S Flashcards
Saccule
A region of sensory cells within the inner ear.
Saliva
A solution of enzymes, salts, and water secreted into the oral cavity to lubricate, dissolve, and disrupt food.
Salt
A neutral molecule composed of an inorganic anion and inorganic cation linked by an ionic bond, such as NaCl (table salt).
Salt Gland
An extrarenal gland found in some marine and desert vertebrates that secrete Na+ and Cl− to reduce body salt content.
Saltatory Conduction
The mode of conduction of action potentials in myelinated axons in which action potentials appear to jump from one node of Ranvier to the next.
Sarcolemma
The cell membrane of a muscle.
Sarcomere
The contractile unit of striated muscle, typically measured from one Z-disk to the next.
Sarcomere Length
The distance between two Z-disks of a sarcomere.
Sarcoplasm
also known as myoplasm
The cytoplasm of a muscle cell.
Sarcoplasmic Reticulum
The endoplasmic reticulum of muscle.
Satellite Cells
A population of omnipotent stem cells found on the surface of striated muscle. When stimulated, satellite cells can enter myogenesis to repair or replace muscle.
Saturated
(1) For respiratory pigments, hormone receptors, and carrier proteins, refers to a situation in which all available proteins are bound to their ligand.
(2) For fatty acids, refers to fatty acid chains that lack double bonds.
Saturated Fatty Acid
A fatty acid with no double bonds.
Scaling
The relationship between a parameter, such as metabolic rate, and body size.
Scaling Coefficient
The slope of a plot of log body mass against log parameter of interest, such as metabolic rate.
Schwann Cell
A type of glial cell in the vertebrates that forms the myelin sheath around axons in the peripheral nervous system.
Sclera
Tough outer surface of a vertebrate eye.
Sclerites
Platelike sections of an invertebrate exoskeleton.
Sclerotization
The hardening of the arthropod exoskeleton arising from formation of crosslinks between proteins.
Second Messenger
A short-lived intracellular messenger that acts as an intermediate in a signal transduction pathway.
Secondary Active Transport
Transport of a molecule across a membrane against its electrochemical gradient, driven by the cotransport of another molecule along its electrochemical gradient.
Secondary Structure
The folding pattern of a macromolecule; an alpha-helix is an example of the secondary structure of protein and DNA.
Secretagogue
A chemical that induces the secretion of another chemical, usually a cell signaling factor such as a hormone.
Secretory Granules
Vesicles of secretory product stored within a cell, prepared for release when the cell receives the appropriate signal.
Selectivity Filter
A part of an ion channel that determines the type of ion that can pass through the pore of the channel.
Semicircular Canals
Structures of the inner ear responsible for the sense of balance and body orientation; part of the vestibular apparatus.
Semilunar Valves
The valves between the ventricles and the arteries of the vertebrate heart.
Seminal Vesicles
A pair of glands that store sperm and secrete nutrients and fluids that form the semen, emptying it into the vas deferens upon ejaculation.
Semipermeable Membrane
A membrane that allows the free movement of some molecules but impedes the movement of others.
Sensillum (plural: sensilla)
Sense organs in the insect cuticle. Involved in the senses of taste, smell, touch, and hearing.
Sensitization
A process by which the response of a neuron to a stimulus is increased.
Sensory Modality
The category of sensory input that a sensory system detects (e.g., light, sound, pressure).
Sensory Neuron
see also afferent neuron
A neuron that conveys sensory information from the periphery to the central nervous system.
Sensory Receptor
A tissue, cell, or protein that detects incoming sensory information.
Sensory Transduction
The process of converting incoming sensory information to changes in cell membrane potential.
Sensory Units
The smallest unit of a sensory response defined by all of the receptor endings of a single afferent neuron.
Septum
Any structure that divides two tissues or cavities.
SERCA
The sarcoplasmic/endoplasmic calcium ATPase.
Series Elastic Components
Elements of a structure that can store elastic energy when they are deformed.
Serosa
see also mucosa
Referring to the outer layer of a tissue or organ.
Serotonin
A neurotransmitter (biogenic amine) involved in setting mood and regulating blood flow to the brain.
