B Flashcards
B Cells
Lymphocytes that are produced in the bone marrow (mammals) and bursa of Fabricus (birds), recognized by their expression of B cell receptors that bind to antigens.
Baroreceptor
A receptor that senses pressure (by sensing the resulting stretch on the cell membrane).
Baroreceptor Reflex
A homeostatic feedback loop that regulates blood pressure. Pressure sensors in the heart and arterial system detect changes in blood pressure and send sensory feedback to the central nervous system that causes physiological responses that
return blood pressure back to the normal range.
Basal Lamina
The extracellular matrix underlying a sheet of epithelial cells; part of the connective tissue formed largely by fibroblasts.
Basal Metabolic Rate (BMR)
see also resting metabolic rate, standard metabolic rate
The metabolic rate of a homeothermic animal at rest, at a thermal neutral temperature, and post-absorptive.
Basal Nuclei
Interconnected groups of gray matter within the mammalian brain.
Base
A molecule that accepts a proton, or otherwise causes a reduction in proton concentration through effects on the dissociation of water.
Basilar Membrane
The location of the auditory hair cells in the mammalian cochlea.
Basophil
A type of white blood cell that releases histamine; involved in the vertebrate immune response.
Batch Reactor
A chemical reactor in which nutrients enter and exit through the same
opening; nutrients are retained in the reactor and digested; the undigested material is then expelled, and replaced by another batch of nutrients to be processed.
Behavioral Thermoregulation
The use of behavior to control the body temperature of a poikilotherm, or to reduce the costs of thermoregulation for a homeotherm.
Beta-Oxidation (β-oxidation)
Pathway of fatty acid catabolism that produces acetyl CoA and reducing equivalents.
Beta-Sheet (β-sheet)
Protein folding pattern in which stretches of amino acids are aligned along another amino acid stretch. This secondary structure is stabilized by hydrogen bonds.
Bicuspid Valve (also called the mitral valve)
The valve between the left atrium and the left ventricle of the mammalian
heart.
Bilateral Symmetry
A body form in which the body can be divided by a single plane such that the right and left sides are approximate mirror images.
Bile
A thick, yellow-green fluid composed of salts, pigments, and lipids produced by the liver and stored by the gallbladder; when released into the small intestine it neutralizes gastric acid and aids in the digestion of nutrients, particularly lipids.
Bile Duct
The connection between the liver and
the small intestine.
Bile Pigments
Nondigestible breakdown products of porphyrins, including the hemes found in hemoglobin and cytochromes.
Bile Salts
Cholic acid conjugated with amino acids, primarily glycine and taurine; assist in emulsification of lipid within the small intestine.
Binocular Vision
The ability to compare the images coming from two eyes to produce three-dimensional perception.
Binocular Zone
The area of overlap between the right and left visual fields of a vertebrate that
allows depth perception.
Biogenic Amine
A class of neurotransmitters derived from amino acids including the catecholamines and dopamine.
Bioluminescence
The production of light by living organisms.
Bipolar Neuron
A neuron with two main processes leading from the cell body, one of which conveys signals toward the cell body, and one of which conveys signals away from
the cell body.
Blastema
A mass of cells that can proliferate and differentiate to regenerate damaged tissues or organs.
Blastocoel
The cavity formed by the inpouching of the blastocyst, which eventually forms the
alimentary canal.
Blastocyst
In mammals, the blastula continues development to form the blastocyst. It contains
an inner cell mass and an outer layer of cells: the trophoblast.
Blastula
One of the early developmental stages of animals prior to the formation of
the embryonic germ layers. In many animals, this consists of a hollow ball of about
100 cells.
Bleaching
The fading of a photopigment following absorption of energy from photons.
In the case of the retinal-opsin complex, absorption of energy from light causes retinal to dissociate from opsin. Opsin is not pigmented, and thus the photopigment loses its color.
Blood
The circulatory fluid in animals with closed circulatory systems. Generally contains
proteins, ions, organic molecules, and various cell types.
Blood-Brain Barrier
A specialized protective barrier made up of glial cells that separates
the circulatory system and the central nervous system in vertebrates.
Blood Vessels
Tubes that carry blood through an animal’s body.
Blubber
Subcutaneous lipid deposits of marine mammals, which provide thermal insulation.
Bohr Effect
A change in hemoglobin oxygen affinity due to a change in pH.
Bolus
A volume of material introduced into a flow-through system that moves through the system as a unit, with some dispersion along the way; often used in the context of a bolus of food moving through the gastrointestinal tract.
Bombesin
A hormone that regulates release of gastrointestinal hormones and control of
gastrointestinal motility in vertebrates.
Bond Energy
The energy required to form a chemical bond.
Bone
In vertebrates, a solid structure composed of mineralized extracellular matrix of osteocytes; with cartilage and tendon, it constitutes the skeleton.
Book Gills
The respiratory surfaces of waterbreathing chelicerates such as horseshoe
crabs.
Book Lungs
The respiratory surfaces of some air-breathing chelicerates such as spiders and scorpions.
Boundary Layer
The region of a solution that is in direct contact or otherwise influenced by a surface; often called an unstirred layer.
Bowman’s Capsule
A cup-shaped expansion of the vertebrate kidney tubule; surrounds the glomerulus.
Brackish Water
Water that is intermediate between freshwater and seawater; typically found in estuaries, salt marshes, or isolated ponds.
Bradycardia
A heart rate that is slower than normal.
Brain
A large grouping of ganglia that act as a sophisticated integrating center. Typically located toward the anterior end of the body in the cephalic (head) region.
Brainstem
A portion of the vertebrate central nervous system that connects the cerebrum of the brain to the spinal cord; contains the pons and medulla, the sites of the respiratory and cardiovascular control centers.
Branchial
Relating to gills.
Breakpoint
Refers to a transition in a relationship, usually indicating the point of convergence of two lines with different slopes; used specifically with Arrhenius plots to show a change in the effects of temperature on a structure or process over different ranges.
Broca’s Area
A region in the frontal lobe of the brain of humans that is involved in speech
production.
Bronchi (singular: bronchus)
Airways of vertebrate lungs leading from the trachea to the bronchioles.
Bronchioles
The smallest branches of the airways of mammalian lungs; lead to the terminal
alveoli.
Brood Spot
A well-vascularized, featherless region on the underside of birds that is important
for warming developing eggs.
Brown Adipose Tissue
Also known as brown fat, a thermogenic tissue found in many small
mammals, often in the back or neck region. Abundant mitochondria in the brown adipocytes possess thermogenin, a protein that uncouples oxidative phosphorylation to enhance heat production.
Brush Border
Abundant microvilli on epithelial cells in the gastrointestinal tract, giving the
tissue a microscopic brushlike appearance.
BTPS
Standardized reference conditions for measuring gas volumes: body temperature, atmospheric pressure, and saturated with water.
Buccal Cavity
Mouth cavity.
Buffer
Chemicals which, when placed in solution, confer on the solution an ability to resist
changes in pH when acid or base is added.
Bulbourethral Bland
A mucus-secreting accessory gland of the male reproductive tract.
Bulbus Arteriosus
see also conus arteriosus
The outflow tract of the heart in bony fishes; non-muscular and elastic.
Bulk Flow
The movement of a fluid as a result of a pressure or temperature gradient.
Bulk Phase (or bulk solution) (see also boundary layer)
The volume of solution that is beyond the influence of the surfaces.
Bundle of His
One of the conducting pathways of the mammalian heart.
Burst Exercise
High-intensity exercise powered by glycolytic muscle fibers; can continue for
only short periods, until glycogen stores are exhausted.
