The approach to the human nervous system within this section of the course is concerned with the structure of individual nerve cells, impulse transmission, and the basic organization and major divisions of the human nervous system. There is emphasis on integrating this material with other domains of biology such as molecular and cell biology. However, in the psychology and sociology portion of the course, you will find additional resources treating the human nervous system. Within that section there is a somewhat different focus, for example, treating with greater depth the anatomical areas of the brain which affect cognition and behavior.
The Nervous System Images
Conceptual Vocabulary Self-Test
Basic Terms Crossword Puzzle
Basic Puzzle Solution
Conceptual Vocabulary for The Nervous System
Neurons are electrically excitable cells in the nervous system that process and transmit information.
The central nervous system represents the largest part of the nervous system, including the brain and the spinal cord.
Nervous tissue is composed of neurons, which transmit impulses, and the neuroglia, which assist propagation of the nerve impulse as well as provide nutrients to the neuron.
An action potential is a spike of electrical discharge that travels along the membrane of a cell.
The resting potential of a cell is the membrane potential that would be maintained if there were no action potentials, synaptic potentials, or other active changes in the membrane potential.
Membrane potential is the electrical voltage across a cell's plasma membrane.
Depolarization is a decrease in the absolute value of a cell's membrane potential.
The brain or encephalon is the control center of the central nervous system.
The telencephalon is the name for the forebrain, a large region within the brain to which many functions are attributed, which many people refer to as the cerebrum.
The peripheral nervous system resides or extends outside the central nervous system serving the limbs and organs.
The somatic nervous system is the part of the peripheral nervous system associated with the voluntary control of body movements and with reception of external stimuli.
The autonomic nervous system is the part of the peripheral nervous system that acts as a control system, maintaining homeostasis in the body.
Motor neurons begin in the central nervous system projecting their axons outside the CNS and directly or indirectly controlling muscles.
The spinal cord is a thin, tubular bundle of nerves that is an extension of the central nervous system from the brain, enclosed and protected by the bony vertebral column.
The sympathetic nervous system is a branch of the autonomic nervous system, always active at a basal level and becoming more active during times of stress.
In a kind of complementary opposition to the sympathetic nervous system, the parasympathetic nervous system is the division of the autonomic nervous system that functions with actions that do not correspond to stress.
Dendrites are the branched projections of a neuron that act to conduct the electrical stimulation received from other neural cells to the cell body of the neuron.
Potassium channels are the most common type of ion channel within the physiology.
Sodium channels are integral membrane proteins that conduct sodium ions through a cell's plasma membrane.
Positive feedback is a feedback system in which the system responds to the perturbation with activity in the same direction as the perturbation.
Myelin is an electrically insulating phospholipid layer that surrounds the axons of many neurons.
Nodes of Ranvier, also known as neurofibril nodes, are regularly spaced gaps in the myelin sheath around an axon or nerve fiber.
Chemical synapses are specialized junctions through which the cells of the nervous system employ neurotransmitters to signal to each other and to non-neuronal cells such as those in muscles or glands.
Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell.
Grey matter is a major component of the central nervous system, consisting of nerve cell bodies, glial cells, capillaries, and short axons and dendrites.
White matter is composed of myelinated nerve cell processes, or axons, which connect various gray matter areas of the brain to each other.
A neural network refers to a network or circuitry of biological neurons.
A reflex action is an automatic (involuntary) neuromuscular action elicited by a defined stimulus.
Sensory neurons are nerve cells within the nervous system responsible for converting external stimuli from the organism's environment into nerve impulses relayed to the central nervous system.
The fight-or-flight response states that animals react to threats with a general discharge of the sympathetic nervous system.
The soma, or perikaryon, is the bulbous end of a neuron, containing the cell nucleus.
Afferent neurons--otherwise known as sensory or receptor neurons--carry nerve impulses from receptors or sense organs toward the central nervous system.
Efferent nerves - otherwise known as motor or effector neurons - carry nerve impulses away from the central nervous system to effectors such as muscles or glands.
Glial cells, commonly called neuroglia, are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system.
Schwann cells are a variety of glial cell that mainly provide myelin insulation to axons in the peripheral nervous system.
In a biological membrane, the reversal potential (or Nernst potential) of a particular ion is the membrane voltage at which there is no net flow of ions from one side of the membrane to the other.
Saltatory conduction is the means by which action potentials are transmitted along myelinated nerve fibers.
A neuromuscular junction is the synapse or junction of the axon terminal of a motoneuron with the motor end plate.
The first neurotransmitter identified, the chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system.
Epinephrine and norepinephrine are fight or flight hormones released from the adrenal glands, which are also neurotransmitters in the central and sympathetic nervous systems.
Cranial nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord.
