Muscle

Question 1

What are the 2 types of muscle?

Answer 1

Striated and Smooth

Question 2

What are the 2 types of Striated muscle?

Answer 2

Skeletal and Cardiac

Question 3

What is Skeletal muscle?

Answer 3

Attached to the skeleton

contraction for force, movement & maintaining body posture

Question 4

What is Cardiac muscle?

Answer 4

Heart Muscle

Contracts to pump blood into vascular system

Question 5

What is smooth muscle?

Answer 5

In wall of hollow organs

controls vessel/ tube diameter

Question 6

What are the levels of skeletal muscle?

Answer 6

Whole muscle -> Muscle Fibre -> Myofibril -> Myofilament

Question 7

Is Actin thin or thick filament?

Answer 7

Thin filament

Myosin is the thick filament

Question 8

Which band contains only thin filaments

Answer 8

I band

Question 9

What does the A band contain

Answer 9

Thick filaments

Question 10

What is the sarcomere?

Answer 10

Segment of myofibril located between z-lines

Question 11

What is the H zone?

Answer 11

Where you only see myosin

Question 12

What is the M line?

Answer 12

Series of proteins that hold thick filaments together

Question 13

What is the Sarcolemma?

Answer 13

Surrounds muscle fibre and allows AP to propagate along it

Question 14

What is the Sarcoplasmic Reticulum?

Answer 14

Surrounds each myofibril & stores/releases calcium ions on demand

Question 15

What’s the Transverse (T) tubular system

Answer 15

Invaginates into muscle fibre from the surface & allows AP to travel down it

Question 16

Why are myosin heads called cross-bridges?

Answer 16

They bridge the gap between myosin and actin.

Question 17

What does Ca2+ bind to in the contractile mechanism of skeletal muscle?

Answer 17

Troponin

Question 18

What is the role of troponin in the contractile mechanism of skeletal muscle?

Answer 18

Troponin moves tropomyosin to reveal the binding site.

Myosin then binds to actin

Question 19

Before the myosin head attaches to Actin, what does it contain?

Answer 19

ADP and Pi

Question 20

What are the functions of skeletal muscle?

Answer 20

Generating force,
Moving parts of the body,
maintaining posture/balance

Question 21

What are the two types of muscle contraction?

Answer 21

Isometric contraction

Isotonic contraction

Question 22

What is Isometric contraction?

Answer 22

Force produced while length of muscle is unchanged

e.g. posture maintenance or supporting weight

Question 23

What is Isotonic Contraction?

Answer 23

Length of muscle changes when force is produced

There are 2 types = Eccentric & Concentric

Question 24

What are the 2 types of Isotonic contraction?

Answer 24

Concentric & Eccentric

Question 25

What is Concentric contraction?

Answer 25

Force produced while shortening muscle Movement occurs in direction of muscle shortening

Question 26

What is Eccentric contraction?

Answer 26

Active force is produced when being stretched by action of other muscles or external forces Movement occurs in opposite direction of muscle contraction

Question 27

What is Excitation-Contraction coupling?

Answer 27

Process by which muscle AP (excitation) causes rise of intracellular Ca2+ & actin-myosin interactions and triggers a contraction.

Question 28

What are Triads?

Answer 28

Composed of a segment of T-tubules between 2 sacs of SR Its the site of physical and functional contact between T-tubules & SR membrane

Question 29

What happens at the Triad?

Answer 29

AP travels down t-tubule. DHP receptor changes shape in response to AP Thus causing a change of shape in the Ryanodine receptor Resulting in Ca2+ to exit SR and interact with myofilaments

Question 30

What are the 3 subunits troponin breaks down into, and what are their functions?

Answer 30

TN-C = Calcium comes into contact with this TN-1 = Binds to Actin TN-T = binds troponin to tropomyosin

Question 31

What is Steric blocking when referring to the contractile mechanism?

Answer 31

Process of having tropomyosin blocking the binding site. Mechanism that enables Ca2+ to operate the ON-OFF switch. (Only in Striated muscle)

Question 32

What is Tetanus?

Answer 32

Mechanical response to multiple stimuli (APs)

Question 33

What is Summation?

Answer 33

Occurs when twitches occur in quick succession & overlap (summate)

Question 34

What is Fused Tetanus?

Answer 34

When sufficient stimuli are present in quick succession Thus giving a prolonged smooth contraction.

Question 35

What are the 3 different types of twitch fibres?

Answer 35

Type IIx Type IIa Type I

Question 36

What type of Motor Unit is Type IIx?

Answer 36

Fast-twitch - not fatigue resistant | Tend to be larger

Question 37

What type of Motor Unit is Type IIa?

Answer 37

Fast-twitch - fairly fatigue resistant

Question 38

What type of Motor Unit is Type I?

Answer 38

Slow-twitch fibre

Question 39

How are Motor Units recruited in contractions?

Answer 39

Smallest MUs recruited first - low force fatigue resistant fibres Largest MUs recruited last - high force, fatigable fibres

Question 40

How are cardiac muscle fibres linked?

Answer 40

Linked mechanically by Desmosomes Linked electrically by gap junctions. Linked at the intercalated disks

Question 41

Does cardiac muscle experience tetanic contraction?

Answer 41

The heart does not experience tetanic contractions The heart must contract & relax at least ~60 times a min It is impossible to get an overlap in contractile responses - as the cardiac muscle twitch finishes before a new AP is generated

Question 42

What is the Treppe effect?

Answer 42

As the heart rate increases, the fall in Ca2+ at the end of each beat is not quite complete thus the intracellular Ca2+ rises slightly and next contraction is stronger

Question 43

What are Ionotropic agents?

Answer 43

They increase intracellular Ca2+ by various mechanisms thus increasing the strength of contraction

Question 44

What are smooth muscle fibres coupled together by?

Answer 44

Membrane dense areas | GAP junctions

Question 45

What doesn't smooth muscle have that striated muscle has?

Answer 45

Smooth muscle has no T-tubules or troponin They also have very little SR

Question 46

What protein does Ca2+ bind to in smooth muscle?

Answer 46

Ca2+ binds to Calmodulin This then binds to enzyme = Myosin light chain kinase (MLCK)