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Kaplan Biology
Kaplan Biology Cards
| Term | Definition |
|---|---|
| Action Potential | A sharp change in the membrane potential of neurons or muscle cells cause by a change in the selective permeability to NA+ and K+ using voltage-gated ion channels. All or nothing events |
| Acrosome | The largest vesicle at the head of a sperm cell containing enzymes that degrade the ovum cell membrane to allow fertilization |
| Adaptive Immunity | A highly specific form of immunity that develops in response to exposure to pathogens; consists of both humoral immunity and cytotoxic immunity. |
| Adrenal Cortex | Synthesizes and releases corticosteroids. Glucocorticoids are stimulated by adrenocorticotrophic hormone (ACTH), whereas mineralocorticoids are stimulated by angiotensin II. Cortical sex hormones include androgens such as testosterone |
| Adrenal Medulla | Synthesizes and releases epinephrine and norepinephrine, which stimulates an increase in the metabolic rate and blood glucose levels |
| Adrenocorticotrophic Hormone (ACTH) | Synthesized and released by the anterior pituitary, stimulates the adrenal cortex to synthesize and secrete glucocorticoids. Is regulated by corticotropin releasing factor (CRF), which is released by the hypothalamus |
| Afferent Neurons | Neurons that carry information to the central nervous system from the periphery. Also called sensory neurons |
| Aldosterone | A steroid 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 acid-derivative hormones act via secondary messengers, while some act in a fashion similar to steroid hormones |
| Amnion | The innermost extraembryonic membrane; produces the amniotic fluid which the growing fetus is suspended |
| Anterior Pituitary | Synthesized and releases many vital hormones, including follicle-stimulating hormone, luteinizing hormone, adrenocorticotrophic hormone, thyroid-stimulating hormone, prolactin, endorphins, and growth hormone (FLAT PEG). Under the hormonal control of the h |
| Antidiuretic Hormone (ADH) | A peptide hormone, also known as vasopressin, that acts on the collecting duct to increase water reabsorption. 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, the pectoral 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. Vessels are muscular and do not have valves |
| Ascending Limb of the Loop of Henle | Portion of the nephron not permeable to water. As the filtrate flows up the ascending limb through a decreasing concentration in the interstitial, 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 located between the atria and the ventricles (tricuspid valve and mitral valve) |
| Axial Skeleton | The skull, vertebral column, ribcage, 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 |
| Bacteriophages | Viruses that can only infect bacteria |
| Bile | An alkaline fluid synthesized in the liver, stored in the gall bladder, and released into the duodenum. Aids in the emulsification, digestion, and absorption of fats |
| Binary Fission | 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 |
| Blastulation | The process by which a morula develops into a blastula with a fluid-filled cavity called a blastocoel |
| Blood Antigens | 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 tr |
| Blood Buffer System | Relies primarily on the carbonic acid buffer system, demonstrated by the equation: CO_2 + H_2O<> H_2CO_3 <> H+ + HCO_3^- Release of carbon dioxide causes increased formation of water and an increase in pH Increase retention of HCO_3^- causes the pH to |
| Calcitonin | Hormone synthesized and released by the thyroid gland that decreases plasma CA^2+ concentration |
| Capillaries | Blood vessels composed of a single layer of endothelial cells, facilitating exchange of gases, nutrients, and waste products between the blood and interstitial fluid |
| Carbonic Anhydrase | 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 |
| Cardiac Muscle | 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 |
| Cartilage | A firm, elastic, translucent connective tissue consisting of collagenous fibers embedded in chondrinid. Produced by cells called chondrocytes. Is the principal component of embryonic skeletons and can harden and calcify into bone (ossify) |
| Catecholamines | Norepinephrine, epinephrine, and dopamine- neurotransmitters; also hormones produced by the adrenal medulla that play a significant role in the sympathetic nervous system |
| Cell-Mediated (Cytotoxic) Immunity | Branch of the immune system in which intracellular pathogens are eliminated by killing their host cells. T-cells are the primary mediators |
| Cell Theory | 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 |
| Central Nervous System | Consist of the brain and the spinal cord |
| Centrosome | The portion of the cell containing the centrioles |
| Chemical Digestion | Enzymatic breakdown of large molecules into smaller molecules |
| Cholecystokinin (CCK) | 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 |