Sertoli Cells
Elongated cells in the seminiferous tubules of the testis that nourish the spermatids during spermatogenesis.
Sertoli Cells
Elongated cells in the seminiferous tubules of the testis that nourish the spermatids during spermatogenesis.
Serum
Blood plasma after the clotting factors have been removed.
Set Point
In a homeostatically controlled system, the level at which the regulated variable is maintained.
Sexual Reproduction
A process in which two cells (each with half the normal genetic complement as a result of meiosis and recombination) fuse to form one descendant cell.
Shivering Thermogenesis
Heat production through uncoordinated stimulation of skeletal muscle contractile units.
Shunt
A pathway that allows flow of blood between the pulmonary and systemic circuits of a tetrapod circulatory system.
Signal Transduction Pathways
Biochemical pathways in which a change in conformation of a receptor protein in the target cell is converted to a change in the activity of that cell.
Sinoatrial Node (SA node)
A remnant of the sinus venosus found at the top of the right atrium of the mammalian heart.
Sinus Venosus
The chamber leading to the atrium of the heart in nonmammalian vertebrates.
Sinusoidal Capillaries
A specialized type of fenestrated capillary with larger intercellular gaps and an incomplete basement membrane that result in extremely high permeability; found only in organs such as liver and bone marrow.
Skeletal Muscle
A general term to describe the striated muscle that works in conjunction with the endoskeleton.
Skeletal Muscle Pump
A process by which rhythmic contraction of the skeletal muscles in the limbs helps to drive venous return of blood to the heart.
Skull
The bone or cartilage that surrounds the brain of a vertebrate.
Sliding Filament Model
A theory that describes the interaction between actin and myosin during cross-bridge cycling.
Smooth Muscle
A type of muscle that has an irregular arrangement of thick and thin filaments, and thus lacks sarcomeres.
SNARES
Proteins involved in the fusion of vesicles to the cell membrane
Solenocytes
The cells that create fluid movements at the end of a protonephridium. Similar to flame cells, but possess one or two flagella rather than a tuft of cilia.
Solubility Coefficient
Parameter describing the ability of a gas to dissolve in a liquid.
Solute
The particles (ions or molecules) dissolved in a solution.
Solution
The fluid in which solutes are dissolved.
Solvent
The liquid in which solutes are dissolved.
Soma
The cell body of a neuron, containing the nucleus.
Somatic Motor Division (of the nervous system)
The portion of the vertebrate peripheral nervous system that controls skeletal muscle.
Sonic Muscles
A general term for diverse muscles that are involved in sound production.
Spatial Summation
The process by which graded potentials at different points in the membrane (occurring at the same time) combine to influence the net graded potential of a cell.
Specific Dynamic Action (SDA)
also known as the heat increment
The heat produced during the digestive process.
Spermatogenesis
Production of spermatozoa.
Spermatogonia (singular: spermatogonium)
After the primordial germ cell enters the testes, it differentiates into a spermatagonium, which undergoes multiple rounds of mitosis before entering meiosis.
Spermatozoa
The smaller gamete in a sexually reproducing species; sperm.
Sphincter
A ring of smooth muscle that controls the diameter of an opening, controlling passage from one region to the next.
Sphingolipid
One class of phospholipid based on a sphingosine backbone.
Spinal Cord
Part of the vertebrate central nervous system extending from the base of the skull through the vertebrae of the spine. The spinal cord is continuous with the hindbrain.
Spinal Nerves
A series of paired nerves that exit at regular intervals along the spinal column.
Spiracles
Small openings leading to the respiratory system; spiracles are the primary opening to the tracheal system of insects. The same word is used for a nonhomologous structure in elasmobranch fishes that provides an alternate opening for the buccal-opercular cavities.
Spiral Fold
Structure in the amphibian heart that allows oxygenated blood to flow preferentially to the systemic arteries.
Spleen
A vertebrate organ that is involved with the immune, lymphatic, and circulatory systems. It can act as a storage site for red blood cells, and removes damaged cells from the circulation. It also generates immune cells called lymphocytes.
