89 Mind and Gut Glossary
Central Nervous System (CNS): the system that includes the brain and the spinal cord.
Peripheral Nervous System (PNS): a way of communication from the central nervous system to the rest of the body by nerve impulses that regulate the functions of the human body.
Somatic Nervous System (SNS): the part of the peripheral nervous system associated with the voluntary control of body movements through the action of skeletal muscles, and also reception of external stimuli.
Autonomic Nervous System (ANS): the part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes.
Enteric Nervous System (ENS): is one of the main divisions of the autonomic nervous system and consists of a mesh-like system of neurons that governs the function of the gastrointestinal tract.
Dendrites: short pieces that come off of the cell body that receive the signals from sensory receptors and other neurons.
Synapses: the gap between two neurons; new synapses lead to learning.
Axon: the part of the neuron that conducts nerve impulses.
Axon Hillock: the prominence on a nerve-cell body from which an axon arises.
Axon Terminal: Small swellings that are found at the terminal ends of axons. Typically the sites where synapses with other neurons are found, and neurotransmitters are stored there to communicate with other neurons via these synapses.
Myelin: a fatty substance that surrounds and insulates the nerve fibers and facilitates the conduction of the nerve impulse transmissions.
Nodes of Ranvier: unmyelinated gaps between sections of myelin.
Glial Cells: Any of the cells that hold nerve cells in place and help them work the way they should.
Blood Brain Barrier: A network of blood vessels and tissue that is made up of closely spaced cells and helps keep harmful substances from reaching the brain. The blood-brain barrier lets some substances, such as water, oxygen, carbon dioxide, and general anesthetics, pass into the brain.
Ligand-gated channel: opens because a signaling molecule, a ligand, binds to the extracellular region of the channel. This type of channel is also known as an ionotropic receptor because when the ligand, known as a neurotransmitter in the nervous system, binds to the protein, ions cross the membrane changing its charge.
Mechanically gated channel: opens because of a physical distortion of the cell membrane. Many channels associated with the sense of touch (somatosensation) are mechanically gated. For example, as pressure is applied to the skin, these channels open and allow ions to enter the cell. Similar to this type of channel would be the channel that opens on the basis of temperature changes, as in testing the water in the shower.
Voltage-gated channel: is a channel that responds to changes in the electrical properties of the membrane in which it is embedded. Normally, the inner portion of the membrane is at a negative voltage. When that voltage becomes less negative, the channel begins to allow ions to cross the membrane.
Leakage channel: is randomly gated, meaning that it opens and closes at random, hence the reference to leaking. There is no actual event that opens the channel; instead, it has an intrinsic rate of switching between the open and closed states. Leakage channels contribute to the resting transmembrane voltage of the excitable membrane.
Summation: The additive effect of several electrical impulses on a neuromuscular junction.
The neuromuscular junction (NMJ): is a synaptic connection between the terminal end of a motor nerve and a muscle.
Parasympathetic nervous system: The part of the involuntary nervous system that serves to slow the heart rate, increase intestinal and glandular activity, and relax the sphincter muscles.
Sympathetic nervous system: The part of the nervous system that increases heart rate, blood pressure, breathing rate, and pupil size.