Chapter 9: Muscle Tissues

What does the membranes of muscle tissue exhibit?

electrical excitability: the ability to generate and transfer electrical energy achieved by the movement of ions

What are the types of muscle tissue? Which are striated?

skeletal, cardiac, smooth

striated: skeletal and cardiac

not striated: smooth

What are the functions of skeletal muscle tissue?

produce skeletal movements, maintain posture and body position, support soft tissues, guard entrances and exits, maintain body temperature, store nutrients reserves

What are the functions of cardiac and smoot muscle tissues?

moving substances through the body, maintaining organ size

How are the connective tissues of a muscle organized?

endomysium, fascicle, perimysium, epimysium

Which connective tissue surrounds a cell?

endomysium

Which connective tissue surround a fascicle?

perimysium

Which connective tissue surrounds an entire muscle?

epimysium

What is aponeurosis?

a flat tendon

What is a sarcolemma?

a cell membrane

What are the transverse tubules?

tubes running through the sarcolemma

What is the sarcoplasm?

cytoplasm

What is myofibril?

bundles of myofilament

What are myofilaments?

protein filaments that are responsible for muscle contraction

What is the sarcoplasmic reticulum?

a modified smooth ER that stores and releases calcium

How is a sarcomere related to the fact that skeletal and cardiac muscles are striated?

the pattern of the myosin and actin

What are the steps initiation of contraction?

1. action potential of motor neurons causes release of ACh at NMJ

2. ACh attaches to receptors on motor end plate of sarcolemma and causes depolarization of sarcolemma → sends a very brief AP throughout sarcolemma

3. AP travels down transverse tubules

4. transmission of AP passes SR causing voltage-gated calcium channels to open and release stored calcium into sarcoplasm

5. calcium is now available to the myofilaments

What are the steps of the contraction phase?

1. calcium binds to troponin C

2. troponin pulls tropomyosin off G-actin, exposing binding sites to myosin heads

3. binding occurs between G-actin and myosin heads

4. energy stored in myosin head is released so that myosin head goes to low energy state, ADP and P are released

5. power stroke ends: myosin head still bound to G-action

6. new ATP binds to myosin head → breaks cross-bridge attachment → myosin detaches from actin

7. hydrolysis of ATP provides energy to return to high energy state

What are the steps to the end of contraction and relaxation?

1. nervous stimulation stops → no more ACh is released

2. ACh attached to receptors is broken down by AChE

3. Ap through sarcolemma stops

4. no stimulus to SR

5. calcium channels close

6. calcium is actively pumped back into SR

7. calcium removed from troponin

8. tropomyosin able to re-cover binding sites → myosin heads unable to bind

9. contraction stops

10. myosin head will cleave ATP and will wait in high energy state until next nervous signal starts process again