Muscles- BP

Question 1

What are the different types of Muscles?

Answer 1

 Skeletal
 Smooth
 Cardiac

Question 2

what is the job of the skeletal muscle?

Answer 2

 moves the body skeleton
 when the muscle contracts (shortens) the tendon pulls on joints causing movement

Question 3

Structure of Skeletal Muscle?

Answer 3

• basic structure = sarcomeres made up of actin and myosin, actin is thin and has tropomysosin wrapped around it, myosin is thick and has heads, when the sarcomere contracts the whole muscle contracts, contracts/shortens by the sliding filament mechanism
• many sarcomeres = myofibril
• many myofibrils = muscle fibre
• muscle fibre is surrounded by a membrane called sarcolemma
• muscle fibres contain myofibrils, fluid called sarcoplasm and tubes called sarcoplasmic reticulum
• many muscle fibres = bundle
• many bundles = whole muscle

Question 4

Locations in a Sarcomere?

Answer 4

 A band = location of myosin [no change in contraction]
 I band = location between the myosin [shortens in contraction]
 H zone = location between the actin [shortens in contraction]
 Z line = end line of sarcomere [moves closer together in contraction]

Question 5

What occurs in Sliding Filament Mechanism?

Answer 5

 the sarcomere shortens
 the myosin heads pull the actin inwards
 the somatic motor neurone connects to the skeletal muscle via a neuro-muscular junction
 one motor neurone connects to a few muscle fibres = motor unit (benefit = simultaneous muscle contraction and can control strength of contraction)
 releases acetylcholine that binds to complementary receptors on the muscle fibre membrane (sarcomere)
 Na+ channels open, Na+ ions enter the muscle fibre causing depolarisation
 wave of depolarisation travels through sarcoplasmic reticulum
 causes release of Ca2+ ions into the sarcoplasm (fluid surrounding sarcomeres/myofibril)
 this moves the tropomyosin on the actin
 exposes binding sites on the actin
 myosin heads now bind to the actin (form actin-myosin cross bridge)
 a power stroke occurs, the myosin pulling the actin inwards
 ATP attaches to myosin head so it detaches
 ATP brokendown by ATPase to release energy
 causes myosin head to go back to its original position
 so it reattaches, pulling the actin further inwards

Question 6

Role of Ca2+ ions and ATP in muscle contraction?

Answer 6

 Ca2+ ions causes the tropomyosin to move exposing binding sites on actin
 Ca2+ ions stimulate ATPase
 ATP causes myosin head to detach
 ATP releases energy so myosin head returns to original position
 ATP actively transports Ca2+ ions back into sarcoplasmic reticulum when the muscle is relaxed

Question 7

What are the 2 types of Muscle Fibres?

Answer 7

Fast Twitch and Slow Twitch

Question 8

How does Fast Twitch Muscle Fibres work?

Answer 8

 provide powerful but short lasting contractions
 found in biceps and sprinters
 adapted for anaerobic respiration
 has thicker myosin for powerful contractions
 contains more enzymes for anaerobic respiration
 contains phosphocreatine, provides phosphate to ADP to reform ATP

Question 9

How does Slow Twitch Muscle Fibres work?

Answer 9

 provide less powerful but long lasting contractions
 found in thigh muscles and marathon runners
 adapted for aerobic respiration
 has a rich blood supply
 contains many mitochondria
 contains glycogen
 contains myoglobin (stores oxygen)