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Science for Medicine > Muscles 1 > Flashcards

Muscles 1 Flashcards

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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 makes up a 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 type of filament is studded with crossheads?

A

(Thick Myosin)

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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

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 does an increase in the overlap of filaments in the sacromere result in?

A

Increased tension

23
Q

What is the result of too much overlap?

A

The filaments interfere with one another

24
Q

What does the A band measure?

A

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

25
Q

What does the H band measure?

A

The distance between the actin filaments (reduced on contraction)

26
Q

What does the I band measure?

A

The distance between the two myosin filaments

27
Q

What is referred to as contraction with constant length?

A

Isometric

28
Q

What is referred to as contraction with shortening length?

A

Isotonic

29
Q

What is referred to as contraction with increasing length?

A

Lenghtening

30
Q

What is a twitch?

A

The contraction of a single muscle fibre

31
Q

What is the latent period?

A

The time before excitation contraction starts

32
Q

What does contraction time depend on?

A

Calcium ion concentration

33
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

34
Q

What is fused tetanus?

A

Constant stimulation by action potentials, no relaxation in the muscle

35
Q

Why is tetanic tension greater than twitch tension?

A

Calcium concentration never gets the chance to decrease and allow troponin/tropomyosin to re-block myosin binding sites

36
Q

What is the optimal length of a muscle?

A

Muscle length for greatest isometric tension.

Science for Medicine (42 decks)

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