The master controlling and communicating system of the body.
These cells are the key to neural communication.
Nerve cells or neurons
The three overlapping functions of the nervous system.
The nervous system uses its millions of receptors to monitor changes occurring inside and outside of the body. The gathered information is called....
The nervous system processes and interprets sensory input and decides what should be done at each moment, a process called.....
The response caused by the nervous system that entails activating effector organs.
The integrating and command center of the nervous system, consisting of the brain and spinal cord.
Central Nervous System (CNS)
The part of the nervous system that is outside of the CNS, consisting of nerves that extend from the brain and spinal cord.
Peripheral Nervous System (PNS)
Nerves that carry impulses to and from the spinal cord.
Nerves that carry impulses to and from the brain.
The two subdivisions of the PNS.
Sensory or afferent division
Motor or efferent division
The division of nerves that carries impulses to the CNS from sensory receptors located throughout the body.
Sensory or afferent division
Sensory fibers that carry impulses from the skin, skeletal muscles and joints.
Somatic afferent fibers
Sensory fibers that carry impulses from the visceral organs.
Visceral afferent fibers
The division of nerves that carries impulses from the CNS to effector organs.
Motor or efferent division
The two main divisions of the motor division.
Somatic nervous system - voluntary
Autonomic nervous system (ANS) - involuntary
The two subdivisions of the ANS.
Sympathetic division - mobilizes fight or flight
Parasympathetic division - conserves energy and performs housekeeping functions
The two principle types of cells in nervous tissues.
Neuroglia - supporting cells
Neurons - excitable nerve cells that transmit electrical signals
The four types of neuroglia found in the CNS.
The most abundant type of neuroglia, shaped like a sea anemone, numerous radiating processes. Connected together by gap junctions.
CNS neuroglia that helps make exchanges between capillaries & neurons, determine capillary permeability, guide migration of young neurons & synapse formation. Also controls chemical environment around neurons, mops up leaked K+ ions & recaptures released neurotransmitters.
Small, ovoid CNS neuroglia cells with long "thorny" processes that touch nearby neurons to monitor their health. Phagocytize dead neurons and invading microorganisms.
CNS neuroglia that has wide variety of shapes, lines central cavities in brain & spinal cord to form permeable barrier between cerebrospinal fluid and tissue fluid of CNS cells. Frequently ciliated, cilia help circulate cerebrospinal fluid.
CNS neuroglia that wraps axons, producing the insulating covering called the myelin sheath.
PNS neuroglia that surrounds neuron cell bodies and are thought to have many of the same functions as astrocytes.
PNS neuroglia that forms the myelin sheath around larger nerve. Functionally similar to oligodendrocytes. Vital to regeneration of damaged PNS fibers.
Large, complex, highly specialized cells that conduct messages in the form of nerve impulses from one part of the body to another, the structural unit of the nervous system.
Neurons or nerve cells
Special characteristics of neurons:
Amitotic (except olfactory & hippocampal regions)
High metabolic rate
This part of a neuron is the site of electrical signaling.
The plasma membrane
Key component of a neuron cell body that is the equivalent of rough ER.
Key component of a neuron cell body that is important in maintaining cell shape and integrity.
A pigment that is a harmless by-product of lysosomal activity and is sometimes called the "aging pigment" because it accumulates in neurons of elderly individuals.
Clusters of cell bodies in the CNS.
Clusters of cell bodies that lie along the nerves in the PNS.
Bundles of neuron processes in the CNS? in the PNS?
Tracts - CNS
Nerves - PNS
The two types of neuron processes.
Processes of motor neurons that are short, tapering, and diffusely branching. The main receptive region of a neuron. The convey incoming messages as graded potentials.
Bulbous or spiky ends on some dendrites which represent points of close contact with other neurons.
The cone-shaped area of a neuron cell body from which an axon extends.
The slender process that extends from a neuron cell body, uniform in diameter. The conducting region.
Branches on an axon that extend at more or less right angles.
The plasma membrane of an axon.
The branches at the end of an axon.
Terminal branches or telodendria
The knob-like distal endings of the terminal branches that function as the secretory region.
Axon terminals, synaptic knobs, boutons
In motor neurons, the junction of the axon hillock and axon, where nerve impulses are generated.
The two cell components that are missing from an axon.
Movement toward the axon terminals. May involve mitochondria, cytoskeletal elements, membrane components, enzymes, etc.
Movement away from the axon terminals and toward the cell body. Usually organelles being returned to the cell body for degradation or recycling.
The whitish, fatty segmented covering of some nerve fibers (axons) that protects & electrically insulates and increases the speed of transmission of nerve impulses.
The exposed part of the plasma membrane of a Schwann cell.
The gaps in the myelin sheath.
Nodes of Ranvier or myelin sheath gaps.
Regions of the brain and spinal cord that contain dense collections of myelinated fibers.
