Muscle

Question 1

Repeating contractile unit that when chained together make a myofibrils

Answer 1

Sacromere

Question 2

Ends of sacromere

Answer 2

Z disk

Question 3

Middle of a sarcomere

Answer 3

M line

Question 4

Thin filaments only

Answer 4

I band

Question 5

Entire length of thick filaments

Answer 5

A band

Question 6

Middle of A band, with thick filaments only

Answer 6

H Zone

Question 7

describes how sarcomeres allow muscles to contract.

Answer 7

Sliding Filaments Theory

Question 8

Muscles are arranged around _____to allow for movement.

Answer 8

joints

Question 9

Muscles that close joints

Answer 9

Flexors

Question 10

Muscles that open joints

Answer 10

Extensors

Question 11

Muscles are _____in opposing patterns, to allow for all directions of movement.

Answer 11

arranged

Question 12

Muscles that have opposite effects on the same joint

Answer 12

Antagonists

Question 13

Muscles that have cooperative effects on the same effect

Answer 13

Synergists

Question 14

Biceps and triceps muscles are arranged around the ____joint

Answer 14

elbow

Question 15

A collection of muscle fibers

Answer 15

Muscle Fascicle

Question 16

A collection of myofibrils (Individual chains of sarcomeres)

Answer 16

Muscle fiber

Question 17

Skeletal muscle contraction is _____—a muscle fiber must be “activated” by a motor neuron via an NMJ.

Answer 17

neurogenic

Question 18

) How does AP in a motor neuron become a Ca2+ signal in the muscle fiber?

Answer 18

Excitation-contracting coupling

Question 19

How does a Ca2+ signal cause sarcomeres to start shortening?→

Answer 19

Sliding filaments theory and Power strokes

Question 20

Wraps around actin to block binding sites on actin

Answer 20

Tropomyosin

Question 21

• AKA: Ca+2- sensing protein

- Binds to Ca+2= causing unbounding of tropomyosin from action- allowing Actin to bind to Myosin

Answer 21

Troponin

Question 22

1. Motor neuron AP reaches axon terminal→Ach in synaptic cleft.
2. Ach binds to nicotinic AchRs. These mixed-cation channels open→Na+ enters cell→depolarization.
   -Graded potential called an endplate potential (EPP).
3. Endo-plate Potential depolarizes Vm to Vthresh, activates VGNaCs and VGKCs→skeletal muscle AP.
4. AP invades t-tubules (indentations in membrane).
5. AP activates dihydropyradine receptors (DHPRs) in t-tubule membrane.
6. DHPRs are physically connected to ryanodine receptors (RyRs) in
   sarcoplasmic reticulum membrane.
   -Activation of DHPR→Activation of RyR.
7. RyRs are Ca2+ channels. Activation of RyR→Ca2+ flow from SR into
   cytosol. Ca2+ signal!

Answer 22

Skeletal Muscle Excitation-Contraction Coupling:

Question 23

is a long filamentous protein with myosin binding sites spaced along it.

Answer 23

Actin

Question 24

is a helical protein wrapped around actin, covering the myosin binding sites (at rest).

Answer 24

Tropomyosin

Question 25

______ is a Ca2+ binding/sensing protein that also interacts with tropomyosin (more soon)

Answer 25

troponin

Question 26

Myosin has “heads” projecting off the filamentous part.

Answer 26

myosin atpase (part of head with ability to bind to and hydrolyze/use ATP

Question 27

Heads can bind to the myosin binding sites on actin, forming a _____ (if binding site is uncovered).

Answer 27

cross-bridge

Question 28

At “rest,” myosin heads have hydrolyzed ______ and are swiveled back into high-energy conformation.

Answer 28

ATP: (holding ADP+Pi)

Question 29

● When ↑[Ca2+], Ca2+ binds to _____.

Answer 29

Troponin

Question 30

________ cycle to actually shorten sarcomere:

Answer 30

Power Stroke

Question 31

Power stroke cycle steps

Answer 31

1. Myosin head binds to actin. 2. Myosin head releases Pi, causes swivel from high-energy to low-energy conformation. -Drags actin—therefore Z-disk—toward M line. 3. Myosin head releases ADP, binds new ATP. 4. ATP binding breaks cross-bridge. 5. Myosin hydrolyzes new ATP, swivels back to high-energy conformation. 6. If Ca2+ still around→go again.

Question 32

To allow relaxation, Ca2+ must get ___from troponin so tropomyosin can cover the myosin binding site again.

Answer 32

away

Question 33

How is Ca+2 cleared from cytosol

Answer 33

Cleared from the cytosol back into the SR by the SR/ER Ca+2 ATPase

Question 34

is used to measure the contraction of a muscle.

