Nervous Systems

Flashcard maker : Evie Nicholson
Acetylcholine
A neurotransmitter that carries information across vertebrate
neuromuscular junctions and some other synapses. It is then broken down
by the enzyme cholinesterase
-all nerve-muscle junctions
-can be excitatory or inhibitory (heart rate)
Action Potential
An impulse in a neuron taking the form of a wave of depolarization or hyperpolarization
– impulse transmission
-rapid transmission over a longer distance
Active Transport
The energy-dependent transport of a substance across a biological membrane
against a concentration gradient– that is, from a region of low
concentration (of one substance) to one of high concentration
Afferent
Carrying to , as in a neuron that carries impulses to the central nervous system
, or a blood vessel that carries blood to a structure
-input
All-or-none
does not vary in strength
Autonomic
The portion of the peripheral nervous system that controls such involuntary
functions as those of guts and glands. Also called the involuntary
nervous system
-involuntary functions; heart rate, digestion, excretion, etc.
Axon
The part of a neuron that conducts action potentials away from the cell body
-rapid passage of action potential
Axon Hillock
The junction between an axon and its cell body, where action potentials are generated
Axon Terminals
The endings of an axon; they form synapses and release neurotransmitter
-multiple contacts with target cell(s)
Cell Body
“decision making”; site of graded potential
Central Nervous System (CNS)
The portion of the nervous system that is the site of most information processing, storage, and retrieval; in vertebrates, the brain and spinal cord.
Peripheral Nervous System (PNS)
The portion of the nervous system that transmits information to and fro the central nervous system, consisting of neurons that extend or reside outside the brain or spinal cord and their supporting cells
Chemically-gated Channel
A type of gated channel that opens or closes depending on the presence or absence of a specific molecule, which binds to the channel protein or to a separate receptor in turn alters the 3-D shape of channel protein
Cholinesterase
breaks down acetylcholine, removes it from receptors
Cranial Nerve
enter brain directly; 12
Craniosacral
neurons exits CNS
Dendrite
A fiber of a neuron which often cannot carry action potentials. Usually
much branches and relatively short compared with the axon, and commonly
carries information to the cell body of the neuron.
-information input ; initial stimulation
Depolarization
A change in the resting potential across a membrane so that the inside of
the cell becomes less negative, or even positive, compared with the
outside of the cell
-causes voltage-gated Na+ channels to open here
-voltage-gated Na+ channels open -> Na+ moves in; inside of axon
becomes positive
Diffusion
Random movement of molecules or other particles, resulting in even distribution of the particles when no barriers are present
Efferent
Carrying outward or away from, as in a neuron that carries impulses outward
-output
Equilibrium Potential
The membrane potential at which an ion is at electrochemical equilibrium, i.e., there is no net flux of the ion across the membrane
Excitation
membrane potential moves closer to threshold, increases chance of triggering an action potential
Excitatory Post-synaptic Potential
Input from a neuron that causes depolarization of the recipient cell
Exocytosis
A process by which a vesicle within a cell fuses with the plasma membrane and releases its contents to the outside
-AP opens voltage-gated Ca++ channels; Ca++ ions cause vesicles to release contents at synapse
Facilitated Diffusion
Passive movement through a membrane involving a specific carrier protein; does not proceed against a concentration gradient
-no ATP needed
Giant Axon
increase speed of action potential
-in larger invertebrates
Hyperpolarization
A change in the resting potential across a membrane so that the inside of
a cell becomes more negative compared with the outside of the cell
-positive ions out (K+)
-more negative; can also occur if negative ions (Cl-) move in
Inhibition
membrane potential moves farther from threshold, decreases chance of action potential
Inhibitory Post-synaptic Potential
Input from a neuron that causes hyperpolarization of the recipient cell
Integration
simultaneous stimulation at many synapses is “evaluated” by cell body
Interneuron
A neuron that communicates information between two other neurons
-processing
connect neuron to neuron in CNS
– source of most complexity in nervous system
Ion Channels
An integral membrane protein that allows ions to diffuse across the membrane in which it is embedded
-Ions diffuse in or out through transmembrane proteins
Medulla Oblongata
The portion of the brainstem that connects to the spinal cord
Membrane Potential
The difference in electrical charge between the inside and the outside of a
cell, caused by a difference in the distribution of ions
-electrical charge difference between the inside and outside of a cell
Midbrain
One of the three regions of the vertebrate brain. Part of the brainstem, it serves as a relay station for sensory signals sent to the cerebral hemispheres
Monosynaptic
A neural reflux that begins in a sensory neuron and makes a single synapse before activating a motor neuron
-sensory neuron synapses directly with motor neuron
Motor Neuron
A neuron carrying information from the central nervous system to a cell that produces movement
-output from CNS to peripheral nervous system (PNS); efferent
-stimulate effectors- muscles or glands
Myelin
Concentric layers of plasma membrane that form a sheath around some axons; provides the axon with electrical insulation and increases the rate of transmission of action potentials
-fat produced by Schwann cells (a type of glial cell)
Na+/K+ pump
Anti-porter responsible for primary active transport; it pumps sodium ions out of the cell and potassium ions into the cell , both against their concentration gradients. Also called a sodium-potassium ATPase.
