Biology Chapters 41, 42, 43, and 48 Vocabulary

A set of vocabulary flashcards defining key physiological and biological terms across Chapters 41, 42, 43, and 48, covering digestion, circulation, immunity, and neurons.

amylase

An enzyme that hydrolyzes starch (a glucose polymer from plants) and glycogen (a glucose polymer from animals) into smaller polysaccharides and the disaccharide maltose.

alimentary canal

A complete digestive tract, consisting of a tube running between a mouth and an anus.

appendix

A small, finger-like extension of the vertebrate cecum; contains a mass of white blood cells that contribute to immunity.

absorption

The third stage of food processing in animals: the uptake of small nutrient molecules by an organism's body.

chylomicron

A lipid transport globule composed of fats mixed with cholesterol and coated with proteins.

digestion

The second stage of food processing in animals: the breaking down of food into molecules small enough for the body to absorb.

duodenum

The first section of the small intestine, where chyme from the stomach mixes with digestive juices from the pancreas, liver, and gallbladder as well as from gland cells of the intestinal wall.

elimination

The fourth and final stage of food processing in animals: the passing of undigested material out of the body.

essential amino acid

An amino acid that an animal cannot synthesize itself and must be obtained from food in prefabricated form.

essential fatty acid

An unsaturated fatty acid that an animal needs but cannot make.

essential nutrient

A substance that an organism cannot synthesize from any other material and therefore must absorb in preassembled form.

ingestion

The first stage of food processing in animals: the act of eating.

large intestine

The portion of the vertebrate alimentary canal between the small intestine and the anus; functions mainly in water absorption and the formation of feces.

leptin

A hormone produced by adipose (fat) cells that acts as a satiety factor in regulating appetite.

liver

A large internal organ in vertebrates that performs diverse functions, such as producing bile, maintaining blood glucose level, and detoxifying poisonous chemicals in the blood.

microvillus

One of many fine, finger-like projections of the epithelial cells in the lumen of the small intestine that increase its surface area.

mineral

In nutrition, a simple nutrient that is inorganic and therefore cannot be synthesized in the body.

pancreas

A gland with exocrine and endocrine tissues.

pepsin

An enzyme present in gastric juice that begins the hydrolysis of proteins.

protease

An enzyme that digests proteins by hydrolysis.

ruminant

An animal, such as a cow or a sheep, with multiple stomach compartments specialized for an herbivorous diet.

salivary glands

A gland associated with the oral cavity that secretes substances that lubricate food and begin the process of chemical digestion.

small intestine

The longest section of the alimentary canal, so named because of its small diameter compared with that of the large intestine; the principal site of the enzymatic hydrolysis of food macromolecules and the absorption of nutrients.

stomach

An organ of the digestive system that stores food and performs preliminary steps of digestion.

vitamin

An organic molecule required in the diet in very small amounts.

interstitial fluid

The fluid filling the spaces between cells in most animals.

heart

A muscular pump that uses metabolic energy to elevate the hydrostatic pressure of the circulatory fluid (blood or hemolymph).

open circulatory system

A circulatory system in which fluid called hemolymph bathes the tissues and organs directly and there is no distinction between the circulating fluid and the interstitial fluid.

closed circulatory system

A circulatory system in which blood is confined to vessels and is kept separate from the interstitial fluid.

blood

A connective tissue with a fluid matrix called plasma in which red blood cells, white blood cells, and cell fragments called platelets are suspended.

artery

A vessel that carries blood away from the heart to organs throughout the body.

vein

(1) In animals, a vessel that carries blood toward the heart. (2) In plants, a vascular bundle in a leaf.

capillary

A microscopic blood vessel that penetrates the tissues and consists of a single layer of endothelial cells that allows exchange between the blood and interstitial fluid.

atrium

A chamber of the vertebrate heart that receives blood from the veins and transfers blood to a ventricle.

endothelium

The simple squamous layer of cells lining the lumen of blood vessels.

systolic pressure

Blood pressure in the arteries during contraction of the ventricles.

diastolic pressure

Blood pressure in the arteries when the ventricles are relaxed.

vasoconstriction

A decrease in the diameter of blood vessels caused by contraction of smooth muscles in the vessel walls.

vasodialation

An increase in the diameter of blood vessels caused by relaxation of smooth muscles in the vessel walls.

lymphatic system

A system of vessels and nodes, separate from the circulatory system, that returns fluid, proteins, and cells to the blood.

lymph

The colorless fluid, derived from interstitial fluid, in the lymphatic system of vertebrates.

plasma

The liquid matrix of blood in which the blood cells are suspended.

platelet

A pinched-off cytoplasmic fragment of a specialized bone marrow cell. Platelets circulate in the blood and are important in blood clotting.

erythrocyte

A blood cell that contains hemoglobin, which transports oxygen; also called a red blood cell.

hemoglobin

An iron-containing protein in red blood cells that reversibly binds oxygen.

leukocyte

A blood cell that functions in fighting infections; also called a white blood cell.

stem cell

Any relatively unspecialized cell that can produce, during a single division, one identical daughter cell and one more specialized daughter cell that can undergo further differentiation.

erythropoietin (EPO)

A hormone that stimulates the production of erythrocytes. It is secreted by the kidney when body tissues do not receive enough oxygen.

heart attack

The damage or death of cardiac muscle tissue resulting from prolonged blockage of one or more coronary arteries.

stroke

The death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head.

immune system

An animal body's system of defenses against agents that cause disease.

innate immunity

A form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encountered previously.

adaptive immunity

A vertebrate-specific defense that is mediated by B lymphocytes (B cells) and T lymphocytes (T cells).

lysozyme

An enzyme that destroys bacterial cell walls; in mammals, found in sweat, tears, and saliva.