Spongy Myocardium
Type of heart muscle found primarily in nonmammalian vertebrates consisting of a meshwork of loosely connected cells.
Standard Conditions
Accepted external conditions under which physical parameters are assessed; may refer to pressure, temperature, concentration, or other such parameters.
Standard Metabolic Rate (SMR)
see also basal metabolic rate, resting metabolic rate
The metabolic rate of a poikilothermic animal at rest and post-absorptive, measured at a defined external temperature.
Stanniocalcin
A polypeptide hormone that acts in the kidney and gut to regulate calcium and phosphate.
Stapes (stirrup)
One of the three small bones of the mammalian middle ear.
Statocyst
Hollow, fluid-filled sense organ in invertebrates that detects the orientation of the body with respect to gravity.
Statolith
Small dense granule (usually of calcium carbonate) found in statocysts.
Steady State
A condition in which there is flux through a reaction or pathway without a change in the concentration of intermediates.
Stenohaline
An animal that is tolerant of a narrow range of external salinities.
Stenotherm
An animal that is tolerant of a narrow range of ambient temperatures.
Stereocilia
The specialized cilia of vertebrate hair cells; involved in the sense of hearing.
Stereopsis
The ability to see in three dimensions.
Steroid Hormones
A large class of hormones derived from cholesterol.
Steroids
A diverse group of nonpolar organic molecules composed of multiple carbon rings.
Stoichiometry
The quantitative relationship between two entities.
Stomach
A general term for an anterior region of a gastrointestinal tract, typically characterized by acidic digestion processes.
Stratum Corneum
The outer layer of the epidermis of tetrapods, consisting mainly of corneocytes.
Striated Muscle
A class of muscle that possesses thick and thin filaments organized into regular arrays; includes cardiac muscle and skeletal muscle.
Stroke Volume
The volume of blood pumped by the heart in a single beat.
Submucosa
The tissue layer that lies beneath the mucosal layer.
Substrate-Level Phosphorylation
An enzymatic reaction that produces a high-energy phosphate.
Sulci (singular: sulcus)
The folds on the surface of the brain in some mammals.
Supercooling
The reduction of temperature of a fluid below its freezing point but without the formation of ice.
Suprachiasmatic Nucleus (SCN)
A region within the hypothalamus of the brain that is responsible for regulating circadian rhythms.
Surface Tension
The force of adhesion that binds molecules of a fluid together at the interface with air.
Surfactant
Substance that lowers the surface tension of liquids; secreted in the lungs of vertebrates.
Swim Bladder
A gas-filled organ that fish use for buoyancy compensation.
Sympathetic Nervous System
Part of the vertebrate autonomic nervous system; active during periods of stressful activity; releases the neurotransmitters epinephrine and norepinephrine onto target organs.
Symport
A transporter that carries two or more entities across a cell membrane in the same direction; also known as a cotransporter.
Synapse
The junction between a neuron and another neuron or effector cell; consists of a presynaptic cell, the synaptic cleft, and a postsynaptic cell.
Synaptic Cleft
The extracellular space between a presynaptic cell and a postsynaptic cell at a synapse.
Synaptic Depression
A decrease in neurotransmitter release in response to repeated action potentials.
Synaptic Facilitation
An increase in neurotransmitter release in response to repeated action potentials.
Synaptic Plasticity
The capacity of synapses to change their structure and function.
Synaptic Transmission
The process of transmitting information across a neural synapse.
Synaptic Vesicles
Neurotransmitter-containing vesicles that release neurotransmitter into a synapse.
Synaptotagmin
A protein involved in the trafficking of neurotransmitter-containing
vesicles to the membrane of the axon terminal.
Syncytium
A multinucleated cell that arises from the fusion of multiple cells.
Synovial Fluid
The viscous fluid found between skeletal joints, serving as a lubricant to reduce friction.
Synergism
A situation in which two agents or processes have a combined effect greater than the sum of the effects of the two agents or processes applied individually.
Systemic Circuit
The part of the tetrapod circulatory system that carries blood from the heart to the body and back.
Systole
The phase of the cardiac cycle in which he heart is contracting.
Systolic Pressure
The arterial blood pressure during systole.
