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Foundations & Anatomy First year > Muscles 1 > Flashcards

Muscles 1 Flashcards

1
Q

What are the three types of muscle that exist in the body?

A

Skeletal and cardiac (striated)
Smooth (blood vessels, airways, uterus, GI tract)

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2
Q

How are skeletal muscle fibres formed?

A

Groups of cells make a large chain which fuses to form a multinucleated fibre.
Formed by mononucleate myoblasts before birth

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3
Q

What surrounds muscle?

A

Groups of fibres encased in a connective tissue sheath

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4
Q

What is the function of satellite cells?

A

They replace damaged cells after injury, they then differentiate to form new muscle fibres

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5
Q

What is the Z line?

A

The border between sarcomeres

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6
Q

What does do the prefixes myo and sarco mean?

A

Muscle and flesh respectively

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7
Q

What is a myofibril?

A

The muscle strand that makes up a muscle cell

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8
Q

What are the thick and thin types of filament?

A

Thick Myosin and thin actin

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9
Q

What are the names given to the accessory proteins that cover actin?

A

Troponin and tropomyosin

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10
Q

What does troponin do to tropomyosin?

A

Holds the tropomyosin in a blocking position on actin

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11
Q

What is the effect of calcium on troponin?

A

Pulls away tropomyosin revealing binding sits on actin for crossheads.

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12
Q

Where are calcium ions released from?

A

The sarcoplasmic reticulum, which is studded with calcium pumps and surrounds each sarcomere

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13
Q

What is the function of the transverse tubules?

A

Conducts electrical signals and allows them to travel deep into the muscle fibre, ensuring the entirety of the muscle fibre receives the command to contract.

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14
Q

What causes the cross head to adopt a high energy configuration?

A

When it hydrolyses an ATP molecule

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15
Q

What causes the cross head to flip?

A

When it attaches to the actin and releases its ADP + Pi

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16
Q

What is the state of rigor?

A

When the cross head is in its low energy conformation whilst it is attached to the actin

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17
Q

What causes cross bridge dissociation?

A

ATP binding to the cross head (relaxation)

18
Q

What is a motor unit?

A

Muscle fibres + motor neurone

19
Q

Why do several motor neurones enter a large muscle group instead of one branched neurone?

A

Prevents paralysis of the large muscle group if the branched motor neurone becomes damaged. Allows small contraction, instead of every muscle fibre being innervated by the single branched neurone

20
Q

What is tension?

A

The force exerted by a muscle

21
Q

What is the load?

A

The force exerted on a muscle

22
Q

What is the result of too much overlap?

A

The filaments interfere with one another

23
Q

What does the A band measure?

A

The length of the myosin filament (remains unchanged during contraction)

24
Q

What does the H band measure?

A

The distance between the actin filaments (reduced on contraction)

25
Q

What does the I band measure?

A

The distance between the two myosin filaments

26
Q

What is referred to as contraction with constant length?

A

Isometric

27
Q

What is referred to as contraction with shortening length?

A

Isotonic

28
Q

What is referred to as contraction with increasing length?

A

Lenghtening

29
Q

What is a twitch?

A

The contraction of a single muscle fibre

30
Q

What is the latent period?

A

The time between AP and start of contraction

31
Q

What does contraction time depend on?

A

Calcium ion concentration

32
Q

What happens to contraction velocity and the distance shortened by a muscle as the load increases?

A

Contraction velocity decreases and the distance shortened decreases

33
Q

What is fused tetanus?

A

Constant stimulation by action potentials, no relaxation in the muscle

34
Q

Why is tetanic tension greater than twitch tension (in a single fibre)?

A

Calcium concentration never gets the chance to decrease and allow troponin/tropomyosin to re-block myosin binding sites due to summation of APs keeping channels open

35
Q

What is the optimal length of a muscle?

A

Muscle length for greatest isometric tension.

36
Q

What is each fascicle encased in?

A

Connective tissue (epimysium)

37
Q

Which fibre do you find cross-heads?

A

Myosin

38
Q

How does AP in neuro-muscular junction lead to muscle contraction?

A

Electrical signal travels through transverse tubules, opens voltage-gated calcium channels allowing outflow of calcium, calcium changes shape of troponin opening binding site for cross bridge allowing sliding contraction

39
Q

How does exercise change muscles?

A

Regular muscle usage results and more contractile protein in sarcomere –> increase in muscle size and contraction strength (as well as duration)

40
Q

What is hypertrophy and when does it occur in muscles?

A

Hypertrophy - rapid enlargement of organ, skin or muscle
Occurs after Muscle damage (permenant) by increasing fibril size to support and compensate for damaged muscle

Foundations & Anatomy First year (104 decks)

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