Biology Flashcards
Synonymous with antibody; produced in response to a specific foreign substance that recognizes and binds to that antigen and triggers an immune response.
Immunoglobulin
Vessels that carry blood toward the heart. These vessels are thin-walled and have valves to prevent backflow.
Veins
Synthesized and released by the thyroid gland, thyroid hormones triiodothyronine (T3) and thyroxine (T4) stimulate cellular respiration as well as protein and fatty acid synthesis and degradation.
Thyroid Hormones
A hormone that is secreted by the duodenum in response to the presence of chyme. CCK stimulates the release of bile and pancreatic enzymes into the small intestine, and promotes satiety.
Cholecystokinin (CCK)
The portion of the cell containing the centrioles.
Centrosome
Describes a situation in which an organism heterozygous for a trait will have a phenotype that expresses both alleles in full. Both alleles, therefore, are dominant.
Codominance
Insulating structure that surrounds axons. Action potentials cannot take place in areas of the axon that are myelinated.
Myelin Sheath
Type of muscle found within the heart; may contain one or two nuclei. Involuntary, like smooth muscle, but appears striated, like skeletal muscle. Able to depolarize independent of the nervous system.
Cardiac Muscle
Hormones that are synthesized by modifying amino acids. Most amino acid-derivative hormones act via secondary messengers, while some act in a fashion similar to steroid hormones.
Amino Acid-Derivative Hormones
Genes coding for alternative forms of a given trait.
Alleles
A surface protein expressed on red blood cells that can induce an immune response. Introduction of Rh factor into the blood of a person who is Rh- may result in a fatal hemolysis reaction.
Rh Factor
Synthesizes and releases many vital hormones, including follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone, thyroid-stimulating hormone, prolactin, endorphins, and growth hormone (“FLAT PEG”). The anterior pituitary is under the hormonal control of the hypothalamus.
Anterior Pituitary
An alkaline fluid synthesized in the liver, stored in the gall bladder, and released into the duodenum. Bile aids in the emulsification, digestion, and absorption of fats.
Bile
The central nervous system consists of the brain and the spinal cord.
Central Nervous System
An organism that makes ATP by aerobic respiration if oxygen is present, but that can switch to fermentation for sufficient ATP when oxygen is not available.
Facultative Anaerobe
The simplest division of a set of values; the middle value that divides the values into the upper half and lower half.
Median
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.
Atria
Much more dense than spongy bone, compact bone consists of Haversian systems (osteons).
Compact Bone
Method of asexual reproduction by which prokaryotes divide. The circular DNA molecule replicates and then moves to the edge of the cell. The cell then divides into two daughter cells of equal size.
Binary Fission
Mutation in which a number of nucleotides (except multiples of three) are either deleted or inserted. Such mutations lead to a shift in the DNA reading frame and often result in the translation of nonfunctional proteins.
Frameshift Mutation
The likelihood of two genes on the same chromosome being separated during crossing over onto two different chromosomes; equal to the proportion of gametes that receive these recombinant chromosomes. If the recombination frequency of two particular traits is high, it can be inferred that they lie far apart from each other.
Recombination Frequency
The stage of the cardiac cycle in which the heart muscle relaxes and collects blood into its chambers.
Diastole
The layer of skin beneath the epidermis that is subdivided into the papillary layer and the reticular layer. It contains the sweat glands, sense organs, blood vessels, and the bulbs of hair follicles; it is derived from the mesoderm.
Dermis
A substance that is bound by an antibody, causing an immune reaction.
Antigen
Stem cells that can differentiate into multiple cell types within a particular group. For example, hematopoietic stem cells are able to differentiate into many different types of blood cells, but not into any other cell type.
Multipotent
Describes an allele that requires two copies to be expressed.
Recessive
Type of natural selection where the average phenotype is favored while those outside the norm are eliminated.
Stabilizing Selection
The fluid discharged during ejaculation. Semen consists of sperm cells and seminal fluid (fluid from the prostate and bulbourethral glands).
Semen
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.
Spongy Bone
Slow-twitch muscle fibers. They are primarily aerobic and contain many mitochondria and high levels of myoglobin.
