Muscle Structure, Function And Contraction

Question 1

What are the 3 types of muscle tissue?

Answer 1

Cardiac muscle
Skeletal muscle and smooth muscle

Question 2

Where is cardiac muscle found?

Answer 2

In the heart

Question 3

Where is smooth muscle found?

Answer 3

In the walls of organs

Question 4

Which of the 3 muscle types is multi-nucleated?

Answer 4

Skeletal muscle

Question 5

Which two muscle groups contract involuntary?

Answer 5

Cardiac and smooth muscle

Question 6

What are the names of the 3 key connective tissues in skeletal muscles?

Answer 6

Epimysium, perimysium, endomysium

Question 7

What are the relative sizes of the 3 key layers of connective tissue (in comparison to one another)?

Answer 7

Epimysium > perimysium > endomysium

Question 8

Name 5 functions of muscles

Answer 8

Produces body movements
Stabilises body positions
Regulates organ volumes (sphincters)
Movement of substances within the body
Produces heat (shivering)

Question 9

Name 5 properties of muscle tissue

Answer 9

Excitability
Conductivity
Contractibility
Extensibility
Elasticity

Question 10

Why does skeletal muscle have multiple nuclei?

Answer 10

Because during development muscles form from multiple myoblasts fusing together. Each myoblast has its own nucleus therefore when they fuse together you end up with multiple nuclei

Question 11

Where does skeletal muscle attach to?

Answer 11

Bone, skin or fascia
Maybe via tendons/aponeuroses

Question 12

What happens to left over myoblasts?

Answer 12

They become satellite cells

Question 13

What are satellite cells?

Answer 13

Stem cells
When there is some damage to the muscle, the stem cell can divide and assist in repair

Question 14

Name the 7 functions of skeletal muscle

Answer 14

Produce skeletal movement
Maintain body position
Support soft/hard tissues
Guard body openings
Maintain body temperature
Stores nutrient reserves
Proprioception (knowing where your body is in space)

Question 15

What is epimysium?

Answer 15

A sheath of connective fascia that surrounds the whole muscle

Question 16

What is epimysium connected to?

Answer 16

Deep fascia

Question 17

Which connective tissue separates surrounding muscles from surrounding tissues?

Answer 17

Epimysium

Question 18

Which connective tissue surrounds muscle fibre bundles (fascicles)?

Answer 18

Perimysium

Question 19

Which connective tissue in the muscle contains blood vessels and nerve supply to fascicles?

Answer 19

Perimysium

Question 20

Which connective tissue surrounds individuals muscle cells?

Answer 20

Endomysium

Question 21

Which connective tissue layer contains satellite cells that repair damage and capillaries and nerve fibres contacting muscle cells?

Answer 21

Endomysium

Question 22

What do endomysium, perimysium and epimysium come together at the ends of muscle to form?

Answer 22

Connective tissue attachment to bone matrix I.e. tendon (bundle) or aponeurosis (sheet)

Question 23

Messages from the central nervous system reach the muscle tissue via what nerve?

Answer 23

A peripheral nerve

Question 24

What is a motor unit?

Answer 24

One motor nerve and the muscle fibres it supplies

Question 25

What are skeletal muscle cells called?

Answer 25

Fibres

Question 26

What is the sarcolemma?

Answer 26

The cell membrane of a muscle cell

Question 27

What is the sarcoplasm?

Answer 27

Cytoplasm of muscle fibre

Question 28

What do T tubules do?

Answer 28

Carry muscle action potentials down into the cell and allow the entire muscle fibre to contract simultaneously

Question 29

What is a T tubule?

Answer 29

An invagination of the sarcolemma into the centre of the cell

Question 30

What is the sarcoplasmic reticulum?

Answer 30

A membranous structure surrounding each myofibril It is a system of tubular sacs similar to smooth endoplasmic reticulum in non-muscle cells

Question 31

What does the sarcoplasmic reticulum do?

Answer 31

Helps transmit action potential to the myofibrils

Question 32

What do terminal cisternae form?

Answer 32

Calcium

Question 33

What does sarcoplasmic reticulum form at each end?

Answer 33

Chambers (terminal cisternae)

Question 34

What does sarcoplasmic reticulum do in a relaxed muscle?

Answer 34

Stores calcium ions

Question 35

How does sarcoplasmic reticulum trigger muscle contraction?

Answer 35

By releasing calcium ions

Question 36

What is a triad made up of?

Answer 36

1 T-tubule and 2 terminal cisternae

Question 37

What are myofibrils made up of?

