Skeletal system - Muscle

Question 1

What are the types of muscle?

Answer 1

• Skeletal
• Cardiac
• Smooth

Question 2

Describe each type of muscle?

Answer 2

• Skeletal: movement of bone & body parts, voluntary
• Cardiac: heart only, develops pressure for arterial blood flow
• Smooth: grouped in walls of hollow organs, move material in GI & reproductive organs

Question 3

What is excitability?

Answer 3

Ability to receive and respond to stimuli

Question 4

What is contractility?

Answer 4

Ability to shorten when stimulated

Question 5

What is extensibility?

Answer 5

Ability to be stretched

Question 6

What is elasticity?

Answer 6

Ability to recoil to resting length

Question 7

List the functions of the skeletal muscle

Answer 7

• Producing movement
• Maintaining posture & body position
• Supporting soft tissues
• Guarding body entrance & exits
• Maintaining body temp
• Storing nutrients

Question 8

What is endomysium?

Answer 8

Loose connective tissue that surrounds individual muscle fibres

Question 9

What is epimysium?

Answer 9

Dense irregular connective tissue surrounding entire muscle

Question 10

What is perimysium?

Answer 10

Collagen & elastic fibres surrounding a group of muscle fibres called a fascicle

Question 11

What do motor neurons do?

Answer 11

Stimulate muscle fibres to contract

Question 12

What do capillary beds surrounding muscle fibres require?

Answer 12

Large amounts of energy

Question 13

What is the sarcolemma?

Answer 13

cell membrane

Question 14

What are myofibrils?

Answer 14

Cylindrical structures within muscle fibre

Question 15

What are myofilaments?

Answer 15

Bundles of protein filaments

Question 16

What is the difference between actin & myosin filaments?

Answer 16

Actin - thin

Myosin - thick

Question 17

What is the sarcomere?

Answer 17

Smallest contractile unit of a muscle fibre

Question 18

What is the difference between thick and thin filaments?

What does the Z disc do?

Answer 18

1) Thick - run the length of A band
2) Thin - run the length of I band & partway into A band
3) Z - coin shaped sheet that anchors the thin filaments & connects myofibrils to each other

Question 19

What is tropomyosin?

Answer 19

An elongated protein winds along the groove of the F actin double helix

Question 20

Troponin composed of 3 subunits (Tn-I, Tn-T, Tn-C), what do they bind to?

Answer 20

• Tn-I = binds to actin
• Tn-T = binds to tropomyosin
• Tn-C = binds to calcium ions

Question 21

What is SR?

Answer 21

Sarcoplasmic reticulum

Question 22

A single T-tubule & 2 terminal cisternae form a ?

Answer 22

triad

Question 23

SR stores what when not contracting?

Answer 23

Ca 2+

Question 24

After contraction, SR pumps the Ca 2+ back into?

Answer 24

SR

Question 25

What is the neuromuscular junction (NMJ) ?

Answer 25

Skeletal muscles stimulated by somatic motor neurons

Question 26

What is released from nerve fibre?

Answer 26

ACh

Question 27

What are the components of the NMJ?

Answer 27

- Synaptic knob swollen end - contains ACh - Motor end plate - Synaptic cleft

Question 28

List the 4 actions involved in muscle

Answer 28

- Excitation - Excitation-contraction coupling - Contraction - Relaxation

Question 29

Describe each action

Answer 29

- Excitation: nerve action potentials lead to action potentials in muscle fibre - ECC: action potentials on sarcolemma activate myofilaments - Contraction: shortening of muscle fibre - Relaxation: return to resting length

Question 30

What is the sliding filament theory?

Answer 30

Explains the relationship between thick & thin filaments as contraction proceeds

Question 31

Cyclic process beginning with Ca release from SR. What does Ca bind to?

Answer 31

Troponin

Question 32

What does ATP allow?

Answer 32

Release of cross bridge

Question 33

ACh binds with nAChR in muscle membrane to allow what to enter?

Answer 33

Na+ ions

Question 34

Na+ ions generate what?

Answer 34

Action pontential in sarcolemma

Question 35

What happens when action potential cease?

Answer 35

Muscles stop contracting

Question 36

What are the functions of ATP in the skeletal muscle contraction?

Answer 36

- Hydrolysis of ATP by myosin - Binding of ATP to myosin - Energises Ca 2+ pumps actively transport Ca 2+ back into SR - Runs the Na+ K+ pump into sarcolemma

Question 37

ATP for muscle contractions, produced from what 3 sources?

Answer 37

- Creatine phosphate ( 1 ATP per CP) - Aerobic respiration (36 ATP per glucose) - Anaerobic resp (Glycolysis) - breakdown of glucose to yield ATP & lactic acid

Question 38

Velocity & duration of contraction influenced by what?

Answer 38

- Muscle fiber type - Load - Recruitment

Question 39

How are skeletal muscle fibres classified?

Answer 39

- Speed of contraction | - Metabolic pathways for ATP synthesis

Question 40

What are the 3 types of fibers?

Answer 40

- Slow oxidative fibers - Fast oxidative fibers - Fast glycolytic fibers

Question 41

What affects influence of load?

Answer 41

↑ load - ↑ latent period, decrease contraction & duration

Question 42

What is a muscle twitch?

Answer 42

Response of a muscle fibre to a single, brief threshold stimulus

Question 43

What are the 3 phases of a muscle twitch?

Answer 43

- Latent period - Contraction phase - Relaxation phase

Question 44

What is a motor unit?

Answer 44

Motor neuron & all the muscle fibres it supplies

Question 45

List the motor unit ratios

Answer 45

Back muscles - 1:100 Finger muscles - 1:10 Eye muscles - 1:1

Question 46

List components of smooth muscle

Answer 46

- More actin than myosin - No sarcomeres - Caveolae: indentations in sarcolemma - Dense bodies instead of Z disks

Question 47

List the groups of smooth muscle

Answer 47

- Longitudinal layer: muscle fibres run parallel to organ's long axis Circular layer: muscle fibres around circumference of organ

Question 48

What is smooth muscle innervated by?

Answer 48

Autonomic nervous system (ANS)

Question 49

What is a multiunit?

Answer 49

Cells/groups of cells act as independent units

Question 50

What does Ca 2+ interact with to activate myosin?

Answer 50

Ca 2+ interacts with calmodulin + myosin light chain kinase (MLCK)

Question 51

Phosphorylated cross bridges interact with _____ to produce _____

Answer 51

actin, shortening

Question 52

_____ muscle _____ when intracellular Ca 2+ levels drop

Answer 52

Smooth | Relaxes

Question 53

What is cardiac muscle?

Answer 53

Involuntary muscle found only in heart wall

Question 54

What are fibers connected by?

Answer 54

- Intercalated discs (thickened cell membranes) | - Gap junctions that allow spread of action potentials

Question 55

What does cardiac muscle not require?

Answer 55

Nerve stimulation nerve

Question 56

Cardiac muscle has its own _______

Answer 56

``` intrinsic pacemaker (conduction system within cardiac muscle) - Initiates cardiac contraction (auto-rhythmicity) ```

Question 57

What do intercalated discs with gap junctions do?

Answer 57

Transmit action potentials from one muscle to the next

Question 58

What is the H zone?

Answer 58

Lighter midregion where filaments do not overlap

Question 59

What is the M line?

Answer 59

Line of protein myomesin that holds adjacent thick filaments together