| Chorion | The outermost extraembryonic membrane, contributes to the formation of the placenta |
| Chromatin | Chromosomes in their uncoiled state. Is not visible as organized chromosomes under a light microscope |
| Chyme | Combination of partially digested food and acid that forms in the stomach |
| Codominance | 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 |
| Collecting Duct | Portion of the nephron permeable to water and ions. As the filtration 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 control |
| Compact Bone | Much more dense than spongy bone, consist of Harversian systems (Osteons) |
| Conjugation | The temporary joining of two organisms via a tube called a pilus, through which genetic material is exchanged; a form of sexual reproduction used by bacteria |
| Corona Radiata | Outer layer of cells surrounding the oocyte. These cells are derived from follicular cells |
| Corpus Luteum | Tissues that form from the collapsed ovarian follicle. Produces and secretes progesterone and estrogen |
| Crossing Over | The exchange of genetic material between homologous chromosomes that occurs during prophase I meiosis. Crossing over aids in evolution and genetic diversity by unlinking genes |
| Dendrite | An extension of the neuron that transmits impulses toward the cell body |
| Depolarization | A process that occurs when the voltage-gated Na+ channels open, allowing Na+ to rush into the cell and depolarize it |
| Dermis | The layer of the kin 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 |
| Descending Limb of the Loop of Henle | 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 |
| Determinate Cleavage | Division of cells during embryogenesis in which each cell specializes early development. By extension, each cell is not necessarily able to differentiate into an entire organism on its own |
| Diaphysis | Cylindrical shaft of a long bone. Filled with bone marrow for the production of blood cells |
| Diastole | The stage of the cardiac cycle in which the heart muscle relaxes and collects blood into its chambers |
| Diploid | Cells with two copies of each chromosome, usually one from the mother and one from the father. Eukaryotic somatic cells are diploid |
| Direct Hormones | Hormones that travel to a target tissue to cause an action without another hormone acting as an intermediary |
| Directional Selection | Type of natural selection where one extreme phenotype is favored over the average phenotype and other extreme phenotypes |
| Disjunction | The separation of homologous chromosomes during anaphase I of meiosis |
| Disruptive Selection | Type of natural selection where both phenotypic extremes are favored over the average phenotype |
| Dizygotic Twins | 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. Also referred to as fraternal twins |
| Dominant | Describes an allele that requires one one copy to be expressed |
| Ductus Arteriosus | A shunt that connects the pulmonary artery to the aorta in order to bypass the fetal lung |
| Ductus Venosus | A shunt that connects the umbilical vein to the inferior vena cava in order to bypass the fetal liver |
| Ectoderm | The outermost of the three primary germ layers; gives rise to the skin, nervous system, lens of the eye, and inner ear |
| Efferent Neurons | Neurons that carry information from the central nervous system to other parts of the body. Also called motor neurons |
| Endocrine Glands | 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 |
| Endoderm | The innermost of the three primary germs layers, gives rise to the linings of the digestive and respiratory tracts and to part of the liver, pancreas, thyroid, and bladder |
| Endometrium | The mucosal lining of the uterus where the embryo implants. Progesterone is necessary for the maintenance of the endometrium during pregnancy |
| Endorphins | Synthesized and released by the anterior pituitary; inhibit the perception of pain |
| Endothelial Cells | 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 |
| Enteric Nervous System | 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 |
| Enteropeptidase | 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 |
| Epidermis | 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 |
| Epiglottis | A flap of cartilage that covers the glottis when swallowing food in order to prevent food particles from entering the larynx |
| Epiphyseal Plate | Portion of the bone where growth occurs; located in the epiphysis |
| Epiphysis | Dilated ends of long bones in the appendicular skeleton |
| Episomes | Plasmids that have the ability to integrate into the host genome |
| Erythrocytes | The oxygen-carrying component of blood. These anerobic cells, which lack organelles, are packed with hemoglobin and have characteristic biconcave, disk-like shape facilitate gas exchange and mobility within blood vessels. Also called red blood cells. |
| Estrogen | Hormone synthesized and released by the ovaries, ovarian follicles, corpus luteum, and placenta. Stimulates the development of the female reproductive tract and secondary sexual characteristics and is partly responsible for the LH spike that causes ovulat |