Red Fibers
Section of the digestive tract that can be subdivided into three sections: duodenum, jejunum, and ileum. Most digestion takes place in the duodenum and most absorption takes place in the jejunum and the ileum.
Small Intestine
Maintenance of a constant internal body temperature.
Thermoregulation
The separation of homologous chromosomes during anaphase I of meiosis.
Disjunction
Expressed as breaths per minute. Raising the respiratory rate can decrease the amount of carbon dioxide in the blood, thus increasing the pH. Likewise, decreasing the respiratory rate increases the concentration of carbon dioxide in the blood, resulting in a lower pH.
Respiratory Rate
Circulatory routes in which blood travels through two capillary beds before returning to the heart. Some examples include the hypophyseal portal system, the hepatic portal system, and the renal portal system.
Portal Systems
A solid ball of cells that develops from the zygote through cleavage. When the interior of the morula becomes hollow, it becomes known as a blastula.
Morula
The organ formed by the uterus and the extraembryonic membranes of the fetus. The placenta contains a network of capillaries through which exchange between the fetal circulation and the maternal circulation takes place.
Placenta
A fertilized egg. Develops into a morula after a number of rounds of cleavage.
Zygote
Fast-twitch muscle fibers. They are primarily anaerobic and fatigue more easily than red fibers.
White Fibers
Fingerlike projections that extend out of the small intestine in order to increase surface area for maximal absorption.
Villi
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.
Ventricles
Synthesized and released by the anterior pituitary, TSH stimulates the thyroid gland to absorb iodine and to synthesize and secrete thyroid hormones. TSH is regulated by thyroid releasing hormone (TRH), which is released by the hypothalamus.
Thyroid-Stimulating Hormone (TSH)
Synthesized and released by the parathyroid gland, PTH increases blood Ca^2+ concentration by increasing Ca2+ reabsorption in the kidneys and by stimulating calcium release from bone.
Parathyroid Hormone (PTH)
The material that passes from the blood vessels into Bowman’s space.
Filtrate
Plasmids that have the ability to integrate into the host genome.
Episomes
Carries nutrients (monosaccharides, amino acids, and small fatty acids) absorbed in the small intestine to the liver, where they are modified to enter circulation.
Hepatic Portal Vein
The group of cells in a blastocyst (mammalian blastula) that develop into the embryo.
Inner Cell Mass
Network of capillaries within Bowman’s capsule that serves as the site of filtration. Blood cells and proteins are too large to be filtered, but ions, glucose, and amino acids readily pass into the filtrate.
Glomerulus
A protein secreted by parietal cells of the stomach that is necessary for vitamin B12 absorption.
Intrinsic Factor
Stores and releases hormones (oxytocin and ADH) synthesized by the hypothalamus. The release of these hormones is triggered by an action potential that originates in the hypothalamus.
Posterior Pituitary
A steroid hormone produced in the adrenal cortex that is responsible for reabsorption of sodium and water and excretion of potassium and hydrogen ions.
Aldosterone
A shunt that connects the right atrium to the left atrium in order to bypass the fetal lung.
Foramen Ovale
Produced and secreted by the δ-cells of the pancreas, somatostatin inhibits the release of glucagon and insulin.
Somatostatin
One of the twelve cranial nerves that provides parasympathetic signaling to the thoracic and abdominal cavities.
Vagus Nerve
Enzyme that catalyzes the conversion of carbonic acid to carbon dioxide and water as well as the formation of carbonic acid from carbon dioxide and water. Important in the bicarbonate buffer system.
Carbonic Anhydrase
A system of tubules that provides channels for ion flow throughout skeletal and cardiac muscle fibers to facilitate the propagation of an action potential.
Transverse Tubules (T-Tubules)
Secreted as pepsinogen by the chief cells of the stomach, this enzyme cleaves peptide bonds, starting the digestion of proteins into individual amino acids.
Pepsin
Glands that synthesize and secrete hormones into the circulatory system. Examples include the hypothalamus, pituitary gland, pineal gland, pancreas, testes, ovaries, adrenal glands, thyroid gland, and parathyroid glands.
