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Nervous and Endocrine System Glossary

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How Does Your Brain Know That Your Finger is Cut?

Your brain is part of one of your body’s nervous system. This system is one of the communication systems of your body. Nerves from your cut finger send messages to your brain.

The endocrine system is your body’s other communication system.

Following is a glossary of terms for these two systems.

action potential

A temporary reversal of neuronal cell membrane potential at one location that results in a conducted nerve impulse down an axon.

afferent division

The division of the peripheral nervous system that carries sensory information toward the central nervous system, having gathered information about the body or environment.

amino acid based hormone

Hormones that are derived from a single amino acid. One of three principal classes of hormones, the other two being peptide and steroid hormones.

anterior pituitary

An endocrine gland that releases two hormones that work directly on target cells and four other hormones that regulate the production of hormones by other endocrine glands. 

antidiuretic hormone (ADH)

Substance that helps control how much water is either sent to the bladder (in urine) by the kidneys or retained in circulation. In a release controlled by the brain’s hypothalamus, ADH increases the permeability of both the distal nephron tubule and the n

antigen

Any foreign substance that elicits a response by the immune system. Certain proteins on the surface of an invading bacterial cell, for instance, act as antigens that trigger an immune response.

autonomic nervous system

That portion of the peripheral nervous system’s efferent division that provides involuntary regulation of smooth muscle, cardiac muscle, and glands.

axon

A single, large extension of the cell body of a neuron that carries signals away from the cell body toward other cells.

central nervous system (CNS)

The portion of the nervous system consisting of the brain and spinal cord.

cerebral cortex

Thin outer covering of the region of the brain known as the cerebrum. Responsible for the highest human thinking and processing.

cerebrospinal fluid

A fluid that circulates in both the brain and spinal cord, supplying nutrients, hormones, and immune system cells and providing the nervous tissue with protection against jarring injury.

cerebrum

The largest region of the human brain, responsible for much of the human capacity for higher mental functioning.

cochlea

The coiled, fluid-filled, membranous portion of the inner ear in which vibrations are transformed into the nervous system signals perceived as

cone

In human vision, photoreceptors that respond best to bright light and that provide color vision.

dendrite

Extensions of a neuron that carry signals toward the neuronal cell body.

efferent divisionThe division of the peripheral nervous system that carries motor commands from the central nervous system (CNS) toward the effectors (muscles and glands).

endocrine glandA gland that releases its materials directly into surrounding tissues or into the bloodstream, without using ducts. Many hormones are produced by endocrine glands.

endocrine systemThe organ system that sends signals throughout the body through use of the chemical messengers called hormones.

estrogenA class of hormones, produced primarily by cells of the ovary, that supports egg development, growth of uterine lining, and development of female sex characteristics.

follicle-stimulating hormone (FSH)A hormone, secreted by the anterior pituitary, that promotes egg development and stimulates secretion of estrogen in women, and supports sperm production and testosterone secretion in men.

ganglionAny collection of nerve-cell bodies in the peripheral nervous system.

glucagonA hormone, secreted by cells in the pancreas, that brings about an increase in blood-levels of glucose.

homeostasisThe maintenance of a relatively stable internal environment in living things.

hormoneA substance that, when released in one part of an organism, goes on to prompt physiological activity in another part of the organism. Both plants and animals have hormones.

hypothalamusPortion of the brain important in drives, and in the maintenance of homeostasis, the latter capacity coming about because of the hypothalamus’ control over a good deal of body’s hormonal release.

insulinA hormone, secreted by cells in the pancreas, that brings about a decrease in blood levels of glucose.

interneuronA type of neuron, located only within the brain or spinal cord, that connects other neurons. These neurons are responsible for the analysis of sensory inputs and the coordination of motor commands.

ionic compoundA compound composed of the linked, ionic forms of two or more elements. Table salt results from ionic bonds formed between the elements sodium and chloride (NaCl).

