Exam 3 (chapter 12)

Question 1

Contraction of a muscle is accomplished by thin filaments from opposite sides of each sarcomere _____ _____ together between thick filaments

Answer 1

sliding closer

Question 2

_____: Force exerted on an object by contracting muscle

Answer 2

Tension

Question 3

____=Force exerted on the muiscle by weight of object

Answer 3

Load

Question 4

_____: Mechanical response of a single muscle fiber to a single AP

Answer 4

Twitch

Question 5

Contraction time of a muscle twitch starts at the _____ and ends when the ______ ends

Answer 5

Action potential

Impulse

Question 6

Isotonic contraction is ______ action potentials

Answer 6

between

Question 7

what connects skeletal muscle to bones?

Answer 7

tendons

Question 8

Bundles of muscle fibers

- contain 100s-1000s of muscle cells

Answer 8

fascicles

Question 9

muscle fibers are surrounded by _______________ tissue

Answer 9

connective (endomysium)

Question 10

plasma membrane of a muscle fiber

Answer 10

sarcolemma

Question 11

muscle fibers are ________nucleated

Answer 11

multi

Question 12

Cytoplasm of a muscle fiber

Answer 12

sarcoplasm

Question 13

Microscopic protein filaments that make up muscle cells.

- actin and myosin

Answer 13

myofibrils

Question 14

Thin Myofilaments are primarily

Answer 14

Actin

Question 15

Thick Myofilaments are primarily of

Answer 15

Myosin

Question 16

Organization of muscle fibrils:

Answer 16

Myofibril->Myofilaments (Thick+thin)

Question 17

The smooth ER of a muscle cell

- stores Ca++

Answer 17

sarcoplasmic reticulum

Question 18

muscle fibers contain ___________ mitochondria

Answer 18

many (high energy)

Question 19

System of tubules that provides channels for ion flow throughout the muscle fibers to facilitate the propagation of an action potential.

Answer 19

T (transverse) tubules

Question 20

Transverse tubules (T-tubules) are extensions of the sarcolemma (muscle cell membrane) that penetrate into the centre of skeletal and cardiac muscle cells. T-tubules are highly specialised structures, that form within the first few weeks of life,[1] containing large amounts of specific proteins known as ion channels that allow for electrical impulses (action potentials) travelling along the sarcolemma, to enter rapidly into the cell, to initiate muscle contraction

Answer 20

ye

Question 21

aka terminal cisternae

• expanded regions of sarcoplasmic reticulum
• associated with T-tubules
• involved in the storage and release of Ca2+ in skeletal muscle cells

Answer 21

Lateral sacs

Question 22

t tubule + two lateral sacs

Answer 22

Triad

Question 23

what gives skeletal and cardiac muscle a striated appearance?

Answer 23

Myofibrils

Question 24

Thin filaments

• contractile protein
• made of G actin

Answer 24

Actin

Question 25

Thick filament - actin binding site - nucleotide binding site for ATP and ATPase

Answer 25

Myosin

Question 26

a globular subunit with an active site for binding myosin head

Answer 26

g actin

Question 27

g actin

Answer 27

a globular subunit with an active site for binding myosin head

Question 28

A fibrous protein made of a long chain of G actin molecules twisted into a double helix; main protein of the thin myofilament

Answer 28

f actin

Question 29

A regulatory protein that covers myosin binding sites along the thin filament (actin), preventing actin and myosin from interacting

Answer 29

tropomyosin (rope)

Question 30

A globular protein that associated with tropomyosin as part of the thin filament - binds Ca2+, causing the conformaiton change in tropomyosin required to expose the myosin-binding sites on actin and initiate muscle contraction

Answer 30

Troponin

Question 31

myosin heads are enzymes, what kind are they?

Answer 31

ATPase

Question 32

shortening of the sarcomere occurs as myosin heads bind to the exposed sites on actin, forming cross bridges and pulling the actin filament along the thick filament, resulting in contraction

Answer 32

Sliding filament model

Question 33

How muscle contractions are turned on and off

Answer 33

excitation contraction coupling

Question 34

Explain the process of excitation contraction coupling

Answer 34

A motor neuron connects to a muscle at the neuromuscular junction, where a synaptic terminal forms a synaptic cleft with a motor-end plate. The neurotransmitter acetylcholine diffuses across the synaptic cleft, causing the depolarization of the sarcolemma. The depolarization of the sarcolemma stimulates the sarcoplasmic reticulum to release Ca2+, which causes the muscle to contract.

Question 35

how muscles generate force

Answer 35

crossbridge cycle

Question 36

Cross bridge cycle part _: reactivation of myosin head: ATP hydrolized to ADP and inorganic phospahte; Energy released during hydrolizes reactivates myosin head returning it to cocked postion

Answer 36

4

Question 37

Cross bridge cycle part _: | the power stroke: ADP released and activated myosin head pivotes; Slides thin myofilament toward center of sarcomere

Answer 37

2

Question 38

Cross bridge cycle part _: cross bridge detachment: Link between mysoin head and actin weakens when another ATP ataches to myosin head; Myosin head detaches

Answer 38

3

Question 39

Cross bridge cycle part _: cross bridge formation:Activated myosin head binds to actin forming a cross bridge; Inorganic phospahte released; Bond between myosin and actin becomes stronger

Answer 39

1

Question 40

how muscle cells provide ATP to drive the crossbridge cycle

Answer 40

muscle cell metabolism

Question 41

shortening of muscle is

Answer 41

contraction

Question 42

according to the sliding filament model, do thick or thin filaments shorten?

Answer 42

no

Question 43

sliding is due to cyclical ___________ and ______ of cross bridges (crossbridge cycle)

Answer 43

formation, breaking

Question 44

cyclical formation of links between actin and myosin, resulting in the sliding of thick filaments toward the middle of the sarcomere - myosin head undergoes conformational changes, swiveling back and forth - relies on hydrolysis of ATP

Answer 44

crossbridge cycle

Question 45

oar paddle

Answer 45

crossbridge

Question 46

oar contact with water

Answer 46

linking of thick filament to thin filament

Question 47

myosin heads move, propelling thin filament toward center of muscle

Answer 47

power stroke (movement of oar propelling boat)

Question 48

oar breaks contact with water

Answer 48

thick and thin filaments detach

Question 49

oar moved to new position, cycle starts again

Answer 49

myosin head returns to the initial position

Question 50

ATP has bound the myosin to the actin... but ATP can't be released without another taking its place, so when dead run out of ATP so no muscle relaxation can occur

Answer 50

Rigor mortus

Question 51

what are the 5 steps of the cross bridge cycle in skeletal muscle?

Answer 51

binding of myosin to actin, power stroke, rigor, unbinding of myosin and actin, cocking of myosin head