Endocrine Glands
A multilayered sac of cells that protects and nourishes the developing ovum.
Follicle
The outermost of the three primary germ layers; gives rise to the skin, nervous system, lens of the eye, and inner ear.
Ectoderm
Created by analyzing recombination frequencies of linked genes; a schematic that shows the distance between two genes or the order of several genes on a chromosome.
Genetic Map
A shunt that connects the pulmonary artery to the aorta in order to bypass the fetal lung.
Ductus Arteriosus
Cells that produce myelin in the peripheral nervous system.
Schwann Cells
The innermost of the three primary germ layers; gives rise to the linings of the digestive and respiratory tracts and to parts of the liver, pancreas, thyroid, and bladder.
Endoderm
Organisms that require a host cell to express their genes and reproduce.
Obligate Intracellular Organisms
A collection of millions of neurons within the gastrointestinal system that governs the function of the GI tract. This system is able to function independently of the brain and spinal cord.
Enteric Nervous System
Hormone synthesized and released by the thyroid gland that decreases plasma Ca^2+ concentration.
Calcitonin
A balance between hydrostatic and oncotic pressure on both sides of a membrane, essential for maintaining proper fluid volumes and solute concentrations inside and outside the vasculature.
Starling Forces
Cells in the bone matrix that are involved in bone degradation.
Osteoclasts
Mutation in which one nucleotide base is substituted by another. The protein products may or may not be functional.
Point Mutation
Synthesizes 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 Cortex
Valves (the aortic valve and the pulmonic valve) that prevent backflow of blood from the arteries into the ventricles.
Semilunar Valves
Synthesizes and releases epinephrine and norepinephrine, which stimulate an increase in the metabolic rate and blood glucose levels.
Adrenal Medulla
The central cavity in the gastrula stage of embryological development; it is lined by endoderm and ultimately gives rise to the adult digestive tract.
Archenteron
Neurons that carry information to the central nervous system from the periphery. Also called sensory neurons.
Afferent Neurons
A unit of DNA that encodes a specific protein or RNA molecule.
Gene
A small, short-lived haploid cell created during oogenesis that receives very little cytoplasm, organelles, or nutrients.
Polar Body
Hormone synthesized and released by the ovaries, corpus luteum, and placenta. During the luteal stage of the menstrual cycle, the corpus luteum secretes progesterone, which, along with estrogen, stimulates the development and maintenance of the endometrial walls for implantation of the embryo.
Progesterone
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.
Superior Vena Cava
Digestive enzyme secreted by cells in the duodenum. This enzyme converts trypsinogen to trypsin. Trypsin is then able to activate other pancreatic enzymes to allow digestion to continue within the duodenum.
Enteropeptidase
The most frequently occurring value in a set of observations.
Mode
The space between the axon terminal of one neuron and the dendrite of another neuron (or membrane of an effector organ) where neurotransmitters are released.
Synapse
Polar hormones incapable of permeating the cell membrane that bind to surface receptors and act through secondary messengers.
Peptide Hormones
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.
Second Messenger
The stage of the cardiac cycle in which the heart muscle contracts and pumps blood.
Systole
The electrical impulse originates in the sinoatrial (SA) node, located in the right atrium. And then travels through the atrioventricular (AV) node, then through the bundle of His, and finally through the Purkinje fibers.
Pathway of the Electrical Impulse in the Heart
Essential organ of the human body responsible for the production of bile, detoxification of ingested substances, production of urea, and the processing and modification of nutrients for storage. The liver also produces albumin (a protein that maintains blood oncotic pressure) and clotting factors.
Liver
A short period of time immediately following an action potential in which neurons or muscle cells are unresponsive to a stimulus (absolute refractory period). In some cases, a stimulus that is much larger than usual causes an action potential in a cell in a refractory period (relative refractory period).
Refractory Period
All cells excluding the germ (reproductive) cells.
Somatic Cells
A highly specific form of immunity that develops in response to exposure to pathogens; consists of both humoral immunity and cytotoxic immunity.
Adaptive Immunity
Hormone secreted by the interstitial cells of the testes. Testosterone is responsible for embryonic sexual differentiation, male sexual development, and the maintenance of masculine secondary sexual characteristics.
