Catos Exam 2 Muscle Physiology I

Front 1

What are the two distinct features of muscle cells?

Back 1

Membranes are excitable
Capeable of actively shortening

Front 2

What are the distinct features of skeletal muscle cells?

Back 2

Very Long and transverse striations, multinucleated w/ nuclei located peripherally.

Front 3

What is the sarcoplasmic reticulum?

Back 3

Paired sac-like structure, called terminal cisternae,

Front 4

What is the fuction of the SR?

Back 4

Storage, release and sequestration of Calcium.

Front 5

What is the sarcomere? How long is it, at rest?

Back 5

Region from one z line to the next.
2.25 micrometers

Front 6

Explain the cleavage of myosin in regards to trypsin and pepsin.

Back 6

trypsin cleaves at the "elbow" separating the myosin into light chain rod and a heavy chain w/ a head group.
Pepsin cleaves the myosin into the S1 head region and the s2 projecting rod

Front 7

Is the light chain covalently linked to the myosin?

Back 7

No, but it may help regulate myosin.

Front 8

What is tropomyosin and its significance?

Back 8

It is a rod-like structure of two peptids in a helix. It binds to troponin, calcium binding to troponin causes a conformation change of troponin to move tropomyosin "off" the actin binding sites.

Front 9

What is the significance of the troponin TnI?

Back 9

It binds to actin in the I band.

Front 10

At rest, low cytoplasmic Ca, ATP is bound to the myosin head group and split to ADP and Pi. Sig?

Back 10

This drastically increases myosins affinity for actin.

Front 11

What is the cause of rigor mortis?

Back 11

ATP is required for myosin's release of actin after the power stroke.

Front 12

Why causes the hydrolysis of ATP?

Back 12

ATP synthase located on the myosin head.

Front 13

The power stroke, myosin sliding of actin from either side occurs when?

Back 13

As ADP and Pi are released.

Front 14

What are the terms in regards to muscle from whole muscle to myofilaments. (6)

Back 14

Whole muscle, Fasciculus, Muscle Fiber, Myofibrils, Sarcomere, Myofilaments

Front 15

Define isometric contraction

Back 15

Muscle generates max tension but does not shorten.

Front 16

Define isotonic contraction

Back 16

Muscle tension is constant while shortening.

Front 17

Define twitch

Back 17

Unit contractile response of skeletal muscle.
1. Action Pot
2. Latency (tension rises and peaks)
3. Relaxes

Front 18

Describe the tetnus length tension curve.

Back 18

Tetnus ooccurs as the frequency of stimulation increases, the responses begin to sum, and eventually there is no relaxtion at all...resulting in a smooth curve.

Front 19

Define temporal & spatial summation.

Back 19

Temporal- vary frequency of nerve impulses.
Spatial- increase number of fibers stimulated simultaneously.

Front 20

Describe a length tension curve.

Back 20

Actively generated tension to length.
Passive tension is generated w/ strech as overlap decreases. (Cardiac muscle always has passive tension.)

Front 21

What makes up a motor unit?

Back 21

A motor neuron and the muscle fibers it innervates.

Front 22

How are muscle fibers formed?

Back 22

Single muscle cells called myocytes fuse to form the larger cells. This is the reason skeletal muscle cells are multinucleated.

Front 23

Sarcolemma

Back 23

Cell membrane of a muscle cell.

Front 24

What is a myofibril?

Back 24

Small cylindrical intracellular units which contain the basic contractile machinery

Front 25

What is inbtwn myofibrils?

Back 25

Mitochondria, other organelles, and the SR

Front 26

How many myosin monomers make up a thick fillament?

Back 26

Many, self-assemble and have regular projections called crossbridges.

Front 27

What is it about the "elbow and wrist" region of myosin that allows it to be cleaved by enzymes?

Back 27

Here, the myosin is less tightly intertwined.

Front 28

What must happen for F-actin to polymerize?

Back 28

ADP must be bound to each G-actin.

Front 29

What is the arrangement of thin and thick filaments in sk muscle?

Back 29

6 thin filaments arranged around each thick filament.

Front 30

The maximum tension that can be generated is proportional to the number of:

Back 30

crossbridges formed. And will therefore fall w/ stretch.

Front 31

What is the significance of a sarcomere measuring 2.25um?

Back 31

This is its resting lenght and also is allowing the maximum interaction btwn thin and thick filaments, w/o them getting in each others way.

Front 32

What is the end plate?

Back 32

The synaptic region of the muscle membrane, where Ach receptors are located. (after it is released from a depolarized nerve ending and traverses the synaptic cleft.) The end plate itself is not excitable.

Front 33

What are the two major differences in action potentials in muscles vs nerves?

Back 33

1. Repolarization is much slower (due to delayed rectifying K channel)
2. It has a prolonged depolarized tail (due to the accumulation of K in the t-tubules

Front 34

Where are t-tubules located?

Back 34

At the z line (A/I Jx)

Front 35

The membranes of t-tubules are excitable and the tts serves to spread the action pot from the surface..

Back 35

deep into the fiber

Front 36

What make up the sarcoplasmic reticulum?

Back 36

Fenestrated collar, lateral sacs and terminal cisternae.

Front 37

What is a triad?

Back 37

Terminal cisterna on either side with t tubule running down the center.

Front 38

Upon stimulation Ca is released into the cytoplasm where it can:

Back 38

Bind to troponin and initiate contraction. When stimulation ceases, the lateral sacs and fenestrated collar can re-squester Ca and move it back to the terminal cisternae (conc due to binding to calsequestrin in terminal cisternae)
Ca sequestration into the SR is mediated by a transport protein in the SR membrane, a calcium ATPase (the Ca pump)

Front 39

The t-tubular membrane has been shown to contain globular proteins dihydropyridine receptors. What is thier significance?

Back 39

Upon depolarization, they deform, causing the Ca release channels to open, allowing the release of Ca from the SR. They close upon repolarization.

Front 40

Excitation

Back 40

surface mem depolarization
depolarization of t-tubules

Front 41

excitation contraction coupling

Back 41

transmission of signal to SR
CRC release Ca

Front 42

Contration

Back 42

short range diffusion resulting in crossbridge formation

Front 43

relaxation

Back 43

SR reaccumulates Ca via active transport (ca pumps) until sarcoplasmic ca is below threshhold