Skeletal muscle

Question 1

Cardiac muscle

Answer 1

pumping blood, conducts contraction of the heart to pump the blood

Question 2

smooth muscle

Answer 2

to control movement of fluids
surrounding the tubes within the body and the level of contraction depends on the diameter. decreasing diameter decreases the flow
autonomic control

Question 3

skeletal muscle

Answer 3

to move and maintain posture (muscles need to be trained for this)
also to generate heat contraction is an active process that generates heat. some energy is used for the force and some is transferred to heat.

Question 4

sarcolemma

Answer 4

plasma membrane of the muscle cell

Question 5

sarcoplasma

Answer 5

cytoplasm of the muscle cell

Question 6

muscle cell

Answer 6

contain around 1000 myofribrils

Question 7

myofibril

Answer 7

contains 15,000 sarcomeres

Question 8

sarcomere

Answer 8

myofilament between 2 Z-disks

basal contractile unit

Question 9

sarcoplasmic rectilium

Answer 9

SR

internal calcium store

Question 10

T-tubule

Answer 10

transverse tubule invaginated sarcolemma

Question 11

Triad

Answer 11

combination of SR and t-tubule, t-tubule is sandwiched between the 2 SR

Question 12

thin filament

Answer 12

made of actin, tropomyosin and troponin
tropomyosin is the thin ling strand that snakes around the outside and it blocks the contractile machinery from functioning
troponin moves the tropomyosin out of the way and is activated when Ca2+ is released into the cell.

Question 13

thick filament

Answer 13

made of myosin and myosin heads
the heads stick out and sides and form the cross bridge links to the thin filament so the thin filament can move along the thick filament and contract the muscle.

Question 14

Excitation

Answer 14

• AP reaches the end of the motor neuron, which causes entry of Ca2+ into the nerve terminal
• synaptic vesicles release Ach which diffuses into the synaptic cleft
• Ach stimulates Ach receptors on the adjacent muscle fibre
• depolarisation of muscle sarcolemma initiating an action potential
• electro chemical electro coupling
• if the person is healthy then it will always be sufficient to reach the threshold and can action potential will be met.

Question 15

excitation - contraction

Answer 15

AP travels over sarcolemma and tubules, triggering the release of Ca2+ ions from the adjacent SR

Question 16

Contraction

Answer 16

• AP travels over the t-tubules, triggering the release of - - - Ca2+ ions from the adjacent SR
• ca2+ ions diffuse to the myofilament to trigger cross bridge formation
• myosin head is in the energised state with ATP bound to it. atp is used to expose the myosin head.
• Ca2+ troponin interaction exposes the active sites
• actin and myosin interact and form a crossbridge
• energised myosin head pulls the actin, power stroke
• each cycle is driven by high energy bonds of ATP

Question 17

Relaxation

Answer 17

no new AP - sarcolemma re-polarises
Ca2+ ions no longer bind to troponin - taken back to the SR so it can be used again
actin and myosin are still bound but not enough Ca2+ ions to initiate new cross bridges.
ATP must bind for actin and myosin to uncouple
muscle fibre return to its resting state and the process happens all over again.