| Exocrine Glands | Glands that synthesize and secrete substances through ducts. The mammary glands and sweat glands are examples |
| Expressivity | Refers to the variability in phenotypes (especially severity of a disease) that can occur with a given genotype |
| Facultative Anaerobe | 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 |
| Filtrate | The materials that passes from the blood vessels into Bowman's space |
| Follicle | A multilayered sac of cells that protects and nourishes the developing ovum |
| Follicle-Stimulating Hormone (FSH) | Synthesized and released by the anterior pituitary, FSH stimulates maturation of ovarian follicles in females and maturation of ovarian follicles in females and maturation of seminiferous tubules and sperm production in makes. Regulated in males. Regulate |
| Foramen Ovalle | A shunt that connects the right atrium to the left atrium in order to bypass the fetal lung |
| Frameshift Mutation | Mutation in which a number of nucleotides (expect) multiples of three) are either deleted or inserted. Such mutation lead to a shift in the a DNA reading frame and often result in the translation of nonfunctional proteins |
| Ganglia | A group of neural cell bodies in the peripheral nervous system. May be sensory or autonomic |
| Gastric Glands | Located in the stomach; secreted HCl and various enzymes (such as pepsin) when stimulated by gastrin |
| Gastrulation | The process by which a single-layered blastula becomes a three-layered gastrula |
| Gene | A unit of DNA that encodes a specific protein or RNA molecule |
| Genetic Drift | Changes in the composition of the gene pool by chance; often more pronounced in small populations |
| Genetic Map | 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 |
| Genotype | The genetic makeup of an individual |
| Glomerulus | Network of capillaries within Bowman's capsule that server as the site of filtration. Blood cells and proteins are too large to be filtrated, but ions, glucose, and amino acids readily pass into the filtrate |
| Glucagon | Produced and secreted by the a-cells of the pancreas, increases blood glucose concentration by promoting gluconeogenesis and the conversion of glycogen to glucose in the liver |
| Glucocorticoids | Synthesized and released by the adrenal cortex, raise blood glucose levels while decreasing protein synthesis |
| Golgi Apparatus | On organelle that plays a role in the packaging and secretion of proteins and other molecules produced intracellularly |
| Growth Hormone (GH) | Synthesized and released by the anterior pituitary gland, stimulates bone and muscle growth as well as glucose conservation. Is inhibited by somatostatin and stimulated by growth hormone releasing hormone (secreted by the hypothalamus) |
| Haploid | Cells with only one copy of each chromosome. Germ cells in humans are this |
| Hemoglobin | A protein found in erythrocytes made up of four polypeptide chains, each containing a heme group. Is responsible for transporting oxygen from the alveoli to the tissues |
| Hepatic Portal Vein | Carries nutrients (monosaccharides, amino acids, and small fatty acids) absorbed in the small intestine to the liver, where they are modified to enter circulation |
| Heterozygous | Organism that contain two different alleles for the same gene on homologous chromosomes |
| Homologous Chromosomes | Chromosomes in a diploid cell that contain alleles for the same trait at corresponding loci |
| Homozygous | Organisms that contain two identical alleles of the same gene on homologous chromosomes |
| Humoral Immunity | The synthesis of specific antibodies by activated B-cells in response to 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 |
| Hyperventilation | An increase in the rate of respiration or tidal volume. Lack of oxygen or a decrease in blood pH |
| Hypodermis | Layer of loose connective tissue below the dermis that binds the dermis to the body |
| Immunoglobulin | Synonymous with antibody; produced in response to a specific foreign substance that recognizes and bonds to that antigen and triggers an immune response |
| Incomplete Dominance | 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 |
| Indeterminate Cleavage | Cell division in embryogenesis that results in each cell maintaining its totipotency, or ability to develop into a complete organism by itself |
| Induction | The influence of a group of cells on the development of other cells. Is achieved by chemical substances known as inducers. The cells secreting these inducers are sometimes called organizers |
| Inferior Vena Cava | A large vein that returns deoxygenated blood from the lower body and the lower extremities to the right atrium of the heart |
| Innate Immunity | 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 |
| Inner Cell Mass | The group of cells in a blastocyst (mammalian blastula) that develop into the embryo |
