1,3 Phys muscles

Question 1

SARCOMERE

Answer 1

Functional unit of contraction laid down serially (one after another) in the myofibril, extends from Z line to Z line, have thick and thin filaments

Question 2

Concentric contraction?

Answer 2

Shortening; firing enough motor units to cause shortening

Question 3

Eccentric contraction?

Answer 3

Lengthening; less muscle fibers contracting to let gravity lengthen the muscle in a controlled manner

Question 4

What happens to the I bands, and H zone in a concentric contraction?

Answer 4

decreases

Question 5

What happens in eccentric contraction?

Answer 5

A-band does not change, everything else increases

Question 6

Z-line

Answer 6

Distance from; decreases with shortening contraction; is where the actin MEETS in I band

Question 7

I-band is?

Answer 7

Area from end of thick filament to end of thick filament; see ONLY thin filaments, includes z-line

Question 8

What happens to A-band in contractions?

Answer 8

It does NOT change because the length of the thick filament never changes

Question 9

What is contraction?

Answer 9

Is tension generation due to cross bridge cycling, can be a shortening or lengthening of fibers

Question 10

Thick filaments

Answer 10

Myosin, cross bridge heads with ATP binding site and actin binding sites

Question 11

Thin filaments

Answer 11

Actin, tropomyosin, troponin

*globulin actin creates filamentous chains, two filamentous chains wrap together

Question 12

What does tropomyosin do?

Answer 12

Covers the active sites in actin in relaxed muscles, this is where myosin cross-bridge heads bind

Question 13

What does troponin do?

Answer 13

Regulates the movement of tropomyosin molecules on and off the active sites on actin. It binds calcium

Question 14

What are the 3 binding sites on troponin?

Answer 14

Calcium, tropomyosin and actin

Question 15

What is the calcium binding molecule in skeletal and cardiac muscle?

Answer 15

Troponin

Question 16

What is the calcium binding molecule in smooth muscle?

Answer 16

calmodulin

Question 17

What creates cross-bridges

Answer 17

Thick filaments have cross bridge heads and thin filaments have active sites that cross bridge heads bind onto; thus creating a cross-bridge

Question 18

What is a cross-bridge? How is it involved in contraction?

Answer 18

An anchoring point at which the cross bridge heads on the thick filaments ratchet inward on active sites of thin filaments and pull the Z line to the center; this is a shortening contraction

Question 19

Muscles hierarchy

Answer 19

Muscle – muscle fasciculus – muscle fiber or cell – myofibril – sarcomere

Question 20

What is sarcolemma?

Answer 20

Membrane that covers the muscle, has invaginations (that are continuous with sarcolemma) called the transverse tubules

Question 21

What are the T-tubules?

Answer 21

A membrane going down in, action potential race along the sarcolemma are conducted down via t-tubules

Question 22

Where does the action potential go after sarcolemma?

Answer 22

Down t-tubules, signals transduction, sarcoplasmic reticulum

Question 23

Big function of sarcoplasmic reticulum?

Answer 23

Calcium reservoir (especially during periods of relaxation)

Question 24

How does action potential get from t-tubules to sarcolemma?

Answer 24

Via signal transduction

Question 25

Where does the sarcoplasmic reticulum release Ca?

Answer 25

Into the sarcomere (into cytosol), which then binds troponin, troponin shifts tropomyosin and you can get cross bridge interaction

Question 26

High calcium concentration=

Answer 26

Activated muscle

Question 27

Low cytosolic concentration=

Answer 27

Relaxed muscle

Question 28

Order of events for cross-bridge binding? *MUST KNOW*

Answer 28

1) Low cytosol, relaxed muscles 2) Calcium dumped into cytosol from sarcoplasmic reticulum, activating muscle 3) Ca binds troponin causing, 4) Tropomyosin to shift 5) This opens up actin active sites 6) Myosin heads will now bind to active sites (due to high affinity) 7) Myosin heads ratchet inward pulling the THIN filament

Question 29

Thin or thick filament moves?

Answer 29

thin

Question 30

Events of cross bridge cycling?