Answer 34

Tension

Question 35

2 types of tension:

Answer 35

- Passive and Active Tension

Question 36

Result of stretch in the muscle

Answer 36

Passive tension

Question 37

Actin/Myosin Cross Bridges

Answer 37

Active tension

Question 38

show the tension a muscle can generate at a given, set length.

Answer 38

Length-Tension Curve

Question 39

The length-Tension Curve for passive tension increases as ___ increases

Answer 39

length

Question 40

The active tension a muscle can generate relies entirely on the_____.

Answer 40

number of myosin heads that can bind to actin

Question 41

What kind of overlap length is required for optimal myosin/actin overlap. generate

Answer 41

Medium lengths→optimal myosin/actin overlap→maximum possible | active tension.

Question 42

As length increases, active tension ___, then plateaus at optimal lengths, then ___.

Answer 42

Increases/ decreases

Question 43

is the tension you’d actually measure in a muscle while it’s contracting

Answer 43

Total tension

Question 44

How to calculate total tension

Answer 44

Total Tension= Active Tension + Passive tension

Question 45

—multiple APs→multiple twitches that happen “on top” of each other→a stronger contraction.

Answer 45

Summation

Question 46

A steady, sustained, maximal contraction in a skeletal muscle resulting from many high-frequency APs

Answer 46

Tetanus

Question 47

The “point” of a muscle contraction is to move a _____.

Answer 47

load

Question 48

are those where the muscle’s tension is constant, but its length changes

Answer 48

Isotonic contraction

Question 49

are those when the muscle builds up tension, but its length never changes

Answer 49

Isometric contraction

Question 50

Three different types of skeletal muscle fiber in humans:

Answer 50

types I, IIA, and IIX.

Question 51

CHECK FIGURE AND GRAPH PG.20 and 17

Answer 51

CHECK FIGURE AND GRAPH PG.20 and 17

Question 52

Every muscle has three fiber types-only the __ changes

Answer 52

Ratio

Question 53

How does Myosin ATPase activity and rate of ATP use explain rate of fatigue

Answer 53

↑ATPase activity→↑ATP use→↓Time to ATP depletion→↑Fatigability.

Question 54

Why are smooth muscles ''SMOOTH?''

Answer 54

No real myofibrils or organized sarcomeres-just in actin and myosin scattered around.

Question 55

differences between smooth and skeletal muscle—smooth muscle:

Answer 55

- Doesn’t really fatigue (myosin ATPase is really slow). - Has small, single-nucleated cells - □ Contraction is entirely involuntary—controlled by autonomic nervous system.

Question 56

2 types of smooth muscle?

Answer 56

- Multi unit: Each smooth muscle cell contracts independently - Single Unit: Smooth muscle cells connected to each other by gap junctions (Waves of depolarization = Waves of contraction)

Question 57

smooth muscle excitation-contraction coupling

Answer 57

1. AP activates voltage-gated Ca2+ channels. 2. Ca2+ binds to the Ca2+-sensing protein Calmodulin (CaM) 3. The Ca2+:CaM complex activates an enzyme called Myosin Light Chain Kinase (MLCK) 4. The function of MLCK is to phosphorylate myosin heads (aka the myosin “light chain”). 5. Phosphorylation of myosin heads→↑Myosin ATPase activity→↑Power Strokes and ↑Contraction 6. To relax, must clear Ca2+ from cytosol back into ECF. Done by Na+/Ca2+ Exchanger and Ca2+ ATPase. 7. Myosin Light Chain Phosphatase (MLCP) dephosphorylates myosin heads

Question 58

How is AP generated in the smooth muscle?

Answer 58

- Single-unit smooth muscle: generate APs on their own | - Multi-unit smooth muscle get depolarized via Ca+2 channel activation= increasing Ca+2 cytosol

Question 59

Examples of multi-unit smooth muscle

Answer 59

Eye Iris ( gets AP from autonomic Neurons )

Question 60

How can | smooth muscles generate their own APs

Answer 60

slow-wave depolarization and pacemaker potential

Question 61

Examples of unstable memebrane potential

Answer 61

Slow-wave Depolarization and Pacemaker potential

Question 62

Vm drifts around, sometimes reaching threshold and causing an AP, other times not.

Answer 62

Slow-wave Depolarization

Question 63

- Vm is driven upward consistently, causing APs at consistent intervals

Answer 63

Pacemaker Potentials

Question 64

Factors that effect smooth muscle

Answer 64

- Hormones that activate Gq-coupled receptors—e.g. oxytocin on oxytocin receptors in uterus—cause contraction. - Hormones that activate Gs-coupled receptors—ie. epinephrine on β2 receptors—cause relaxation. - Can happen totally independent of membrane potential changes—just need to activate Ca2+ channels.