Histology - Muscle

Question 1

What kind of muscle is shown in each image?

Answer 1

Question 2

Answer 2

Question 3

Answer 3

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

What type of muscle is this?

Label the indicated structures.

Answer 8

Cardiac

Question 9

What type of muscle is shown?

Which cells were cut in cross-section?

Which cells were cut longitudinally?

Answer 9

Smooth muscle

Question 10

Answer 10

Question 11

What structures and cells are present in the perimysium and endomysium?

Answer 11

The Perimysium contains a bundle of muscle fibers, vasculature and nerves. The endomysium contains a single muscle fiber.

Question 12

What is a muscle fascicle, and which layer of connective tissue defines the boundaries of a fascicle?

Answer 12

It is a bundle of muscle fibers that are individually wrapped in a perimysium.

Question 13

What does the A-band represent?

Answer 13

A-bands are the anisotropic bands of the sarcomere and contain both myosin and actin myofilaments.

Question 14

What does the I-band represent?

Answer 14

I-bands are isotropic bands of the sarcomere and contain only actin myofilaments.

Question 15

What does the Z-line represent?

Answer 15

Z-lines are partitions within muscle fibers that section it into sarcomeres and are attached to actin (thin) myofilaments.

Question 16

During a muscle contraction what happens to the A-band, I-band, and Z-lines?

Answer 16

The Z lines come closer together, the I bands shrink, but the A-bands do not change.

Question 17

What is the function of the following accessory proteins?

• Titin
• alpha - Actinin
• Desmin
• Myomesin
• Dystrophin

Answer 17

• 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

Question 18

What is the function of the muscle spindle?

Answer 18

The muscle spindle senses length, tension, and velocity of the muscle contraction.

Question 19

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)?

Answer 19

Muscle increases force of contraction by recruiting additional muscle fibers.

Question 20

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?

Answer 20

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.

Question 21

Where in the body can you find smooth muscle?

Answer 21

Blood vessels, lung, GI tract, GU tract, skin, uterus