11-1 Muscle Tissue

Question 1

Name the 3 types of muscle

Answer 1

Skeletal, cardiac, smooth

Question 2

What are the functions of skeletal muscle?

Answer 2

Movement-respiration
Stability- maintain posture and body position
Support and protects soft tissues
Control entrances and exits
Maintain body temperature (generates heat)
40% Work 60% heat

Question 3

What are the properties of muscle?

Answer 3

• Contractility- muscle shortens with FORCE
• Excitability- capacity of muscle to respond to a stimulus
• Extensibility- muscle can be stretched to normal resting length and beyond to a limited degree
• Elasticity-recoil to original resting length after stretched
• Conductivity- excitation wave travels a distance away from where muscle fiber was stimulated. Does not just cause a local effect.

Question 4

Endomysium

Answer 4

A sheath that Covers muscle fiber (myofiber)

Question 5

Fascicles

Answer 5

a bundled group of muscle fibers surrounded by perimysium

Question 6

Epimysium

Answer 6

Surrounds entire muscle group of fascicles

Question 7

True or False: The perimysium and epimysium contain blood vessels and nerves

Answer 7

TRUE

Question 8

Tendons (aponeuroses)

Answer 8

attach muscle to bone or muscle

Question 9

What are the characteristics of muscle fibers?

Answer 9

• Derived from stem cells called myoblasts during development
• maintained by satellite cells for repair
• large
• multi-nucleated
• striated

Question 10

Sarcolemma

Answer 10

muscle cell membrane

Question 11

sarcoplasm

Answer 11

muscle cell cytoplasm

Question 12

sarcoplasmic reticulum

Answer 12

• modified endoplasmic reticulum

- stores and releases calcium

Question 13

Transverse tubules (T-tubules)

Answer 13

infoldings in the muscle membrane

Question 14

What are myofibrils?

Answer 14

• BUNDLES of thick and thin filaments

- muscle contraction

Question 15

sarcomeres

Answer 15

regular arrangement of myofibrils

Question 16

Myofibril

Answer 16

• thick filaments-made of myosin
• thin filaments-made of actin
• organized whee there is partial overlap between two bands

Question 17

A-bands

Answer 17

dark bands of thick filaments

Question 18

Overlap zone

Answer 18

contains thick and thin filaments

Question 19

H-zone

Answer 19

contains thick filaments only

Question 20

M-line

Answer 20

dark band in center where myosin bands connect

Question 21

I-bands

Answer 21

light bands that contain thin filaments only

Question 22

Z-line

Answer 22

where sarcomers connect

Question 23

What are thick filaments made out of?

Answer 23

• mostly made of myosin

- titan protein holds it in place

Question 24

What proteins make up thin filaments?

Answer 24

• F actin- main protein is ACTIN
• tropomyosin-twists around actin and covers active sites that bind with mysosin
• troponin-binds to actin and holds tropomyosin in place by binding to tropomyosin and actin; controlled by calcium
• nebulin and dystrophin-binding molecules

Question 25

What is the structure of myosin bundles?

Answer 25

- myosin molecules have long tail and globular head - heads form cross-bridges with actin during contraction - interactions between G-actin and myosin are prevented by tropomyosin during rest

Question 26

What are the steps of the sliding filament theory?

Answer 26

1. Calcium is released from the SR 2. Calcium binds to troponin 3. Troponin changes shape, moving tropomyosin and exposing actin active site 4. Myosin head forms cross-bridge and bends toward M-line 5. ATP allows release of cross-bridge

Question 27

What are the steps of the contraction cycle?

Answer 27

1. resting sarcomere-myosin attached to ADP and Phospate; high energy state 2. SR releases calcium; calcium binds to troponin; active site exposed 3. Myosin forms cross-bridge, changes its shape, 4. ADP, Phosphate and energy are released bending head of myosin towards M line 5. ATP binds to myosin, which releases actin; detaches cross-bridge 6. myosin reactivation

Question 28

True or False: Muscle fibers shorten and pull but cannot push (lengthen)?

Answer 28

TRUE

Question 29

What is a neuromuscular junction?

Answer 29

where a neuron meets a muscle

Question 30

What are the steps in excitation of a muscle?

Answer 30

1. Arrival of nerve signal 2. 2(ACh) are released 3. ACh binds to receptors 4. Opening of ligand-regulated ion gate; creation of end-plate potential 5. Opening of voltage-regulated ion gates; creation of action potential

Question 31

What are the steps in excitation contraction coupling?

Answer 31

1. Action potentials move down t-tubules 2. Calcium released from terminal cistern 3. Calcium binds to troponin 4. Tropomyosin shifts, exposing active sites on actin

Question 32

What are the steps in Relaxation?

Answer 32

1. Acetylcholinesterase (AChE) breaks down ACh 2. SR reabsorbs calcium ions 3. Loss of calcium ions from troponin 4. Tropomyosin rotates back over active site of actin 5. Elastic fibers pull muscle back to original position