A reflex arc is the neural pathway that mediates a reflex action.
The limbic system is the part of the human brain involved in emotion, motivation, and emotional association with memory.
Parasympathetic ganglia are mostly small terminal ganglia or intramural ganglia lying near or within the organs they innervate.
The axon hillock is the anatomical part of a neuron that connects the cell body called soma to the axon.
The neuron doctrine is the now fundamental idea that neurons are the basic structural and functional units of the nervous system.
Hyperpolarization is any change in a cell's membrane potential that makes it more polarized.
Synaptic vesicles store the various neurotransmitters that are released during calcium-regulated exocytosis into the synaptic cleft of a synapse.
An acetylcholine receptor is an integral membrane protein that responds to the binding of the neurotransmitter acetylcholine.
A neuropeptide is any of the variety of peptides found in neural tissue. Examples include the endorphins and enkephalins.
Reuptake is the reabsorption of a neurotransmitter by the neurotransmitter transporter of a pre-synaptic neuron after it has performed its function of transmitting a neural impulse.
Cerebrospinal fluid is a clear bodily fluid that occupies the subarachnoid space and the ventricular system around and inside the brain.
Located just below the thalamus, the hypothalamus links the nervous system to the endocrine system via the pituitary gland.
In the autonomic nervous system, fibers from the CNS to the ganglion are known as preganglionic fibers.
A synapse is cholinergic if it uses acetylcholine as its neurotransmitter.
The enteric nervous system is the part of the nervous system that directly controls the gastrointestinal system.
The meninges is the system of membranes which envelope the central nervous system.
Astrocytes are characteristic star-shaped glial cells in the brain.
Oligodendrocytes are a variety of neuroglia whose main function is the myelination of axons exclusively in the central nervous system of the higher vertebrates.
Electrophysiology is the study of the electrical properties of biological cells and tissues.
Choline acetyltransferase is an enzyme which joins Acetyl CoA to choline, resulting in the formation of the neurotransmitter acetylcholine.
Catecholamines are chemical compounds derived from the amino acid tyrosine containing catechol and amine groups.
Dopamine is a phenethylamine hormone and neurotransmitter. As a hormone, it inhibits the release of prolactin from the anterior lobe of the pituitary. As a neurotransmitter in the brain, it activates five types of receptors and their variants.
Serotonin is a monoamine neurotransmitter synthesized in serotonergic neurons in the central nervous system and enterochromaffin cells in the gastrointestinal tract.
Gamma-aminobutyric acid (usually abbreviated to GABA) is the chief inhibitory neurotransmitter in the central nervous system and also in the retina.
Synaptic plasticity is the ability of the connection, or synapse, between two neurons to change in strength.
G-protein-coupled receptors are a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses.
The medulla oblongata is the lower portion of the brainstem.
The ventricular system is a set of structures in the brain continuous with the central canal of the spinal cord through which cerebrospinal fluid flows.
The cerebellum is a region of the brain that plays an important role in the integration of sensory perception and motor control, using constant feedback on body position to fine-tune motor movements.
The pineal gland is a small endocrine gland in the brain which produces melatonin.
Broca's area is a section of the human brain that is involved in language processing, speech production, and comprehension.
A ganglion is a tissue mass composed mainly of somata and dendritic structures. They are often interconnected with each other to form a complex known as a plexus.
The dorsal root ganglion is a nodule on a dorsal root that contains cell bodies of neurons in afferent spinal nerves.
The optic nerve, also called cranial nerve II, is the nerve that transmits visual information from the retina to the brain.
The term spinal nerve generally refers to one of 31 paired mixed nerves formed from dorsal and ventral roots and exiting from the vertebrae through the intervertebral foramen.
Tryptamine is a monoamine alkaloid chemically related to the amino acid tryptophan, found in trace amounts in the brain and believed to play a role as a neuromodulator or neurotransmitter.
Neurophysin II is a carrier protein which binds vasopressin.
The epithalamus is a dorsal posterior segment of the diencephalon which includes the habenula, the stria medullaris and the pineal body.
The corpus callosum is a structure of the brain in the longitudinal fissure that connects the left and right cerebral hemispheres. It is the largest white matter structure in the brain.
The dura mater, or pachymeninx, is the tough and inflexible outermost of the three layers of the meninges surrounding the brain and spinal cord.
Axoplasm is the cytoplasm within the axon of a neuron.
The axolemma is the membrane of a neuron's axon.
Neurofilaments are the intermediate filaments found specifically in neurons.
A multipolar neuron is a type of neuron that possesses a single axon and many dendrites.
Axon guidance (also called axon pathfinding) describes the means by which neurons send out axons to reach the correct targets.
Radial glial cells, also called Bergmann glia, are a pivotal cell type in the developing central nervous system involved in key developmental processes.