luteinizing hormone (LH)A hormone secreted by the anterior pituitary; in women, LH induces ovulation and stimulates the ovary to secrete estrogens and progestins to prepare the body for possible pregnancy. In men, LH stimulates the testes to produce androgens such as testosteron

mammary glandsA set of glands that, in female mammals, provide milk for the young.

membrane potentialThe electrical charge difference that exists from one side of a neuron’s plasma membrane to the other.

myelinMembranous covering of some neuronal axons, provided by glial cells, that allows faster nerve signal transmission through these axons.

nerveA bundle of axons in the peripheral nervous system that transmits information to or from the central nervous system.

motor neuronA neuron that sends instructions from the central nervous system (CNS) to such structures as muscles or glands. Given the direction of this transmission, motor neurons are efferent neurons.

nervous systemThe organ system that monitors an animal’s internal and external environment, integrates the sensory information received, and coordinates the animal’s responses. This system consists of all the body’s neurons, plus the supporting neuroglia cells, plus th

neurotransmitterA chemical, secreted into a synaptic cleft by a neuron, that affects nervous system signaling by binding with receptors on an adjacent neuron or effector cell.

olfactionThe sense of smell.

ovary

In flowering plants, the area, located at the base of the carpel, where fertilization of the egg and early development of the embryo occur. In animals, the female reproductive organ in which eggs develop.

pancreasIn digestion, a gland that secretes, into the small intestine through ducts, digestive enzymes along with buffers that raise the pH of chyme. In nutrient metabolism, a gland that secretes, directly into the bloodstream, the hormones insulin and glucagon,

parasympathetic divisionThe division of the autonomic nervous system that generally has relaxing effects on the body.

peptide hormoneHormones composed of chains of amino acids, with these chains ranging from small polypeptides to proteins composed of hundreds of amino acids. One of three principal classes of hormones, the other two being amino-acid-based and steroid hormones.

peripheral nervous system (PNS)The part of the nervous system that includes all of the neural tissue outside the central nervous system (brain and spinal cord). The PNS brings information to and carries it from the central nervous system; it also provides voluntary control of the skele

peripheral proteinA protein of the plasma membrane that lies on the inside or outside of the membrane but is not attached to the membrane’s hydrophobic interior.

photoreceptorSensory receptor cell for vision, located in the eye’s retina, that transforms light into nervous system signals. Photoreceptors come in two varieties: rods, which function in low-light situations but provide only black-and-white vision; and cones, which

posterior pituitaryAn endocrine gland that receives its hormones directly from the hypothalamus, then stores these hormones and later releases them.

reflexAutomatic nervous system response that helps an organism avoid danger or preserve a stable physical state. The knee-jerk response is a well-known reflex.

retinaA layer of tissue at the back of the human eye whose cells convert light signals into neural signals.

rodPhotoreceptors that function in low-light situations, but that do not provide color vision.

sensory neuronA neuron that senses conditions both inside and outside the body and conveys that information to neurons in the central nervous system.

skinIn humans, an organ consisting of two tissue layers, an outer epidermis and inner dermis, and covering the outside of the body. The skin protects the body and receives signals from the environment.

somatic nervous systemThat portion of the peripheral nervous system’s efferent division that provides voluntary control over skeletal muscle.

steroid hormoneHormones such as testosterone and estrogen that are constructed around the chemical framework of the cholesterol molecule. One of three principal classes of hormones, the other two being peptide and amino-acid-based hormones.

sympathetic divisionThe division of the autonomic nervous system that generally has stimulatory effects on the body.

synapseAn area in the nervous system consisting of a sending neuron, a receiving neuron or effector cell (i.e., a muscle cell), and the gap between them, called the synaptic cleft.

synaptic cleftTiny gap that exists between a neuron sending a nervous system signal and a neuron (or effector cell) that is receiving this signal.

target cellThe set of cells in the body that will be affected by a given hormone. The target cells for each hormone bear receptors capable of binding with that hormone.

testisThe organ in the male reproductive system in which sperm begin development and testosterone is produced.

thalamusPortion of the brain through which most sensory perceptions are channeled before being relayed to the cerebral cortex.