Chapter 11: Muscular Tissue

Question 1

3 types of muscular tissue

Answer 1

Skeletal, Cardiac, Smooth

Question 2

Excitability (responsiveness)

Answer 2

chemical signals, stretch, and electrical changes across the plasma membrane

Question 3

Conductivity

Answer 3

Local electrical excitation sets off a wave of excitation that travels along the muscle fiber

Question 4

Contractility

Answer 4

Shortens when stimulated

Question 5

Extensibility

Answer 5

Capable of being stretched between contractions

Question 6

Elasticity

Answer 6

Returns to its original rest length after being stretched

Question 7

Myofiber

Answer 7

Muscle cell/Muscle Fiber as long as 30 cm

Question 8

Connective tissue wrappings

Answer 8

Endomysium: connective tissue around muscle cell
Perimysium: connective tissue around muscle fascicle
Epimysium: connective tissue surrounding entire muscle

Question 9

Collagen

Answer 9

Stretches slightly under tension and recoils when released
Resists excessive stretching and protects muscle from injury
Returns muscle to its resting length
Contributes to power output and muscle efficiency

Question 10

Sarcolemma

Answer 10

Plasma membrane of a muscle fiber

Question 11

Sarcoplasm

Answer 11

Cytoplasm of a muscle fiber

Question 12

Myofibrils

Answer 12

long protein cords occupying most of sarcoplasm

Question 13

Glycogen

Answer 13

carbohydrate stored to provide energy for exercise

Question 14

Myoglobin

Answer 14

red pigment; provides some oxygen needed for muscle activity

Question 15

Myoblasts

Answer 15

stem cells that fused to form each muscle fiber early in development

Question 16

Satellite Cells

Answer 16

unspecialized myoblasts remaining between the muscle fiber and endomysium

Question 17

Sarcoplasmic Reticulum

Answer 17

Forms network around each myofibril. Acts as a calcium reservoir; it releases calcium through channels to activate contraction

Question 18

Thick Filaments

Answer 18

Made of several hundred myosin molecules. Double myosin head shaped like golf clubs.

Question 19

Thin Filaments

Answer 19

Two intertwined strands of fibrous actin.
String of globular (G) actin subunits each with an active site that can bind to head of myosin molecule
Tropomyosin blocks active sites on G (actin)
Troponin molecule: small, calcium-binding protein on each tropomyosin molecule

Question 20

Elastic Filaments

Answer 20

Titin: huge, springy protein
Run through core of thin filament and anchor it to Z disc and M line
Help stabilize and position the thick filament
Prevent overstretching and provide recoil

Question 21

Contractile Proteins

Answer 21

myosin and actin do the work of contraction

Question 22

Regulatory Proteins

Answer 22

tropomyosin and troponin
Act like a switch that determines when fiber can (and cannot) contract
Contraction activated by release of calcium into sarcoplasm and its binding to troponin
Troponin changes shape and moves tropomyosin off the active sites on actin

Question 23

Dystrophin

Answer 23

clinically important protein
Links actin in outermost myofilaments to membrane proteins that link to endomysium
Transfers forces of muscle contraction to connective tissue ultimately leading to tendon
Genetic defects in dystrophin produce disabling disease muscular dystrophy

Question 24

A-Band (Dark)

Answer 24

“A” stands for anisotropic
Darkest part is where thick filaments overlap a hexagonal array of thin filaments
H band: not as dark; middle of A band; thick filaments only
M line: middle of H band

Question 25

I-Band (Light)

Answer 25

“I” stands for isotropic The way the bands reflect polarized light Z disc: provides anchorage for thin filaments and elastic filaments Bisects I band

Question 26

Sarcomere

Answer 26

segment from Z disc to Z disc | Functional contractile unit of muscle fiber

Question 27

Somatic Motor Neurons

Answer 27

Nerve cells whose cell bodies are in the brainstem and spinal cord that serve skeletal muscles

Question 28

Somatic Motor Fibers

Answer 28

their axons that lead to the skeletal muscle

Question 29

Motor Unit

Answer 29

one nerve fiber and all the muscle fibers innervated by it. Average motor unit contains 200 myofibrils

Question 30

Resting Membrane Potential

Answer 30

about −90 mV in skeletal muscle cells | Maintained by sodium–potassium pump

Question 31

ECF

Answer 31

Excess Na+

Question 32

ICF

Answer 32

Excess K+

Question 33

Excitation

Answer 33

Process in which nerve action potentials lead to muscle action potentials

Question 34

Excitation- Contraction Coupling

Answer 34

Events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them to contract

Question 35

Contraction

Answer 35

Step in which the muscle fiber develops tension and may shorten

Question 36

Relaxation

Answer 36

When stimulation ends, a muscle fiber relaxes and returns to its resting length