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Biology A Level > Muscle (3.6.3) > Flashcards

Muscle (3.6.3) Flashcards

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1
Q

What is a Skeletal Muscle also known as?

A

Striped / Striated Muscle

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2
Q

Why is a Skeletal Muscle also known as a Striped / Striated Muscle?

A

Due to its striped appearance when viewed under a microscope due to alternate light bands of protein filaments

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3
Q

What is a muscle attached to?

A

Bone

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4
Q

What stimulates a muscle to contract?

A

Nerves

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5
Q

What does a muscle act as?

A

Effector

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6
Q

What are 2 features of muscle fibres?

A
  • Multinucleate

* Many Mitochondria

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7
Q

Explain the Structure of Muscles:

A
  • Consists of cells, muscle fibres that are multinucleate and contain many mitochondria
  • Elongated with bundles of myofibrils
  • Sarcolemma = cell surface membrane, folded deeply into muscle fibre (t – tubules)
  • Sarcoplasm
  • Sarcoplasmic Reticulum containing Ca2+
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8
Q

What are the 2 protein filaments in Myofibrils?

A

1) Thick Filaments – Myosin

2) Thin Filaments - Actin

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9
Q

What line is Actin attracted to?

A

Z – Line

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10
Q

What is the part of the myofibril between 2 Z – lines called?

A

Sarcomere

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11
Q

What line is Myosin attracted to?

A

M – Line

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12
Q

What does the A – Band include?

A

This is where Myosin Filaments + Actin Filaments

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13
Q

What does the I – Band include?

A

Only Actin Filaments

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14
Q

What does the H – Band include?

A

Only Myosin Filaments

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15
Q

What Theory explains Muscle Contraction

A

Sliding Filament Theory

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16
Q

How are the Bands affected when a muscle contracts?

A
  • I Band is reduced as Actin slides between myosin
  • A Band remains the same as Myosin length is unchanged
  • H Zone is reduced as overlap between Actin + Myosin increases
  • Sarcomere is reduced in length
17
Q

What stops myosin heads from binding to Actin in a resting muscle?

A

The binding sites, in a resting muscle, will be blocked by a protein called Tropomyosin

18
Q

What causes the unblocking of myosin binding sites?

A

The release of Calcium ions as they cause Tropomysoin to change shape and expose the myosin binding sites on the Actin filament

19
Q

What causes the release of Calcium ions?

A

When an action potential spreads along the t-tubules

20
Q

Events for Each Myosin Head:

A
  • Myosin Head attaches to myosin binding site on Actin filaments forming actinomyosin bridge
  • Myosin head tilts in a rowing action, sliding actin filaments iver myosin filaments towards the centre of Sarcomere
  • ATP binds to the myosin head and causes it to release the actin filament
  • ATP hydrolase (in the head) hydrolyses ATP releasing energy which causes the myosin head to flip back into its original position
  • Cycle Repeats
21
Q

What happens when the action potentials stop arriving?

A
  • Calcium ions actively pumped back into Sarcoplasmic reticulum via Active transport – ATP needed)
  • Tropomyosin returns to original shape + myosin heads no longer attach to Acton filaments
  • The muscle remains in its contracted state as Action filaments only slide in 1 direction towards centre of Sarcomere.
22
Q

Why are the muscles described to work in antagonistic pairs?

A

As they work against an incompressible skeleton which means when 1 contracts, the other muscle in the pair relaxes

23
Q

When is energy needed in muscle contraction?

A
  • Movement of myosin heads (detach + return to original position)
  • Return of Ca2+ ions into Sarcoplasmic reticulum by active transport
24
Q

State 2 sources where Energy is supplied from?

A
  • ATP

* Phosphocreatine

25
Q

Why must energy be supplied by another source?

A

This is because hydrolysis of ATP releases energy + ADP + Pi. Muscle fibres only store small quantities enough for 3-4 secs of muscle contractions and it takes 10 secs to generate ATP from anaerobic respiration, so it must be supplied by another source

26
Q

Why is Phosphocreatine useful?

A

This is because Muscle fibres can store it; producing ATP rapidly

27
Q

What is the formula to produce ATP using Phosphocreatine?

A

ADP + Phosphocreatine  ATP + Creatine

28
Q

What happens with Phosphocreatine when muscle fibre stops contracting?

A

It is resynthesised

29
Q

What are the 2 types of Muscle Fibre?

A
  • Slow Twitch Fibres

* Fast Twitch Fibres

30
Q

Explain the basic function of Slow twitch fibres

A
  • Rely on ATP generated by aerobic respiration

* Contract slowly over long periods of time (standing, walking, balancing etc.)

Biology A Level (7 decks)

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