Part 6 Flashcards
Scalar elcetrocardiogram
signal measured in any of the Einthoven leads, corresponding to the projection of the electrical vector of the heart onto a line connecting two electrodes, thus transforming the vector into a scalar variable
Schwann cell
glia cell forming myelin sheet around axons at the periphery
Second messengers
small molecules whose concentration changes after the first messenger (signal) attaches to the membrane receptor
Secondary structure of proteins
formation of regular structures (a-helix, b-sheet) in the peptide chain stabilized by H-bonds
Semilunar valves
valves at the orifice of the aorta and pulmonary artery
Semipermeable membrane
membrane separating two solutions and limiting the penetration of some solvents from one side to the other
Septum
muscular tissue separating the left and right atria and ventricle
Side chain
a group bond to the -carbon atom of amino acids; amino acids are distinguished by the chemical composition of this group
Sinoatrial node
specialized cardiac tissue in the right atrium acting as the pacemaker of the heart
Sliding filament hypothesis
generally accepted theory explaining muscle contraction by sliding of actin and myosin filaments on each other
Space constant
externally induced and electrotonically conducted potential changes in the membrane decrease to 37% after traveling a distance equal to the space constant
Specificity
due to its spatial structure, a receptor, enzyme or transporter molecule can only bind a limited number of substrate molecules
Spirometer
device to measure lung volumes and aspects of breathing
Starling´s hypothesis
theory to explain the production and absorption of interstitial fluid
Strength (energy) of a bond
energy released during the formation of the given bond between atoms - this energy is needed to break apart the atoms
Sucrose
disaccharide built up by glucose and fructose; it its the most common commercially available sweetener
Summation
he process by which multiple or repeated stimuli can produce a response in a nerve, muscle, or other part that one stimulus alone cannot produce.
Surface active agent
amphipathic molecule bearing both hydrophilic and hydrophobic groups
Surface active substance
its molecules possess both hydrophilic and hydrophobic parts; they tend to line up at the boarder separating two fieerent phases (lipid-water, water-air etc) with the hydrophilic and hydrophobic parts located in the appropriate phase
Surfactant
surface active agent lining the inner surface of the alveoli and decreasing surface tension
Systole
the portion of the heart beat when the heart muscle is contracting
Tercier structure of proteins
3D, spatial form of the protein chain stabilized by weak-interactions (electrostatic, van der Waals)
Tetanic contraction
uninterrupted muscular contraction caused by high-frequency motor impulses
Thrombosis
blockade of a vessel due to a blood clot formed in the vessel
Tidal volume
volume of air moved during a relaxed inspiration or expiration
Tight junction
area of membrane fusion between adjoining cells that prevents the passage of extracellular material between the cells
Time constant
time required for an externally induced potential change in the membrane to decrease to 37% of the original potential
Trace elements
elements needed in a very low concentration for the normal functioning of the organism
Trachea
large respiratory passageway connecting the pharynx with the bronchi of the vertebrate lung
Tricuspid valve
valve between the right atrium and ventricle
Triglycerides
lipid molecules composed of three fatty acid residues esterified to glyceorl
T-tubules
invagination of the sarcolemma, carrying excitation to the sarcoplasmic reticulum
Turbulent flow
a flow pattern in which particles of the fluid move irregularly in all directions of the space
Unipolar neuron
nerve cell with only one process
Unsaturated fatty acid
fatty acid containing one or more double bonds
Valsalva´s maneuver
sustained expirational effort against a closed glottis
van der Waals forces
relatively weak attraction between atoms and molecules with hydrophobic properties due to the random fluctuation of the electron clouds
Vena cava
empty vein; large veins returning from the body to the right atrium were named vena cavae, because they were found empty in hanged persons dissected during medieval times
Ventilation
air exchange between the lungs and the ambient air
Venule
small vessel connecting the capillaries to veins
Vesicle
small, spherical compartment in the cell surrounded by a membrane (e.g. synaptic vesicle)
Viscosity
physical property of fluids that determines the ease with which the layers of a fluid move past each other
Vital capacity
the maximum volume of air that can be inhaled to or exhaled from the lungs