Nicotinic acetylcholine receptors are ionotropic receptors that form ligand gated ion channels in cells' plasma membranes whose opening is triggered both by the neurotransmitter acetylcholine and also nicotine.
Muscarinic receptors are those membrane-bound acetylcholine receptors that are more sensitive to muscarine than to nicotine.
Axoplasmic transport, also called axonal transport, is responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts to and from a neuron's cell body through the cytoplasm of its axon.
Monoamine neurotransmitters, such as the catacholamines or melatonin, are neurotransmitters and neuromodulators that contain one amino group that is connected to an aromatic ring by a two-carbon chain.
N-Acetylaspartylglutamate (NAAG) is the third most prevalent neurotransmitter in the nervous system.
Metabotropic receptors do not form an ion channel pore; rather, they are indirectly linked with ion-channels on the plasma membrane of the cell through signal transduction mechanisms.
The rhombencephalon is a developmental categorization of portions of the central nervous system in vertebrates, sometimes called the hindbrain.
The pons is a structure located on the brain stem rostral to the medulla oblongata, caudal to the midbrain, and ventral to the cerebellum.
The mesencephalon, or midbrain, is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals.
The prosencephalon (or forebrain) is the rostral-most portion of the brain.
The diencephalon is the region of the brain that includes the thalamus, hypothalamus, epithalamus, prethalamus or subthalamus and pretectum. It is derived from the prosencephalon.
The thalamus is a pair and symmetric part of the brain constituting the main part of the diencephalon.
The suprachiasmatic nucleus is a region of the brain, located in the hypothalamus, that is responsible for controlling endogenous circadian rhythms.
The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.
A Brodmann area is a region in the brain cortex defined based on its cytoarchitecture, which is the organization of the cortex as observed when a tissue is stained for nerve cells.
The primary auditory cortex is the region of the brain that is responsible for processing of auditory information.
The parietal lobe is a lobe in the brain positioned above the occipital lobe and behind the frontal lobe which integrates sensory information from different modalities, particularly determining spatial sense and navigation.
The olfactory nerve is the first of twelve cranial nerves, transmitting sensory information arising from the sense of smell.
The oculomotor nerve is the third of twelve paired cranial nerves which controls most of the eye movements, constriction of the pupil, and holding the eyelid open.
The vestibulocochlear nerve, also known as the auditory or acoustic nerve, is the eighth of twelve cranial nerves, and is responsible for transmitting sound and equilibrium information from the inner ear to the brain.
A pyramidal cell is a multipolar neuron located in the hippocampus and cerebral cortex.
Purkinje cells are a class of GABAergic neuron located in the cerebellar cortex, some of the largest neurons in the human brain.
The ependyma is the thin epithelial membrane lining the ventricular system of the brain and the spinal cord canal.
Phenethylamine is an alkaloid monoamine believed to function as a neuromodulator or neurotransmitter. It is biosynthesized from the amino acid phenylalanine by enzymatic decarboxylation.
Neurotensin is a 13 amino acid neuropeptide that is implicated in the regulation of luteinizing hormone and prolactin release and has significant interaction with the dopaminergic system.
The NMDA receptor is an ionotropic receptor for glutamate which allows flow of sodium ions and small amounts of calcium ions into the cell and potassium out of the cell.
Neuropeptide Y is a peptide neurotransmitter found in the brain and autonomic nervous system that augments the vasoconstrictor effects of noradrenergic neurons.
Pinealocytes are the main cells of the pineal gland which produce and secrete melatonin.
The vagus nerve, the tenth cranial nerve, is the only nerve that starts in the brainstem. It extends through the jugular foramen, down below the head, to the neck, chest and abdomen.
The occipital lobe is the visual processing center of the mammalian brain, containing most of the anatomical region of the visual cortex.
The sympathetic trunk is a bundle of nerve fibers, a chain of ganglia, that runs from the base of the skull to the coccyx.
A neural pathway is a neural tract connecting one part of the nervous system with another, usually consisting of bundles of elongated, myelin insultated neurons, known collectively as white matter.
The corticospinal or pyramidal tract is a massive collection of axons that travel between the cerebral cortex of the brain and the spinal cord.
The arachnoid mater is one of the three meninges. It is interposed between the more superficial dura mater and the deeper pia mater.
The pia mater is the delicate innermost layer of the meninges.
A Nissl body is a large granular body found in nerve cells. These are rough ER.
A dendritic spine is a small membranous extrusion that protrudes from a dendrite and forms one half of a synapse.
A bipolar cell is a type of neuron having two extensions, which is a specialized sensory neuron for the transmission of special senses.