Regions of the brain and spinal cord that contain mostly nerve cell bodies and unmyelinated fibers.
The two ways that neurons are classified.
Structurally - by the number of processes
Functionally - by the direction in which impulses travel in relation to the CNS
Neurons having three or more processes, one axon and the rest dendrites. These are the most common type, making up over 99% of neurons in the human body.
Neurons having two processes, an axon and a dendrite, that extend in opposite directions from the cell body. These are rare, found in special sense organs such as the retina of the eye or the olfactory mucosa.
Neurons that have a single short process that emerges from the cell body and divides T-like into proximal (central process) and distal (proximal process) branches. Found chiefly in ganglia in the PNS where they function as sensory neurons.
Unipolar neurons or pseudounipolar neurons
Neurons that transmit impulses from sensory receptors toward or into the CNS. Virtually all of these are unipolar and cell bodies are located in sensory ganglia outside the CNS.
Sensory or afferent neurons
Neurons that carry impulses away from the CNS to effector organs. These neurons are multi-polar and, except for some neurons of the ANS, their cell bodies are located in the CNS.
Motor or efferent neurons
Neurons that lie between motor and sensory neurons and shuttle signals through CNS pathways where integration occurs. These neurons are mostly confined within the CNS and make up over 99% of the neurons in the body. Almost all are multi-polar, but there is considerable diversity in size and branching patterns.
Interneurons or association neurons
The response created when a neuron is adequately stimulated.
Action potential or nerve impulse
The human body is:
A) Positively charged B) Neutrally charged
C) Negatively charged
B) Neutrally charged
(this multiple choice question has been scrambled)
The measure of potential energy generated by separated charge. Always measured between two points.
The units used to measure voltage.
Volts (V) or millivolts (mV)
Voltage is also call the ___________ between two points.
Potential or potential difference
The flow of electrical charge from one point to another.
The hindrance to charge flow provided by substances through which the current must pass.
Substances that have high electrical resistance.
Substance with low electrical resistance.
The relationship between voltage, current and resistance.
In the body, electrical currents reflect the flow of ____ across cellular membranes.
Channels in cellular membranes are made up of this.
These cell membrane channels are always open.
Leakage or non-gated channels
These cell membrane channels only open when the appropriate chemical binds to it.
Chemically gated or ligand-gated channels
These cell membrane channels open and close in response to changes in membrane potential.
These cell membrane channels open in response to physical deformation of a receptor.
Mechanically gated channel
The potential difference of electrical charge between the inside and outside of a neuron. Typically around -70 mV, but can vary from -40 mV to -90 mV depending on the type of neuron.
Resting membrane potential
A reduction in membrane potential, the inside of the membrane becomes less negative than the resting potential.
An increase in membrane potential, the inside of the membrane becomes more negative than the resting potential.
Short-lived, localized changes in membrane potential that can be either depolarizations or hyperpolarizations. They decrease in magnitude as they get further from their source.
The principal way that neurons send signals over long distances. They do NOT decrease in magnitude as they get further from their source.
The two different types of voltage-sensitive gates on an Na+ channel.
The depolarization level that must be reached in order to generate and action potential.
The restoration of the negativity of the resting neuron.
The period during which a patch of neuron membrane is generating an AP and it's voltage-gated sodium channels are open and cannot respond to another stimulus.
Absolute refractory period
The period during which most Na+ channels have returned to their resting state, some K+ channels are still open and repolarization is occurring. Threshold is substantially increased but if stimulus is strong enough, can still create another AP.
Relative refractory period.
The rate at which an action potential travels is determined by these two factors.
Axon diameter - larger=faster
Degree of myelination
The type of conduction of an AP on an unmyelinated axon that is relatively slow.
The type of conduction of an AP on a myelinated axon that is 20-30x faster.
An autoimmune disease in which the immune system attacks myelin proteins, gradually destroying myelin sheaths in the CNS.
Multiple sclorosis (MS)
The classification of nerve fibers (long axons) that have the largest diameter, thick myelin sheaths, & conduct impulses up to 150 m/s. Includes mostly somatic sensory & motor fibers serving the skin, skeletal muscles and joints.
Group A fibers
The classification of nerve fibers (long axons) that are lightly myelinated of intermediate diameter, transmit impulses around 15 m/s. Includes ANS visceral motor and sensory fibers & smaller somatic sensory fibers transmitting afferent impulses from the skin.
Group B fibers
The classification of nerve fibers (long axons) that have the smallest diameter, are unmyelinated, & conducte impulses at 1 m/s or less. Includes ANS visceral motor and sensory fibers & smaller somatic sensory fibers transmitting afferent impulses from the skin.
Group C fibers
A junction that mediates information transfer from one neuron to the next or from a neuron to an effector cell.
A synapse between the axon endings of one neuron and the dendrites of other neurons.
