✅Muscle Tissue

Question 1

What are the functions of skeletal muscle?

Answer 1

-Produce skeletal movement
• Maintain posture and body position
• Support soft tissue
• Guard entrances and exits
• Maintain body temperature
• Store nutrient reserves

Question 2

What are the 3 layers of connective tissue that muscles have?

Answer 2

1. Epimysium
2. Perimysium
3. Endomysium

Question 3

Describe Epimysium

Answer 3

– Exterior collagen layer
– Connected to deep fascia
– Separates muscle from surrounding tissues

Question 4

Describe perimysium

Answer 4

-Surrounds muscle fibre bundles (fascicles)
– Contains blood vessel & nerve supply to fascicles

Question 5

Describe endomysium

Answer 5

-Surrounds individual muscle cells (muscle fibres)
– Contains capillaries & nerve fibres contacting muscle cells
– Separates & electrically insulates muscle cells from each other

Question 6

When do Endomysium, perimysium & epimysium come together?

Answer 6

-At ends of muscles
– To form connective tissue attachment to bone matrix
– i.e. tendon (bundle) or aponeurosis (sheet)

Question 7

Muscles have extensive vascular systems that…

Answer 7

• Supply large amounts of oxygen

* Supply nutrients
• Carry away wastes

Question 8

Are skeletal muscles voluntary or involuntary?

Answer 8

Voluntary

Question 9

What are skeletal muscle controlled by?

Answer 9

nerves of the central nervous system (brain + spinal cord)

Question 10

Thick & thin myofilaments form alternating light & dark bands (striations) along the myofibril.

T or F

Answer 10

True

Question 11

What is the sliding filament theory?

Answer 11

• Thin filaments of sarcomere slide toward M line, alongside thick filaments, H,I bands get smaller
• Zones of overlap get larger
• The width of A zone stays the same
• Z lines move closer together

Question 12

What is myosin?

Answer 12

A complex protein

Question 13

What is myosin structure?

Answer 13

A molecule with a head, a hinge and a tail

Question 14

What to myosin head have in thick filaments?

Answer 14

An ATP binding site, the enzyme, ATPase

Question 15

How are myosin proteins bound in thick filaments?

Answer 15

By the tail

Question 16

What is actin?

Answer 16

Strands of globulin protein molecules

Question 17

What does actin consist of?

Answer 17

2 strands wound together to make a thin filament

Question 18

What does each actin have?

Answer 18

A myosin binding site

Question 19

What is wrapped around actin filaments?

Answer 19

Regulatory protein, tropomyosin

Question 20

What is bound to tropomyosin strands?

Answer 20

Calcium-binding protein, troponin

Question 21

What does the process of skeletal muscle contraction involve?

Answer 21

• Neural stimulation of sarcolemma
  – Causes excitation–contraction coupling
• Muscle fibre contraction
  – Interaction of thick and thin filaments
• Tension (force) production

Question 22

What is a motor neuron and all of the muscle cells it stimulates called?

Answer 22

A motor unit

Question 23

How does a muscle contact?

Answer 23

• Muscle contraction is initiated by neural
stimulation which induces Calciumion (Ca2+) release
• (Ca2+) is released from the SR of the myofilament

Question 24

How is contraction initiated?

Answer 24

(Ca2+) binds to actin and initiates contraction by exposing myosin binding site

Question 25

What are the stages of the contractile cycle (skeletal muscle)

Answer 25

1. Contraction Cycle Begins 2. Active-Site Exposure 3. Cross-Bridge Formation 4. Myosin Head Pivoting 5. Cross-Bridge Detachment 6. Myosin Reactivation

Question 26

What happens at stage 1?

Answer 26

The arrival of calcium ions within the zone of overlap.

Question 27

What happens at stage 2?

Answer 27

Calcium ions bind to troponin, weakening the bond between actin and the troponin– tropomyosin complex. The troponin molecule then changes position, rolling the tropomyosin molecule away from the active sites on actin and allowing interaction with the energized myosin heads.

Question 28

What happens are stage 3?

Answer 28

Once the active sites are exposed, the energized myosin heads bind to them, forming cross-bridges.

Question 29

What happens at stage 4?

Answer 29

After cross-bridge formation, the energy that was stored in the resting state is released as the myosin head pivots toward the M line. This action is called the power stroke; when it occurs, the bound ADP and phosphate group are released.

Question 30

What happens at stage 5?

Answer 30

When another ATP binds to the myosin head, the link between the myosin head and the active site on the actin molecule is broken. The active site is now exposed and able to form another cross-bridge.

Question 31

What happens at stage 6?

Answer 31

Myosin reactivation occurs when the free myosin head splits ATP into ADP and P. The energy released is used to recock the myosin head.