Topic 7 Muscles

Front 1

Role of ATP

Back 1

• binds to myosin > causes bond between actin & myosin to break

• hydrolysis of ATP on myosin head > use of enzyme ATPase > releases energy, ADP & Pi

• Pi is released from the myosin head causing it to move

• ATP is used in active transport to transport Ca ions back into the SR

Front 2

Role of calcium

Back 2

• calcium ions activate ATPase

• binds to troponin > causes tropomyosin to move

Front 3

Muscle contraction - preliminary step

Back 3

1) action potential arrives at MN > stimulates the muscle cell > depolarised the sarcolemma > depolarisation spreads down the t tubules to SR

2) causes release of calcium ions from the sarcoplasmic reticulum

Front 4

Muscle contraction (stage 1 - binding)

Back 4

1) ca ions bind to troponin > changes shape

2) pulls (displaces) attached tropomyosin away from actin myosin bonding site (/ changes shape of tropomyosin)

3) myosin head able to bind > actin myosin cross bridge forms

Hint 4

Front 5

Muscle contraction process (stage 2 - contraction)

Back 5

1) ca ions activate enzyme ATPase

2) > ATPase breaks down ATP into ADP + Pi + energy

3) energy released moves myosin head (back & forth) > pulls actin filament along using a rowing action (sarcomere shortens)

Hint 5

Front 6

Muscle contraction process (stage 3 - breaking cross bridge)

Back 6

1) ATP provides energy to break the actin myosin cross bridge > myosin head detaches

2) myosin head reattaches to different binding site further along

3) many cross bridges form & break (rapidly) until ca ions supply runs out

Hint 6

Front 7

Muscle contraction (stage 4 - relaxation)

Back 7

1) ca ions moved into the sacroplasmic reticulum by active transport (ATP)

2) troponin returns to original shape > tropomyosin pulled > blocks the actin myosin binding site

3) myosin head x attach > actin filaments slides back into relaxed position > sarcomere lengthens (muscle relaxes)

Hint 7

Front 8

Myosin

Back 8

• globular heads (hinged > can move back & forth > allows filaments to slide > contraction)

• myosin head has a binding site for actin & ATP

Front 9

Actin filaments

Back 9

binding sites for myosin head

Front 10

Troponin

Back 10

• Site at which calcium ions bind to determine whether tropomyosin is/isn’t blocking

• ^ ca ion > binds to troponin > tropomyosin moves

Front 11

Tropomyosin

Back 11

• blocks the A-M binding site > myosin head X bind > myofilaments X slide past each other

• located on actin filament

Front 12

What 2 muscle fibres are skeletal muscles made of?

Back 12

Slow and fast twitch muscle fibres

Front 13

Slow twitch muscle fibre

Back 13

- x produce lactic acid > fatigue resistant/ gd endurance

- lots of mitochondria > so efficient at aerobic respiration

- lots of myoglobin (appear red) > stores oxygen

- extensive network of capillaries give a good oxygen supply

(- slower energy release > slow contraction)

Front 14

Fast twitch muscle fibres

Back 14

- produces lactic acid > fatigue quickly/ low endurance

- little mitochondria > so anaerobic respiration

- little myoglobin (appear white) > stores oxygen

(- quicker energy release > fast contraction)

Front 15

Joints

Back 15

• Junction/where 2 bones are attached

• Pivot for movement

Front 16

Tendons

Back 16

Connective tissue that attaches (skeletal) muscle & bone

Front 17

Ligament

Back 17

Connective tissue joining bone to bone

Front 18

Sacrolemma (Define)

Back 18

Cell membrane of a muscle cell

Front 19

What are the dark spots shown in this image?

Back 19

Nuclei of the muscles cells which are multinucleated

Front 20

Flexor

Back 20

Muscle that contracts to bend joint/ limb

Front 21

Extensor

Back 21

Muscle that contracts to straightens joint/ limb

Front 22

Antagonist

Back 22

• Muscle relaxing > allows movement

• Sarcomere lengthens

Front 23

Example of antagonistic pair - bicep/tricep for STRAIGHTENING arm

Back 23

• Agonist - tricep muscle contracts (FLEXOR)

• Antagonist - bicep muscle relaxes (EXTENSOR)

Hint 23

Front 24

Agonist

Back 24

• Muscle contracting > creates movement

• Sarcomere shortens

Hint 24

Front 25

Example of antagonistic pair - bicep/tricep for BENDING arm

Back 25

• Agonist - bicep muscle contracts (FLEXOR)

• Antagonist - tricep muscle relaxes (EXTENSOR)

Hint 25

Front 26

How do muscles move

Back 26

• muscles can only pull on bone > ONLY work in ONE direction

• therefore need to create opposite forces > so must have extensors & flexors

• 2 muscles needed for movement (antagonistic pair)

Front 27

Transverse (T) tubules

Back 27

Inwards folding of the sarcolemma (into the sarcoplasm) > important in initiating muscle contraction

Front 28

Sarcoplasmic reticulum

Back 28

stores ca+ ions used in muscle contraction

Front 29

Mitochondria

Back 29

Muscle fibres have many mitochondria > provide lots of ATP to power muscle contraction

Front 30

Multiple nuclei

Back 30

Needed as one nuclei can x effectively control the metabolism of such a long cell

Front 31

What is the difference between a muscle cell and fibre?

Back 31

THERE ISNT ONE APPARENTLY

Front 32

Is a muscle fibre a myofibril?

Back 32

No a myofibril is an organelle within muscle cells (fibres)

Front 33

What is a muscle made of?

Back 33

Made of many bundles of muscle fibres (muscle cells/ myocytes)

Front 34

muscle fibre (define)

Back 34

muscle fibres = long cylindrical, multinucleated single muscle cell surrounded by sarcolemma

Front 35

What is a muscle fibre made of?

Back 35

Made of many myofibrils (long cylindrical organelles)

Front 36

What is a myofibril made of?

Back 36

Made of many myofilaments (actin & myosin)