A synapse between axon endings of one neuron and cell bodies of other neurons.
A synapse between axons.
A type of synapse that consists of gap junctions and transmit synapses very rapidly, providing a means to synchronize the activity of all interconnected neurons. Heart muscle.
A type of synapse that uses the release and reception of neurotransmitters.
A fluid-filled space approximately 30-50 nm that separates pre- and post-synaptic neurons.
Depolarization of the cell membrane opens voltage-gated channels for these two ions.
Sodium (Na+) & Calcium (Ca2+)
The three ways that neurotransmitters are removed from the synaptic cleft.
Reuptake by astrocytes or the presynaptic terminal
Degradation by enzymes
Diffusion away from the synapse
A local, graded depolarization that occurs at excitatory postsynaptic membranes. A result of the opening of a chemically-gated ion channel that simultaneously allows Na+ & K+ to diffuse across the membrane in opposite directions.
Excitatory post-synaptic potentials (EPSP)
Hyperpolarization that occurs on a postsynaptic membrane by making the membrane more permeable to K+ or Cl-.
Inhibitory postsynaptic potentials (IPSP)
A postsynaptic neurons ability to add together numerous incoming impulses towards generation of an action potential.
Summation that occurs when one or more presynaptic neurons transmit impulses in rapid-fir order and bursts of neurotransmitter are released in quick succession.
Summation that occurs when a large number of terminals stimulate the same postsynaptic neuron.
A partially depolarized neuron is more easily excited by successive depolarization events.
Repeated or continuous use of a synapse that enhances the presynaptic neuron's ability to excite the postsynaptic neuron, producing larger-than-expected potentials.
This occurs when the release of excitatory neurotransmitter is inhibited by the activity of another neuron firing via an axoaxonic synapse.
How many neurotransmitters or neurotransmitter candidates have been identified?
More than 50
The first neurotransmitter identified, it is released at neuromuscular junctions. Excitatory at nicotinic (direct) receptors, but can be either excitatory or inhibitory at muscarinic (indirect via second messengers) receptors.
The chemical class of neurotransmitters that are amino acid derived-amines and includes epinephrine, norepinephrine, serotonin, dopamine, & histamine.
The chemical class of neurotransmitters that includes gamma-aminobutyric acid (GABA), glycine, aspartate and glutamate.
The chemical class essentially strings of amino acids and includes endorphins (dynorphin, enkephalins), tachykininis (substance P, neurokinin), somatostatin, cholecystokinin.
The chemical class of neurotransmitters that includes ATP & adenosine (the inhibitor that caffeine blocks in the brain).
The chemical class of neurotransmitters that includes nitric oxide (NO), carbon monoxide (CO) and endocannabinoid. This group has only recently been discovered.
Gases & lipids
The two classification of neurotransmitters by function.
Effects - excitatory (depolarization) vs. inhibitory (hyperpolarization)
Actions - direct (binds to ion channels) vs. indirect (binds to a receptor, triggering release of a second messenger)
The term used to describe a chemical messenger released by a neuron that does not directly cause EPSPs or IPSPs but instead affects the strength of synaptic transmissions.
Ligand-gated ion channels that mediate direct transmitter action, composed of several proteins subunits arranged in a "rosette" around a central pore. Always located precisely opposite sites of neurotransmitter release.
Channel-linked receptors or ionotropic receptors
Type of receptor that mediates indirect, complex, slow and often prolonged activation. Also called metabotropic receptors due to their their tendency to bring about widespread metabolic changes.
G protein-linked receptors
Cyclic AMP, cyclic GMP, diacylglyceror and Ca2 are all examples of....
Functional groups of neurons that integrate incoming information in the CNS and forward the information to other destinations.
The area of a neuronal pool that receives the bulk of the synaptic contact.
The area of the neuronal pool that is on the edge of the discharge zone.
The synaptic connection pattern in neuronal pools where one incoming fiber triggers responses in ever-increasing numbers of neurons farther along the circuit in order to amplify the signal.
The synaptic connection pattern in neuronal pools where the responses are funneled in order to concentrate the signal.
The synaptic connection pattern in neuronal pools where incoming signals travel through a chain of neurons which make collateral synapses with neurons in a previous part of the pathway, creating positive feedback.
Reverberating or oscillating circuits
The synaptic connection pattern in neuronal pools where incoming fiber stimulates several neurons in parallel arrays that then narrow back down to a common output cell.
Parallel after-discharge circuit
Type of sensory input processing in which input travels along one pathway to a specific destination, such as spinal reflexes.
Type of sensory input processing in which input travels along several different pathways to be integrated in different CNS regions, such as the smell of a pickle may trigger salivation, memories of making pickles with mom, make you think of your daughter who loves pickles.
The CNS derives from this embryonic tissue.
In an embryo, the growing tip of an axon (a prickly, fanlike structure) is called....