Ch 35: Animal Movement, Muscles and Skeletons

Question 1

Fibers

Answer 1

In angiosperms, a narrow cell with thick walls that provides mechanical support in wood. In animals, a muscle cell, which produces forces within an animal’s body and exerts forces on the environment.

Question 2

Force

Answer 2

An interaction that changes the movement of an object, such as a push or pull by one object interacting with another object.

Question 3

Filament

Answer 3

In animals, a thin thread of proteins that interacts with other filaments to cause muscles to shorten. In plants, the part of the stamen that supports the anther.

Question 4

Striated Muscle

Answer 4

Skeletal muscle and cardiac muscle, which appear striped under a light microscope due to regular thick (myosin) and thin (actin) myofilament spacing.

Question 5

Skeletal Muscle

Answer 5

Striated muscle that connects to the body skeleton to move an animal’s limbs and torso.

Question 6

Cardiac Muscle

Answer 6

Muscle cells that make up the walls of the atria and ventricles and contract to pump blood through the heart.

Question 7

Smooth Muscle

Answer 7

The muscle in the walls of arteries, the respiratory system, and the digestive and excretory systems; smooth muscle appears uniform under the light microscope.

Question 8

Myofibrils

Answer 8

A long rodlike structure in muscle fibers that contains parallel arrays of actin and myosin filaments.

Question 9

Thin Filament

Answer 9

Two helically arranged actin polymers twisted together that form the actin filament within muscle sarcomeres.

Question 10

Tropomyosin

Answer 10

A protein that runs in the grooves formed by the actin helices and blocks the myosin-binding sites on the actin filament.

Question 11

Thick Filament

Answer 11

A parallel grouping of myosin molecules that form the myosin filament within muscle sarcomeres.

Question 12

Z Disks

Answer 12

A protein backbone found regularly spaced along the length of a myofibril.

Question 13

Sacromere

Answer 13

The region of myofilaments located within muscle myofibrils that span from one Z disc to the next; the basic contractile unit of a muscle.

Question 14

Sliding Filament Model

Answer 14

The hypothesis that striated muscles produce force and change length by the sliding of actin filaments relative to myosin filaments.

Question 15

Cross Bridge

Answer 15

The binding of the head of a myosin molecule to actin at a specific site between the myosin and actin filaments.

Question 16

Cross Bridge Cycle

Answer 16

Repeated sequential interactions between myosin heads that bind to and release from sites on actin filaments, forming and unforming cross-bridges, that cause a muscle fiber to contract.

Question 17

Power Stroke

Answer 17

The stage in the muscle cross-bridge cycle in which the myosin head pivots and generates a force, causing the myosin and actin filaments to slide relative to each other.

Question 18

Motor Endplate

Answer 18

The post-synaptic region on a muscle cell where acetylcholine binds with receptors.

Question 19

Sacroplasmic Reticulum

Answer 19

A modified form of the endoplasmic reticulum surrounding the myofibrils of muscle cells.

Question 20

Troponin

Answer 20

A protein that moves tropomyosin away from myosin-binding sites, allowing cross-bridges between actin and myosin to form and the muscle to contract.

Question 21

Excitation-contraction coupling

Answer 21

The process that produces muscle force and movement, by coupling the excitation of the muscle cell by a motor neuron to contraction of the muscle.

Question 22

Calmodulin

Answer 22

A protein that binds with Ca2+ and activates the enzyme myosin kinase.

Question 23

Antagonist Muscles

Answer 23

Muscle pairs that pull in opposite directions at a joint to produce opposing motions.

Question 24

Flexion

Answer 24

The joint motion in which bone segments rotate closer together.

Question 25

Extension

Answer 25

The joint motion in which bone segments move apart.

Question 26

Agonist Muscles

Answer 26

Muscle pairs that combine to produce similar motions.

Question 27

Isometric

Answer 27

Describes the generation of muscle force without a change in muscle length.

