Histology - Muscle Flashcards
What kind of muscle is shown in each image?
What type of muscle is this?
Label the indicated structures.
Cardiac
What type of muscle is shown?
Which cells were cut in cross-section?
Which cells were cut longitudinally?
Smooth muscle
What structures and cells are present in the perimysium and endomysium?
The Perimysium contains a bundle of muscle fibers, vasculature and nerves. The endomysium contains a single muscle fiber.
What is a muscle fascicle, and which layer of connective tissue defines the boundaries of a fascicle?
It is a bundle of muscle fibers that are individually wrapped in a perimysium.
What does the A-band represent?
A-bands are the anisotropic bands of the sarcomere and contain both myosin and actin myofilaments.
What does the I-band represent?
I-bands are isotropic bands of the sarcomere and contain only actin myofilaments.
What does the Z-line represent?
Z-lines are partitions within muscle fibers that section it into sarcomeres and are attached to actin (thin) myofilaments.
During a muscle contraction what happens to the A-band, I-band, and Z-lines?
The Z lines come closer together, the I bands shrink, but the A-bands do not change.
What is the function of the following accessory proteins?
- Titin
- alpha - Actinin
- Desmin
- Myomesin
- Dystrophin
- Titin: Acts as a spring responsible for the passive elasticity of muscle in addition to keeping myosin molecules in place
- alpha - Actinin: attachment of actin filaments to the Z-lines in skeletal muscle cells, and to the dense bodies in smooth muscle cells.
- Desmin: integrates the sarcolemma, Z disk, and nuclear membrane within the sarcomeres. It also regulates sarcomere architecture
- Myomesin: anchors the thick filament of the sarcomere to additional filaments.
- Dystrophin: connects the cytoskeleton of a muscle fiber to the extracellular matrix via the cell membrane
What is the function of the muscle spindle?
The muscle spindle senses length, tension, and velocity of the muscle contraction.
Skeletal muscle fiber contraction is an “all-or-none” twitch. How does a muscle increase its force of contraction (e.g., lifting a heavier weight)?
Muscle increases force of contraction by recruiting additional muscle fibers.
Sympathetic stimulation of the heart leads to an increase in contractility (i.e., increase in the force of contraction – positive inotropic effect). How does this increase in force of contraction differ from that seen in skeletal muscle?
In skeletal muscle, it is possible to recruit more muscle fibers or to increase the length/tension relationship to increase contractility. In cardiac muscle, more calcium is released to make a stronger and more efficient contraction.
Where in the body can you find smooth muscle?
Blood vessels, lung, GI tract, GU tract, skin, uterus