Testosterone
A valve located between the right atria and the right ventricle. The valve consists of three cusps and prevents backflow of blood from the right ventricle to the right atrium.
Tricuspid Valve
Located in the testes, the seminiferous tubules are the site of sperm production.
Seminiferous Tubules
Ends of axons that form one side of the synaptic cleft; the location where vesicles of neurotransmitters are stored.
Synaptic Terminals
Subsequent infections by pathogens that trigger a more immediate response from the memory cells produced during the primary immune response.
Secondary Response
Stem cells that have the ability to become any cell within any system of the body. Embryonic stem cells are totipotent.
Totipotent
Portion of the nephron permeable only to water. The filtrate becomes more concentrated (loses water) as it travels through the descending limb due to the increasing concentration of the interstitium.
Descending Limb of the Loop of Henle
Portion of the nephron permeable to water and ions. As the filtrate flows down the collecting duct through the increasing concentration of the interstitium, the filtrate is concentrated. The degree of water reabsorption in the collecting duct is controlled by the action of the hormone ADH.
Collecting Duct
Cells that line blood vessels. These cells are able to produce and release chemicals that aid in vasodilation and vasoconstriction. In addition, damage to these cells results in the release of mediators that aid in clotting.
Endothelial Cells
Gaps between segments of myelin sheath where action potentials can take place, allowing for saltatory conduction.
Nodes of Ranvier
A means by which action potentials jump from node to node along an axon.
Saltatory Conduction
Division of the peripheral nervous system that is responsible for voluntary movement.
Somatic Nervous System
A process that occurs when the voltage-gated Na^+ channels close and voltage-gated K^+ channels open during an action potential, allowing K^+ to rush out of the cell and repolarize it.
Repolarization
Involuntary muscular contractions that push food down the digestive tract.
Peristalsis
The oxygen-carrying component of blood. These anaerobic cells, which lack organelles, are packed with hemoglobin and have a characteristic biconcave, disk-like shape that facilitates gas exchange and mobility within blood vessels. Also called red blood cells.
Erythrocytes
A cross between an organism of an undetermined genotype and another that is homozygous recessive for the trait of interest.
Test Cross
Site where glucose, amino acids, and other important organic molecules are reabsorbed. The proximal convoluted tubules lie in the cortex of the kidney.
Proximal Convoluted Tubule
Chemical messengers released from synaptic terminals of a neuron that can bind to and stimulate a postsynaptic cell.
Neurotransmitters
A hormone synthesized and released by the anterior pituitary that stimulates milk production and secretion in female mammary glands.
Prolactin
A valve between the stomach and the small intestine that regulates the flow of chyme into the duodenum.
Pyloric Sphincter
The genetic makeup of an individual.
Genotype
Liquid portion of blood, an aqueous mixture of nutrients, salts, respiratory gases, hormones, and blood proteins.
Plasma
Cells in the bone tissue that secrete the organic constituents of the bone matrix. Osteoblasts develop into osteocytes.
Osteoblasts
All neurons that are not part of the central nervous system, including sensory and motor neurons that connect to the central nervous system. Can be divided into the somatic nervous system and the autonomic nervous system.
Peripheral Nervous System
Breakdown of food particles into smaller particles through such activities as biting, chewing, and churning.
Mechanical Digestion
A process that occurs when the voltage-gated Na^+ channels open, allowing Na^+ to rush into the cell and depolarize it.
Depolarization
Describes an allele that requires only one copy to be expressed.
Dominant
Its exocrine functions include secreting pancreatic amylase, trypsinogen, chymotrypsinogen, procarboxypeptidases A and B, and pancreatic lipase into the small intestine. Its endocrine functions include secretion of insulin and glucagon.
Pancreas
Blood vessels composed of a single layer of endothelial cells, facilitating exchange of gases, nutrients, and waste products between the blood and interstitial fluid.
Capillaries
Hormone synthesized and released by the ovaries, ovarian follicles, corpus luteum, and placenta. Estrogen stimulates the development of the female reproductive tract and secondary sexual characteristics and is partly responsible for the LH spike that causes ovulation.
