next to the myofibrils?
19. What is the sliding filament mechanism in muscle contraction? Understand how this works at the
level of the sarcomere, the myofibril, and the whole cell.
20. Know all of the steps in skeletal muscle contraction, starting with an action potential in an alpha
motor neuron, and ending with sliding of contractile filaments. Understand what is happening at each
step, and understand why each step is important.
21. Describe a neuromuscular or myoneural junction. Explain motor end plate, synaptic cleft, ACH,
junctional folds, exocytosis, ACHE, depolarization, threshold, action potential, end plate potential.
Know how these relate to muscle contraction.
22. What is excitation-contraction coupling? Explain how the electrical communication of an alpha
motor neuron is translated into a signal to the myosin head to start the contractile process.
23. Understand the contraction cycle of a myosin head. Explain how repeated cycling of myosin
heads results in shortening of sarcomeres. .
24. Understand the role of ATP in the contraction cycle. How do the mitochondria fit into this?
25. Explain how muscle relaxes include the function of Ca, Calcium pumps, troponin and tropomyosin
in the process.
26.Know all the ways that tension develops in a muscle: muscle length, number of cross bridges
formed, frequency of nerve stimulation and recruitment.
27. Why does muscle contraction generate heat?
28. Explain how length and tension are related. What does this have to do with degree of overlap.
29. What is a muscle twitch? Do twitches happen during normal movement? Why or why not?
Describe the latent, contraction, and relaxation phases of a muscle twitch, give their durations and be
able to draw the myogram of a twitch. What happens inside the muscle cell during each of these
phases, with regard to action potentials, Ca++ movements, and sliding of contractile filaments?
30. What is summation of twitches? Describe incomplete tetanus. What is tetanus? Know how these
would look in a myogram. Do these occur during normal movement? What happens inside the
muscle cells with regard to action potentials, Ca++ movements, and sliding of contractile filaments?
Why do sarcomeres shorten more than during a single muscle twitch? Explain how frequency of
contractions contributes to tetanus.
31. Describe treppe and how it comes about. How does calcium play into treppe? Know what treppe
looks like on a myogram.
32. What is motor unit recruitment? How does the nervous system use this to grade muscle force?
What is a motor unit? What do motor units have to do with tension development? When is recruitment
used.
33. Describe asynchronous recruitment. Explain how the nervous system can use a combination of
motor unit recruitment and modulation of action potential frequencies to grade the amount of
contraction in a muscle.
34. Know isotonic and isometric contractions. Know concentric and eccentric contractions. Know
what happens in each type of contraction and when.
35. Know where the energy comes from for muscle contraction: glycogen, creatinine phosphate,
glycolysis and cellular respiration.
36. Know where the energy comes from for different amounts of exertion.
37. List the types of muscle fibers: slow and fast twitch. Know what they contain and why they are
specialized for their specific functions. Which one is long acting and which is short acting. Which can
generate the most force.
38. Give ways muscle fibers can change with exercise and types of exercise needed for the change.
39. Describe smooth muscle cells. Give its functions. Describe its innervation. Know the difference
between single and multi unit smooth muscle cells.
40. Explain the rate of ATP use in a muscle cell when it contracts compared to resting state. Name
the 3 major mechanisms for ATP synthesis in a skeletal muscle cell. Which occur in mitochondria and
which occur in the cytoplasm?
41. Know how creatine phosphate is used in muscle contractions and when. When is it stored and not
used? What is the advantage of being able to synthesize ATP by this mechanism? Why is it that this
mechanism can continue only for a short time?
42. Know aerobic metabolism-Kreb’s cycle-when it is used and where it is conducted.
43. Aerobic metabolism includes which 3 metabolic pathways? When is this mechanism used for
ATP synthesis in skeletal muscle cells? What does aerobic mean? What are the products of aerobic
metabolism? When is aerobic metabolism used for muscle contraction?
44. When and where does anaerobic glycolysis occur in skeletal muscle cells? What are the
products of anaerobic glycolysis? What is the advantage of being able to synthesize ATP by this
mechanism? What are the disadvantages? Why is it that anaerobic glycolysis can continue only for a
short time?
45. Explain how muscle soreness and fatigue are byproducts of anaerobic metabolism.
46. Know how smooth muscle and skeletal muscle contractions are alike and not alike; know how the
cells are different and how they are alike. Know where calcium comes from for contraction in both.