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Y1 Science For Medicine > Muscle 1 > Flashcards

Muscle 1 Flashcards

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1
Q

What are the 2 types of Muscle?

A

Smooth and striated

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2
Q

What two subtypes make up striated muscle?

A

Skeletal (voluntary muscle and diaphragm)

Cardiac

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3
Q

What does smooth muscle make up?

A

Blood vessels, airways, uterus etc

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4
Q

What makes up each skeletal muscle fibre?

A

Each fibre is a large multinucleic cell packed with protein pushing the nulcei to the edge

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5
Q

How do skeletal muscle fibres form?

A

In Utero from mononucleate myoblasts

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6
Q

What encases the bundles of fibres that make muscles?

A

A connective tissue sheath

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7
Q

What connects muslce tbone?

A

Tendons

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8
Q

What cells replace injured skeletal muscle cells?

A

Satellite Cells

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9
Q

Why cant muscles fully recover from injury and what is done to compensate?

A

Theres a limited supply of satellite cells

Other fibres undergo hypertrophy to compensate for the damaged fibres.

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10
Q

What is a myofibril?

A

Every muscle fibre is packed with protein in the form of myofibrils that are like lon chains of myosin and actin filaments.

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11
Q

What is the sarcomere?

A

The sarcomere is the repeating unit of the myofibril

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12
Q

How are actin and myosin filaments arranged in the myofibrils?

A

The thick myosin filaments are arranged in triangles and the thin actin filaments in hexagons. This way every myosin filament is evenly surrounded by 6 actin filaments.

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13
Q

What binds myosin and actin filaments together?

A

Cross bridges on the myosin fliament

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14
Q

What happens to the filaments when muscle contracts?

A

The cross bridges drag the actin filament along, sliding the two filament types along eachother.

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15
Q

What binds to myosin cross-bridges?

A

They have actin binding sites and ATP binding sites.

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16
Q

What are the 4 steps of the cross-bridge cycle?

A

[Ca2+] in the cell rises and the energized cross-bridge binds to actin.
The cross-bridge moves draggin the actin along and releases ADP + Pi (products of the last cycle)
ATP binds to the myosin causing the cross-bridge to detach
Hydrolysis of the ATP energizes the cross-bridge ready for the next cycle.

17
Q

What are the two accessory proteins wrapped around actin?

A

Troponin and Tropomyosin

18
Q

What is the function of tropomyosin?

A

Tropomyosin partially covers the myosin binding site preventing random connection of cross-bridges (rnadom muscle contraction).

19
Q

What is the function of troponin?

A

Troponin hlds tropomyosin in position and when bound to by Ca2+ it pulls away the tropomyosin allowin contraction.

20
Q

What and where is the sarcoplasmic reticulum?

A

The muscle cells internal store of calcium ions
Its a spread of fine tubules throughout the whole cell to allow rapid and even dispersion of calcium throughout the cell.

21
Q

How is calcium taking rapidly back into the sarcoplasmic reticulum after contraction?

A

By Ca2+ATPase (calcium pump)

22
Q

Why cant calcium be allowed to remain in the cell any longer than necessary?

A

It is highly toxic and in fact rapid release of Ca2+ is how cells commit suicide.

23
Q

What makes up a motor unit?

A

A motor neuron attached to many muscle fibres by neuromuscular junctions.

24
Q

What makes muscle fibres able to withstand damage to to motor neurones?

A

Muscle fibres from a motor neuron can be spread throughout a muscle and multiple motor neurons are often linked to different fibres in a muscle.

25
Q

Define tension and load

A

Tension is the force exerted by muscle

Load is the force exerted on muscle

26
Q

Define isometric contraction

A

Contraction with a constant length. E.g. a weightlifter holding a weight above his head

27
Q

Define iostonic contraction

A

Contaction with shortening length. E.g. runnin

28
Q

Define Lenghtening contraction

A

Contraction with increasing length. E.g. The muscles on the back of the leg when sitting down

29
Q

What is a twitch contraction?

A

When a single AP is fired and causes a muscle fibre to contract slightly and suddenly. Often used for studying muscles and motor neurons

30
Q

What is the latent period of a twitch contraction?

A

The time before excitation contraction starts (i.e. the time for the signal to travel and signal tranduction to occur)

31
Q

What is contraction time?

A

The time between the start of tension and peak tension

32
Q

What effects contraction time?

A

Type of muscle fibre
[Ca2+]
Load

33
Q

How does load affect contraction?

A

As the load increases the contraction velocity decreases as does the distance shortened.

34
Q

How is Isometirc contraction differnt in terms of latent period and contraction time?

A

Isometric contraction has a longer contraction event but a shorter latent period.

Y1 Science For Medicine (35 decks)

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