Leslie - Physiology - Valentine: Skeletal, Cardiac And Smooth Muscle

Front 1

How is skeletal muscle involved in metabolic function?

Back 1

- body temperature
- interacting with thyroid hormone
- involvement in glucose metabolism

Front 2

How is it best to understand the functional attributes of muscles?

Back 2

Include the gross architecture of the entire muscle, the microscopic features of the cells that make up the muscle, and the biochemical makeup of the muscle fibers.

Front 3

In this picture locate the Z and M lines and the A, I and H bands, mitochondria and granular glycogen in the sarcoplasm.

Back 3

From Valentine's notes:
In this ultrastructural photograph you can see portions of two skeletal muscle fibers with a fibroblast in between. The fibroblasts are the cells that produce the interstitial collagen. In this photograph you should be able to identify the Z and M lines and the A, I, and H bands. Mitochondria and granular glycogen can also be seen within the sarcoplasm. Be sure that you can identify these structures.

Front 4

What would happen to a muscle cell with dysfunctional mitochondria or with no glycogen?

Back 4

Both come down to oxidative phosphorylation - no mitos, no oxidative phosphorylation; no glycogen, no glucose to feed Kreb's cycle to feed oxidative phosphorylation.

Front 5

What are terminal cisternae extensions of?

Back 5

The sarcoplasmic reticulum.

Front 6

What are the T-tubules an extension of?

Back 6

The sarcolemma, but they are linked to the SR through a slow release Ca channel activating the ryanodine receptor at the triad.

Front 7

Where is Ca stored in skeletal muscle?

Back 7

The terminal cisternae (extensions of the SR)

Front 8

What does the SR regulate?

Back 8

Ionized Ca release and uptake.

Front 9

Where is Ca stored in skeletal muscle?

Back 9

The terminal cisternae

Front 10

T/F the slow Ca channel in skeletal muscle is involved in generation of the action potential?

Back 10

F. It is involved in activating the ryanodine receptor through a channel conformational change. This change causes release of Ca from SR terminal cisternae into the sarcoplasm and contraction of the myofibrils.

Front 11

What would abnormalities in the ryanodine receptor of skeletal muscle cause?

Back 11

Malignant hyperthermia, as the activation of excitation-contraction coupling would be unregulated. This leads to excessive muscle contraction and heat generation.

Front 12

Be sure that you understand the series of electrical and molecular events that are involved in muscle contraction and relaxation. Identify the myosin and actin filaments, the A and I bands, and the Z line in the diagram.

Back 12

Diagrammatic representation of excitation-contraction coupling in normal skeletal muscle. Action potentials (AP) generated by nerves are propagated along the sarcolemma to the t-tubule and travel down the t-tubule; depolarization of the t-tubules activates the slow calcium channels at the triads that interact, through a protein-protein interaction mechanism, with the ryanodine receptors within the membrane of the terminal cisternae of the sarcoplasmic reticulum (SR). This causes release of calcium from the SR into the sarcoplasm and results in contraction of the myofibrils.

Front 13

Are the Ca ions that enter the cell through the protein-protein interaction involved in the action potential activity?

Back 13

No, blocking the calcium channel activity of these structures does not interfere with excitation contraction coupling. It is the protein-protein interaction with the ryanodine receptor that is important.

Front 14

The numbers in this diagram are in sequence. Name the steps

Back 14

(1) opening of presynaptic voltage-gated calcium channels as a result of a decrease in membrane potential, (2) calcium activated fusion of synaptic vesicles to the nerve terminal membrane and release of acetylcholine (ACh), (3) binding of ACh to ACh receptors causing influx of sodium ions into the muscle cell and generation of a muscle membrane action potential, (4) muscle membrane action potential activated opening of muscle membrane voltage gated sodium channels resulting in propogation of the action potential, and (5) opening of voltage gated calcium channels in the transverse tubules leading to ryanodine receptor activation on the membrane of the terminal cisternae of the sarcoplasmic reticulum, and release of stored calcium into the sarcoplasm to result in actin/myosin interaction and contraction.

Front 15

How would hypocalcemia effect skeletal muscle?

Back 15

The ability of the T tubules and sarcoplasmic reticulum at the triads to regulate the cycling of calcium ions into and out of the sarcoplasmic reticulum is critical for the muscle to exhibit sustained or repeated contraction and to allow relaxation. Calcium plays a vital role in this process, and alterations of available calcium ions can result in severe skeletal muscle dysfunction. A common example of this occurs in dairy cattle with “milk fever” in which hypocalcemia (lowered blood calcium) results in severe muscle weakness and the animal becomes recumbant. Therapy with intravenous calcium-containing solutions can result in rapid recovery.

Front 16

How do gradations in the force of muscle contractions occur?

Back 16

AP's spread from the neuromuscular junction to initiate all or nothing contractions. To vary the force of the muscle contractions, you vary the number of recruited fibers.

