A neurotransmitter used in the neuromuscular junction to stimulate muscle contraction; acetylcholine is also used by parasympathetic nerves to slow the heart.
Abnormal ballooning of the wall of a blood vessel.
The artery that carries blood from the left ventricle to the rest of the body.
Smaller vessels that branch off from arteries.
One of the vessels that carry blood away from the heart.
Hardening of the arteries.
atrioventricular (AV) node
A special tissue that conducts electrical signals from one part of the heart to the other.
The valves between the atria and ventricles of the heart.
One of the smaller thin-walled entrance chambers of the heart, through which blood enters the adjacent ventricle.
One of the minute blood vessels that brings blood in closest contact with tissues; capillaries connect the finest arterioles with the finest venules.
The blood, the heart, and the blood vessels together.
The route of the blood throughout the cardiovascular system.
closed circulatory system
A circulatory system in which blood runs only within enclosed vessels.
The half of the cycle of the heart in which both the atria and the ventricles are relaxed.
In the circulatory system, the epithelial cells that line the capillaries.
A hormone, made in the adrenal medulla, that speeds the heart, dilates the blood vessels, and increases the liver's production of glucose from glycogen.
A red blood cell.
In the heart, continuous disorganized contractions.
The muscular organ responsible for pushing the blood through the circulatory system.
A sometimes fatal failure of the blood supply to the heart that causes the heart to beat irregularly or to stop beating.
The number of contractions (beats) per minute.
The oxygen-binding protein that makes red blood cells red.
The amino acid histidine minus the carboxyl group, a major stimulus for the inflammatory response; it is released by cells in damaged tissues; it dilates capillaries and increases their tendency to leak fluid.
White blood cell.
low-density lipoprotein (LDL)
A carrier protein in the blood that binds to cholesterol.
A space enclosed by a membrane (as in the endoplasmic reticulum) or epithelium (as in the gut).
Fluid containing dead or foreign cells and waste proteins that passively moves through the lymphatic system.
Regions in the lymphatic veins where filterlike tissue separates cells and other detritus from the lymph.
The network of lymphatic vessels and nodes that provides a secondary route for fluids from the extracellular space to the bloodstream.
One of a class of white blood cells that develop within the lymphoid tissues (including lymph nodes, spleen, thymus, and tonsils); the cells responsible for the immune response.
A signaling molecule that transmits signals from a nerve cell either to another nerve cell or to a muscle or a gland.
A neurotransmitter derived from tyrosine; norepinephrine is used by the central nervous system and the sympathetic nervous system.
open circulatory systems
A circulatory system in which blood mixes freely with extracellular fluids and bathes the organs of the body.
A group of the cells of the heart muscle capable of rhythmic spontaneous contractions that set the pace of contraction for the rest of the heart
A fibrous sac that encloses the heart itself within a watery lubricating fluid.
The fluid part of blood.
A small, membrane-enclosed element that is a component of mammalian blood; it is formed as a cytoplasmic fragment of a precursor cell in the bone marrow; platelets contribute to clotting.
Relating to the lungs.
The artery that carries deoxygenated blood from the heart to the lungs.
Circulation from heart to lungs to heart.
The veins that carry oxygenated blood from the lungs to the heart.
sinoatrial (SA) node
The pacemaker, which lies near the top of the right atrium in the mammalian heart.
Failure of the blood supply to the brain.
In the action of the heart, the volume of blood delivered by a ventricle.
sympathetic nervous system
A division of the autonomic nervous system; the sympathetic nervous system initiates the "fight or flight" reaction.
The route of the blood through the body, minus pulmonary circulation.
The part of the heartbeat in which the atria and ventricles contract.
Contraction of the smooth muscles surrounding the arterioles.
A process causing arterioles to increase in size with consequent blood flow increase and reddening on the skin.
In vertebrates, the vessels that carry blood back to the heart. In plants, the vascular tissue in the leaves.
vena cava (superior and inferior)
The two largest veins, which run up through the center of the body and carry deoxygenated blood from the body to the right atrium.
In the heart, a thick-walled pumping chamber.
The smallest veins.