Lecture 4- Muscular Tissue

Question 1

What are the three types of muscle tissue?

Answer 1

1. Skeletal- striated, voluntary, attached to skeleton
2. Cardiac- striated, involuntary, heart
3. Smooth- smooth, involuntary, bladder, organs, blood vessels

Question 2

What does the term “muscle” mean?

Answer 2

Many muscles fibers (cells) surrounded by connective tissue

Question 3

What is the endomysium?

Answer 3

Surrounding of the muscle fiber or cell

Question 4

What is the perimysium?

Answer 4

Surrounds the muscle fascicle

Question 5

What is the epimysium?

Answer 5

Surrounding of the entire muscle

Question 6

Why is there more than one nucleus per muscle fiber?

Answer 6

The nucleus divided and the cell did not divide or myoblasts fused during development to form muscle fibers.

Question 7

What are myofibrils and why is skeletal muscle striated?

Answer 7

Myofibrils are composed of Actin (thin) and Myosin (thick) filaments and are striated because of the orientation of these fibers

Question 8

What is the Z-Disc made of?

Answer 8

A spider web of thin filaments including:

1. Alpha-Actinin

Question 9

What is the role of titin?

Answer 9

Titin connects the thick filaments to the Z disk

Question 10

What are the boundaries of the sarcomere?

Answer 10

Z-line to Z-line

Question 11

What are the boundaries of the H Zone?

Answer 11

The central region between Z-lines containing the M line in the absolute center.

Question 12

What is the I band (isotropic)?

Answer 12

The band containing the Z line, stained light

Question 13

What is the A band (anisotropic)?

Answer 13

The band containing the thick filaments housing the H zone and the M line.

Question 14

Do skeletal muscle fibers also have other organelles?

Answer 14

Yes, lots of mitochondria.

Question 15

What is the main role of the sarcoplasmic (SR)?

Answer 15

Store calcium to release during contractions

Question 16

How does Ca get released from the SR to cause contraction?

Answer 16

Excitation-contraction (E-C) coupling

Question 17

What controls contraction of the skeletal muscle?

Answer 17

Somatic Nervous System

Question 18

What is the neuropathway of contraction (E-C coupling)?

Answer 18

1. Neurotransmitter (ACh) released from the neuron
2. ACh binds to its receptor on the sarcolemma or muscle cell membrane
3. Initiates a muscle or electrical impulse to spread along the sarcolemma
4. Impulse travels down into the muscle cell via t-tubules
5. triggers the release of Ca++ from the SR

Question 19

What does the Ca++ do?

Answer 19

1. Calcium binds to troponin C

2. Initiates contraction

Question 20

What happens to the Z line, I band, A band, and sarcomere during contraction?

Answer 20

1. Z lines narrow
2. I band narrows
3. Sarcomere shortens
4. A band stays the same

Question 21

What are the different types of muscle fibers?

Answer 21

1. Slow twitch
2. Intermediate twitch
3. Fast twitch

Question 22

What is the difference between cardiac muscle and skeletal muscle?

Answer 22

1. Cardiac muscle contain nuclei in the center
2. The cells are branched
3. Cells have intercalated disks

Question 23

What is the advantage of cell branching?

Answer 23

Branching helps organize the muscle in the heart chamber so it ejects more blood with each contraction.

Question 24

What are the advantages of intercalated disks?

Answer 24

Intercalated disks bind cells firmly together. It helps with intercellular communication so the ventricles and atria can contract as one unit.

Question 25

What structures in the intercalated disk helps bind cells firmly together?

Answer 25

1. Desmosomes

2. Fascia adherens (resembles zonula adherens)

Question 26

What structure helps the intercalated disk with intercellular communication?

Answer 26

Gap Junctions

Question 27

What is the advantage of having the gap junctions?

Answer 27

Communication

Question 28

What are the components of thin filaments?

Answer 28

1. Actin
2. Tropomyosin
3. Troponin C, I, T

Question 29

What type of organelles are found in cardiac cells?

Answer 29

Mitochondria

Question 30

What is the terminal cisternae?

Answer 30

The endpoint of the sarcoplasmic reticulum. There is only one so it is a dyad.

Question 31

How can you describe smooth muscle?

Answer 31

• few mitochondria
• no T tubules
• Actin & Myosin not organized in sarcomeres
• no striations
• cells are small and squished together

Question 32

What is the function of dense bodies in smooth muscles?

Answer 32

They function as Z-discs as the attachment for:

• alpha actinin
• intermediate filaments
• thin filaments

Question 33

What causes the corkscrew configuration in smooth muscle?

Answer 33

The configuration of smooth muscle during contraction.

Question 34

Does smooth muscle contain desmosomes or gap junctions?

Answer 34

No, they don’t contain desmosomes, but they do contain gap junctions.