Terminology

9+2 Array - Arrangement scheme of microtubules in the internal part of an axoneme.
'A' bands - Region of sarcomere encompassing full length of thick filaments. Contains thick filaments, ends of adjacent thin filaments, and H zone. (Figures 8.8, 8.9a, 8.10).
'A' Fiber - A complete microtubule composing one of the nine microtubule doublets in the 9+2 array of a cilium.
Actin - A protein which, in combination with myosin, ATP, and calcium, provides contractile motion in cells.
and Tubulin - Subunits of tubulin present in equimolar quantities (Figure 8.19).
Axoneme - In a cilium, a highly organized bundle of microtubules enveloped by an extension of the plasma membrane (Figure 8.22b).
Axons - Long projections that allow one nerve cell to contact another.
'B' Fiber - An incomplete microtubule, carrying only 10 or 11 protofilaments in one of the nine microtubule doublets in the 9+2 array of a cilium.
Basal Body - In a cilium, an anchoring structure to which an axoneme is attached (Figure 8.22b).
Cardiac Muscle - A specialized form of striated muscle found in the heart.
Chemotaxis The process by which bacteria sense a concentration gradient of a particular substance in the medium and move either up or down the gradient (Figure 8.31).
Cleavage Furrow - Ringed structure that forms between dividing cells during cytokinesis. It defines a plane perpendicular to the mitotic spindle (Figure 8.15).
Creatine Kinase - Enzyme that catalyzes the reaction Creatine phosphate + ADP <=> Creatine + ATP
Creatine Phosphate - High-energy compound that maintains high ATP levels for muscular contraction.
Cross-bridges - Stable structural links that form between the actin and myosin filaments during muscular contraction.
Cytokinesis - The division of cells in the last stages of mitosis.
Cytoplasmic Dynein - In a cell, a protein responsible for transport from the plus end of a microtubule toward the minus end by 'walking' along a microtubule track.
Cytoskeleton - An organized network of rodlike and fiberlike proteins that pervades a cell and helps give it its shape and motility. It includes actin filaments, microtubules, and a diverse group of filamentous proteins collectively called intermediate filaments.
Dynein - 'Sidearms' of an outer doublet structure in the 9+2 array of cilia (Figure 8.23).
F-actin - A long, helical polymer of actin resulting from binding of ATP by the actin monomer.
Flagellin - Protein composing a bacterial flagellum.
Flagellum - Bacterial appendage providing motility (Figure 8.29).
G-actin - The monomeric form of actin.
H zone - Region in center of A band of sarcomere between adjacent ends of thin filaments (Figures 8.8, 8.9a, 8.10).
Headpiece - Portion of myosin molecule involved in binding to actin during contractile motion.
Heavy Meromyosin - A fragment of myosin produced by action of trypsin cleavage in the tail of myosin (Figure 8.4).
I bands - Region between ends of adjacent thick filaments. Contains Z line (Figures 8.8, 8.9a, 8.10).
Kinesin - In a cell, a protein responsible for transport from the minus end of a microtubule toward the plus end by 'walking' along a microtubule track.
Kinetochore Microtubules - Part of the mitotic spindle attached to the kinetochores of the individual chromosomes. They appear to function to pull the chromatids to the poles in telophase of mitosis (Figure 8.28).
Light Meromyosin - A fragment of myosin produced by action of trypsin cleavage in the tail of myosin (Figure 8.4).
Microtubule Associated Proteins (MAPs) - Proteins that bind to microtubules.
Microtubules - Long, tubular structures built from a helical wrapping of the protein tubulin. They are found in places as diverse as the mitotic spindle, protozoan and sperm flagella, and nerve axons.
Myofibers - Individual muscle fibers (Figure 8.8).
Myofibrils - A bundle of protein structures that produce muscular contraction within a myofiber (Figure 8.8).
Myosin - A protein which, in combination with actin ATP, and calcium, provides contractile motion in cells.
Nexin - A protein connecting the outer doublets in the 9+2 array of cilia (Figure 8.23).
Polar Microtubules - Part of the mitotic spindle that extends between the centrioles, apparently pushing them apart (Figure 8.28).
Radial Spokes - Connections between the nine microtubule doublets and the two central microtubules of a 9+2 array of a cilium.
Red Muscle - A type of striated muscle designed for relatively continuous use.
S1 Fragments - Pieces of myosin produced by papain cleavage of heavy meromyosin (Figure 8.4).
Sarcomere - A basic contracting unit of striated muscle. (Figures 8.8, 8.9a, 8.10).
Sarcoplasmic Reticulum - Structure surrounding each myofibril that releases calcium in response to stimulation by the nervous system (Figure 8.15).
Sliding Filament Model of Muscular Contraction - Model proposed by Hugh and Andrew Huxley to explain muscular contraction (Figure 8.10, Figure 8.11).
Smooth Muscle - Type of muscle controlling involuntary muscular movement. It surrounds internal organs, such as blood vessels, intestines, and gallbladder and produces slow, sustained contractions.
Striated Muscle - Type of muscle controlling voluntary muscular movement. Found in arms, legs, etc.
Tau () - Microtubule Associated Protein (MAP) found in neuronal tissue whose phosphorylation results in dissociation from microtubules and their destabilization. Hyperphosphorylation of results in formation of tangles of -filaments in neural axons - a major cellular symptom of Alzheimer's disease.
Thick Filaments - Parts of a sarcomere composed of myosin (Figure 8.9a).
Thin Filaments - Parts of a sarcomere composed of actin (Figure 8.9a).
Transverse Tubules - Invaginations of the plasma membrane that connect at periodic intervals with the sarcoplasmic reticulum to ensure that signals from the nervous system are transmitted across the entire sarcoplasmic reticulum (Figure 8.15).
Tropomyosin - A fibrous protein that exists as elongated dimers lying along, or close to, the groove in the F-actin helix (Figure 8.13).
Troponin C - Part of the troponin complex that binds to calcium (Figure 8.13).
Troponin Complex - Three proteins (Troponins I, C, and T) that make up a structure that controls access of myosin heads to actin, thereby regulating cross-bridge formation and muscular contraction (Figure 8.13).
White Muscle - A type of striated muscle employed for occasional, often rapid motions.
Z line (Z disks) - Region in center of I band of sarcomere forming a dark line (Figures 8.8, 8.9a, 8.10).