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Science for Medicine > Muscles > Flashcards

Muscles Flashcards

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1
Q

What are muscles?

A

Bundles of fibres wrapped in connective tissue sheaths

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2
Q

What are skeletal muscles?

A

Multi nucleated striated fibres that contain sarcomeres that are made in utero by myoblasts

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3
Q

How are skeletal muscles classified?

A

According to their speed and wether or not they are oxidative or glycosidic

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4
Q

What are oxidative fibres?

A

Red fibres that have a small diameter and contain many mitochondria, contain myoglobin and are more vascular

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5
Q

What are the benefits of being vascular?

A

Enhanced delivery of oxygen and nutrients

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6
Q

What is the function of myoglobin?

A

Enhances the delivery of oxygen

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7
Q

Where is mitochondria used?

A

Oxidative phosphorylation

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8
Q

What is the function of slow oxidative fibres?

A

Resistance of fatigue

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9
Q

What is the function of fast oxidative fibres?

A

Intermediate resistance of fatigue

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10
Q

What are glycolytic fibres?

A

White fibres with a large diameter and contain few mitochondria. They have a decreased blood supply but a high concentration of glycolytic enzymes and glycogen

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11
Q

What happens to fast glycolytic fibres

A

They fatigue quickly

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12
Q

What is fatigue?

A

Prevents a lot of ATP from being used in breaking/reforming cross bridges in order to sustain contractions

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13
Q

What causes fatigue?

A

Repeated muscle stimulation

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14
Q

What is tetanus?

A

State of extended contraction due to the summation of APs which prevents Ca from returning to the sarcoplasmic reticulum so tropomyosin remains in it’s unblocked state, so cross bridges are not broken

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15
Q

Why can Ca not re-enter the sarcoplasmic reticulum due to tetanus?

A

Tetanic tension > twitch tension

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16
Q

What is the process of recruitment?

A

As load increases, more motor fibres are needed to compensate so more muscles can be involved in the movement

17
Q

What is an isotonic twitch?

A

Contraction with shortening length

18
Q

What is another name for isotonic twitches?

A

Concentric

19
Q

What is an isometric twitch?

A

Contraction with constant length

20
Q

What is an eccentric twitch?

A

Contraction with increasing length

21
Q

What is the process of excitation-coupling contraction?

A

Muscle fires APs, Ca ions are released from the SR, Ca ions bind to troponin on actin filaments, tropomyosin is removed, binding sites are exposed, myosin binds to actin, cross-bridges form, contraction occurs, Ca ions return to the SR, tropomyosin returns to its original shape, cross-bridges break, contraction ends

22
Q

What does contraction cause?

A

Various changes in the sarcomere

23
Q

What happens when filaments slide over each other?

A

A band and H zone decrease

24
Q

What is the A band?

A

Myosin

25
Q

What is the I band?

A

Actin

26
Q

What is the H zone?

A

Space between opposite actin filaments

27
Q

What is a Z line?

A

Dark line that separates each sarcomere

28
Q

What is smooth muscle?

A

Involuntary, mono nucleated muscles that is supplied by the ANS and contains no striation but contains myosin and actin

29
Q

How are myosin and actin arranged in smooth muscle?

A

Diagonally, anchored to membranes and cell structures by dense bodies

30
Q

Where does smooth muscle exist?

A

Hollow organs

31
Q

What are examples of hollow organs?

A

GI tract, bladder and airways

32
Q

How do smooth muscles operate?

A

By forming cross-bridges between myosin and actin but by a different mechanism than skeletal muscle

33
Q

What type of muscle can sustain contractions for longer?

A

Smooth muscle

34
Q

Why is smooth muscle useful in BVs?

A

Smooth muscle can sustain contractions for longer so they can stay open for longer periods of time

35
Q

How do contractions occur in smooth muscle?

A

APs released from muscle, Ca ions released from SR, Ca ions bind to calmodulin, calmodulin binds to light chain kinase, myosin to phosphorylated by ATP, cross-bridges form with actin, contraction occurs

36
Q

How does relaxation occur in smooth muscle?

A

Myosin light chain phosphatase dephosphorlyates the cross bridges

Science for Medicine (19 decks)

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