Estrogen
The mucosal lining of the uterus where the embryo implants. Progesterone is necessary for the maintenance of the endometrium during pregnancy.
Endometrium
Branch of the immune system in which intracellular pathogens are eliminated by killing their host cells. T-cells are the primary mediators of cytotoxic immunity.
Cell-Mediated (Cytotoxic) Immunity
Portion of the bone where growth occurs; located in the epiphysis.
Epiphyseal Plate
Dilated ends of long bones in the appendicular skeleton.
Epiphysis
Results when two ova are fertilized by two different sperm. Because the two resulting embryos develop from distinct zygotes, they do not have identical alleles.
Dizygotic Twins
Valve located between the atria and the ventricles (tricuspid valve and mitral valve).
Atrioventricular Valves
Nonstriated muscle, responsible for involuntary action. Controlled by the autonomic nervous system.
Smooth Muscle
Primary germ layer that lies between the ectoderm and endoderm. Gives rise to the musculoskeletal system, circulatory system, excretory system, gonads, connective tissue throughout the body, and portions of the digestive and respiratory organs.
Mesoderm
The charge difference across the cell membrane of a neuron or a muscle cell while at rest. Most often maintained by the sodium-potassium pump.
Resting Potential
A modified form of endoplasmic reticulum; stores calcium that is used to trigger contraction when muscle is stimulated.
Sarcoplasmic Reticulum
The temporary joining of two organisms via a tube called a pilus, through with genetic material is exchanged; a form of sexual reproduction used by bacteria.
Conjugation
Refers to the variability in phenotypes (especially severity of a disease) that can occur with a given genotype.
Expressivity
Enzymatic breakdown of large molecules into smaller molecules.
Chemical Digestion
The structural unit of compact bone that consists of a central canal (either a Haversian or Volkmann’s canal) surrounded by a number of concentric rings of bony matrix called lamellae.
Osteons
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.
Zona Pellucida
An enzyme in retroviruses that uses RNA strands as templates for synthesizing cDNA molecules.
Reverse Transcriptase
A valve located between the left atrium and the left ventricle. The valve consists of two cusps and prevents backflow of blood from the left ventricle to the left atrium.
Mitral Valve
Changes in the composition of the gene pool by chance; often more pronounced in small populations.
Genetic Drift
A cross between two organisms where only one trait is being studied.
Monohybrid Cross
A form of chromosomal rearrangement in which a portion of one chromosome swaps with a portion of a nonhomologous chromosome.
Translocation
Connects the vasculature of the fetus to the placenta.
Umbilical Cord
Stem cells that can become other cells within the same primary germ layer. For example, after gastrulation, cells of the endodermal layer can only become derivatives of endoderm.
Pluripotent
Nonspecific immunity provided by structures and cells. Structures, such as the skin, and cells, such as macrophages, are able to recognize invaders and kill them. Some cells of the innate immune system, such as macrophages and dendritic cells, are able to signal the presence of an invader to the adaptive immune system.
Innate Immunity
The influence of a group of cells on the development of other cells. Induction is achieved by chemical substances known as inducers. The cells secreting these inducers are sometimes called organizers.
Induction
Collectively, the four chromatids involved when a pair of homologous chromosomes synapse during prophase I of meiosis.
Tetrad
The bones of the pelvis, the pectoral girdles, and the limbs.
Appendicular Skeleton
Cell division in embryogenesis that results in each cell maintaining its totipotency, or ability to develop into a complete organism by itself.
Indeterminate Cleavage
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.
Sister Chromatids
Organelle that contains hydrogen peroxide and participates in the breakdown of very long chain fatty acids.
Peroxisome
The innermost extraembryonic membrane; produces the amniotic fluid in which the growing fetus is suspended.
Amnion
The process by which a single-layered blastula becomes a three-layered gastrula.
Gastrulation
The failure of homologous chromosomes or sister chromatids to separate properly during meiosis I or meiosis II, respectively. This usually results in gametes that lack certain genes or have multiple copies of those genes.
Nondisjunction
White blood cells; the component of blood involved in cell defense and Immunity. Neutrophils, basophils, eosinophils, lymphocytes, and monocytes are types of leukocytes.
