Biology Flashcards
Sarcoplasmic Reticulum
A modified form of endoplasmic reticulum; stores calcium that is used to trigger contraction when muscle is stimulated.
Acrosome
The large vesicle at the head of a sperm cell containing enzymes that degrade the ovum cell membrane to allow fertilization.
Action Potential
A sharp change in the membrane potential of neurons or muscle cells caused by a change in the selective permeability to Na+ and K+ using violated-gated ion channels. Action Potentials are all-or-nothing events.
Schwann Cells
Cells that produce myelin in the peripheral nervous system.
Second Messenger
A small molecule that transduces a hormonal signal from the exterior of the cell to the interior. Usually released when a peptide hormone binds to its receptor; cAMP is a common example.
Secondary Response
Subsequent infections be pathogens that trigger a more immediate response from the memory cells produced during the primary immune response.
Semen
The fluid discharged during ejaculation. Semen consists of sperm cells and seminal fluid (fluid from the prostate and bulbourethral glands).
Semilunar Valves
Valves (the aortic valve and the pulmonic valve) that prevent backflow of blood from the arteries into the ventricles.
Seminiferous Tubules
Located in the testes, the seminiferous tubules are the site of sperm production.
Signaling Cascade
Series of events, starting with the binding of a peptide hormone to a surface receptor. This sequence of events ultimately results in a change in cellular behavior.
Sister Chromatids
The relationship between the strands of DNA after replication. Each chromosome consists of two identical chromatids held together at a central region called the centromere. After the mitotic spindle pulls the sister chromatids apart, each chromatid is referred to as a chromosome on its own.
Skeletal Muscle
Type of muscle responsible for voluntary movement, consisting of multi nucleated, striated (striped) muscle fibers.
Small Intestine
Section of the digestive tract that can be divided into three sections: Duodenum, jejunum, and ileum. Most digestion takes pace in the duodenum and most absorption takes place in the jejunum and the ileum.
Smooth Muscle
Nonstriated muscle, responsible for involuntary action. Controlled by the autonomic nervous system.
Sodium-Potassium Pump
A protein that hydrolyzes one ATP to transport three NA+ out of the cell for every two K+ it transports into the cell.
Somatic Cells
All cells excluding the germ (reproductive) cells.
Somatic Nervous System
Division of the peripheral nervous system that is responsible for voluntary movement.
Somatostatin
Produced and secreted by the O-cells of the pancreas, somatostatin inhibits the release of glucagon and insulin.
Spermatozoa
Mature sperm specialized for transporting the genetic information from the male to the ovum.
Spongy Bone
Lighter and less dense than compact bone, it consists of an interconnecting lattice of bony spicules (trabeculae). The cavities between the spicules contain bone marrow.
Stabilizing Selection
Type of natural selection where the average phenotype is favored while those outside the norm are eliminated.
Starling Forces
A balance between hydrostatic and oncotic pressures on both side of a membrane essential for maintaining proper fluid volumes and soluate concentrations inside and outside the vasculature.
Steroid Hormones
Nonpolar hormones that cross the cell membrane and act by binding intracellular receptors.
Superior Vena Cava
A large vein that returns deoxygenated blood from the head and neck regions, as well as the upper extremities, to the right atrium of the heart.
Surfactant
A liquid substance produced by the lung that reduces surface tension in the alveoli. Surfactant prevents lung collapse and decreases the effort needed to expand the lungs (inhale).
Synapse
The space between the axon terminal of one neurons and the dendrite of another neuron (or membrane of an effector organ) where neurotransmitters are released.
Synaptic Terminals
Ends of axons that form on side of the synaptic cleft; the location where the vesicles of neurotransmitters are stored.
Systole
The stage of the cardiac cycle in which the heart muscle contracts and pumps blood.
Test Cross
A cross between an organism of an undetermined genotype and another that is homozygous recessive for the trait of interest.
Testosterone
Hormone secreted by the interstitial cells of the testes. Testosterone is responsible for embryonic sexual differentiation, male sexual development, and the Maintainance of masculine secondary sexual characteristics.
Tetrad
Collectively, the four chromatids involved when a pair of homologous chromosomes synapse during prophase I of meiosis.
Thermoregulation
Maintenance of a constant internal body temperature.
Threshold Voltage
The minimal voltage that must be reached in order for an action potential to be fired at the axon hillock.
Thyroid Hormones
Synthesized and released by the thyroid gland, thyroid hormones triidothyronine (T3) and thyroxine (T4) stimulate cellular respiration as well as protein and fat acid synthesis and degradation.
Thyroid-Stimulating Hormone (TSH)
Synthesized and released by the anterior pituitary, TSH stimulates the thyroid gland to absorb iodine and to synthesize ad secrete thyroid hormones. TSH is regulated by thyroid releasing hormone (TRH), which is released by the hypothalamus.