Question 28

Lengthening Contraction

Answer 28

The contraction of a muscle against a load greater than the muscle’s force output, leading to a lengthening of the muscle.

Question 29

Twitch

Answer 29

A muscle contraction that results from a single action potential.

Question 30

Tetanus

Answer 30

A muscle contraction of sustained force resulting from multiple action potentials.

Question 31

Motor Unit

Answer 31

A vertebrate motor neuron and the population of muscle fibers that it innervates.

Question 32

Slow-twitch fiber

Answer 32

Describes muscle fibers that contract slowly, resist fatigue, and consume less ATP than do fast-twitch fibers to produce force.

Question 33

Fast-twitch fiber

Answer 33

Describes muscle fibers that generate force quickly, producing rapid movements, but that also consume more energy and fatigue more quickly than slow-twitch fibers.

Question 34

Myoglobin

Answer 34

An oxygen-binding protein in the cells of vertebrate muscles, related to hemoglobin, that facilitates oxygen delivery to mitochondria.

Question 35

Hydrostatic Skeleton

Answer 35

A skeletal system in which fluid contained within a body cavity is the supporting element.

Question 36

Exoskeleton

Answer 36

A rigid skeletal system that lies external to the animal’s soft tissues.

Question 37

Endoskeleton

Answer 37

A skeleton that develops within the body, as the bones of vertebrates.

Question 38

Intervetebral Discs

Answer 38

A gel-filled support structure found between the bony vertebrae of the backbone that enables flexibility and provides cushioning of loads.

Question 39

Cartilage

Answer 39

A type of connective tissue found, for example, in the walls of intervertebral discs and the joint surfaces between adjacent bones.

Question 40

Cuticle

Answer 40

In plants, a protective layer of a waxy substance secreted by epidermal cells that limits water loss; in animals, an exoskeleton that covers the bodies of invertebrates such as nematodes and arthropods.

Question 41

Chitin

Answer 41

A modified polysaccharide containing nitrogen that makes up the cell walls of fungi and the hard exoskeletons of arthropods.

Question 42

Molting

Answer 42

Periodic shedding, as of an exoskeleton.

Question 43

Tendons

Answer 43

A collagen structure that attaches vertebrate muscles to the skeleton and transmits muscle forces over a wide range of joint motion.

Question 44

Axial

Answer 44

Describes the part of the vertebrate skeleton that consists of the skull and jaws of the head, the vertebrae of the spinal column, and the ribs.

Question 45

Appendicular

Answer 45

Describes the part of the vertebrate skeleton that consists of the bones of the shoulder, pelvis, and limbs.

Question 46

Extracellular Matrix

Answer 46

A meshwork of proteins and polysaccharides outside the cell; the main constituent of connective tissue.

Question 47

Osteoblasts

Answer 47

A type of cell that forms bone tissue.

Question 48

Hydroxyapitate

Answer 48

The calcium phosphate mineral found in bone.

Question 49

Collagen

Answer 49

A strong protein fiber found in bone, artery walls, tendons, and other connective tissues.

Question 50

Osteoclasts

Answer 50

A type of cell that digests and removes bone tissue.

Question 51

Compact Bone

Answer 51

Dense, mineralized bone tissue that forms the walls of a bone’s shaft.

Question 52

Spongy Bone

Answer 52

Vertebrate bone tissue consisting of trabeculae, and thus lighter than compact bone, found in the ends of limb bones and within vertebrae.

Question 53

Trabeculae

Answer 53

Small plates and rods with spaces between them, found in spongy bone.

Question 54

Bone Marrow

Answer 54

A fatty tissue between trabeculae and within the central cavity of a bone that contains many important cell populations.

Question 55

Growth Plates

Answer 55

A region of cartilage near the end of a bone where growth in bone length occurs.

Question 56

Diaphysis

Answer 56

The middle region of a bone.

Question 57

Epiphysis

Answer 57

The end region of a bone; blood vessels invading the epiphysis and diaphysis trigger the transformation of cartilage into bone.