Satellite cells are a type of glial cell lining the exterior surface of neurons in the peripheral nervous system and which also surround neuron cell bodies within ganglia.
Chromaffin cells are neuroendocrine cells found in the medulla of the adrenal gland and in other ganglia of the sympathetic nervous system, which secrete epinephrine, norepinephrine, and enkephalin into the bloodstream.
The dopamine transporter is a membrane spanning protein that binds the neurotransmitter dopamine and moves it from the synapse into a neuron.
The norephinephrine transporter is a transmembrane protein which transports the neurotransmitter norephinephrine from the synapse back to its vesicles for storage until later use.
Octopamine is a biogenic amine which is closely related to noradrenaline, and has a similar action to dopamine.
The tachykinin neuropeptide, substance P, has been associated in the regulation of mood disorders, anxiety, stress, reinforcement, neurogenesis, respiratory rhythm, neurotoxicity, nausea / emesis and pain.
The spinal canal or cavity is the space in the vertebrae through which the spinal cord passes.
The reticular formation is a part of the brain which is involved in stereotypical actions, such as walking, sleeping, and lying down.
The optic chiasm is the part of the brain where the optic nerves partially cross.
The rhinencephalon is a part of the brain involved with olfaction, which includes the olfactory bulb, the olfactory tract, the olfactory tubercle and striae, the anterior olfactory nucleus and parts of the amygdala and the piriform cortex.
A gyrus is a ridge on the cerebral cortex, generally surrounded by one or more sulci.
Alpha motor neurons are large lower motor neurons of the brainstem and spinal cord which innervate extrafusal muscle fibers of skeletal muscle.
Lower motor neurons are the motor neurons connecting the brainstem and spinal cord to muscle fibers, bringing the nerve impulses out to the muscles.
A motor unit is a single alpha motor neuron and all of the corresponding muscle fibers it innervates.
Gamma motor neurons are a component of the fusimotor system, the system by which the central nervous system controls muscle spindle sensitivity.
The trigeminal nerve, the fifth cranial nerve, is responsible for sensation in the face.
The facial nerve, the seventh cranial nerve, controls the muscles of facial expression, and taste to the anterior two-thirds of the tongue and supplies preganglionic parasympathetic fibers to several head and neck ganglia.
Granule cells are tiny neurons found within the granular layer of the cerebellum, layer 4 of cerebral cortex, the dentate gyrus of the hippocampus, and in the olfactory bulb.
Basket cells are inhibitory GABAergic interneurons found in the molecular layer of the cerebellum which synapse on the cell bodies of Purkinje cells.
Betz cells are pyramidal cell neurons located within the fifth layer of the grey matter in the primary motor cortex.
Renshaw cells are inhibitory interneurons found in the gray matter of the spinal cord.
Glial fibrillary acidic protein is an intermediate filament protein that is found in glial cells such as astrocytes.
Myelin basic protein is a protein believed to be important in the process of myelination of nerves in the central nervous system.
Myelin oligodendrocyte glycoprotein is a glycoprotein believed to be important in the process of myelinization of nerves in the central nervous system.
Phenylethanolamine N-methyltransferase is an enzyme found in the adrenal medulla that converts norepinephrine to epinephrine.
The neuropeptide neurokinin A is a neurotransmitter with various roles roles in human physiology. It is produced by the same gene as substance P.
Anandamide, also known as AEA, is an endogenous cannabinoid neurotransmitter found in human organs, especially in the brain.
The trochlear nerve, the fourth cranial nerve, is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.
The abducens nerve, the sixth cranial nerve, is a motor nerve that controls the movement of a single muscle, the lateral rectus muscle of the eye.
The glossopharyngeal nerve is the ninth cranial nerve, which exits the brainstem just rostral to the vagus nerve.
The accessory nerve is a nerve that controls specific muscles of the neck, considered a cranial nerve because part of it originates in the brain.
The hypoglossal nerve is the twelfth cranial nerve, arising from the hypoglossal nucleus and emerging from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid.
The WikiPremed MCAT Course is a comprehensive course in the undergraduate level general sciences. Undergraduate level physics, chemistry, organic chemistry and biology are presented by this course as a unified whole within a spiraling curriculum. Please read our policies on Privacy and Shipping & Returns. Contact Us. MCAT is a registered trademark of the Association of American Medical Colleges, which does not endorse the WikiPremed Course. WikiPremed offers the customers of our publications or our teaching services no guarantees regarding eventual performance on the MCAT.
WikiPremed is a trademark of Wisebridge Learning Systems LLC. The work of WikiPremed is published under a Creative Commons Attribution NonCommercial ShareAlike License. There are elements of work here, such as a subset of the images in the archive from WikiPedia, that originated as GNU General Public License works, so take care to follow the unique stipulations of that license in printed reproductions.