Front 17

Which type of muscle are high in mitochondria and fat content and low in glycogen content.

Back 17

Type 1, slow-twitch

pOstural, slow (One, pOstural, slOw, Oxidative, mitOchondrial plethora)

Front 18

Which muscle type is oxidative, fatigue resistant and aerobic?

Back 18

Type 1, slow-twitch

pOstural, slow (One, pOstural, slOw, Oxidative, mitOchondrial plethora)

Front 19

Describe type 2A muscles

Back 19

Fast twitch, oxidative and glycolytic, fatigue resistant.

Front 20

Which muscle type has intermediate numbers of mitochondria, fat and glycogen content?

Back 20

Type 2A Fast-Twitch

Front 21

T/F Muscle type 2A can be described as fast-twitch, glycolytic, fatigue sensitive, and anaerobic.

Back 21

False, 2B Fast-twitch is the anaerobic muscle. It has low mitochondrial numbers and fat content. It also has high glycogen content.

Front 22

What do denervated muscle cells undergo?

Back 22

Atrophy.

Front 23

Will exercise result in increased fiber numbers?

Back 23

No, but it will result in increased fiber diameter.

Front 24

What is the mosaic pattern? What do alterations to the pattern indicate?

Back 24

the intermingling of the type 1 (light staining) and type 2 (dark staining) fibers. Alterations of this normal mosaic pattern are often due to pathologic conditions that affect the muscle’s innervation.

Front 25

What is a motor unit?

Back 25

The group of muscle fibers innervated by a single nerve is called the motor unit.

Front 26

What is the signifigance of the size of motor units?

Back 26

The size of motor units also influences the type of movement the muscle is capable of performing. For example, extraocular muscles have many nerves, each innervating a small number of fibers. This allows for fine movements of the globe. In contrast, the quadriceps muscle has fewer nerves innervating a larger number of fibers, which allows for maximum strength of contraction without as much fine motor control.

Front 27

These are all possible arrangements of skeletal muscle fibers within muscles. Name them.

Back 27

In order from left to right:
Parallel, Fusiform, Unipennate, Bipennate, Multipennate

Front 28

How does the contraction of cardiac muscles differ from the contraction of skeletal muscle?

Back 28

Cardiac myocytes contain T tubules and sarcoplasmic reticulum similar to skeletal muscle fibers, but the sarcoplasmic reticulum is less well-developed.

They have intercalated disks for the transmissal of the contractile impulses.

They have inherent rhythmicity.

Front 29

What are the two purposes of intercalated disks?

Back 29

1. Firmly bind adjacent cells together to prevent separation in contraction.

2. Provide areas for communication of the impulses for contraction.

Front 30

What are the Z-bands of smooth muscle?

Back 30

The intermediate, actin and myosin filament structures interacting.

It has been suggested that the contractile force developed by the sliding contractile filaments is transmitted to the intermediate filament harness causing shortening of the long axis of the fiber.

Front 31

How do smooth muscle depolarizations initiate?

Back 31

Spontaneous membrane depolarization, circulating hormones, local environments (like pH), quick muscle stretch (like when you swallow too much and can feel it getting squeezed down).

Front 32

How do smooth muscle stimulations propagate?

Back 32

Cell to cell through gap junctions.

Front 33

T/F Smooth muscle cells have pacemakers.

Back 33

True, though not like in the heart. Areas of high neurotransmittor content may act as “pacemakers” to control the force and direction of peristalsis.

Front 34

Is there sarcoplasmic reticulum in smooth muscle?

Back 34

It is poorly developed.

Front 35

Are there T-tubules in smooth muscle?

Back 35

No.

Front 36

Compare and contrast the biochemistry of smooth muscle contraction to skeletal muscle contraction. Start with Ca.

Back 36

Smooth muscle contraction also involves calcium, but the biochemical events are different than those occurring in skeletal muscle contraction. Smooth muscle does not contain the molecule troponin that is so important in initiating contraction of skeletal muscle. Instead, calmodulin and inositol triphosphate are thought to play major roles in excitation-contraction coupling in smooth muscle.

Front 37

What type of muscle (smooth, cardiac, or skeletal) has the longest contraction?

Back 37

Smooth. The cycling time for the formation and release of cross bridges between actin and myosin and subsequent release is much longer in smooth muscle than in skeletal muscle

Front 38

What type of muscle (smooth, cardiac, or skeletal) contraction requires the least amount of ATP?

Back 38

Smooth.

Front 39

What type of muscle (smooth, cardiac, or skeletal) is capable of a graded contraction, rather than all or none?

Back 39

Smooth

Front 40

Did you know that there are undifferentiated cells in skeletal muscle that are available to be made into myocytes when repair is necessary?

Back 40

It's true. They are called satellite cells and they can re-establish skeletal muscle.

Smooth muscle can divide and repair on its own. Cardiac muscle can't.