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.
Bacteriophages
Viruses that can only infect bacteria
Bile
An alkaline fluid synthesized in the liver, stored in the gall bladder, and release into the duodenumd. Bile 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 triggered, leading to hemolysis
Blood Buffer System
Relies primarily on the carbonic acid buffer system, demonstrated by the following equation- CO2+H2O=H2CO3=H(+)+HCO-3
Release of carbon dioxide causes increased formation of water and an increase in pH
Increased retention of HCO-3 causes the pH to rise as well.
Calcitonin
Hormone synthesized and released by the thyroid gland that decreases plasma CA2+ 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 chondrin. Produced by cells called chondrocytes. Cartilage is the principle component of embryonic skeletons and can harden to 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 of cytotoxic immunity.
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
The central nervous system consists 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. Chromatin itself 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 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
Compact bone
Much more dense than spongy bone, compact bone consists of Haversian 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 later of cells surrounding the oocyte. These cells are derived from follicular cells
Corpus Luteum
Tissue that forms 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 of meiosis. Crossing over aids in evolution and genetic diversity by unlinking linked genes.
Dendrite
And 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 skin beneath the epidermis that is subdivided into the papillary later 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 in 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 causes 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
Dominant
Describes an allele that requires only 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 Neruons
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 germ layers; gives rise to the linings of the digestive ad respiratory tracts and to parts 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 inferior pituitary, endorphins 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 the skin, which is composed of the following sub layers: 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
Epihyseal 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 anaerobic cells, which lack organelles, are packed with hemoglobin ad have a characteristic biconcave, disk-like shape that facilitates 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. Estrogen stimulates the development of the female reproductive tract ad secondary sexual characteristics and is partly responsible for the LH spike that causes ovulation
Exocrine glands
Glands that synthesize ad secrete substances through ducts. The mammary glands and sweat glands are examples of exocrine glands
Expressivity
Refers to the variability in the phenotypes (especially severity of a disease) that can occur with a given genotype
Facultative Anaerobes
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 material that passes from the blood vessels into Bowman’s space
Follicle
A multilayered sac of cells that protects and nourishes the developing ovum
Foramen Ovale
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 (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
Ganglia
A group of neural cell bodies in the peripheral nervous system. May be sensory or autonomic
Gastric Glands
Located in the stomach; secrete CHl 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 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
Glucagon
Produced and secreted by he A-cells of the pancreas, glucagon increases blood glucose concentration by promoting gluconeogenesis and the conversation of glycogen to glucose in the liver
Glucocorticoids
Synthesized and released by the adrenal cortex, glucocorticoids raise blood glucose levels while decreasing protein synthesis
Golgi apparatus
An 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, 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)
Haploid
Cells with only one copy of each chromosome. Germ cells in humans are haploid.
Hemoglobin
A protein found in erythrocytes made up of four polypeptide chains, each containing a heme group. Hemoglobin 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
Organisms 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 traits 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 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
Hyperventilation
An increase in the rate of respiration or tidal volume. Lack of oxygen or a decrease in blood pH promotes hyperventilation
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 binds to the antigen and triggers an immune response
Nuclear Membrane
Surrounds the Nucleus of the cell, and contains nuclear pores for allowing exchange of material between cytoplasm and nucleus
His tones
Linear DNA is wound around proteins called histones
Mitral Valve
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
Mode
The most frequently occurring value in a set of observations
Mendel’s Law of Segregation
Mendel’s postulation that there are alternate versions of genes that account fir 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.
Osteons
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
Pancreas
It’s exocrine functions include secreting pancreatic amylase, trypsinogen, chymotrypsinogen, procarboxypeptidases A and B, and pancreatic lipase into the small intestine. It’s endocrine functions include secretion of insulin and glucagon
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
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
Result 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 of the morula becomes hollow, it becomes known as as 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
