Glossary
Acetylcholine - Neurotransmitter responsible for muscle contraction. Involved in the activation of REM sleep and dreams. It causes vasodilatation, promotes peristalsis among other parasympathetic effects.
Agonist - Refers to an enhancing effect of a chemical. For example, a dopamine agonist, will promote the effect of dopamine.
Alpha motor neurons - Neurons that innervate the skeletal muscle fibers (extra fusal fibers) directly. Activation of alpha motor neurons causes contraction of muscle fibers. In other words, these cells cause muscle contraction
.
Alpha waves - Irregular electrical impulses of about 9-12 Hz recorded from the brain. It indicates a relaxed or not very active brain activity. It's usually present when we close our eyes or when there is not much arousal or stimulation.
Antagonist - Refers to an inhibiting effect of a chemical. An acetylcholine antagonist for example, will use some mechanism to diminish or inhibit the effect of acetylcholine.
Atonia - Loss of muscle tone. A phenomena present during REM sleep to prevent us from "acting out" our dreams by causing muscle paralysis.
Basal ganglia - A group of nuclei located sub cortically. The basic function discovered so far of the basal ganglia is movement control.
Beta waves - Irregular electrical impulses of about 13-30 Hz recorded from the brain. Beta waves are present when we are wide awake, alert.
Brain stem - The part of the brain that connects the medulla and the diencephalon. Cells in the brain stem control vital functions like respiration, heart rate, muscle tone, blood pressure, etc.
Cerebral activation - refers to the electrical energy that spreads across the two cerebral halves of the brain.
Cerebral cortex - The "bark" of the brain. A newly evolved feature of great proportions in humans. It receives sensory information and is responsible in carrying out its analysis and planning an adequate response. It is that part of the brain where we intellectualize, plan, execute, feel pleasure, pain, move and see.
Cholinergic - refers to choline synapses. These synapses release choline, which is a chemical, along with acetate, that composes the neurotransmitter acetylcholine.
Delta waves - A more steady and regular kind of brain wave of less than 4Hz. Its appearance marks the deepest stages of sleep.
Desynchrony - When cells fire randomly, without any sort of orchestration. It is a sign of mental activity, present when we are awake.
Dopamine - Neurotransmitter involved in attention, learning, movement, and reinforcement of behavior. It has an inhibitory or excitatory effect depending on which receptors it falls into. It is a precursor of norepinephrine and an alpha-adrenergic agonist.
Dopaminergic - refers to the synpases that release the chemical dopamine.
Dopaminergic mesolimbic structures - the entities of one of three systems that contain dopaminergic neurons. This system projects its neurons to the limibic system, which is a ciruit of brain structures that are involved in emotion and motivation.
Electroencephalogram or EEG - A recording device that using electrodes attached to the scalp, measures brain activity in the form of electrical impulses. It is helpful for detecting abnormal brain activity and to diagnose diseases such as epilepsy, narcolepsy, for example.
Electromyogram or EMG - It records muscle activity by placing electrodes on the skin that are sensitive to electrical activity.
Electrooculogram or EOG - It detects muscle activity of the eyes. In other words, it records eye movements by placing electrodes on the skin surrounding the eyes.
Forebrain - The most rostral section of the brain divided in two major areas: the telencephalon and the diencehphalon. These areas include the cerebral hemispheres and cerebral cortex, the limbic system, thalamus and hypothalamus among several others.
Fos protein - Stimulation or activity of neurons causes the production of Fos protein. Staining techniques targeting Fos protein can tell us how much Fos protein was produced inside neurons. The more Fos protein there is, the more active the neuron is.
GABA - The most common inhibitory neurotransmitter in the nervous system. Like glutamate, it is also an amino acid that has a long phylogenetical history.
Glutamate - The major excitatory neurotransmitter of the nervous system and the most abundant. Common in most species, therefore probably one of the oldest neurotransmitter nature has designed. Glutamate is also an amino acid.
Gonadotropin - Hormones related to sexual development. They work by stimulating the gonads to produce their own hormones.
