Muscle structure and function

Question 1

What do all body movements require?

Answer 1

Muscles

Question 2

What are muscles composed of?

Answer 2

Specialised cells that use chemical energy to contract

Question 3

What are the functions of muscles besides movement?

Answer 3

Provide muscle tone
Poprel body fluids and food
Generate the heartbeat
Distribute heat

Question 4

What are the 3 types of muscle?

Answer 4

Skeletal
Smooth
Cardiac

Question 5

What is the water content of muscle cells?

Answer 5

75%

Question 6

What percentage of muscle is protein?

Answer 6

20%

Question 7

What makes up the remaininf 5% of muscle cell content/

Answer 7

Salts
Enzymes
Ions (Na+, K+, Cl-)
Fuels (amino acids, fats, proteins)

Question 8

What are the contractile filaments of skeletal muscle?

Answer 8

Actin
Myosin

Question 9

What protein keeps actin and myosin aligned?

Answer 9

Titin

Question 10

What is sarcolemma?

Answer 10

A sheath of connective tissue surrounding each muscle fibre

Question 11

What surrounds the myofibril and stores calcium?

Answer 11

Sarcoplasmic Reticulum (SR)

Question 12

What is the epimysium?

Answer 12

Connective tissue that surrounds an entire muscle

Question 13

What is the perimysium?

Answer 13

Connective tissue that groups muscle fibres into fascicles

Question 14

What is the endomysium?

Answer 14

Connective tissure that surrounds each individual muscle fibre

Question 15

What is a muscle fibre?

Answer 15

A single muscle cell that contracts when stimulated

Question 16

What gives muscle fibres their striated appearance?

Answer 16

The arrangement of actin and myosin filaments

Question 17

What is the function of T-tubules?

Answer 17

Transmit nerve impulsed and transport nutrients

Question 18

What does the SR store and release?

Answer 18

Calcium ions (Ca2+)

Question 19

What is the functional unit of a myofibril?

Answer 19

Sarcomere

Question 20

What connects sarcomeres end-to-end?

Answer 20

z-disks (a-actinin)

Question 21

What are the contractile proteins?

Answer 21

Myosin
Actin

Question 22

What are the regulatory proteins?

Answer 22

Tropomyosin
Troponin

Question 23

Name structural proteins in muscle

Answer 23

Titin
a-Actinin
Myomesin
Nebulin
Dystrophin

Question 24

What is the thick filament?

Answer 24

Myosin

Question 25

WHat is the structure of a myosin molecule?

Answer 25

Two twisted protein strands with globular heads

Question 26

What makes up the actin filament?

Answer 26

Actin (backbone) Troponin (at intervals) Tropomysoin (tube-shaped)

Question 27

Where is smooth muscle found?

Answer 27

Bladder Intestines Sphincters

Question 28

Can smooth muscle sustain long contractions?

Answer 28

Yes

Question 29

Where does the motor impulse originate?

Answer 29

Brian or spinal cord

Question 30

What is released at the neuromuscular junction?

Answer 30

Acetylcholine (ACh)

Question 31

What triggers Ca2+ release from the SR?

Answer 31

Actin potential via T-tubules

Question 32

What exposes the actin binding site?

Answer 32

Ca2+ binding to troponin --> lifts tropomyosin

Question 33

What causes the power stroke?

Answer 33

Pi release from the myosin head

Question 34

What detaches the myosin from actin?

Answer 34

Binding of new actin

Question 35

What re-cocks the myosin head?

Answer 35

ATP hydrolysis to ADP + Pi

Question 36

Which muscles have gap junctions?

Answer 36

Cardiac and some smooth muscle

Question 37

Why are gap junctions important?

Answer 37

They enable fast electrical communication

Question 38

What is the threshold stimulus?

Answer 38

Minimum stimulus strength to trigger contraction

Question 39

What is a muscle twitch?

Answer 39

Breif contraction following a single action potential

Question 40

What are the 3 phases of a twitch?

Answer 40

Latent Contraction Relaxation

Question 41

What principle describes all-or-nothing contraction?

Answer 41

All-or-none principle

Question 42

How is contraction force increased?

Answer 42

By recruiting more motor units and increasing firing frequency

Question 43

What is wave summation?

Answer 43

Successive stimuli cause greater contraction

Question 44

What is tetnus (in muscle terms)?

Answer 44

Sustained muscle contraction from high-frequency stimulation