muscle contraction

Question 1

Sliding filament theory

Answer 1

• theory of muscle contraction is the mechanism by which muscles are thought to contract at a cellular level

Question 2

What is each muscle fibre made up of?

Answer 2

• myofibrils which are smaller fibres
• contain structures called actin and myosin filaments
• these filaments slide in and out between each other to form a muscle contraction

Question 3

structure of a muscle

Answer 3

myofibril- a cylindrical organelle running the length of a muscle fibre
- sarcomere - functional unit of myofibril, divided into I, A, and H bands
- Actin - thin contractile protein filament, containing active or binding sites
- myosin - thick, contractile protein filament with protrusions known as myosn heads
-tropomyosin - an actin binding protein that regulates muscle contraction
- troponin - a complex of 3 proteins

Question 4

steps in muscle contraction
1) nerve impulse

Answer 4

-nerve impulse arrives at neuromuscular junction
- causes a release of a chemical
- chemical travels throughout the muscles by transverse tubules
- calcium is then released from sarcoplasmic reticulum as a result of this

Question 5

transverse tubules

Answer 5

• help to spread electrical impulses throughput the sarcoplasm so they reach all parts of the muscle fibre

Question 6

2) calcium binds to troponin

Answer 6

• in prescence of high conc of calcium it binds to troponin which changes its shape
  -moves tropomyosin from the active site of the actin
• myosin filaments attatch to actin filaments which forms a cross bridge that enables contraction

Question 7

3) ATP breaks down

Answer 7

breakdown of ATP releases energy which enables the myosin to pull the actin filaments inwards
-occurs along the entire length of myofibril in the muscle cell

Question 8

4) Myosin detaches

Answer 8

myosin detaches from the actin and cross bridge is broken when an ATP molecule binds to myosin head
-the myosin heads release ADP +P in this process
-

Question 9

Basic contractile unit of a muscle fibre?

Answer 9

the sarcomere
- short unit
- ends are marked with a z line and in the middle is the m line

Question 10

What membane surrounds the muscle fibre units?

Answer 10

sarcolemma
-cell membrane of muscle fibre cells
- bits of the sarcolemma fold inwards across the muscle fibre

Question 11

Name of the cytoplasm muscle fibres

Answer 11

sarcoplasm

Question 12

mitochondria

Answer 12

• provides ATP that is needed for muscle contraction

Question 13

sarcoplasmic reticulum

Answer 13

stores and releases calcium ions needed for muscle contraction

Question 14

multinucleate

Answer 14

• when something contains multiple nuclei
• multiple nuclei help enable skeletal tissue to acquire more oxygen and nutrients while helping the repair of injured muscles

Question 15

3 types of muscles

Answer 15

• cardiac - only found in the heart, involuntary and contracts and relaxes
• skeletal - attached to the bones and controls its contractions and relaxations
• smooth - found in the linings and hollow walls of the organs
  like arteries and veins