Ch 35: Animal Movement, Muscles and Skeletons Flashcards
Fibers
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.
Force
An interaction that changes the movement of an object, such as a push or pull by one object interacting with another object.
Filament
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.
Striated Muscle
Skeletal muscle and cardiac muscle, which appear striped under a light microscope due to regular thick (myosin) and thin (actin) myofilament spacing.
Skeletal Muscle
Striated muscle that connects to the body skeleton to move an animal’s limbs and torso.
Cardiac Muscle
Muscle cells that make up the walls of the atria and ventricles and contract to pump blood through the heart.
Smooth Muscle
The muscle in the walls of arteries, the respiratory system, and the digestive and excretory systems; smooth muscle appears uniform under the light microscope.
Myofibrils
A long rodlike structure in muscle fibers that contains parallel arrays of actin and myosin filaments.
Thin Filament
Two helically arranged actin polymers twisted together that form the actin filament within muscle sarcomeres.
Tropomyosin
A protein that runs in the grooves formed by the actin helices and blocks the myosin-binding sites on the actin filament.
Thick Filament
A parallel grouping of myosin molecules that form the myosin filament within muscle sarcomeres.
Z Disks
A protein backbone found regularly spaced along the length of a myofibril.
Sacromere
The region of myofilaments located within muscle myofibrils that span from one Z disc to the next; the basic contractile unit of a muscle.
Sliding Filament Model
The hypothesis that striated muscles produce force and change length by the sliding of actin filaments relative to myosin filaments.
Cross Bridge
The binding of the head of a myosin molecule to actin at a specific site between the myosin and actin filaments.
Cross Bridge Cycle
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.
Power Stroke
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.
Motor Endplate
The post-synaptic region on a muscle cell where acetylcholine binds with receptors.
Sacroplasmic Reticulum
A modified form of the endoplasmic reticulum surrounding the myofibrils of muscle cells.
Troponin
A protein that moves tropomyosin away from myosin-binding sites, allowing cross-bridges between actin and myosin to form and the muscle to contract.
Excitation-contraction coupling
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.
Calmodulin
A protein that binds with Ca2+ and activates the enzyme myosin kinase.
Antagonist Muscles
Muscle pairs that pull in opposite directions at a joint to produce opposing motions.
Flexion
The joint motion in which bone segments rotate closer together.
Extension
The joint motion in which bone segments move apart.
Agonist Muscles
Muscle pairs that combine to produce similar motions.
Isometric
Describes the generation of muscle force without a change in muscle length.
Lengthening Contraction
The contraction of a muscle against a load greater than the muscle’s force output, leading to a lengthening of the muscle.
Twitch
A muscle contraction that results from a single action potential.
Tetanus
A muscle contraction of sustained force resulting from multiple action potentials.
Motor Unit
A vertebrate motor neuron and the population of muscle fibers that it innervates.
Slow-twitch fiber
Describes muscle fibers that contract slowly, resist fatigue, and consume less ATP than do fast-twitch fibers to produce force.
Fast-twitch fiber
Describes muscle fibers that generate force quickly, producing rapid movements, but that also consume more energy and fatigue more quickly than slow-twitch fibers.
Myoglobin
An oxygen-binding protein in the cells of vertebrate muscles, related to hemoglobin, that facilitates oxygen delivery to mitochondria.
Hydrostatic Skeleton
A skeletal system in which fluid contained within a body cavity is the supporting element.
Exoskeleton
A rigid skeletal system that lies external to the animal’s soft tissues.
Endoskeleton
A skeleton that develops within the body, as the bones of vertebrates.
Intervetebral Discs
A gel-filled support structure found between the bony vertebrae of the backbone that enables flexibility and provides cushioning of loads.
Cartilage
A type of connective tissue found, for example, in the walls of intervertebral discs and the joint surfaces between adjacent bones.
Cuticle
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.
Chitin
A modified polysaccharide containing nitrogen that makes up the cell walls of fungi and the hard exoskeletons of arthropods.
Molting
Periodic shedding, as of an exoskeleton.
Tendons
A collagen structure that attaches vertebrate muscles to the skeleton and transmits muscle forces over a wide range of joint motion.
Axial
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.
Appendicular
Describes the part of the vertebrate skeleton that consists of the bones of the shoulder, pelvis, and limbs.
Extracellular Matrix
A meshwork of proteins and polysaccharides outside the cell; the main constituent of connective tissue.
Osteoblasts
A type of cell that forms bone tissue.
Hydroxyapitate
The calcium phosphate mineral found in bone.
Collagen
A strong protein fiber found in bone, artery walls, tendons, and other connective tissues.
Osteoclasts
A type of cell that digests and removes bone tissue.
Compact Bone
Dense, mineralized bone tissue that forms the walls of a bone’s shaft.
Spongy Bone
Vertebrate bone tissue consisting of trabeculae, and thus lighter than compact bone, found in the ends of limb bones and within vertebrae.
Trabeculae
Small plates and rods with spaces between them, found in spongy bone.
Bone Marrow
A fatty tissue between trabeculae and within the central cavity of a bone that contains many important cell populations.
Growth Plates
A region of cartilage near the end of a bone where growth in bone length occurs.
Diaphysis
The middle region of a bone.
Epiphysis
The end region of a bone; blood vessels invading the epiphysis and diaphysis trigger the transformation of cartilage into bone.
Hinge Joint
A simple joint that allows one axis of rotation, like the elbow and knee.
Ball and Socket Joint
A joint that allows rotation in many axes, like the hip and shoulder.
Why is calcium necessary for muscle contraction?
Calcium is needed to activate troponin so that tropomyosin can be moved to expose the myosin-binding sites on the actin filament.
T/F: Actin and myosin filaments overlap more when a muscle is contracted than when it is relaxed.
True
What type of contraction generates the greatest force
lengthening contractions
The exoskeleton of insects is composed mainly of:
Chitin
T/F: Osteoclasts help bones increase in diameter by laying down new bone material on the external surface.
False
T/F: Thick filaments consist of parallel bundles of myosin molecules.
True
What contraction type generates a force without either positive or negative shortening?
isometric contractions
T/F: Every animal possesses a unique, singular skeleton that can (only) be classified as an endoskeleton, exoskeleton, or hydrostatic skeleton.
False
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?
In all bones
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:
Tropomyosin
If all of the collagen were removed from a bone, how would the properties of that bone be altered?
The bone would be more brittle and easier to break.
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?
Osteoclasts played a key role in the formation of this eggshell by providing calcium from the skeleton.
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:
Molting
At the level of actin and myosin molecules, what is producing force when a skeletal muscle contracts?
The binding of myosin to actin.
The light bands in skeletal muscle that contribute to its striated appearance are formed by:
actin
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.
True
T/F:
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.
When muscles combine to produce similar motions at a joint, they are called:
Agonists
What role does ATP play in the cross-bridge cycle?
The binding of ATP to myosin causes myosin to detach from actin.
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:
antagonists
The power stroke corresponds to which event in muscle contraction?
sliding of actin relative to myosin filaments
A researcher is comparing the size of sarcomeres in mice to those in elephants. What will he find?
Sarcomere size is relatively constant in vertebrates. As a result, mouse and elephant sarcomeres will likely be equal in size.