| Insulin | Produced and secreted by the B-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 |
| Interphase | Phase of the cell cycle in which cell division does not take place. Includes G_1 phase, S phase, and G_2 phase. cells in this phase may or may not be growing |
| Interstitial Cells | Also called Leydig cells, are located in the testes and secrete testosterone and other androgens |
| Intestinal Glands | Contains brush-border enzymes such as maltase, sucrase, and lactase to digest disaccharides. Other enzymes of these glands include aminopeptidase, dipeptidase, and enteropeptidase |
| Intrapleural Space | The space between two membranes (visceral pleura and parietal pleura) that cover the lungs |
| Intrinsic Factor | A protein secreted by parietal cells of the stomach that is necessary for vitamin B_12 absorption |
| Inversion | A form of chromosomal arrangement in which a portion of a chromosome breaks off and rejoins the same chromosome in the reverse position |
| Large Intestine | Section of the GI tract that consists of the cecum, the colon, and the rectum. Main function is to absorb salts, water, and some vitamins |
| Leukocytes | White blood cells; the component of blood involved in cell defense and immunity. Neutrophils, basophils, eosinophils, lymphocytes, and monocytes are types |
| Liver | 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. Also produces albumin (a protein that maintains blood oncoti |
| Luteinizing Hormone (LH) | Synthesized and released by the anterior pituitary, stimulates ovulation and the formation of corpus luteum. Is regulated by estrogen, progesterone, and gonadotropin releasing hormone |
| Lymph Nodes | Swelling along the lymph vessels where lymph is filtered by leukocytes to remove antigens |
| Lymphatic System | A system of vessels and lymph nodes that collect interstitial fluids and return them to the circulatory system, thereby maintaining fluid balance. Also involved in lipid absorption and lymphocyte activation |
| Lysogenic Cycle | Phase of viral replication in which DNA of the bacteriophage becomes integrated in the host's genome and replicates as the bacteria replicates |
| Lysosome | A membrane-bound vesicle that contains hydrolytic enzymes used for intracellular digestion |
| Lytic Cycle | Phase in viral replication in which the host cell is lysed and releases new virions |
| Mean | The average, calculated as the sum of observed values divided by the number of observed values |
| Mechanical Digestion | Breakdown of food particles into smaller particles through such activities as biting, chewing, and churning |
| Median | The simplest division of a set of values; the middle value that divides the values into the upper half and lower half |
| Meiosis | A two-phase cell division in germ cells that results in the formation of up to four haploid cells from one diploid cell |
| Mendel's Law of Independent Assortment | 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 Segregation | Postulate 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 |
| Mesoderm | Primary germ layer that lies between the ectoderm and the 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 |
| Mitochondria | The site of aerobic respiration that provides the cell with a majority of its energy in the form of ATP. Is a semiautonomous organelle enclose by two membranes with an intermembrane space between the two membranes and a matrix enclosed by the inner membra |
| Mitosis | Cell division or nuclear division in somatic cells that results in the daughter nucleus receiving a full complement of the organism's genome |
| Mitral Valve | A valve located between the left atrium and the left ventricle. Valve consists of two cusp and prevents backflow from the left ventricle to the left atrium |
| Mode | The most frequent occurring value in a set of observations |
| Monohybrid Cross | A cross between two organisms where only one trait is being studied |
| Monosynaptic Reflex | Reflex pathway that has only one synapse between the sensory neuron and the motor neuron (such as the knee-jerk reflex) |
| Monozygotic Twins | Results when a zygote splits into two embryos. Because both embryos contain identical alleles, they are often called identical twins |
| Morula | A solid ball of cells that develops from the zygote through cleavage. When the interior becomes hollow, it becomes know as a blastula |
| Multipotent | 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 |
| Myelin Sheath | Insulating structure that surrounds axons. Action potentials cannot take place in areas of the axon that are myelinated |
| Negative Pressure Breathing | 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 |
| Nephron | The functional unit of the kidney. Can be subdivided inti Bowman's capsule, proximal convoluted tubule, descending limb of the loop of Henle, distal convoluted tubule, and collecting duct |
| Neural Crest Cells | 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 |
