Chapter 2 - The body's physical systems

neurotransmitter

a chemical involved in the transmission of impulses across the synapse from one neuron to another.

central nervous system

that part of the nervous system consisting of the brain and spinal cord.

cerebrum

the upper and largest portion of the human brain. It has primary control over motor and mental activity.

limbic system

a set of structures in the forebrain that seems to play a role in emotional expression.

thalamus

a structure in the forebrain that serves as a relay station for sensory impulses to and commands from the cerebrum.

hypothalamus

a part of the forebrain that contains control centers for many body functions, such as eating, drinking, and sexual activity.

cerebellum

a large portion of the brain that coordinates motor activities and maintains body balance.

brainstem

the lowest portion of the brain, located at the top of the spinal cord, consisting of the midbrain, reticular system, pons, and medulla.

spinal cord

the major neural pathway that carries impulses between the brain and the peripheral nervous system.

peripheral nervous system

the network of nerve fibers that carries messages between the central nervous system and the skin, skeletal muscles, and internal organs. This network has two parts: the somatic and autonomic nervous systems.

somatic nervous system

a division of the peripheral nervous system that transmits sensory and motor impulses.

automatic nervous system

a division of the peripheral nervous system that carries messages between the central nervous system and the internal organs. It has two parts: the sympathetic and parasympathetic nervous systems.

sympathetic nervous system

a division of the autonomic nervous system that enables the body to mobilize and expend energy during physical and emotional arousal.

parasympathetic nervous system

a division of the autonomic nervous system that helps the body conserve energy and restore the normal body state after arousal.

endocrine system

an array of glands that secrete hormones into the bloodstream.

hormones

chemical substances secreted by endocrine glands that affect body functions and behavior.

pituitary gland

an endocrine gland that has connections to the brain and secretes hormones that stimulate other endocrine glands to secrete.

adrenal glands

endocrine glands that secrete several hormones, such as cortisol, epinephrine, and norepinephrine, which are involved in stress reactions.

digestive system

the network of organs that processes ingested food by breaking it down for the body’s use and excreting the remains.

enzymes

substance that increase the speed of chemical reactions in cells.

metabolism

the chemical reactions of the body’s cells that synthesize new cell material, regulate body processes, and create energy.

respiratory system

a network of organs that supply oxygen for metabolism and expel carbon dioxide.

cardiovascular system

a network of organs that circulates blood to supply oxygen and nutrients to the body’s cells and removes wastes and other substances.

blood pressure

the force of the blood against the inner walls of the arteries.

lipids

fatty materials, such as the cholesterol found in blood.

atherosclerosis

the condition in which fatty patches (plaques) form an artery walls.

arteriosclerosis

a condition in which fatty patches have accumulated and hardened onto artery walls, thereby reducing the elasticity of these walls.

immune system

the organs and structures that protect the body against harmful substances or agents, such as bacteria and viruses.

antigen

any substance that can trigger the immune system to respond.

lymphocytes

various types of white blood cells that have several important functions in the body’s immune response.

phagocytes

certain types of white blood cells that engulf and ingest any kind of invading particles.

cell-mediated immunity

the immune process that operates at the cellular level, using T cells to attack infected cells.

T cells

a class of lymphocytes; some attack antigens directly, and some work to regulate other immune functions.

antibody-mediated immunity

the immune process that employs antibodies to attack antigens while they are still in body fluids and before they have invaded the cells.

B cells

lymphocytes that lead tot he formation of antibodies.

antibodies

protein molecules created to protect against specific antigens in body fluids.