Toll like receptor (TLR)

A membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to a set of pathogens.

neutrophil

The most abundant type of white blood cell. Neutrophils are phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days.

macrophage

A phagocytic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as an antigen-presenting cell.

dendritic cell

An antigen-presenting cell, located mainly in lymphatic tissues and skin, that is particularly efficient in presenting antigens to helper T cells, thereby initiating a primary immune response.

natural killer cell

A type of white blood cell that can kill tumor cells and virus-infected cells as part of innate immunity.

complement system

A group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens.

inflammatory response

An innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the infiltration of white blood cells, and aid in tissue repair and destruction of invading pathogens.

histamine

A substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses.

mast cell

A vertebrate body cell that produces histamine and other molecules that trigger inflammation in response to infection and in allergic reactions.

lymphocyte

A type of white blood cell that mediates immune responses. The two main classes are B cells and T cells.

thymus

A small organ in the thoracic cavity of vertebrates where maturation of T cells is completed.

T cells

The class of lymphocytes that mature in the thymus; they include both effector cells for the cell-mediated immune response and helper cells required for both branches of adaptive immunity.

B cells

The lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response.

antigen

A substance that elicits an immune response by binding to receptors of B cells, antibodies, or of T cells.

antibody

A protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen; also called immunoglobulin. All antibodies have the same Y-shaped structure and in their monomer form consist of two identical heavy chains and two identical light chains.

memory cells

One of a clone of long-lived lymphocytes, formed during the primary immune response, that remains in a lymphoid organ until activated by exposure to the same antigen that triggered its formation. Activated memory cells mount the secondary immune response.

clonal selection

The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen.

antigen presenting cell

A cell that upon ingesting pathogens or internalizing pathogen proteins generates peptide fragments that are bound by class II MHC molecules and subsequently displayed on the cell surface to T cells.

allergen

An antigen that triggers an exaggerated immune response.

autoimmune disease

An immunological disorder in which the immune system turns against self.

immunodeficiency

A disorder in which the ability of an immune system to protect against pathogens is defective or absent.

Neuron

A nerve cell; the fundamental unit of the nervous system, having structure and properties that allow it to conduct signals by taking advantage of the electrical charge across its plasma membrane.

Brain

Organ of the central nervous system where information is processed and integrated.

Central nervous system

The portion of the nervous system where signal integration occurs; in vertebrate animals, the brain and spinal cord.

Peripheral nervous system

The sensory and motor neurons that connect to the central nervous system.

Nerve

A fiber composed primarily of the bundled axons of PNS neurons.

Sensory neurons

A nerve cell that receives information from the internal or external environment and transmits signals to the central nervous system.

Interneuron

An association neuron; a nerve cell within the central nervous system that forms synapses with sensory and/or motor neurons and integrates sensory input and motor output.

Motor neuron

A nerve cell that transmits signals from the brain or spinal cord to muscles or glands.

Cell body

The part of a neuron that houses the nucleus and most other organelles.

Dendrite

One of usually numerous, short, highly branched extensions of a neuron that receive signals from other neurons.

Axon

A typically long extension, or process, of a neuron that carries nerve impulses away from the cell body toward target cells.

Synapse

The junction where a neuron communicates with another cell across a narrow gap via a neurotransmitter or an electrical coupling.

Neurotransmitter

A molecule that is released from the synaptic terminal of a neuron at a chemical synapse, diffuses across the synaptic cleft, and binds to the postsynaptic cell, triggering a response.

Glial cells/glia

Cells of the nervous system that support, regulate, and augment the functions of neurons.

Membrane potential

The difference in electrical charge (voltage) across a cell's plasma membrane due to the differential distribution of ions.

Resting potential

The membrane potential characteristic of a nonconducting excitable cell, with the inside of the cell more negative than the outside.

Action potential

An electrical signal that propagates (travels) along the membrane of a neuron or other excitable cell as a nongraded (all-or-none) depolarization.

Voltage gated ion channels

A specialized ion channel that opens or closes in response to changes in membrane potential.

Threshold

The potential that an excitable cell membrane must reach for an action potential to be initiated.

Refractory period

The short time immediately after an action potential in which the neuron cannot respond to another stimulus, owing to the inactivation of voltage-gated sodium channels.

Myelin sheath

Wrapped around the axon of a neuron, an insulating coat of cell membranes from Schwann cells or oligodendrocytes.

Oligodendrocytes

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the central nervous system.

Schwann cells

A type of glial cell that forms insulating myelin sheaths around the axons of neurons in the peripheral nervous system.

Nodes of Ranvier

Gap in the myelin sheath of certain axons where an action potential may be generated. In saltatory conduction, an action potential is regenerated at each node, appearing to “jump” along the axon from node to node.

Ligand gated ion channel

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling molecule (ligand), allowing or blocking the flow of specific ions; also called an ionotropic receptor.