Totipotent
Stem cells that have the ability to become any cell within any system of the body. Embryonic stem cells are totipotent.
Translocation
A form of chromosomal rearrangement in which a portion of one chromosome swaps with a portion of a non homologous chromosome.
Transverse Tubules (T-Tubules)
A system of tubules that provides Chanel’s for ion flow throughout skeletal and cardiac muscle fibers to facilitate the propagation of an action potential.
Tricuspid Valve
A valve located between the right atria and the right ventricle. The valve consists of three cusps and prevents back flow of blood form the right ventricle to the right atrium.
Tropic hormones
Hormones that travel to a target tissue and cause the release of another hormone. A hormone downstream will cause physiological effect.
Umbilical Cord
Connects the vasculature of the fetus to the placenta.
Vague Nerve
One of the twelve cranial nerves that provides parasympathetic signaling to the thoracic and abdominal cavities.
Veins
Vessels that carry blood toward the heart. These vessels are thin-walled and have valves to prevent backflow.
Ventricles
The muscular lower chambers of the heart. The right ventricle pumps deoxygenated blood to the lungs through the pulmonary arteries while the left ventricle pumps oxygenated blood throughout the body through the aorta.
Viili
Finger like projections that extend out of the small intestine in order to increase surface area for maximal absorption.
White Fibers
Fast-twitch muscle fibers. They are primarily anaerobic and fatigue more easily than red fibers.
Zona Pellucida
Inner layer of glycoproteins surrounding the oocyte. These glycoproteins are secreted by follicular cells and the oocyte itself. Penetration of the zona pellucida by a sperm cell forces the secondary oocyte to undergo meiosis II
Zygote
A fertilized egg. Develops into a morula after a number of rounds of cleavage
Adaptive Immunity
A highly specific form of immunity that develops in response to exposure pathogens; consists of both moral immunity and cytotoxic immunity
Adrenal Cortex
Synthesized and releases corticosteroids. Glucocorticoids are stimulated by adrenocorticotropic hormone (ACTH), whereas mineralocorticoids are stimulated by angiotensin II. Cortical sex hormones include androgens like testosterone
Adrenal Medulla
Synthesizes and releases epinephrine and norepinephrine, which stimulate an increase in the metabolic rate and blood glucose levels.
Adrenocorticotropic Hormone (ACTH)
Synthesized and released by the anterior pituitary, ACTH stimulates the adrenal cortex to synthesize and secrete glucocorticoids. ACTH is regulated by corticotropin releasing factor (CRF), which is released by the hypothalamus.
Afueren Neurons
Neurons that carry information to the central nervous system from the periphery. Also called sensory neurons.
Aldosterone
A steroid hormone produced in the adrenal cortex that is responsible for reabsorption of sodium and water and excretion of potassium and hydrogen ions.
Allantois
The embryonic membrane that contains the growing embryo’s waste products.
Alleles
Genes coding for alternative forms of a given trait
Amino Acid-Derivative Hormones
Hormones that are synthesized by modifying amino acids. Most amino derivative hormones act via secondary messengers, while some act in a fashion similar to steroid hormones.
Amnion
The innermost extraembryonic membrane; produces amniotic fluid in which the growing fetus is suspended.
Anterior pituitary
Synthesizes and releases many vital hormones, including follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone, thyroid-stimulating or one, prolactin, endorphins, and growth hormones (“FLAT PEG”). The anterior pituitary is under the hormonal control of the hypothalamus.
Antidiuretic Hormone (ADH)
A peptide hormone, also known as vasopressin, which acts on the collecting duct to increase water reabsorption. ADH is produced by the hypothalamus and stored in the posterior pituitary
Antigen
A substance that is bound by an antibody, causing an immune reaction
Appendicular Skeleton
The bones of the pelvis, pelvis girdles, and the limbs.
Archenteron
The central cavity in the gastrula stage of embryological development; it is lined by endoderm and ultimately gives rise to the adult digestive tract
Arteries
Vessels that carry blood away from the heart. These vessels are muscular and do not have valves.
Ascending Limb of the Loop of Henle
A portion of the nephron not permeable to water. As the filtrate flows up the ascending limb through a decreasing concentration in the interstitium, NaCl is first passively, then actively removed from the filtrate, decreasing filtrate concentration.
Atria
The two thin-walled upper chambers of the heart the right atrium receives deoxygenated blood from the venae cavae, while the left atrium receives oxygenated blood from the pulmonary veins.
Atrioventricular Valves
Valves coated between the atria and the ventricles (tricuspid valve and mitral valve).
Axial skeleton
The skull, vertebral column, rib cage, and hyoid bone.
Axon Hillock
The portion of the neuron that connects the cell body (soma) to the axon. The impulses the neuron receives from all the dendrites are summed up at the axon hillock to determine whether or not an action potential will be initiated.