Muscles

Question 1

What may make up muscle?

Answer 1

Muscle tissue, connective tissue, blood supply

Question 2

What are muscle fibres?

Answer 2

Long, cynlindrical cells
Multinucleate
Have a sarcolemma - plasma membrane
Have a sarcoplasmic reticulum - specialised endoplasmic reticulum, contains Ca+ for muscle contraction
Lots of mitochondria - aerobic respiration for ATP production used in muscle production

Question 3

What specialised organelles do muscle fibres contain?

Answer 3

Microfibrils, made up of proteins actin and myosin in repeating sections

Question 4

What are the three muscle types?

Answer 4

Cardiac (muscle tissue in heart)
Smooth (controlled by autonomic nervous system)
Striates/skeletal (under conscious control, attached to bone), moves the skeleton

Question 5

What are antagonistic pairs?

Answer 5

One contracts and one relaxes, contracted is shorter, relaxed is longer

Question 6

Draw a cross section of a muscle fibre

Answer 6

See cursive online drawing

Question 7

What is a sarcomere?

Answer 7

Functional unit of a muscle cell, area between 2 z lines

Question 8

Draw a sarcomere

Answer 8

See cursive online drawing

Question 9

What is an M line?

Answer 9

Connecting point between myosin filaments

Question 10

What is a Z line?

Answer 10

Connecting point between sarcomeres, overlapping

Question 11

What is an A band?

Answer 11

Dark band, myosin, between actin filaments

Question 12

What is an I band?

Answer 12

Light band, actin only

Question 13

What is the H zone?

Answer 13

Gap between actin filaments

Question 14

What is myosin?

Answer 14

Thick filament
Fibrous protein
Each myosin molecule has a tail bound to the M line and a head with 2 protruding swellings
Heads stick out to form the cross bridges
Head contains ATPase

Question 15

What is actin?

Answer 15

Thin filament
Globular protein linked together into a chain
2 chains twist together to form acting filament
Fibrous protein tropomyosin twists around double chain
Troponin complexes attached to the actin chain at regular intervals
When muscle not contracting, tropomyosin lies over, covers actin mysoin binding sites

Question 16

What does the sarcoplasmic reticulum contain?

Answer 16

Calcium ions

Question 17

What do the calcium ions in the sarcoplasmic reticulum do?

Answer 17

When an action potential reaches a muscle fibre it causes the calcium ions to be released, allowing muscle contractions to occur.

Question 18

Outline the sliding filament model

Answer 18

See cursive online drawing

Question 19

What is a neuromuscular junction?

Answer 19

Where a motor neurone comes into contact with muscle fibre

Question 20

What is a motor unit?

Answer 20

All of the muscle fibres supplied by a single motor neuron
Motor neuron can branch and create many motor end plates, each on a different muscle fibre

Question 21

How can the force of muscle of contraction be altered for a less powerful contraction?

Answer 21

For a less powerful contraction, only one motor neuron is stimulated, so a few muscle fibres contract

Question 22

How can the force of muscle of contraction be altered for a more powerful contraction?

Answer 22

For a more powerful muscle contraction, many motor neurones supplying that muscle are stimulated, so many motor units are stimulated, many muscle fibres contract

Question 23

Outline the events at a neuromuscular junction?

Answer 23

See cursive online drawing (NEED TO DO IT)

Question 24

What roles do calcium ions play at a neuromuscular junction?

Answer 24

Causes vesicles containing neurotransmitter to fuse with presynaptic membrane

Question 25

What are three uses of ATP in muscular contraction?

Answer 25

Break actin-myosin cross bridge Hydrolysis of ATP releases energy to reset myosin head ATP used in active transport to pump sodium ions back into sarcoplasmic reticulum when muscle is relaxed

Question 26

How is ATP supply maintained for contracting muscles?

Answer 26

Stored in sarcoplasm, enough for 1-2s of contraction, afterwards must be regenerated Creatine phosphate stores in sarcoplasm, acts as reserve of phosphate, catalysed by creatine phosphotransferase, supports contraction for another 2-4s, used up quickly, source of ATP in short burst of vigorous activity Aerobic resipration, if oxygen supplied, long periods of low exercise Anaerobic in muscle fibre sarcoplasm, only for few seconds as lactate build up

Question 27

What is rigor mortis?

Answer 27

Occurs after death when limbs stiffen due to lack of ATP

Question 28

What occurs to cause rigor mortis?

Answer 28

Myosin heads remain attached to actin Calcium ions no longer held in sarcoplasmic reticulum via active transport, diffuse and attach to troponin, exposing actin myosin sites, allowing all myosin heads to bind to actin

Question 29

What are slow twitch muscles?

Answer 29

Fibres contract slowly Less powerful contractions but over longer period Used for endurance as do not tire easily Gain energy from anaerobic respiration Rich in myoglobin, bright red protein which stored oxygen, fibres appear red Rich supply of blood and mitochondria

Question 30

What are fast twitch muscles?

Answer 30

Fibres contract very quickly Produce powerful contractions, only short periods Short bursts of speed/power, tire easily Gain energy from aerobic respiration Pale coloured as low levels of myoglobin and blood vessels Contain more, thicker myosin filaments Store creatine phosphate, a molecule that can rapidly generate ATP from ADP in anaerobic conditions