Growth Hormone (GH) or somatotropin - A hormone released by the pituitary gland. Its function is to promote cell reproduction and cell growth, especially on the skeletal and muscle systems. It has a healing and repairing effect on other tissues as well.
Hindbrain - region of the brain that is comprised of the back portions, such as the cerebellum and the pons.
Hippocampus. A forebrain structure of the temporal lobe, part of the limbic system. The hippocampus is heavily involved in memory consolidation and learning.
Histamine - A hormone involved in the inflammatory process. As a neurotransmitter its involved in arousal and cortical excitation.
Hyperpolarization - A neuron is hyperpolarized when is less responsive to fire an action potential.
Hypnogogic hallucinations - It's the phenomena in which a person is having vivid dreams while being awake and paralyzed. It's a symptom of narcolepsy.
Hypothalamus - The brain structure located under the thalamus. Involved in species-typical behavior, regulation of pituitary gland and autonomic behavior.
Lateral genicualte nucleus - Thalamic nuclei that receives visual information from the optic nerve, it reorganizes it and from there it relays the visual information to the primary visual cortex.
Lesion - synonymous with ablation studies, or the destruction of a particular area of the brain.
Locus coerulus - Group of cells in the pons that secrete norepinephrine.
Medulla - The "tail" of the brain, it connects the spinal chord to the brain. So all information that must run between spinal chord and brain goes through here. The reticular formation starts its ascension from the medulla.
Mesencephaon or midbrain - The section of the brain that is in between the brain stem and the forebrain. Divided in two areas: tectum and tegmentum. It surrounds the cerebral aqueduct. The tectum contains the superior culliculi (part of the visual system) and inferior culliculi (part of auditory system); tegmentum contains important areas in the production of neurotransmitters involved in motor activity (substantia nigra/ red nucleus), there are areas where many motor nucleus of cranial nerves are located; the reticular formation runs through the tegmentum as well. Other important regions of the tegmentum are the periaqueductal gray matter, the ventral segmental area, etc.
Medial pontine reticular formation (MPRF) - Region involved in the activation of REM sleep.
Nervous System - Includes the brain, spinal chord and nerves.
Neuron - The basic cell of the nervous system. Neurons are the individual signaling elements of the brain. It consists of a cell body or soma. Out of the soma thousands of spikes emerge to connect with other neurons. Also from the soma comes an axon, which resembles a long neck. At the end of the axon the neuron connects to another neuron, or to hundreds or thousands. These neural connections are called synapses.
Neurotransmitter - Chemical messengers secreted by neurons to communicate with each other. Secreted in the synapse (connections among neurons) by the post-synaptic neuron, they are received by the post-synaptic neurons, and cause an excitatory or an inhibitory effect.
Noradrenergic - refers to the synpases that contain norepinephrine.
Norepinephrine. Neurotransmitter involved in vigilance and arousal. We have a norepinephrine boost when we are scared, alert or when we encounter emergency.
Nucleus basalis - A nucleus in the basal forebrain that contains acetylcholine secreting cells which innervate the cerebral cortex, activating it.
PCPA (p-chlorophenylalanine) - A serotonin antagonist. It inhibits tryptophan hydroxylase, a key enzyme in the production of serotonin, thus it slows or inhibits the production of serotonin.
Peribrachial area - A dorsolateral region of the pons composed of acetylcholinergic neurons involved in the initiation of REM sleep.
PET scan (Positron emission tomography) - A device that measures the metabolic activity of the brain. It works sort of like this: a patient is given a harmless dose of a radioactive sugar (remember that sugar is the main energy source of the brain), the parts of the brain that the patient will use more are the ones that will consume more energy, more sugar. The radioactive sugar emits positrons (subatomic particle) and the scanner picks that up. The scanner can tell us in color images what areas of the brain are being more active by the emission of positrons.
Pineal Gland - A gland directly connected to the brain through the hypothalamus. It is the master gland because it directs and regulates the production and activity of the endocrine system. It secretes many hormones involved in sleep/wake cycle, growth cycle, reproductive cycle, etc.