Leukocytes
Air travels through the nasal or oral cavity, pharynx, larynx, trachea, bronchi, bronchioles, and finally the alveoli (site of gas exchange).
Pathway of the Respiratory Tract
Produced and secreted by the β-cells of the pancreas, insulin decreases blood glucose concentrations by facilitating the uptake of glucose by muscle and adipose cells and the conversion of glucose to glycogen in muscle and liver cells.
Insulin
A two-phase cell division in germ cells that results in the formation of up to four haploid cells from one diploid cell.
Meiosis
A two-phase cell division in germ cells that results in the formation of up to four haploid cells from one diploid cell.
Meiosis
Synthesized and released by the anterior pituitary, FSH stimulates the maturation of ovarian follicles in females and maturation of the seminiferous tubules and sperm production in males. FSH is regulated by estrogen and gonadotropin releasing hormone (GnRH).
Follicle-Stimulating Hormone (FSH)
An increase in the rate of respiration or tidal volume. Lack of oxygen or decrease in blood pH promotes hyperventilation.
Hyperventilation
Cell division or nuclear division in somatic cells that results in the daughter nucleus receiving a full complement of the organism’s genome.
Mitosis
Outer layer of cells surrounding the oocyte. These cells are derived from follicular cells.
Corona Radiata
Tissue that forms from the collapsed ovarian follicle. Produces and secretes progesterone and estrogen.
Corpus Luteum
Section of the GI tract that consists of the cecum, the colon, and the rectum. The main function of the large intestine is to absorb salts, water, and some vitamins.
Large Intestine
The site of aerobic respiration that provides the cell with a majority of its energy in the form of ATP. The mitochondrion is a semiautonomous organelle enclosed by two membranes with an intramembrane space between the two membranes and a mitochondrial matrix enclosed by the inner membrane.
Mitochondria
Phase in viral replication in which the host cell is lysed and releases new virions.
Lytic Cycle
The alleles of different genes sort independently from one another during meiosis. We now know that this is true only for unlinked genes.
Mendel’s Law of Independent Assortment
Cells with only one copy of each chromosome. Germ cells in humans are haploid.
Haploid
The structural unit of striated muscle. It is composed of thin (mostly actin) and thick (mostly myosin) filaments.
Sarcomere
The outermost extraembryonic membrane; contributes to the formation of the placenta.
Chorion
The embryonic membrane that contains the growing embryo’s waste products.
Allantois
The synthesis of specific antibodies by activated B-cells in response to an antigen. These antibodies bind to the antigen and either clump together to become insoluble, neutralize the antigen, or attract other cells that engulf and digest the pathogen.
Humoral Immunity
Mature sperm specialized for transporting the genetic information from the male to the ovum.
Spermatozoa
The process by which a morula develops into a blastula with a fluid-filled cavity called a blastocoel.
Blastulation
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.
Ascending Limb of the Loop of Henle
A system of vessels and lymph nodes that collect interstitial fluids and return them to the circulatory system, thereby maintaining fluid balance. The lymphatic system is also involved in lipid absorption and lymphocyte activation.
Lymphatic System
Also called Leydig cells, interstitial cells are located in the testes and secrete testosterone and other androgens.
Interstitial Cells
The average, calculated as a sum of observed values divided by the number of observed values.
Mean
The physical manifestation of an individual’s genotype.
Phenotype
A protein that hydrolyzes one ATP to transport three Na^+ out of the cell for every two K^+ it transports into the cell.
Sodium-Potassium Pump
Result when a zygote splits into two embryos. Because both embryos contain identical alleles, they are often called identical twins.
Monozygotic Twins
An organelle that plays a role in the packaging and secretion of proteins and other molecules produced intracellularly.
Golgi Apparatus
A flap of cartilage that covers the glottis when swallowing food in order to prevent food particles from entering the larynx.
Epiglottis
The contraction of the diaphragm and the intercostal muscles increases the volume of the thoracic cavity, reducing the pressure in the intrapleural space. This decrease in pressure creates a vacuum that causes the lungs to suck in air.