| Neurotransmitters | Chemical messengers released from synaptic terminals of a neuron that can bind to and stimulate a postsynaptic cell |
| Nodes of Ranvier | Gaps between segments of myelin sheath where action potentials can take place, allowing for saltatory conduction |
| Nondisjunction | The failure of homologous chromosomes or sister chromatids to separate properly during meiosis I or meiosis II, respectively. Usually results in gametes that lack certain genes or have multiple copies of those genes |
| Obligate Intracellular Organisms | Organisms that require a host cell to express their genes and reproduce |
| Osmoregulation | Maintenance of water and solute concentrations |
| Osteoblasts | Cells in the bone tissue that secrete the organic constituents of the bone matrix. Develop into osteocytes |
| Osteoclasts | Cells in the bone matrix that are involves in bone degradation |
| Osteons | The structural unit 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 |
| Pancreas | Its exocrine functions include secreting pancreatic amylase, trypsinogen, chymotrypsin, procarboxypeptidases A and B, and pancreatic lipase into the small intestine. Its endocrine functions include secretion of insulin and glucagon |
| Parathyroid Hormone (PTH) | Synthesized and released by the parathyroid gland, increases blood Ca^2+ concentration by increasing Ca^2+ reabsorption in the kidneys and by stimulating calcium release from bone |
| Pathway of the Electrical Impulse in the Heart | The electrical impulse originates in the sinoatrial (SA) node, located in the right atrium. It then travels through the atrioventricular (AV) node, then through the bundle of His, and finally through the Purkinje fibers |
| Pathway of the Respiratory Tract | Air travels through the nasal or oral cavity, pharynx, larynx, trachea, bronchi, bronchioles, and finally the alveoli (site of gas exchange) |
| Penetrance | The percentage of people in a population with a certain genotype who express the associated phenotype |
| Pepsin | Secreted as pepsinogen by the chief of cells of the stomach, this enzyme cleaves peptide bonds, starting the digestion of proteins into individual amino acids |
| Peptide Hormones | Polar hormones incapable of permeating the cell membrane that bond to the surface receptors and act through secondary messengers |
| Peripheral Nervous System | 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 |
| Peristalsis | Involuntary muscular contractions that push food down the digestive tract |
| Peroxisome | Organelle that contains hydrogen peroxide and participates in the breakdown of very long chain fatty acids |
| Phenotype | The physical manifestation of an individual's genotype |
| Placenta | The organ formed by the uterus and the extraembryonic membranes of the fetus. Contains a network of capillaries through which exchange between the fetal circulation and maternal circulation takes place |
| Plasma | Liquid portion of blood, an aqueous mixture of nutrients , salts, respiratory gases, hormones, and blood proteins |
| Platelets | Cell fragments involved in the clotting process. Come from megakaryocytes in the bone marrow |
| Pluripotent | 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 |
| Point Mutation | Mutation in which one nucleotide base is substituted by another. The protein products may or may not be functional |
| Polar Body | A small, short lived haploid created during oogenesis that receives very little cytoplasm, organelles, or nutrients |
| Portal Systems | Circulatory routes in which blood travels through two capillary beds before returning to the heart. Some examples include the hypophyseal portion system, the hepatic portal system, and the renal portal system |
| Posterior Pituitary | 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 |
| Primary Response | The initial response to a specific antigen. T- and B- cells are activated and specific antibodies and memory cells for the antigen are produced |
| Primary Spermatocytes | Diploid cells that undergo meiosis I to form two haploid secondary spermatocytes |
| Progesterone | Hormone synthesizes and released by the ovaries, corpus luteum, and placenta. During the luteal phase of the menstrual cycle, the corpus luteum secretes progesterone, which, along with estrogen, stimulates the development and maintenance of the endometria |
| Prolactin | A hormone synthesized and released by the anterior pituitary that stimulates milk production and secretion in female mammary glands |
| Proximal Convoluted Tubule | Portion of nephron where glucose, amino acids, and other important organic molecules are reabsorbed. Lies in the cortex of the kidney |
| Pyloric Glands | Glands located in the walls of the stomach that secrete the hormone gastrin to increase gastric acid production |
| Pyloric Sphincter | A valve between the stomach and the small intestine that regulates the flow of chyme into the duodenum |
| Recessive | Describes an allele that requires two copies to be expressed |