Pons - The bulgy section of the brain stem. The reticular formation runs through it. It connects the mesencephalon and medulla.
Pontine-geniculate-occipital (PGO) wave - A synchronized burst of electrical activity that originates in the pons and like a wave it activates the lateral geniculate nucleus (first relay of visual information) and then the occipital lobe, specifically in the visual cortex (which receives and puts together the visual information that comes from the lat. geniculate nucleus). PGO waves appear seconds before and during REM sleep.
Posterior dorsal - the area both toward the bottom and back of a structure.
Primary motor and somatosensory areas - They are part of the cerebral cortex, located on opposing sides of the central sulcus, a major fissure in the brain. The primary motor area contains a "map" of our body. The map is composed of neurons that control movement of that part of the body. The primary somatosensory area is also a "map" of our body. The cells here, receive information about sensation in very specific parts of our body.
Primary visual cortex - The occipital region of the cerebral cortex, which receives input from visual system. It analyzes and puts together visual images.
Prolactin (PRL)or lactogenic hormone - Along with other hormones (oxytocin) it initiates and maintains the production and secretion of milk by the mammary glands. In males PRL enhances the effect of luteinizing hormone in promoting the production of testosterone.
Raphe nuclei - Clusters of cells located in the medulla, pons and midbrain. Raphe nuclei are responsible for the production of serotonin.
REM-On cells - Neurons in the peribrachial area that when activated, initiate REM sleep.
REM without atonia - Patients with this disorder act out their dreams. This is a disorder in which the neural mechanisms involved in sleep paralysis of REM are damaged (subcoerulear region--magnocellular nucleus).
Receptors - Neurotransmitters are the key and receptors are the lock. Receptors are binding organelles of cells for receptors. Each neurotransmitter has a specific set of receptors. Cells have different receptors and number of receptors, depending where the cells are in the body. When a neurotransmitter binds with a receptor, receptors get activated and turn on a series of specific activities within a cell. These activities will have specific results, depending on the neurotransmitter. Some neurotransmitters will make the neuron hyperpolarize or it will depolarize the cell.
Reticular formation - A complex mesh of neurons that runs midline through the brain stem. Neurons here are involved in the vital functions of the nervous system, like respiration, heart rate, muscle tone, blood pressure, as well as arousal and reflexes. It receives sensory information and relays it to the cortex, thalamus and spinal cord.
Reuptake - This is a cellular mechanism to recycle unused neurotransmitters. In reuptake the neuron reabsorbs the remaining neurotransmitter left in the synaptic space.
Serotonin - A neurotransmitter involved in the control of the sleep/wake cycle, eating and arousal. It is involved in pain modulation as well as in mood regulation and dreaming.
Sleep apnea - A sleeping disorder in which the ability to breath and sleep at the same time is affected. Strongly associated with snoring. Many cases are due the obstruction of airways (excessive fatty tissue is a common cause of obstruction). Patients with sleep apnea wake up in the middle of the time several times (sometimes dozens of occasions at night) gasping for air. The oxygen levels go down from not breathing properly, certain body mechanisms sense this and cause the patient to wake up gasping for air. As soon as they regain normal levels of oxygen (usually it takes a few seconds), they fall asleep again and the sleep apnea begins again.
Substantia nigra - A dark cluster of cells in the tegmentum, responsible for the production of dopamine.
Synapses - Synapses are junctions between the transmitting cell and the receiving cell. They act to facilitate the sending of messages from one neuron to another.
Synchrony - When cells fire together, harmoniously and organized, in sync. It is a sign of mental restfulness.
Thalamus - A fore brain structure that receives sensory information directly, (except olfactory) and projects it into the cerebral cortex. It regulates what information reaches the cerebral cortex.
Thyroid Stimulating Hormone (TSH) - Stimulates the synthesis and secretion of thyroid gland hormones. These hormones will regulate metabolism, energy balance, regulation of body development and growth and also nervous system activity in terms of reactivity.
Tuberomammilary nucleus - A nucleus responsible for the production of histamine in the brain. Located in the hypothalamus.