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PHGY 209 > Muscle - Lecture 1 > Flashcards

Muscle - Lecture 1 Flashcards

1
Q

3 types of muscle + Vol. or involuntary

A

1) Skeletal muscle : vol
2) Cardiac muscle : Invol
3) Smooth muscle : invol

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2
Q

Skeletal muscle what it does

A

Posture and locomotion/arms legs etc

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3
Q

Cardiac muscle responsible for

A

rhythmic contractions of the heart

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4
Q

Smooth muscle causes contraction in (4) etc

A

blood vessels, gut, bronchi and uterus

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5
Q

What does each end of muscle do

A

Attached to tendons which attach to bones on both sides of joint

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6
Q

2 muscles states

A

Contracted : shorter

Relaxed : longer

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7
Q

What defines muscle function

A

How they interact with the body and the skeletal frame

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8
Q

Tendon constitution

A

strong connective tissue

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9
Q

Skeletal muscle cells name and how they’re organized and max length

A

muscle fibers (cells) organized in bundles called fascicles. muscle fiber up to 1ft long

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10
Q

Vertical stripes seen on muscle microscope image what they represent

A

Light and dark regions on muscle fibers (cells) that are organized horizontally

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11
Q

Why we see regular stripes in ‘‘side’’ view of muscle fibers (light/dark regions)

A

Organized to work synchronously/are coordinated

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12
Q

muscle microscope image black spots and something particular

A

black spots = nuclei

muscle fibers are multinucleated cells

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13
Q

Name of muscle fibers precursor cells in development (in utero) and how many nuclei

A

myoblasts - 1 nucleus

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14
Q

How muscle fibers formed during development

A

fusion of myoblasts to form multinucleated cells

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15
Q

2 advantages of having multiple nuclei for the muscle fiber

A
  1. Huge lot of protein required can be constantly made (multiple nuclei = multiple copies of a gene)
  2. Less need for protein exportation within the cytoplasm of the long muscle fiber
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16
Q

What constitutes skeletal muscle fibers

A

myofibrils (cylindrical shape)

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17
Q

Components of muscle from large scale to small scale

A

Muscle/fascicles/muscle fiber(cells)/myofibrils

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18
Q

3 important regions found repetitively on a myofibril

A

Light I-band
Dark A-bands
Z line in the center of each I band / in the center of each light band

19
Q

what is the contractile unit of the skeletal muscle and how do you delimitate it

A

Sarcomeres : Region between 2 Z lines. From Z line in the middle of a I-band (light), A-band (dark), Z-line in the middle of the next I-band (light)

20
Q

What happens to sarcomere during contraction

A

gets smaller : Z-lines get closer

21
Q

Special region in A-band/why + its middle line

A

Lighter region in A band is called H-ZONE .

Middle line of the H-zone is the M-line

22
Q

Sarcomere structure summary

A

I-band (light) + Z-line in its middle, A band + H-zone w/ M-line in its middle, I band (light) + Z line in its middle

23
Q

Where do thick filaments extend in the sarcomere

A

From one end to the other end of the A-band (dark)

24
Q

Where do thin filaments extend in the sarcomere

A

Start at Z-line. Go in I-band (light) and part of the A-band (dark)

25
Q

What would be the A-band and the H-zone

A

A-band : where thin and thick filaments overlap H-zone within it = only thick filaments

26
Q

Anchor point in the sarcomere

A

Z-line

27
Q

What are crossbridges

A

Structures found on thick filaments and that interact with thin filaments in the A-band. Are what allows myofibril to contract

28
Q

Microscope cut in the A zone of a myofibril what do we see

A

Thin and thick filaments. Each thin has 3 thick around it. Each thick has 6 thin around it. (Myofibril constituted of lots of filaments)

29
Q

Microscope cut in the I band of a myofibril what do we see

A

Thin filaments only

30
Q

Microscope cut in the H-zone of a myofibril what do we see

A

Thick filaments only

31
Q

What protein constitutes THIN filaments. Shape + interactions

A

Actin. 2 chains of globular actin interacting together form a helix

32
Q

General function of actin in all cells

A

Part of cell skeleton

33
Q

What protein makes up THICK filaments. Shape and organization

A

Myosin. Twisted protein with 2 head groupes at its end.
Myosin forms bundles with head groupes going in the same direction
M line (H-zone) seperates bundles of myosine with head groupes going in opposite directions

34
Q

What is found around a bundle of myosin in the A-zone

A

Thin filaments that surround it

35
Q

What happens to myosin during muscle contraction

A

Head groups repeatedly grab, pull and release the thin filaments.

36
Q

3/4 steps of sliding filament model

A

1) Energized (ATP hydrolysis) myolin binds to actin in thin filaments.
2) Power stroke (pulls thin filaments towards M-line
3) Myosin unbinds and is reenergized

37
Q

Something particular about all head groups functioning

A

Don’t work together but there’s always some head groups attached to the thin filaments so are never left free

38
Q

What happens to length of myofibril upon contraction

A

Reduced (and Z-lines get closer together)

39
Q

Relationship between maximal tension in a muscle fiber and its length : what it depends on

A

depends on degree of overlap of thick and thin filaments

40
Q

Interesting point in the relationship between muscle fiber length and its maximal tension

A

There’s a point of optimal overlapping between thick and thin filaments where maximal tension in the muscle fiber reaches a maximum

41
Q

What happens when thin and thick filaments overlap too much

A

Maximal tension in the muscle fiber is decreased because when thick filaments run into the Z-line, contraction is no more possible (some thick filaments will take off ?)

42
Q

What happens when thin and thick filaments don’t overlap enough

A

Maximal tension in the muscle fiber is decreased because there is less interaction between thin and thick filaments

43
Q

How are muscles designed in respect to thin and thick filaments overlapping

A

Are designed to work at an optimal range of overlapping in order to maximize tension.

PHGY 209 (17 decks)

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