Muscles (Smith) week 1

Question 1

Skeletal muscle characteristics

Answer 1

Single, very long, cylindrical, multinucleate,

obvious striations, voluntary, not self stimulating, high energy requirement, fast contrating

Question 2

Cardiac muscle characterisitcs

Answer 2

branching chains of cells,uninucleate, striation, Involuntary, self stimulating, under control of nervous and endocrine system intermediate energy requirement, intermediate speed of contraction

Question 3

Smooth muscle charateristics

Answer 3

Single cells, fusiform, uninucleate, with no striations, self stimulating, under control of nervous and endocrine systems, lower energy requirement, slow rhythmic contractions

Question 4

Motor unit

Answer 4

functional unit of the muscle and is composted of the alpha motor neuron and all the muscle cells in innervates

Question 5

Site of motor unit inntervation

Answer 5

neuromuscular junction (NMJ)

Question 6

T/F: Each alpha motor neuron’s axon branch and synapse with up to thousands of different muscle fibers?

Answer 6

True

Question 7

T/F Each individual muscle fiber is connected to only on neuron?

Answer 7

True

Question 8

What is the sarcoplasmic reticulum (SR)?

Answer 8

intrancellular organelle that stores and releases calcium ions

Question 9

Terminal cisternae

Answer 9

the enlarged portion of the SR nearest the t-tubules

Question 10

Calcium is released from the SR via channels called?

Answer 10

ryanodine receptors (RyRs)

Question 11

Transverse or T- tubules

Answer 11

• smaller tube like structures that run perpendicular to the sarcolemma.
• action potentials travel down the T-tubules during excitation-contraction coupling.

Question 12

Sarcomere

Answer 12

extends from one Z-disc to the other

functional unit of muscle cell

Question 13

A-band

Answer 13

myosin containing band, dark in color

Question 14

I-band

Answer 14

the lighter band, and includes the Z-disc and the actin filaments
shortens during contraction

Question 15

H-zone

Answer 15

center of the A-band, where acting and myosin DO NOT over lap, M-line is in center of H-zone
shortens during contraction

Question 16

M-line

Answer 16

in center of H-zone and accessory proteins anchor myosin the M-line

Question 17

Titins

Answer 17

anchor thick filaments to Z-discs and runs with the thick filaments to the M-line

• holds myosin in place
• helps muscle spring back into shape

Question 18

T/F: myosin and actin change length during contraction

Answer 18

FALSE

Question 19

Tropomyosin

Answer 19

blocks binding site on myosin, moves in high concentrations of Calcium

Question 20

troponin

Answer 20

troponin binds to calcium and shifts and moves the tropomyosin to allow binding of acting to myosin.
-ON ACTIN

Question 21

Excitation-contraction coupling

Answer 21

the physiological process of converting an electrical stimulus (AP) to a mechanical response (contraction) and the NMJ

Question 22

Cause of striations in skeletal and cardiac muscles

Answer 22

intercalated disks and fused together via desmosomes

in cardiac there are gap junctions to allow the electric impulse to propagate

Question 23

Cardiac muscles unique characteristics

Answer 23

• no external innervation needed
• almost exclusive aerobic respiration
• Large mitochondria
• High myoglobin content hence the dark color of the heart

Question 24

Smooth muscle unique characteristics movement

Answer 24

actin fibers attached to cell wall and dense body in the cytoplasm. When activated the actin fibers slide over myosin bundles and cause the walls to shorten, crinkle the cell

• No troponin
• relaxation of smooth muscle does not always happen when Calcium levels decrease
• Have few mitochondria