-maintains the unequal distribution of Na+ and K+; active transport (uses ATP)
-moves Na+ out, K+ in; requires energy
returns ions to their original locations after a graded or action potential
neuroglia
glial cells – (= “nerve glue”) – support neuron functions; variable in structure
Neuron
A nervous system cell that can generate and conduct action potentials along an axon to a synapse with another cell
-function is based on changes in electrical charge of the cell
-3 categories
-a cell
-excitable – transmit impulses
Neurotransmitter
A substance produced in and released by a neuron (the presynaptic cell) that diffuses across a synapse and excites or inhibits another cell
-release at the axon terminal is caused by the action potential
-bind to receptors
-signaling molecule
Nodes of Ranvier
A gap in the myelin sheath covering an axon; the point where the axonal membrane can fire action potentials
-Electrically gated ion channels are concentrated at gaps in the myelin sheath
Norepinephrine
A neurotransmitter found in the central nervous system and also at the postganglionic nerve endings of teh sympathetic nervous system. Also called noradrenaline
-(= noradrenaline): autonomic nervous system, inhibitory or excitatory; a tyrosine derivative
Parasympathetic
The division of the autonomic nervous system that works in opposition to the sympathetic nervous system
-1 of the 2 autonomic system divisions
-Promotes low levels of activity and maintenance functions (digestion, excretion): – “rest and digest”
Polysynaptic
-one sensory neuron, one or more interneurons, one motor neuron
Examples – postural reflexes, pain reflexes
Post-synaptic
The cell that receives information from a neuron at a synapase
Pre-synaptic
The neuron that transmits information to another cell at a synapse
-reabsorption (reuptake)
Primary Motor Cortex
An area of the frontal lobe that controls muscles’ neurons in this area are arranged according to the parts of the body with which they communicate
Primary Somatorsensory Cortex
An area of the parietal lobe that receives touch and pressure information from the body; neurons in this area are arranged according to the parts of the body wit which they communicate
Reflex Arc
-simplest nerve circuit
result in invariable (“hard-wired”) reaction to specific stimulus
– can be entirely in the spinal cord -> rapid response
– response occurs before the brain processes the info
Refractory Period
The time interval after an action potential during which another action potential cannot be elicited from an excitable membrane
Repolarization
-return to resting potential
-Na+ channels close, inactivate
– gated K+ channels open –> K+ moves out
– inside of cell returns to negative charge (slightly hyperpolarized
Resting Potential
The membrane potential of a living cell at rest. In cells at rest, the interior is negative to the exterior
-the membrane potential of a neuron is -60-70 mV (millivolts)
– stays constant unless neuron is stimulated
-ion locations stable; no change in charge
Saltatory Conduction
The rapid conduction of action potentials in myelinated axons’ so called because action potentials appear to “jump”
-AP “jumps” from one node to the next
between nodes of Ranvier along the axon
Schwann Cell
A type of glial cell that myelinates axons in the peripheral nervous system
-produces fat (myelin)
Self-propagating
-starts at axon hillock, passes undiminished as a “wave” down the axon
1. Na+ ions move in here, cause local depolarization and diffuse down axon
2.depolarization causes voltage-gated Na+ channels to open here
Spatial Summation
In the production or inhibition of action potentials in a postsynaptic cell, the interaction of depolarizations and hyperpolarizations produced at different sites on the postsynaptic cell
-simultaneous stimulation from two or more nearby synapses; each synapse can be excitatory or inhibitory
Spinal Nerve
-connect to spinal cord; 31 in humans
Sympathetic
The division of the autonomic nervous system that works in opposition to the parasympathetic nervous system
-Promotes high levels of activity – “fight or flight”
Synapse
A specialized type of junction where a neuron meets its target cell (which can be another neuron or some other type of cell) and information in the form of neurotransmitter molecules is exchanged across a synaptic cleft
-Chemical signaling between neuron and target cell
-neurotransmitter release to target cells
-junction between axon terminal and target cell (nerve, muscle or gland)
Synaptic Cleft
The space between the presynaptic cell and the postsynaptic cell in a chemical synapse
-minute separation between axon and target cell; 10-20 nanometers
Synaptic Vesicle
where neurotransmitters are stored
Temporal Summation
In the production or inhibition of action potentials in a postsynaptic cell, the interaction of depolarizations or hyperpolarizations produces by rapidly repeated stimulation of a single point of the postsynaptic cell
– multiple stimulation at one synapse in a short period of time – additive (same effect)
Thoracolumbar
Threshold
The level of depolarization that causes an electrically excitable membrane to fire an action potential
-critical level
Voltage-gated Channel
A type of gated channel that opens or closes when a certain voltage exists across the membrane in which it is inserted
Voluntary
done, made, brought about, undertaken, etc., of one’s own accord or by free choice

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