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bio topic 6 > muscle structure and contraction > Flashcards

muscle structure and contraction Flashcards

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Biology 101 flashcards
1
Q

Motor Neurone Structure [2]

A
  • Each motor neurone has several ‘end plates’.
  • This allows coordinated contraction along the muscle, and also control of the amount of force

Small force = fewer stimulated
Larger force = more stimulated

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2
Q

Neuromuscular Junction Structure [3]

A
  • Where a motor neurone meets a muscle
  • The function of the synapse is the same as a cholinergic synapse
  • Instead of receptors on a post-synaptic neurone, they are on the membrane of the muscle and this is depolarised
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3
Q

Similarities between cholinergic synapses and the neuromuscular junction [4]

A
  • Acetylcholine is the neurotransmitter
  • Acetylcholinesterase breaks this down
  • Acetylcholine attaches to receptors, which cause sodium ion channels to open
  • Both have sodium-potassium pumps in the membrane
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4
Q

Differences between cholinergic synapses and the neuromuscular junction [5]

A

CHOLINERGIC SYNAPSE
- Excitatory or inhibitory
- Neurone to neurone
- Sensory, intermediate and motor can be involved
- Stimulates a new action potential
- Receptors on the post-synaptic neurone membrane

NEUROMUSCULAR JUNCTION
- Only excitatory
- Neurone to muscle
- Only motor neurones
- No new action potential
- Receptors on the muscle fibre membrane

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5
Q

Muscle Structure [5]

A

Skeletal (striated) muscle is made up of specialised cells called muscle fibres. Each fibre contains:
- several nuclei
- many mitochondria
- an extensive sarcoplasmic reticulum (specialised endoplasmic reticulum, Ca2+ store)
- contractile elements called myofibrils (organelles with highly organised cytoskeleton, sliding filaments)

Each myofibril consists of a chain of repeating units called sarcomeres with a characteristic pattern of lines, zones and bands.

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6
Q

Role of Bones in Human Movement

A

Act as levers

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7
Q

Role of Ligaments in Human Movement

A

Attach to the skeleton across joints, stabilizing them

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8
Q

Role of Muscles in Human Movement

A

Provide the force by contracting to move the bones

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9
Q

Role of Tendons in Human Movement

A

Attach muscle to bone

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10
Q

Role of Nerves in Human Movement

A

Coordination of muscle contraction

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11
Q

Muscles & The Skeleton [4]

A
  • Skeletal muscles cause the skeleton to move at joints
  • They are attached to skeleton by tendons
  • Tendons transmit muscle force to the bone
  • Tendons are made of collagen fibres and are
    very strong and stiff
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12
Q

Antagonistic Muscle Action [5]

A
  • Muscles are either contracted or relaxed
  • When contracted the muscle exerts a pulling force, causing it to shorten
  • Since muscles can only pull (not push), they work in pairs called antagonistic muscles
  • The muscle that bends the joint is called the flexor muscle
  • The muscle that straightens the joint is called the extensor muscle
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13
Q

3 Types of Muscle

A

Cardiac Muscle
Smooth Muscle
- Involuntary and controlled by autonomic nervous system

Skeletal Muscle (striped/striated)
- Voluntary and controlled by somatic nervous system

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14
Q

Muscle Structure

A
  • A single muscle contains approx 1000 muscle fibres
  • These fibres run the whole length of the muscle
  • Muscle fibres are joined together at the tendons
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15
Q

What makes up muscles? [5]

A

Muscle
Muscle Fibre Bundle
Muscle Firbre
Myofibrils
Myofilaments

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16
Q

What is Sarcoplasm?

A

Muscle cytoplasm

17
Q

Myofibrils and Sarcomeres [3]

A
  • Each myofibril is made up of many sarcomeres.
  • The sarcomere is mainly composed of two proteins, actin and myosin
  • The arrangement of actin and myosin give the striped appearance of the myofibril
18
Q

Myosin

A

Many of these myosin molecules stick together to form a thick filament

19
Q

Actin [3]

A
  • The thin filament consists of a protein called actin
  • The thin filament also has another protein, tropomyosin wrapped around it
  • Tropomyosin can move, exposing myosin binding sites
20
Q

What is The Sliding Filament Theory? [4]

A
  • When the muscle contracts the sarcomeres become shorter
  • The actin and myosin do not change in length
  • Instead they slide past each other (overlap)
  • Actin filaments are pulled past the myosin
    filaments
21
Q

Neuromuscular Junction [3]

A
  • Action potentials arrive at motor end plates, which release the transmitter acetylcholine.
  • Acetylcholine binds to receptors on the muscle fibre membrane, causing depolarisation.
  • Depolarisation spreads through the transverse tubules to the sarcoplasmic reticulum, which releases Ca2+ ions.
22
Q

Sliding Filament Theory [7]

A
  • Ca2+ ions causes tropomyosin to move away from actin binding sites, exposing them.
  • The myosin head can now attach to the actin filament, forming actinomyosin cross-bridges (The myosin head has an
    ADP and Pi attached to it).
  • The myosin head moves, pulling the thin actin filament along. (This movement causes the ADP and Pi to be released).
  • The actinomyosin cross-bridge is broken as a new ATP attaches to the myosin head.
  • The myosin head ‘re-sets’ using energy from the hydrolysis of ATP.
  • The ATPase that does this is located in the myosin heads and is activated by Ca2+ ions.
  • If the calcium ion concentration drops, tropomyosin moves back and covers the myosin binding sites.
23
Q

Repetition of the cycle [3]

A
  • One ATP molecule is split by each actinomyosin bridge in each cycle. This takes only a few milliseconds
  • During a contraction 1000’s of actinomyosin bridge in each sarcomere go through this cycle
  • However the bridges are all out of synch, so there are always many cross bridges attached at any one time to maintain force
24
Q

Muscle fibres and ATP production [3]

A
  • Muscle cells need to be able to access to large supply of ATP when intense exercise begins
  • ATP has to be resynthesized during exercise
    They have 3 ways of producing ATP:
  • From creatine phosphate or phosphocreatine (first 10s of exercise)
  • Anaerobic respiration
  • Aerobic respiration
25
Q

Creatine Phosphate [5]

A
  • As ADP levels increase, creatine kinase converts creatine phosphate into creatine
  • The energy released converts ADP back into ATP
  • This action is known as substrate level phosphorylation
  • Muscle cells are able to store much more CP compared to ATP
  • ONLY muscle cells use CP for ATP
26
Q

2 types of muscle fibre [2]

A
  • Fast & Slow Twitch Fibres
  • Most animals have both present, although the proportions may vary significantly
27
Q

Slow-twitch fibres

A
  • Contract more slowly and less powerfully
  • Work for longer periods of time
28
Q

How are slow-twitch fibres adapted for aerobic respiration? [3]

A
  • Large store of myoglobin, an oxygen-storage molecule
  • Good blood supply
  • Many mitochondria
    (used for long distance running)
29
Q

Fast-twitch fibres

A
  • Contract rapidly and more powerfully
  • Work for shorter periods of time
30
Q

How are fast-twitch fibres adapted for anaerobic respiration?

A
  • High concentration of enzymes for anaerobic respiration
  • Phosphocreatine store
  • High concentration of glycogen
    (used during sprinting, weight lifting)

bio topic 6 (8 decks)

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