Answer 30

1) Binding, engagement of actin 2) Release of ADP and inorganic phosphate; This causes power stroke 3) ATP binds to myosin again, head detaches due to lost affinity 4) ATP hydrolysis again, repeat

Question 31

What causes the power stroke?

Answer 31

The release of ADP and Pi

Question 32

What causes myosin to lose affinity for actin?

Answer 32

Binding of ATP, disengages the active site

Question 33

What are the products of ATP hydrolysis?

Answer 33

ADP and Pi

Question 34

Explain rigor mortis

Answer 34

Soon after death, muscles become rigid because the ATP machinery stops functioning. You need that ATP to stimulate that disengagement of the actin active site

Question 35

Do muscles after death/rigor mortis ever loosen up?

Answer 35

Yes. 24-48 hours after death on temperature bc proteolytic enzymes start breaking up the proteins

Question 36

Motor neuron steps (action potential)

Answer 36

1) Motor neuron action potential 2) Ca enters voltage gated channels 3) Acetylcholine release 4) Na entry 5) Local current between depolarized end plates and adjacent muscle plasma membrane 6) Muscle fiber action potential 7) Propagation action potential in muscle plasma membrane acetylcholine degradation

Question 37

Point of action potential?

Answer 37

To release the neurotransmitter

Question 38

The neurotransmitter in skeletal muscles?

Answer 38

Acetylcholine

Question 39

Nicotinic receptor has the receptor for what to bind?

Answer 39

Acetylcholine

Question 40

What is the motor end plate?

Answer 40

The area of synapse between the motor neuron and skeletal muscle

Question 41

What is found at the motor end plate? They are part of?

Answer 41

Nicotinic receptor that binds acetylcholine, simple translocation channel protein (so when acetylcholine binds, the nicotinic receptor pops open and Na can come in WHICH DEPOLARIZES the area)

Question 42

What is the end plate potential?

Answer 42

The depolarization from Na coming in and acetylcholine leaving the end plate

Question 43

So what happens if the end plate depolarizes enough?

Answer 43

You get action potential that race along the sarcolemma

Question 44

What does acetylcholinesterase do? Released by?

Answer 44

Releases by muscle; Breaks down acetylcholine into an acetate choline so it can no longer stimulate the muscle

Question 45

Signal transduction from t-tubule to sarcoplasmic reticulum?

Answer 45

1) Depolarization of t-tubule 2) Activation of dihydropyridine receptor 3) Activation of ryanodine receptor 4) Opening of Ca channel 5) Release of Ca from SR to cytosol

Question 46

Ryanodine receptor is physically a part of? Does what?

Answer 46

A Ca+ channel protein on the sarcoplasmic reticulum; therefore, it OPENS Ca channel and there is an efflux/free diffusion of Ca

Question 47

***skeletal muscle contraction requires?

Answer 47

Neural stimulation!

Question 48

SIDENOTE: In cardiovascular your must have what SPECIFIC order?

Answer 48

1) Membrane depolarization leading to 2) Muscle contraction leading to 3) Pressure generation leading to 4) Blood ejection

Question 49

Nicotinic acetylcholine receptors are _____ gated receptors?

Answer 49

ligand

Question 50

Myastenia gravis is?

Answer 50

An autoimmune disorder in which the body’s immune system recognizes proteins that make up the acetylcholine-gated receptor complex as foreign, thus initiating an immunological attack on those proteins

Question 51

Myastenia gravis results in loss of?

Answer 51

oss of Ach-gated receptors and nerve to muscle signaling ability; leads to muscle weakness

Question 52

Myastenia gravis treatment?

Answer 52

Anti-acetylcholinesterase drugs

Question 53

H zone

Answer 53

Subdivision of A band where there is ONLY thick myosin

Question 54

I band

Answer 54

Thin (actin) only, lighter area

Question 55

A band

Answer 55

Actin and myosin area of overlap (BOTH thin and thick filaments). Does not shrink during contraction

Question 56

How do you remember Actin is thin?

Answer 56

actIN thIN = I band