Skeletal muscle

Question 1

What are sarcomeres

Answer 1

Contractile units of skeletal and cardiac muscle

Question 2

What are sarcomeres held in register by

Answer 2

Cross connections at the level of every z disk and the middle of each sarcomere formed by intermediate filaments

Question 3

What do thick and thin filaments appear as in fibres

Answer 3

Striations

Question 4

What do lots of myofibrils make

Answer 4

muscle fibre

Question 5

What is muscle fibre

Answer 5

Syncytium (lots of precursor cells fused to form a fibre)

Question 6

What is a fascicle

Answer 6

Fibre bundle

Question 7

What does the amount of force developed by a sarcomere depend on

Answer 7

The degree of overlap between thick and thin filaments

Question 8

What’s the force a muscle can develop dependent on?

Answer 8

The starting length

Question 9

What is the length tension relationship

Answer 9

1) at full stretch, few of the myosin heads have access to actin in the thin filament and the force is weak
2) At optimal length, all of the myosin filaments have access to actin and the force is maximal
3) at full contraction, the ends of the thin filament get in each others way and the force is reduced

Question 10

What’s the actin and myosin like at full stretch and what is the force like?

Answer 10

Few of the myosin heads have access to actin in the thin filament
-force is weak

Question 11

What are the actin and myosin like at optimal length

-what’s the force like?

Answer 11

All of the myosin filaments have access to actin

-force is maximal

Question 12

What’s the actin and myosin like at full contraction?

-What is the force like?

Answer 12

Ends of the thin filament get in each others way

-force is reduced

Question 13

What stain is used to stain muscle?

Answer 13

Goldner trichrome

Question 14

What color are muscle fibers after staining

Answer 14

brown-purplish

Question 15

What color is connective tissue after staining

Answer 15

Green

Question 16

What is endomysium

• What does it surround
• What does it connect to

Answer 16

Loose connective tissue with some delicate and strong fibers

• Surrounds each muscle fibre
• Connects to basement membrane

Question 17

What is perimysium

Answer 17

Mixed connective tissue, some dense, some loose

Question 18

What does the perimysium do

Answer 18

Separates groups of muscle fibers into fascicles

-main venue for nerves and supporting blood vessels

Question 19

What’s a fascicle held together by

Answer 19

Bundle of muscle fibers held together by perimysia

Question 20

What is epimysium

Answer 20

Relatively loose connective tissue between fascia and muscle body

Question 21

What is fascia

Answer 21

Dense layer of connective tissue covering the muscle

Question 22

Wh does cardiac muscle perform a wringing motion when contracting

Answer 22

Spiral, fibre like arrangement of the heart muscle cells

Question 23

How is cardiac muscle different from skeletal muscle

Answer 23

Not built of syncytial fibers like skeletal muscles

Question 24

What does cardiac muscle contain

Answer 24

single or mono or dinuclueated cells with limb like extensions

Question 25

What is myocardium mean

Answer 25

Cardiac muscle tissue

Question 26

What are the nuclei like in cardiac muscle

Answer 26

Centrally located nuclei

Question 27

What are the extensions like in muscle cells and what do they do

Answer 27

Extensions connect them to neighboring cells and form fibre like networks that produce force in the direction of the cell’s axis

Question 28

What do the extensions in cardiac connect connect them to neighbouring cells via

Answer 28

Intercalated discs

Question 29

What are cardia muscle tightly packed with

Answer 29

myofibrils

Question 30

What does each cardiac muscle have

Answer 30

a basement membrane

Question 31

What are some crucial features of intercalated discs

Answer 31

• Desmosomes

- Gap junctions

Question 32

What is the role of desmosomes in cardiac muscle

Answer 32

Allow longitudinal force transfer due to their strong adherence

Question 33

What is the role of gap junctions in cardiac muscle

Answer 33

Allow transfer of membrane depolarizations (e.g. action potentials)

Question 34

What do skeletal muscles fibers not have

Answer 34

Gap junctions

Question 35

What happens during smooth muscle contraction

Answer 35

Actin filaments pulled across each other

Question 36

Why can smooth muscle contract further than striated muscle

Answer 36

Because in striated muscle, thick filaments hit the z line

Question 37

What prevents over stretching

Answer 37

Intermediate filaments form a scaffold that prevent over-stretching

Question 38

What are actin filaments held together by

Answer 38

Patches of cytoskeletal proteins called dense bodies

Question 39

What is needed for muscle extension

Answer 39

An antagonistic force is necessary

Question 40

What antagonistic force is used in

• skeletal muscle
• cardiac muscle
• smooth muscle

Answer 40

• angatonistic muscles
• blood pressure, atrium for ventricles
• tube pressure

Question 41

How is contraction of skeletal muscle controlled

Answer 41

motor units, controlled by central nervous system

Question 42

What is cardiac muscle contraction controlled by

Answer 42

By pacemaker consisting of specialized cardiomyocytes

Question 43

What is smooth muscle contraction controlled by

Answer 43

autonomous nervous system that has centers throughout the central parts of the bod