L21: Muscle Tissues

Question 1

What are the four main tissue types?

Answer 1

• Epithelial;
• Connective;
• Muscle;
• Nervous.

Question 2

What is the function of muscle tissues?

Answer 2

Specialised for contraction

Question 3

Provide an example of muscle tissue.

Answer 3

Cardiac cells

Question 4

Describe the control, structure and type of somatic muscle tissue.

Answer 4

• Somatic, voluntary;
• Striated;
• Skeletal.

Question 5

Describe the control, structure and type of autonomic muscle tissues.

Answer 5

Cardiac:

• Autonomic, involuntary;
• Striated;
• Cardiac.

Smooth:

• Autonomic, involuntary;
• Non-striated;
• Smooth.

Question 6

Describe the structure of skeletal muscle.

Answer 6

• Elongated, unbranched cylindrical cells (muscle fibres);
• Multiple peripheral nuclei;
• Numerous myofibrils;
• Arrangement of myofibrils causes striated appearance.

Question 7

What structure separates individual muscle fibres of skeletal muscle?

Answer 7

Endomysium

Question 8

What is the name for a group of skeletal muscle fibres?

Answer 8

Fasciculi

Question 9

What is the difference between a perimysium and epimysium?

Answer 9

• Perimysium - loose CT - surrounds each fascicule;

- Epimysium - dense CT - surrounds entire muscle.

Question 10

What is the name of the specialised plasma membrane of skeletal muscle?

Answer 10

Sarcolemma

Question 11

What separates each myofibril?

Answer 11

A thin layer called the sarcoplasm

Question 12

How are myofibrils arranged in skeletal muscle?

Answer 12

In parallel, with many mitochondria between them

Question 13

What repeating unit makes up myofibrils?

Answer 13

Myofilaments

Question 14

Thick myofilaments are composed of…

Answer 14

myosin

Question 15

Thin myofilaments are composed of…

Answer 15

actin

Question 16

Myosin appears…

Answer 16

dark

Question 17

Actin appears…

Answer 17

light

Question 18

Light bands are directed by…

Answer 18

Z lines

Question 19

Z-lines divide each myofibril into…

Answer 19

contractile units called sarcomeres

Question 20

What is the name of a contractile unit in skeletal muscle?

Answer 20

Sarcomere

Question 21

What is the process by which sarcomeres, in skeletal muscle, contract?

Answer 21

Sliding filament mechanism

Question 22

Explain the sliding filament mechanism:

Answer 22

• ATP allows myosin to bind to actin;
• This causes a conformational change which allows the filaments to slide over each other;
• This causes the sarcomere to shorten (contract).

Question 23

How is skeletal muscle innervated?

Answer 23

Through somatic motor neurones

individual motor neurones innervate multiple muscle fibres, a motor unit

Question 24

What neurotransmitter is detected on muscle fibres to lead to a contraction?

Answer 24

Acetylcholine

Question 25

Explain the sarcolemma and sarcoplasmic reticulum.

Answer 25

Sarcolemma: - Specialised plasma membrane that invaginates into sarcoplasm to form T-tubules Sarcoplasmic reticulum: - Network of tubules associated with T-tubules and myofibrils; - Store and supply Ca2+.

Question 26

What is myocardium?

Answer 26

Specialised striated muscle tissue, found in the heart

Question 27

Describe the structure of cardiac muscle.

Answer 27

- Elongated, branched cylindrical cells; - One or two centrally located nuclei; - Arrangement of myofibrils causes striated appearance.

Question 28

What are the three layers of the heart wall?

Answer 28

- Pericardium (P): outer, support layer; - Myocardium (M): cardiac muscle tissue; - Endocardium (E): single layer of endothelial cells.

Question 29

What type of connective tissue surrounds cardiac muscle fibres?

Answer 29

Reticular, supports rich capillary network

Question 30

In cardiac muscle, intercellular junctions (between cardiac cells) are called...

Answer 30

intercalated discs

Question 31

What is the process by which sarcomeres, in cardiac muscle, contract?

Answer 31

Sliding filament mechanism

Question 32

What are the main contraction differences between skeletal and cardiac muscle?

Answer 32

- Cardiac is involuntary, skeletal is voluntary; - In cardiac muscle, the sarcoplasmic reticulum slowly releases Ca2+ for continuous contraction; - Modified cardiac cells, conducting system (SA node - pacemaker cells); - Cardiac cells modulated by autonomic and hormonal stimuli.

Question 33

Describe the structure of smooth muscle.

Answer 33

- Elongated, small, spindle-shaped fibres; - Single, centrally located nucleus; - No sarcomeres, no striations.

Question 34

Where is smooth muscle found?

Answer 34

Lining hollow organs

Question 35

Describe the structure of the GI tract.

Answer 35

- 2 muscle layers; - Circular, inner; - Longitudinal, outer.

Question 36

What are the roles of the 2 muscle layers, in the GI tract, during peristalsis?

Answer 36

- Circular, constricts; | - Longitudinal, shortens

Question 37

What is the process by which smooth muscle contracts?

Answer 37

- Presence of actin and myosin; | - Sliding-filament mechanism.

Question 38

What is the role of focal densities?

Answer 38

Anchoring of actin and myosin to the cytoplasm and cell membrane in smooth muscle

Question 39

What initiates contraction of smooth muscle?

Answer 39

Stretch

Question 40

What modulates contraction of smooth muscle?

Answer 40

Autonomic NS and/or hormonal stimulation