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Anatomy & Physiology > Muscle Contraction and Muscle Action > Flashcards

Muscle Contraction and Muscle Action Flashcards

1
Q

Structure of a myosin filament

A
  1. Hinged globular head
  2. Binding site for actin
  3. Binding site for ATP
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2
Q

Structure of an actin filament

A
  1. Actin-myosin binding site

2. Tropomyosin & troponin nearby

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3
Q

What are troponin and tropomyosin?

A

Proteins

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4
Q

What happens when a muscle is relaxed?

A
  • tropomyosin covers actin-myosin binding site
  • tropomyosin held in place by troponin
  • myosin head unable to bind to actin filament
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5
Q

First stage of muscle contraction

A
  1. Action potential occurs, stimulating the muscle cell
  2. Sarcolemma depolarises
  3. Sarcoplasmic reticulum releases stored calcium ions in to the sarcoplasm
  4. Calcium ions bind to troponin, causing it to change shape
  5. Tropomyosin pulled out of actin-myosin binding site
  6. Myosin head now able to bind to the exposed binding site
  7. Actin-myosin cross-bridges are formed
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6
Q

Second stage of muscle contraction

A
  1. Calcium ions activate ATPase
  2. ATPase breaks down ATP
  3. The energy released from this causes the myosin heads to rotate towards the centre of the sarcomere, pulling the actin filament over the top of the myosin filament
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7
Q

Final stage of muscle contraction

A
  1. Action potential stops
  2. ATP binds to myosin head, causing it to detach from actin-myosin binding site
  3. Calcium ions detach from troponin
  4. Troponin returns to its original shape
  5. Therefore, troponin and tropomyosin re-cover the actin-myosin binding site
  6. Calcium ions return to the sarcoplasmic reticulum via active transport
  7. Myosin head can no longer bind to the actin filament so the muscle relaxes
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8
Q

Why do slow-twitch muscles fibres appear red in colour but fast-twitch muscle fibres do not?

A

Slow-twitch muscle fibres contain lots of myoglobin whereas fast-twitch fibres do not.

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9
Q

What is myoglobin?

A

A red-coloured globular protein that stores oxygen

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10
Q

Why do slow-twitch muscle fibres need large amount of myoglobin but fast-twitch fibres do not?

A

Slow-twitch fibres carry out aerobic respiration in order to fuel their long periods of slow contraction whereas fast-twitch fibres contract quickly for short periods of time so respire anaerobically to obtain energy.

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11
Q

Which muscle fibre contains lots of blood vessels and mitochondria?

A

Slow-twitch fibres

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12
Q

Sarcolemma

A

Muscle fibre cell membrane

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13
Q

Endomysium

A

Connective tissue that wraps around each individual muscle fibre.

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14
Q

Perimysium

A

Connective tissue that wraps bundles of muscle fibres together. These bundles are known as fascicles.

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15
Q

Epimysium

A

Connective tissue that wraps around the whole muscle

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16
Q

Fascia

A

Thickened connective tissue that covers the entire muscle and connects skeletal muscles together.

17
Q

Transverse (T) tubules

A

Inward folds of the sarcolemma

18
Q

Function of T-tubules

A

They spread electrical impulses through the sarcoplasm so that muscle contraction can occur.

19
Q

Smooth muscle structure

A
  • fusiform cells
  • one nucleus per cell
  • non-striated
  • involuntary muscle
20
Q

Cardiac muscle structure

A
  • branching cells
  • one/two nuclei per cell
  • striated
  • involuntary muscle
21
Q

Isometric contraction

A
  • muscle contracts but is held at the same length

- the force generated depends on the length of the muscle during contraction

22
Q

Concentric contraction

A

Muscle shortens during contraction

23
Q

Eccentric contraction

A

Muscle lengthens during contraction

24
Q

Acute responses to exercise

A
  1. Increased blood flow to brain, respiratory system, heart and bones
  2. Vasodilation
  3. Vasoconstriction to extremities
  4. Increased heart rate
  5. Increased breathing rate
  6. Increased stroke volume
  7. Increased minute ventilation
  8. Increased oxygen content of blood
  9. Increased gas exchange
  10. Increased cardiac output
25
Q

Chronic adaptions to exercise

A
  1. Increased plasma volume, red blood cell mass and total blood volume
  2. Increased maximum stroke volume and cardiac output
  3. Increased ventricular compliance, ventricular dimensions, venous return and myocardial activity
26
Q

Fast-twitch muscle fibre properties

A
  • fast rate of ATP consumption
  • high contractile velocity
  • high force
  • fatigable
  • anaerobic
27
Q

Slow-twitch muscle fibre properties

A
  • slow rate of ATP consumption
  • slow contractile velocity
  • low force
  • fatigue resistant
  • aerobic
28
Q

Composition of muscle tissue

A
  • 80% water
  • proteins
  • minerals
  • biomolecules
  • organelles
29
Q

Function of water

A
  • reduces friction

- maintains shape & size of muscle

30
Q

Proteins found in muscle tissue

A
  • enzymes
  • contractile
  • elastic
  • structural
31
Q

Biomolecules found in muscle tissue

A
  • carbohydrates

- lipids

32
Q

Minerals found in muscle tissue

A
  • calcium ions (initiate muscle contraction)
  • magnesium ions (for muscle contraction)
  • sodium and potassium ions (set action potentials)
33
Q

Organelles found in muscle tissue

A
  • nucleus
  • mitochondria
  • spindles

Anatomy & Physiology (17 decks)

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