Biology Flashcards
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 sharpe 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.
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 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 stimulate an increase in the metabolic rate and blood glucose levels.
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.
Afferent 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 of these hormones act via secondary messengers, while some act in a fashion similar to steroid hormones.
Amnion
the innermost extraembryonic membrane; produces the amniotic fluid in which the growing fetus is suspended.
Anterior Pituitary
Synthesizes and releases many vital hormones, including FSH, lutenizing hormone, adrenocorticotropic hormone, TSH, prolactin, endorphins, and growth hormone (FLAT PEG). This is under the hormonal control of the hypothalamus.
Antidiuretic Hormone (ADH)
A peptide hormone, also known as vasopressin, that acts on the collecting duct to increase water reabsorption. It is produced by the hypothalamus and store 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. These 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 fluid, NaCl is first passively then actively removed from the filtrate, decreasing filtrate concentration.
Atria
The 2 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 and mitral valves).
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 AP will be initiated.
Bacteriophages
Viruses that can only infect bacteria.
