Muscle - Lecture 1

Question 1

3 types of muscle + Vol. or involuntary

Answer 1

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

Question 2

Skeletal muscle what it does

Answer 2

Posture and locomotion/arms legs etc

Question 3

Cardiac muscle responsible for

Answer 3

rhythmic contractions of the heart

Question 4

Smooth muscle causes contraction in (4) etc

Answer 4

blood vessels, gut, bronchi and uterus

Question 5

What does each end of muscle do

Answer 5

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

Question 6

2 muscles states

Answer 6

Contracted : shorter

Relaxed : longer

Question 7

What defines muscle function

Answer 7

How they interact with the body and the skeletal frame

Question 8

Tendon constitution

Answer 8

strong connective tissue

Question 9

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

Answer 9

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

Question 10

Vertical stripes seen on muscle microscope image what they represent

Answer 10

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

Question 11

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

Answer 11

Organized to work synchronously/are coordinated

Question 12

muscle microscope image black spots and something particular

Answer 12

black spots = nuclei

muscle fibers are multinucleated cells

Question 13

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

Answer 13

myoblasts - 1 nucleus

Question 14

How muscle fibers formed during development

Answer 14

fusion of myoblasts to form multinucleated cells

Question 15

2 advantages of having multiple nuclei for the muscle fiber

Answer 15

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

Question 16

What constitutes skeletal muscle fibers

Answer 16

myofibrils (cylindrical shape)

Question 17

Components of muscle from large scale to small scale

Answer 17

Muscle/fascicles/muscle fiber(cells)/myofibrils

Question 18

3 important regions found repetitively on a myofibril

Answer 18

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

Question 19

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

Answer 19

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)

Question 20

What happens to sarcomere during contraction

Answer 20

gets smaller : Z-lines get closer

Question 21

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

Answer 21

Lighter region in A band is called H-ZONE .

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

Question 22

Sarcomere structure summary

Answer 22

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

Question 23

Where do thick filaments extend in the sarcomere

Answer 23

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

Question 24

Where do thin filaments extend in the sarcomere

Answer 24

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

Question 25

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

Answer 25

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

Question 26

Anchor point in the sarcomere

Answer 26

Z-line

Question 27

What are crossbridges

Answer 27

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

Question 28

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

Answer 28

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

Question 29

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

Answer 29

Thin filaments only

Question 30

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

Answer 30

Thick filaments only

Question 31

What protein constitutes THIN filaments. Shape + interactions

Answer 31

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

Question 32

General function of actin in all cells

Answer 32

Part of cell skeleton

Question 33

What protein makes up THICK filaments. Shape and organization

Answer 33

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

Question 34

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

Answer 34

Thin filaments that surround it

Question 35

What happens to myosin during muscle contraction

Answer 35

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

Question 36

3/4 steps of sliding filament model

Answer 36

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

Question 37

Something particular about all head groups functioning

Answer 37

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

Question 38

What happens to length of myofibril upon contraction

Answer 38

Reduced (and Z-lines get closer together)

Question 39

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

Answer 39

depends on degree of overlap of thick and thin filaments

Question 40

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

Answer 40

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

Question 41

What happens when thin and thick filaments overlap too much

Answer 41

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 ?)

Question 42

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

Answer 42

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

Question 43

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

Answer 43

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