Question 58

Hinge Joint

Answer 58

A simple joint that allows one axis of rotation, like the elbow and knee.

Question 59

Ball and Socket Joint

Answer 59

A joint that allows rotation in many axes, like the hip and shoulder.

Question 60

Why is calcium necessary for muscle contraction?

Answer 60

Calcium is needed to activate troponin so that tropomyosin can be moved to expose the myosin-binding sites on the actin filament.

Question 61

T/F: Actin and myosin filaments overlap more when a muscle is contracted than when it is relaxed.

Answer 61

True

Question 62

What type of contraction generates the greatest force

Answer 62

lengthening contractions

Question 63

The exoskeleton of insects is composed mainly of:

Answer 63

Chitin

Question 64

T/F: Osteoclasts help bones increase in diameter by laying down new bone material on the external surface.

Answer 64

False

Question 65

T/F: Thick filaments consist of parallel bundles of myosin molecules.

Answer 65

True

Question 66

What contraction type generates a force without either positive or negative shortening?

Answer 66

isometric contractions

Question 67

T/F: Every animal possesses a unique, singular skeleton that can (only) be classified as an endoskeleton, exoskeleton, or hydrostatic skeleton.

Answer 67

False

Question 68

A researcher is staining young mouse embryonic sections for Sox9, a marker of chondroblasts and the earliest stage of cartilage (precursor of future bone) development. Where will the researcher observe Sox9 staining in these sections?

Answer 68

In all bones

Question 69

Imagine that a researcher has dissected out a single muscle bundle from a triceps muscle biopsy. She sections this bundle and stains it for a variety of muscle-associated proteins. After staining, when the researcher zooms in on a sarcomere, she notices that a certain protein always dots the periphery along the length of the thin filaments. This protein is most likely:

Answer 69

Tropomyosin

Question 70

If all of the collagen were removed from a bone, how would the properties of that bone be altered?

Answer 70

The bone would be more brittle and easier to break.

Question 71

Imagine that you have found the remnants of a robin’s egg on the ground. From your biology course, you know that this eggshell is composed of calcium. What else can be said of this eggshell?

Answer 71

Osteoclasts played a key role in the formation of this eggshell by providing calcium from the skeleton.

Question 72

As arthropods grow, they shed their exoskeletons at periodic intervals, allowing growth before formation of a new exoskeleton. This process of shedding the exoskeleton is known as:

Answer 72

Molting

Question 73

At the level of actin and myosin molecules, what is producing force when a skeletal muscle contracts?

Answer 73

The binding of myosin to actin.

Question 74

The light bands in skeletal muscle that contribute to its striated appearance are formed by:

Answer 74

actin

Question 75

T/F: When compared to the leg muscles of an Olympic sprinter, the muscles of an Olympic marathoner would likely show a greater proportion of oxidative slow-twitch fibers.

Answer 75

True

Question 76

T/F:

Answer 76

Calcium for skeletal muscle contraction enters the cell from the sarcoplasmic reticulum and through voltage-gated calcium channels in the plasma membrane, whereas the calcium for smooth muscle contraction enters the cell from the sarcoplasmic reticulum only.

Question 77

When muscles combine to produce similar motions at a joint, they are called:

Answer 77

Agonists

Question 78

What role does ATP play in the cross-bridge cycle?

Answer 78

The binding of ATP to myosin causes myosin to detach from actin.

Question 79

Two groups of muscles that oppose each other’s action may be flexors or extensors, such as the biceps and triceps of your arm. These muscle groups are known as:

Answer 79

antagonists

Question 80

The power stroke corresponds to which event in muscle contraction?

Answer 80

sliding of actin relative to myosin filaments

Question 81

A researcher is comparing the size of sarcomeres in mice to those in elephants. What will he find?

Answer 81

Sarcomere size is relatively constant in vertebrates. As a result, mouse and elephant sarcomeres will likely be equal in size.