10.2 Physiology of skeletal muscle contraction

Question 1

Describe the structure of actin and how G and F actin play a role in this.

Answer 1

G-actin are the needs on the necklace strands. The F-actin strands are the strings of the necklace.

Question 2

define myofilaments

Answer 2

actin and myosin strands

Question 3

sarcomere

Answer 3

Repeating, microscopic, cylindrical units. These are the functional contractile unit of muscle.

Question 4

What are z-disks

Answer 4

perpendicular to the actin and myosin and serve as anchoring points for them.

Question 5

I-band

Answer 5

Parallel to the z-disk and is composed of only thin filaments. I band only visible when the muscle is relaxed. When it contracts, the overlapping myosin filaments overlap the thin filaments and the thin filaments are no longer visible.

Question 6

A-band

Answer 6

central region of a sarcomere that contains the entire thick filament. Thin filaments partially overlap the end of the thick filaments on each end of the A-band.

Question 7

H-band

Answer 7

Most central portion of the A-band where no overlap is occurring and only the myosin filament is visible.

Question 8

M-line

Answer 8

transverse protein network that the myosin filaments attach too. Very center of the A-band.

Question 9

Connectin

Answer 9

Also called titan- thin filament that connects the z-line to the myosin filaments. These are coiled and spring like to allow passive tension when the sarcomere contracts.

Question 10

Dystrophin

Answer 10

Protein complex that anchors myofibrils that are adjacent to the sarcoma to the sarcolema. These also extend to the endomysium that encloses the muscle fiber.

Question 11

What causes muscular dystrophy?

Answer 11

Abnormal formation or numbers of dystrophin.

Question 12

Average number of mitochondria per muscle fiber?

Answer 12

300

Question 13

What else do muscle fibers contain?

Answer 13

Glycogen stores called glycosomes.

Question 14

Myoglobin

Answer 14

Unique to muscular protein. Reddish globular protein. Binds oxygen when the muscle is at rest and releases it during muscle contraction.

Question 15

Creatine phosphate

Answer 15

Provides muscle fibers with a very rapid means of supplying ATP.

Question 16

Somatic neurons

Answer 16

Nerve cells that transmit electrical signals to muscle

Question 17

Motor unit

Answer 17

A single motor neuron and the skeletal muscles it controls.

Question 18

How many neuromuscular junctions do individual muscle fibers have?

Answer 18

1

Question 19

What are the parts of the neuromuscular junction?

Answer 19

Synaptic knob, motor end plate, synaptic cleft.

Question 20

What is the order that vesicles are released from the synaptic knob?

Answer 20

1) Ca2+ pumps establish a concentration gradient with m ore calcium outside the knob that inside it.
2) Electrical signal arrives
3) Voltage gated calcium channels open due to electric signal and allow for an influx of Ca2+.
4) This triggers the exocytosis for vesicles containing ACh.
5) ACh is pushed into the synaptic cleft.

Question 21

Define resting membrane potential (RMP)

Answer 21

The way the cytosol inside the plasma membrane is less positive than the charge in the interstitial fluid outside it.

Question 22

What is the RMP of skeletal muscle fibers?

Answer 22

-90 millivolts. When they depolarize it changes to -65 millivolts.