Muscles

Question 1

What are the three types of muscle tissue in mammals?

Answer 1

skeletal muscle, cardiac muscle and involuntary/smooth muscle

Question 2

What are skeletal muscles attached to the skeleton by?

Answer 2

tendons

Question 3

What is skeletal muscle used for?

Answer 3

used in conscious or voluntary movement

Question 4

What does skeletal muscle consist of?

Answer 4

fibres

Question 5

What are the fibres in skeletal muscle shaped like?

Answer 5

long tubes

Question 6

What does each fibre in skeletal muscle contain?

Answer 6

a number of nuclei

Question 7

What is the appearance of skeletal muscle fibres?

Answer 7

the fibres have a striped or striated appearance and are arranged in a regular pattern

Question 8

During contraction what happens to skeletal muscle fibres?

Answer 8

all the fibres contract in the same direction

Question 9

Can skeletal muscle fibres contract rapidly?

Answer 9

Yes

Question 10

Do skeletal muscle fibres stay contracted for a long period of time?

Answer 10

No

Question 11

Where is cardiac muscle found?

Answer 11

found only in the heart

Question 12

Is cardiac muscle under voluntary or involuntary control?

Answer 12

involuntary control

Question 13

What type of muscle cells are branched?

Answer 13

cardiac muscle cells

Question 14

What feature allows cardiac muscle cells to contract together?

Answer 14

cardiac muscle cells are connected to each other at the ends

Question 15

Usually, how many nuclei does each cardiac muscle cell have?

Answer 15

only one nucleus

Question 16

Cardiac muscle cell form fibres with a what appearance?

Answer 16

striped or striated appearance

Question 17

What is the difference between the striations in cardiac muscle than in skeletal muscle?

Answer 17

cardiac muscle fibres’ striations are fainter than in skeletal muscles

Question 18

Cardiac muscle cells contract without the need for a what? And what is this called?

Answer 18

without a nervous signal and scientists say that they are myogenic

Question 19

Where is involuntary/smooth muscle found?

Answer 19

all over the body

Question 20

What is peristalsis?

Answer 20

Where involuntary muscle in the walls of the intestines contracts to move digested material along the digestive system

Question 21

What type of muscle is found in the walls of blood vessels?

Answer 21

involuntary/smooth muscle

Question 22

Is involuntary muscle striated?

Answer 22

No

Question 23

Is involuntary muscle under voluntary control?

Answer 23

no

Question 24

How many nuclei do involuntary muscle cells usually have?

Answer 24

a single nucleus per cell

Question 25

Is smooth/involuntary muscle arranged regularly?

Answer 25

No - not as regular as cardiac or skeletal muscle

Question 26

Do involuntary muscle cells contract in the same direction?

Answer 26

involuntary muscle cells do not all contract in the same direction

Question 27

Does involuntary muscle contract rapidly or slowly? And does involuntary muscle contract for a long or short period of time?

Answer 27

unlike skeletal and cardiac muscle, involuntary muscle contracts slowly but can contract for a relatively long time

Question 28

What is the sarcoplasm?

Answer 28

the cytoplasm of the muscle cell is called the sarcoplasm

Question 29

What is the sarcolemma?

Answer 29

the cell membrane of the muscle cell is called the sarcolemma. The sarcolemma folds up on itself to form transverse tubules - these help to transmit electrical impulses very quickly through the whole muscle fibre.

Question 30

What is the sarcoplasmic reticulum?

Answer 30

The endoplasmic reticulum of the muscle cell is called the sarcoplasmic reticulum. It forms a network of internal membranes that store calcium ions to aid muscle contraction.

Question 31

Muscle contraction works via what model?

Answer 31

the sliding filament model

Question 32

What are the two proteins called that skeletal muscle fibres contain?

Answer 32

actin and myosin

Question 33

What kind of filaments does myosin form?

Answer 33

thick filaments

Question 34

What kind of filaments does actin form?

Answer 34

actin forms thin filaments

Question 35

What happens when an action potential arrives at the motor neurone?

Answer 35

acetylcholine is released from the presynaptic knob

Question 36

What does the acetylcholine trigger in a neuromuscular junction?

Answer 36

the acetylcholine triggers the sarcolemma of the muscle fibre to depolarise

Question 37

What happens when the sarcolemma of the muscle fibre has depolarised?

Answer 37

this depolarisation triggers Ca2+ to be released from the sarcoplasmic reticulum

Question 38

What does an increased concentration of Ca2+ released from the sarcoplasmic reticulum cause?

Answer 38

triggers the actin and myosin filaments to slide together

Question 39

What is the structure of myosin?

Answer 39

Firstly, myosin has a long fibrous tail structure. These myosin tails are clustered together, forming the filament. Secondly, each myosin molecule has a globular head group. The myosin head groups point outwards. Each myosin head group has a binding site for actin and a binding site for ATP.

Question 40

What is the structure of an actin filament?

Answer 40

Actin forms two strands wrapped together into a helical structure. Running along the actin filament we have binding sites for myosin. These are called actin-myosin binding sites. However, in an uncontracted muscle, these actin-myosin binding sites are blocked by a threadlike protein called tropomyosin. Tropomyosin is held in position by troponin.

Question 41

How is muscle contraction triggered?

Answer 41

when Ca2+ are released from the sarcoplasmic reticulum

Question 42

Where does the Ca2+ ions bind to trigger muscle contraction?

Answer 42

the Ca2+ bind to the troponin molecules

Question 43

Ca2+ binding to the troponin molecules causes what to happen?

Answer 43

the troponin molecules to change shape, moving the tropomyosin away from the actin-myosin binding sites

Question 44

Once the actin-myosin binding sites are exposed, what happens?

Answer 44

the myosin head groups can now bind to the actin-myosin binding sites (this is called an actin-myosin cross-bridge)

Question 45

Once an actin-myosin cross-bridge has been formed, what happens?

Answer 45

the myosin head flexes (changes its angle) which pulls the actin filament along

Question 46

What happens at the same time as the actin filament being pulled along be the myosin head?

Answer 46

the ADP molecule is released from the myosin head

Question 47

After the ADP molecules has been released from the myosin head, what happens?

Answer 47

a molecule of ATP attaches to the myosin head

Question 48

A molecule of ATP attaching to the myosin head causes what to happen?

Answer 48

the myosin head to detach from the actin-myosin binding site. Now the myosin head acts as an ATPase hydrolysing the ATP molecule to ADP and phosphate

Question 49

What is the ATPase activity activated by?

Answer 49

the high concentration of Ca2+ in the sarcoplasm

Question 50

What happens to the energy from ATP hydrolysis?

Answer 50

it is used to return the myosin head to its original angle