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Module 1 vetmed > Skeletal muscle > Flashcards

Skeletal muscle Flashcards

1
Q

Features of skeletal muscle

A

Striated
Attached by bones
Support and movement of skeleton
Voluntary- somatic nervous system
Have multiple nuclei formed by fusion of mononuclear myoblasts in utero
All normal organelles and myofibrils

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2
Q

Transverse section looks like

A

Nuclei moved to the outside
Myofibrils- pink in histology

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3
Q

Longitudal section looks like

A

Peripheral nuclei
Striated
Long fibres
Limited CT between fibres

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4
Q

What are myofibrils made up of

A

Repeated sacromeres- made up of thin and thick filaments

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5
Q

What are thick filaments made up of

A

6 Myosin molecules

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6
Q

What is the structure of myosin

A

Two long proteins twist to form tail of myosin molecule and two globular proteins

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7
Q

How is myosin arranged

A

Tails together with heads popping out at right angles which fixes them in place

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8
Q

Is a structural protein in different orientation

A

Yes

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9
Q

What is M line

A

Where base of muscle is

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10
Q

What is A band

A

Total length covered by two of our thick filaments

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11
Q

What are thin filaments made out of

A

Actin molecules

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12
Q

How are thin filaments structured

A

Arranged in long chain
Wrap them around each other to form a helix
Wrapped around actin molecule is tropmyosin molecule and holding tropomysoin is troponin molecule

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13
Q

What molecule determines the set length

A

Actin

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14
Q

What is Z line

A

When actin molecule is attached to structural protein

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15
Q

Where is the myosin binding site

A

In the actin molecule.
The binding site is covered in troponin molecule attached to structural protein which leads to Z line.

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16
Q

What causes the stripy appearance of muscle

A

The rise of Z line as thick and thin filaments overlap

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17
Q

Where do repeated sacromeres run

A

Along the Longitudal axis

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18
Q

How do we contract the muscle

A

Change amount of overlapping by moving thick and thin filaments relative to each other

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19
Q

What decreases M and Z line distance

A

Contracting of the muscle

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20
Q

What is A band

A

Overall length of thick filaments- not going to change

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21
Q

What is H zone

A

Where there are only thick filaments and no thin filaments

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22
Q

Does H zone decrease when muscles are contracting

A

Yes because greater degree of overlap is occurring

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23
Q

What is I band

A

Where there is only thin filaments and no thick filaments

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24
Q

What is the sacromere

A

Difference between two Z lines
When you contract muscle it only shortens in one direction

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25
Q

What does Cross bridge cycling require

A

Requires use of myosin head and thin filament

26
Q

What is in the myosin head

A

Actin binding site
ATP binding site
ATPase activity

27
Q

What happens to myosin head in resting state

A

ATP will bind to myosin and activate the myosin.
Splits ATP to ADP

28
Q

What happens when the myosin is activated

A

A cross bridge will be formed

29
Q

What is a cross bridge

A

Physical link between the mysoin head and thin filament

30
Q

What happens when actin binds to myosin head

A

Change in shape of myosin head and releases ADP and phosphate but also changes orientation of myosin head relative to the tail and causes it to bend.

31
Q

How can ATP bind to myosin heads

A

Open binding site for ATP to bind to myosin head as ADP has moved across. So this causes cross bridges to break and will revert back to vertical position.

32
Q

Pathway of cross bridge cycling

A

ATP binds
Forms cross bridge
Bends
ATP binds again
Breaks cross bridge
Back to vertical position
Forms New Cross bridge
Binds again

33
Q

What causes rigamortous

A

No ATP to break cross bridges, so muscle becomes rigid as thick and thin filaments are held relative to each other

34
Q

What causes falccidity

A

Eventually the body will use up ATP and cross bridging will break causing flaccidity

35
Q

Why does the myosin binding site need to be inhibited

A

ATP is always present so constant binding and rigidity would occur

36
Q

There are three troponin binding sites, what are they?

A

Tropmyosin molecule
Actin binding site
Calcium binding site

37
Q

At resting is the calcium binding site in troponin occupied

A

No it is not

38
Q

What happens if we increase amount of intracellular calcium

A

Calcium will bind to that binding site and will change shape of the troponin molecule and cause the tropomyosin to swing away from the myosin binding site. So this forms ability to make cross bridges

39
Q

What can we regulate the contraction of the muscle with

A

Concentration of intracellular calcium levels

40
Q

What is a sacroplasmic reticulum

A

A bag like structure
Contains vast quantities of calcium- calcium store
Has voltage gated calcium channels on the surface

41
Q

What happens when an AP passes along the sacroplasmic reticulum

A

Opening of calcium voltage gated channel and calcium will flow out out of sacroplasmic reticulum and into the cell cytoplasm

42
Q

Why does calcium need reuptake

A

So there isn’t consistent contraction

43
Q

How do we bring about calcium reuptake

A

Calcium ATPase pump
If there is a defect in this pump then there is constant rigidity

44
Q

Lag time

A

When it takes a while for calcium to be released and be repackaged.

45
Q

Isotonic contraction

A

Tension within muscle does not change- shorten the muscle due to cross bridge cycling

46
Q

Isometric contraction

A

Muscle is held in position were it can’t physically shorten, creating more cross bridges- no movement of filaments- more tension

47
Q

Tetanic contraction

A

Lots of twitches summed together

48
Q

Length tension relationship

A

Amount of tension we can generate in the muscle changes with the length of the muscle when we send an electrical signal to it

49
Q

Maximum tension

A

Maximum overlap of thick and thin filaments- optimal length

50
Q

What happens if we stretch the muscle to the point were our thin filament are no longer in contact with our thick filament

A

Generate no tension
No cross bridge cycling occurs

51
Q

Resting length is

A

The optimal length

52
Q

How do we get ATP

A

Free ATP
Create ATP-
Creatine phosphate and ADP
Break down food stuff by aerobic glycolysis

53
Q

What is myoglobin

A

Oxygen store in muscle cells

54
Q

What are the three types of skeletal muscle

A

Slow oxidative
Fast oxidative
Fast glycolysis

55
Q

Tension developed by each fibre is formed by

A

Action potiential frequency
Fibre length
Fibre diameter
Fatigue

56
Q

If you induce more fibres to contract what happens

A

Bigger twitch

57
Q

What fibres is small tension related to

A

Slow oxidative

58
Q

What fibres is medium tension related to

A

Fast oxidative

59
Q

What fibres is large tension related to

A

Fast glycolysis

60
Q

If you want a fine movement

A

One motor unit

Module 1 vetmed (22 decks)

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