Muscles

Question 1

What is the difference in location of the T system between cardiac and skeletal muscle?

Answer 1

Cardiac; T system located at Z lines

Skeletal: Ty system located at A and I junctions

Question 2

What is the difference in action potential between cardiac non-pacemaker and pacemaker cells?

Answer 2

Non-pacemaker; have a plateau phase during repolarization due to prolonged release of Calcium
Pacemaker; don’t have a plateau phase

Question 3

What are the 3 types of muscle fibers in skeletal muscles?

Answer 3

Type I, Type IIA, Type IIB

Question 4

What is a secondary source of energy for muscles?

Answer 4

Phosphorylcreatinine

Question 5

Which type of skeletal muscle fiber shows a high oxidative capacity?

Answer 5

The slow oxidative or type 1 fibers

Question 6

What is the composition of a sarcotubular system?

Answer 6

1. T system; made of transverse tubules which are extensions of cell membrane
2. Sarcoplasmic reticulum

Question 7

Define sarcolema

Answer 7

The plasma membrane of a muscle fiber cell

Question 8

What is the role of the sarcoplasmic reticulum?

Answer 8

Storage of Ca2+ ions

Question 9

At which point on the muscle fiber does the sarcoplasmic reticulum come into contact with the
T tubules?

Answer 9

at juntion of Dark (A) and Light (I) bands

Question 10

Why is the Sarcotubular system called a triad?

Answer 10

Composed of a T system surrounded on either side by cisternae of sarcoplasmic reticulume

Question 11

Explain the significance of the distrophin-glycoprotein complex.

Answer 11

Provides a scaffold for myofibrils

Anchors myofibrils to ECM

Question 12

What are the 2 main types of muscle receptors that communicate to the CNS?

Answer 12

Muscle spindles/Stretch receptors

Golgi tendon organs

Question 13

Which type of sensory receptor detects the length of skeletal muscle?

Answer 13

Muscle spindles/Stretch receptors

Question 14

Why, unlike skeletal and cardiac muscle, do smooth muscles have no striations?

Answer 14

Their filaments not arranged in sarcomeres. They are still parallel, but they run obliquely in different directions.

Question 15

Which molecule found in skeletal muscle is not found in smooth muscle?

Answer 15

Tropomyosin

Question 16

Dystrophin connects a)______ filaments to b)_________ transmembrane proteins.

Answer 16

Dystrophin connects ACTIN filaments to BETA-DYSTROGLYCAN transmembrane proteins.

Question 17

How is Beta-dystroglycan connected to the ECM?

Answer 17

By meisoin, it is connected to alpha dystroglycan

Question 18

What two types of transmembrane proteins are dystrophins associated with?

Answer 18

Dystroglycans

Sarcoglycans

Question 19

The dystrophin-glycoprotein complex is formed by which two molecules?

Answer 19

Dystrophin

Sarcoglycans

Question 20

What are the consequences of disruption to the dystrophin-glycoprotein complex?

Answer 20

Duchenne muscular dystrophy

Becker Muscular dystrophy

Question 21

Compare and contrast Duchenne and Becker Muscular dystrophy.

Answer 21

Similarities

• muscle weakness and eventual failure
• x-linked recessive conditions

Differences

• Duchenne’s is more extreme
• In Becker’s, symptoms appear later and progress at a slower rate

Question 22

What type of calcium voltage-gated receptors on the sarcoplasmic reticulum open upon dipolarization of the T tubules?

Answer 22

Dehydropyridine

Question 23

What is Calcineurin?

Answer 23

A protein activated by Calcium-Calmodulin complex that deactivates Calcium channels by dephosphorylating them

Question 24

State 3 ways Calcium is removed from the cytosol.

Answer 24

1. Pumped back into sarcoplasmic reticulum by ATP-dependent Calcium pumps
2. Pumped out of cell via ATP dependent pumps or Sodium-Calcium exchangers
3. Sequestered with other proteins in the cell

Question 25

What is a concentric isotonic contraction?

Answer 25

In which muscle length shortens and joint angle reduces