Skeletal Muscles

Question 1

what are the types of muscles?

Answer 1

• smooth muscles
• cardiac muscles
• skeletal muscles

Question 2

how do muscles act?

Answer 2

• in antagonistic pairs
  –> contracting muscle is the agonist
  –> relaxing muscle is the antagonist

Question 3

what are myosin filaments?

Answer 3

• have globular heads that are hinged, so move back and forth
• each myosin head has a binding site for actin and a binding site for ATP

Question 4

what are actin filaments?

Answer 4

• have binding sites for myosin heads
• actin-myosin binding sites
• tropomyosin is found between actin filaments

Question 5

explain the sliding filament mechanism.

Answer 5

• calcium ions diffuse into the myofibrils from the sarcoplasmic reticulum
• calcium ions cause tropomyosin to move away from actin’s binding sites making them available for myosin
• myosin heads attach to the exposed filaments forming actinomysoin cross bridges
• myosin head executes a power stroke which pulls actin filament along, and ADP is released
• ATP attached to myosin head and this causes myosin head to detach from actin
• calcium ions activates myosin’s ATPase activity releasing energy
• energy is used to revert myosin head into the original position
• myosin head reattaches to actin binding site further along the filament

Question 6

when muscles contract, what part of the sacromere remains constant and what part shortens?

Answer 6

• constant = A
• shortens = HI

Question 7

what are fast twitches?

Answer 7

• found in arms and legs
• short burst of activity
• they are short and wide

Question 8

what are slow twitches?

Answer 8

• found in the back and neck
• endurance work
• long and thin

Question 9

what are the adaptations of slow twitches?

Answer 9

• large store of myoglobin.= has a higher affinity for oxygen, so more efficient aerobic respiration
• rich blood vessel supply = provides oxygen to respiring cells
• many mitochondria = site of aerobic respiration

Question 10

what are adaptations of fast twitches?

Answer 10

• more myosin filaments = increases ability of muscles to generate greater force
• higher concentration of glycogen = hydrolysed to glucose (respiratory substrate)
• stores phosphocreatine = hydrolysed to give phosphates
• high concentration of enzymes involved in anaerobic respiration = more anaerobic respiration

Question 11

what type of respiration for fast and slow twitch muscles?

Answer 11

• fast = anaerobic
• slow = aerobic