| Recombination Frequency | The likelihood of two genes on the same chromosome being separated onto two different chromosomes during crossing over; equal to the proportion of gametes that receive these recombinant chromosomes. If the recombination frequency of two particular traits |
| Red Fibers | Slow-twitch muscle fibers. They are primarily aerobic and contain many mitochondria and high levels of myoglobin |
| Refractory Period | A short period of time immediately following an action potential in which neurons or muscle cells are unresponsive to a stimulus. In some cases, a stimulus that is much larger than usual causes an action potential in a cell in a refractory period. |
| Repolarization | 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 |
| Respiration Rate | Expressed as breaths per minute. Raising it can decrease the amount of carbon dioxide in the blood, thus increasing the pH. Likewise, decreasing it increases the concentration of carbon dioxide in the blood, resulting in a lower pH. |
| Resting Potential | The change difference across the cell membrane of a neuron or a muscle cell while at rest. Most often maintained by the sodium-potassium pump |
| Reverse Transcriptase | An enzyme in retroviruses that uses RNA strands as templates for synthesizing cDNA molecules |
| Rh Factor | A surface protein expressed on red blood cells that can induce an immune response. Introduction of this into the blood of a person who is a different factor of this may result in a fatal hemolysis reaction |
| Ribonucleic Acid (RNA) | A nucleic acid found in both the nucleus and cytoplasm and most closely linked with transcription and translation, as well as some gene regulation |
| Saltatory Conduction | A means by which action potentials jump from node to node along an axon |
| Sarcomere | The structural unit of striated muscle. It is composed of thin (mostly actin) and thick (mostly myosin) filaments |
| Sarcoplasmic Reticulum | A modified form of endoplasmic reticulum; stores calcium that is used to trigger contraction when muscle is stimulated |
| 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 by pathogens that trigger a more immediate response from the memory cells produced during the primary immune response |
| Semen | The fluid discharged during ejaculation. Consist 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 teste, 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 | |
| Skeletal Muscle | Type of muscle response for voluntary movement, consisting of multinucleated, striated (striped) muscle fibers |
| Small Intestine | 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 |
| 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 call 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 !-cells of the pancreas, 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 Force | A balance between hydrostatic and oncotic pressures on both sides of a membrane, essential for maintaining proper fluid volumes and solute 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 bye the lung the reduces surface tension in the alveoli. Prevents lung collapse and decreases the effort needed to expand the lungs |
| Synapse | 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 |
| Synaptic Terminals | Ends of axons that form one side of the synaptic cleft; the location where 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 maintenance 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 by 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 triiodothyronine (T_3) and thyroxine (T_4) stimulate cellular respiration as well as protein and fatty acid synthesis and degradation |
| Thyroid-Stimulating Hormone (TSH) | Synthesized and released by the anterior pituitary, stimulates the thyroid gland to absorb iodine and to synthesize and secret thyroid. Is regulated by thyroid releasing hormones (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 nonhomologous chromosome |
| Transverse Tubules (T-Tubules) | A system of tubules that provides channels 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. Consists of three cusps and prevents backflow of blood from 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 the physiological effect |
| Umbilical Cord | Connects the vasculature of the fetus to the placenta |
| Vagus Nerve | One of the twelve cranial nerves; provides parasympathetic signaling to the thoracic and abdominal cavities |
| Veins | Vessels that carry blood towards the heart. The vessels are thin-walled and have valves to prevent backflow |
| Ventricles | The muscular lower chambers of the heart. The right side pumps deoxygenated blood to the lungs through the pulmonary arteries, while the left side pumps oxygenated blood throughout the body through the aorta |
| Villi | Fingerlike projections that extend out of the small intestine in order to increase 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 are secreted by follicular cells and the oocyte itself. Penetration of this 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 |
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