Negative Pressure Breathing
Diploid cells that undergo meiosis I to form two haploid secondary spermatocytes.
Primary Spermatocytes
Proteins or sugars found on the erythrocyte cell surface. Three antigens used to differentiate blood groups are A, B, and Rh. If a host organism is transfused with erythrocytes containing antigens that the host does not have, an immune response will be triggered, leading to hemolysis.
Blood Antigens
Division of cells during embryogenesis in which each cell specializes early in development. By extension, each cell is not necessarily able to differentiate into an entire organism on its own.
Determinate Cleavage
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.
Axon Hillock
Type of natural selection where both phenotypic extremes are favored over the average phenotype.
Disruptive Selection
The skull, vertebral column, ribcage, and hyoid bone.
Axial Skeleton
Hormones that travel to a target tissue to causes an action without another hormone acting as an intermediary.
Direct Hormones
Norepinephrine, epinephrine, and dopamine - neurotransmitters; also, hormones produced by the adrenal medulla that play a significant role in the sympathetic nervous system.
Catecholamines
Chromosomes in their uncoiled state. Chromatin itself is not visible as organized chromosomes under a light microscope.
Chromatin
Vessels that carry blood away from the heart. These vessels are muscular and do not have valves.
Arteries
Located in the stomach; secrete HCl and various enzymes (such as pepsin) when stimulated by gastrin.
Gastric Glands
A group of neuronal cell bodies in the peripheral nervous system. Maybe sensory or autonomic.
Ganglia
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 voltage-gated ion channels. Action potentials are all-or-nothing events.
Action Potential
The functional unit of the kidney. Can be subdivided into Bowman’s capsule, proximal convoluted tubule, descending limb of the loop of Henle, ascending limb of the loop of Henle, distal convoluted tubule, and collecting duct.
Nephron
A firm, elastic, translucent connective tissue consisting of collagenous fibers embedded in chondrin. Produced by cells called chondrocytes. Cartilage is the principal component of embryonic skeletons and can harden and calcify into bone (ossify).
Cartilage
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.
Adrenocorticotropic Hormone (ACTH)
Combination of partially digested food and acid that forms in the stomach.
Chyme
A foundational belief in modern biology that all living things are composed of cells, the cell is the basic functional unit of life, that all cells arise from preexisting cells, and that DNA is the genetic material.
Cell Theory
Viruses that can only infect bacteria.
Bacteriophages
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.
Antidiuretic Hormone (ADH)
Cylindrical shaft of a long bone. Filled with bone marrow for the production of blood cells.
Diaphysis
Organisms that contain two different alleles for the same gene on homologous chromosomes.
Heterozygous
Nonpolar hormones that cross the cell membrane and act by binding intracellular receptors.
Steroid Hormones
Chromosomes in a diploid cell that contain alleles for the same trait at corresponding loci.
Homologous Chromosomes
Glands located in the walls of the stomach that secrete the hormone gastrin to increase gastric acid production.
Pyloric Glands
Type of natural selection where one extreme phenotype is favored over the average phenotype and other extreme phenotypes.
Directional Selection
A nucleic acid found in both the nucleus and cytoplasm and most closely linked with transcription and translation, as well as some gene regulation.
Ribonucleic Acid (RNA)
Type of muscle responsible for voluntary movement, consisting of multinucleated, striated (striped) muscle fibers.
Skeletal Muscle
The initial response to a specific antigen. During a primary response, T- and B-cells are activated and specific antibodies and memory cells for the antigen are produced.
Primary Response
A form of chromosomal rearrangement in which a portion of a chromosome breaks off and rejoins the same chromosome in the reverse position.
Inversion
Hormones that travel to a target tissue and cause the release of another hormone. A hormone downstream will cause the physiological effect.
Tropic Hormones
The space between the two membranes (visceral pleura and parietal pleura) that cover the lungs.
Intrapleural Space
The percentage of people in a population with a certain genotype who express the associated phenotype.
Penetrance
The outermost layer of skin, which is composed of the following sublayers: stratum basalis, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum. Serves as a protective barrier against microbial attack. Derived from the ectoderm.
