Chapter 50.5

Question 1

What is muscle activity

Answer 1

a response to nervous system input

Question 2

What is required for muscle function

Answer 2

protein filaments physically interacting

Question 3

What does muscle cell contraction rely on?

Answer 3

thin filaments and thick filaments interacting

Question 4

thin filaments

Answer 4

actin

Question 5

thick filaments

Answer 5

staggered arrays of myosin

Question 6

moves bones and the body

Answer 6

vertebrate skeletal muscles

Question 7

characterized by a hierarchy of smaller and smaller units

Answer 7

skeletal muscle

Question 8

consists of a bundle of long fibers, each a single cell, running parallel to the length of the muscle

Answer 8

skeletal muscle

Question 9

What is each muscle fiber itself

Answer 9

a bundle of smaller myofibrils arranged longitudinally

Question 10

Why is skeletal muscle also called striated muscle

Answer 10

How the myofilaments are arranged creates a pattern of light and dark bands

Question 11

the functional unit of a muscle

Answer 11

sarcomere

Question 12

what is sarcomere bordered by

Answer 12

Z lines

Question 13

Z lines

Answer 13

where thin filaments attach

Question 14

thin and thick filaments slide past each other longitudinally, what are they powered by?

Answer 14

myosin molecules

Question 15

What does the sliding of filaments rely on

Answer 15

interaction between actin and myosin

Question 16

What does muscle contraction require

Answer 16

repeated cycles of binding and release

Question 17

what does the “head” of a myosin molecule

Answer 17

binds to an actin filament

Question 18

What does the binding of the actin filament and the head of a myosin molecule form

Answer 18

a cross-bridge (and pulls the thin filament toward the center of the sarcomere

Question 19

what two things generage the ATP needed to sustain muscle c ontraction

Answer 19

glycolysis and aerobic respiration

Question 20

regulatory protein that binds to actin strands on thin filaments when a muscle fiber is at rest

Answer 20

tropomyosin and the troponin complex

Question 21

What does the binding of tropomyosin and actin strands prevent

Answer 21

actin and myosin from interacting

Question 22

What must be true for a muscle fiber to contract

Answer 22

myosin-binding sites have to be uncovered

Question 23

how do myosin-binding sites become uncovered

Answer 23

when calcium ions bind to the troponin complex and expose the myosin-binding sites

Question 24

When does contraction occur?

Answer 24

when there’s a high concentration of Ca2+

Question 25

When does muscle fiber contraction stop

Answer 25

when the concentration of Ca2+ is low

Question 26

what is the stimulus leading to contraction of a muscle fiber

Answer 26

an action potential in a motor neuron that makes a synapse with the muscle fiber

Question 27

What does the synaptic terminal of the motor neuron release

Answer 27

the neurotransmitter acetylcholine

Question 28

what occurs when acetylcholine depolarizes the muscle

Answer 28

it produces an action potential

Question 29

How do action potentials travel to the interior of the muscle fiber?

Answer 29

along transvers (T) tubules

Question 30

what does the action potential along T tubules cause

Answer 30

sarcoplasmic reticulum (SR) to release Ca2+

Question 31

a specialized endoplasmic reticulum

Answer 31

sarcoplasmic reticulum

Question 32

binds to the troponin comlex on the thin filaments

Answer 32

Ca2+

Question 33

what does the binding of Ca2+ to the troponin complex do

Answer 33

exposes myosin-binding sites and allows the cross-bridge cycle to proceed

Question 34

What happens when motor neuron input stops

Answer 34

the muscle cell relaxes

Question 35

What do transport proteins in the SR do

Answer 35

pump Ca2+ out of the cytosol

Question 36

What do regulatory proteins bound to thin filaments do

Answer 36

shift back to the myosin-binding sites

Question 37

interferes with the excitation of skeletal muscle fibers

Answer 37

amyotrophic lateral sclerosis (ALS)

Question 38

an autoimmune disease that attacks acetylcholine receptors on muscle fibers

Answer 38

myasthenia gravis

Question 39

What does "contraction of a whole muscle is graded" mean

Answer 39

the extent and strength of its contraction can be voluntarily altered

Question 40

Two basic mechanisms by which the nervous system produces graded contractions

Answer 40

1. varying the number of fibers that contract | 2. varying the rate at which fibers are stimulated

Question 41

although each fiber is controlled by only one motor neuron, what could occur?

Answer 41

each motor neuron may synapse with multiple muscle fibers

Question 42

consists of a single motor neuron and all the muscle fibers it controls

Answer 42

a motor unit

Question 43

What does the strength of the resulting contraction depend on

Answer 43

how many muscle fibers the motor neuron controls

Question 44

how many motor units may be in the whole muscle

Answer 44

hundreds

Question 45

what does recruitment of multiple motor neurons result in

Answer 45

stronger contractions

Question 46

what does a twitch result from

Answer 46

a single action potential in a motor neuron

Question 47

what do more rapidly delivered action potentials produce

Answer 47

a graded contraction by summation

Question 48

a state of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials

Answer 48

tetanus

Question 49

There are several distinct types of skeletal muscles, each of which...

Answer 49

is adapted to a particular function

Question 50

what are skeletal muscles classified by

Answer 50

either the source of ATP powering the muscle activity or the speed of muscle contraction

Question 51

what do oxidative fibers rely mostly on to generage ATP

Answer 51

aerobic respiration

Question 52

What do oxidative fibers have

Answer 52

1. many mitochondria 2. a rich blood supply 3. a large amount of myoglobin

Question 53

a protein that binds oxygen more tightly than hemoglobin does

Answer 53

myoglobin

Question 54

what do glycolytic fibers use as their primary source of ATP

Answer 54

glycolysis

Question 55

What is the difference between glycolytic fibers and oxidative fibers

Answer 55

glycolytic fibers have less myoglobin and get tired more easily

Question 56

In poultry and fish, what is light meat composed of

Answer 56

glycolytic fibers

Question 57

In poultry and fish, what is dark meat composed of

Answer 57

oxidative fibers

Question 58

contract more slowly bus sustain longer contractions

Answer 58

slow-twitch fibers

Question 59

what are all slow-twitch fibers

Answer 59

oxidative

Question 60

contract more rapidly but sustain shorter contractions

Answer 60

fast-twitch fibers

Question 61

what are fast-twitch fibers

Answer 61

either glycolytic or oxidative

Question 62

What do most skeletal muscles contain in barying ratios

Answer 62

both slow-twitch and fast-twitch

Question 63

In additon to skeletal muscle, what do vertebrates also have

Answer 63

cardiac muscle and smooth muscle

Question 64

found only in the heart

Answer 64

cardiac muscle

Question 65

consists of striated cells electrically connected by intercalated disks

Answer 65

cardiac muscle

Question 66

what can cardia muscle do without neural input

Answer 66

generate action potentials

Question 67

found mainly in walls of hollow organs such as those of the digestive tract

Answer 67

smooth muscle

Question 68

contractions are relatively slow and may be initiated by the muscles themselves

Answer 68

smooth muscles

Question 69

what may smooth muscle contractions also be caused by

Answer 69

stimulation from neurons in the autonomic nervous system