Answer 37

Bundles of protein filaments (myofilaments)

Question 38

What are myofilaments?

Answer 38

The contractile proteins of muscles

Question 39

What does the sarcoplasm contain?

Answer 39

Glycogen and fats for energy as well as mitochondria

Question 40

What does the I band contain?

Answer 40

Only thin filaments (actin)

Question 41

What does the A band contain?

Answer 41

Thick (myosin) filaments

Question 42

What is a sarcomere?

Answer 42

The contractile unit of a muscle

Question 43

What is the importance of titan?

Answer 43

It is thought to be quite important in terms of use of eccentric muscle contraction Titan attaches the myosin filament to the Z line so prevents the muscle from over stretching and it helps it to recoil back to its normal size

Question 44

What are thick filaments composed of?

Answer 44

Myosin

Question 45

What are thick filaments held in place by?

Answer 45

M line proteins

Question 46

What are thin filaments made up of?

Answer 46

Actin, troponin and tropomyosin

Question 47

What is the myosin binding site on each actin molecule covered by in a relaxed muscle?

Answer 47

Tropomyosin

Question 48

What are thin filaments held in place by?

Answer 48

Z lines

Question 49

What does the M line connect to?

Answer 49

Titan and adjacent thick filaments

Question 50

What is nebulin?

Answer 50

An in elastic protein that helps align the thin filaments

Question 51

What does dystrophin do?

Answer 51

Links thin filaments to sarcolemma and transmits the tension generated by the tendon

Question 52

What type of muscle contraction does the sliding filament mechanism look at specifically?

Answer 52

Concentric isotonic muscle contraction

Question 53

For contraction to occur there needs to be some sort of stimulation of the muscle, how is it stimulated?

Answer 53

Happens in the form of a nerve impulse or an action potential

Question 54

Describe the stimulation of muscle contraction

Answer 54

Nerve impulses reaches an axon terminal Synaptic vessels release acetyl choline Acetyl choline diffuses to receptors on the sarcolemma This causes sodium ion channels to open Sodium ions rush into the cell A muscle action potential spreads over the sarcolemma and down into the T tubules Action potential reaches a triad Terminal cisternae release calcium ions into the sarcoplasm Calcium ions bind to troponin and causes troponin-tropomyosin complex to move and reval binding sites on actin Excitation - contraction coupling Contraction cycle begins

Question 55

What are the 3 essential components for the contraction cycle to happen?

Answer 55

Neural stimulus Enough calcium ions Enough ATP

Question 56

What are the 6 steps of the contraction cycle of a muscle?

Answer 56

Exposure of active sites on actin ATP hydrolysis into ADP, Pi and energy Attachment of myosin to actin to form cross-bridges Power stroke Detachment of myosin from actin Reactivation of myosin

Question 57

What is the contraction cycle of a muscle ?

Answer 57

Repeating sequence of events that causes the thin filaments to slide between the thick filaments

Question 58

What is the power stroke?

Answer 58

Pivoting of myosin head, pulling in the thin filament

Question 59

What are the 9 steps of relaxation of a muscle?

Answer 59

Acetylcholinesterase breaks down acetyl choline within the synaptic cleft Muscle action potential ceases Calcium ion channels close Calcium ions detach from troponin Active transport pumps calcium ions back into storage in the terminal cisternae of the sarcoplasmic reticulum Calcium ion concentration falls Tropomyosin- troponin complex recovers binding site on the actin molecules Contraction ends Relaxation occurs, muscle return passively to resting length

Question 60

What is a neuromuscular junction?

Answer 60

The site of the signal exchange, this is where the synaptic bulb of an axon terminal and muscle fibre connect

Question 61

What happens when a muscle is above or below optimal length?

Answer 61

Fewer cross bridges exist and less force is produced

Question 62

What are the 3 sources of ATP production within a muscle?

Answer 62

Creatine phosphate Anaerobic cellular respiration Aerobic cellular respiration

Question 63

What is used to form creatine phosphate?

Answer 63

Excess ATP within the resting muscle

Question 64

How long does creatine phosphate sustain maximal contraction for?

Answer 64

15 seconds

Question 65

How many times more plentiful is creatine phosphate in comparison to ATP within the muscle?

Answer 65

3-6 x

Question 66

How long can glycolysis continue to anaerobically provide ATP for?

Answer 66

30-40 second of maximal activity

Question 67

How long aerobic respiration provide ATP for?

Answer 67

Any activity lasting over 30 seconds