Chapter 1

Question 1

What is the layer of connective tissue that surrounds skeletal muscle called?

Answer 1

epimysium

Question 2

What is a fasciculus or fascicle?

Answer 2

a bundle of muscle fibers

Question 3

What is the connective tissue that surrounds each fasciculus called?

Answer 3

perimysium

Question 4

What is the primary function of the sarcolemma?

Answer 4

It is the plasma membrane of the muscle fiber that 1. encloses the contents of the cell 2. regulates the passage of materials glucose in and out of the cell 3. receives and conducts stimuli in the form of electrical impulses (action potential).

Question 5

Where is the muscle cell’s energy stored?

Answer 5

Energy sources such as ATP, phosphocreatine, glycogen, and fat droplets are stored in the muscle’s cytoplasm (i.e., sarcoplasm).

Question 6

What is the function of the sarcoplasmic reticulum?

Answer 6

it stores calcium and regulates the muscle contractions process by altering the intracellular calcium concentration.

Question 7

What are t-tubules?

Answer 7

the means by which the sarcoplasmic reticulum releases calcium into a muscle after an action potential passes through the interior of the cell.

Question 8

What is the columnar protein structures that runs parallel to the muscle fiber that is a bundle of myofilaments called?

Answer 8

myofibrils

Question 9

Is myosin a thick or thin myofilament?

Answer 9

thick

Question 10

Is actin a thick or thin myofilament?

Answer 10

thin

Question 11

When does eccentric muscle action occur?

Answer 11

When the force of the outside weight is greater than that of the muscle, making the muscle lengthen.

Question 12

What is the function of the protein structures tropomyosin and troponin in the actin filament?

Answer 12

they regulate the interaction of myosin and actin, the contractile proteins

Question 13

What does tropomyosin do?

Answer 13

When the muscle cell is at rest, tropomyosin lies over the myosin binding sites on actin.

Question 14

What does troponin do?

Answer 14

As each end of the tropomyosin filament is is attached to troponin, the troponin causes the tropomyosin filaments to move when it binds with calcium.

Question 15

What is a neuromuscular junction?

Answer 15

the place where a muscle fiber receives a stimulus from the nervous system.

Question 16

What is an action potential?

Answer 16

an electrical impulse that serves as a stimuli for muscles action

Question 17

What is ATPase and what does it do?

Answer 17

adenosine triphosphatase, an enzyme that causes the splitting of ATP mpolecules

Question 18

What does the sliding filament theory state?

Answer 18

A muscle shortens or lengthens because the actin and myosin filaments slide past each other, without the filaments themselves changing length.

Question 19

What is the series of events that occurs during muscle action?

Answer 19

1. Neuron action potential arrives at end of motor neuron leading to the release of acetylcholine (ACh).
2. ACh migrates across synaptic cleft and binds with receptors on the motor endplate of the muscle fiber.
3. This leads to generation of an action potential along the sarcolemma pf the muscle fiber. Also, the movement of action potential down the t-tubules triggers the release of calcium from the endoplasmic reticulum.
4. Once released into the sarcoplasm, the calcium migrates to the and binds with troponin molecules along the length of the actin filaments.
5. The binding of calcium to troponin causes a conformational change in the shape of the troponin. Because myosin is attached to troponin , this move troponin such that binding sites on actin are exposed to the myosin head.