Epidermis
Reflex pathway that has only one synapse between the sensory neuron and the motor neuron (such as the knee-jerk reflex).
Monosynaptic Reflex
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.
Signaling Cascade
The minimal voltage the must be reached in order for an action potential to be fired at the axon hillock.
Threshold Voltage
An extension of the neuron that transmits impulses toward the cell body.
Dendrite
A large vein that returns deoxygenated blood from the lower body and the lower extremities to the right atrium of the heart.
Inferior Vena Cava
Cells at the tip of the neural fold; this group of cells gives rise to many components of the peripheral nervous system and a number of other cell types throughout the body.
Neural Crest Cells
Neurons that carry information from the central nervous system to other parts of the body. Also called motor neurons.
Efferent Neurons
Cell fragments involved in the clotting process. Come from megakaryocytes in the bone marrow.
Platelets
Cells with two copies of each chromosome, usually one from the mother and one from the father. Eukaryotic somatic cells are diploid.
Diploid
Glands that synthesize and secrete substances through ducts. The mammary glands and sweat glands are examples of exocrine glands.
Exocrine Glands
Synthesized and released by the anterior pituitary, LH stimulates ovulation and the formation of the corpus luteum. LH is regulated by estrogen, progesterone, and gonadotropin releasing hormone (GnRH).
Luteinizing Hormone (LH)
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).
Surfactant
Organisms that contain two identical alleles of the same gene on homologous chromosomes.
Homozygous
The exchange of genetic material between homologous chromosomes that occurs during prophase I of meiosis. Crossing over aids in evolution and genetic diversity by unlinking linked genes.
Crossing Over
Maintenance of water and solute concentrations.
Osmoregulation
Produced and secreted by the α-cells of the pancreas, glucagon increases blood glucose concentration by promoting gluconeogenesis and the conversion of glycogen to glucose in the liver.
Glucagon
Mendel’s postulation that there are alternate versions of genes that account for genetic variation. Each individual has two alleles for each gene, with one maternal and one paternal in origin. During meiosis, these two alleles separate into two gametes each.
Mendel’s Law of Segregation
Synthesized and released by the anterior pituitary, endorphins inhibit the perception of pain.
Endorphins
Synthesized and released by the adrenal cortex, glucocorticoids raise blood glucose levels while decreasing protein synthesis.
Glucocorticoids
A membrane-bound vesicle that contains hydrolytic enzymes used for intracellular digestion.
Lysosome
Swelling along the lymph vessels where lymph is filtered by leukocytes to remove antigens.
Lymph Nodes
Phase of the cell cycle in which cell division does not take place. Includes the G1 phase, S phase, and G2 phase. Cells in this phase may or may not be growing.
Interphase
Describes a situation in which an organism heterozygous for a trait will have a phenotype that is intermediate between both homozygous phenotypes. Neither allele, therefore, is dominant or recessive.
Incomplete Dominance
Layer of loose connective tissue below the dermis that binds the dermis to the body.
Hypodermis
Synthesized and released by the anterior pituitary, GH stimulates bone and muscle growth as well as glucose conservation. GH is inhibited by somatostatin and stimulated by growth hormone releasing hormone (secreted by the hypothalamus).
Growth Hormone (GH)
Contains brush-border enzymes such as maltase, sucrase, and lactase to digest disaccharides. Other enzymes of these glands include aminopeptidase, dipeptidase, and enteropeptidase.
Intestinal Glands
Phase of viral replication in which the DNA of the bacteriophage becomes integrated in the host genome and replicates as the bacteria replicates.
Lysogenic Cycle
The large vesicle at the head of a sperm cell containing enzymes that degrade the ovum cell membrane to allow fertilization.
Acrosome
Relies primarily on the carbonic acid buffer system, demonstrated by the equation:
CO2 + H2O ⇌ H2CO3 ⇌ H^+ + HCO3^-
Release of carbon dioxide causes increased formation of water and an increase in pH. Increased retention of HCO3^- causes the pH to rise as well.
Blood Buffer System
A shunt that connects the umbilical vein to the inferior vena cava in order to bypass the fetal liver.
Ductus Venosus
