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neuroscience test 2

electrical synapse an electric current that flows from one neuron to the next
chemical synapse information is transferred from one neuron to the next by chemical neurotransmitters;
presynaptic The first neuron
postsynaptic target cells
gap junction Electrical synapses occur here.Allow ionic current to transfer from one cell to the next. Specialized junction where a narrow gap between 2 cells is spanned by protein channels(connexons)-allow ions to pass directly from 1 cell to annother
connexon formed by six connexins
connexins, a cluster of special proteins that span the narrow gap that separates the membranes of two cells.
electrically coupled Most gap junctions allow the flow of ions in both directions, so electrical synapses are bidirectional, and cells connected in this manner are electrically coupled.
postsynaptic potential (PSP) The flow of ions from the presynaptic neuron to the postsynaptic neuron creates a postsynaptic potential (PSP) in the postsynaptic neuron. Because the flow is bidirectional, the PSP is regenerated in the presynaptic neuron.
synaptic cleft Separates the pre- and postsynaptic synapses .Is filled with a matrix of fibrous extracellular proteins that adhere the pre- and postsynaptic membranes to each other
presynaptic element the presynaptic side of the synapse, is usually an axon terminal. The terminal contains synaptic vesicles.
neurotransmitters the chemicals that communicate with postsynaptic neurons
secretory granules larger vesicles in axon terminal. Contains peptides intended for secretion by exocytosis.
membrane differentiations are dense accumulations of protein adjacent to and within the membrane on either side of the synaptic cleft.
active zones the presynaptic side, proteins form pyramids at the active zones, the sites of neurotransmitter release.
postsynaptic density is the accumulation of proteins along the postsynaptic membrane. It contains the neurotransmitter receptors.
axodendritic Axon to dendrite
axosomatic Axon to Soma
axoaxonic Axon to axon
dendrodendritic Dendrite to dendrite
neuromuscular junction Chemical synapses also occur between the axons of the motor neurons of the spinal cord and skeletal muscle. is one of the largest synapses in the body.
motor end-plate contains a number of folds that are packed with neurotransmitter receptors.
glutamate amino acids that are the building blocks of proteins, and are abundant in all types of cells, including neurons. (AMINO ACID)
GABA are made only by neurons that release them.(AMINO ACID)
glycine amino acids that are the building blocks of proteins, and are abundant in all types of cells, including neurons. (AMINO ACID)
acetylcholine (ACh) mediates fast synaptic transmission at all neuromuscular junctions.(AIMES)
transporters special proteins in the vesicle membrane, are responsible for uptaking and accumulating these neurotransmitters inside the vesicles
voltage-gated ion channels a membrane protein forming a pore that is permeable to ___ ions and gated by depolarization of the membrane.
transmitter-gated ion channels a membrane protein forming a pore that is permeable to ions and gated by neurotransmitter.
G-protein-coupled receptors a membrane protein that activates G-proteins when it binds neurotransmitter
metabotropic receptors a G-protein coupled receptor whose primary action is to stimulate an intracellular biochemical response
autoreceptor a receptor in the membrane of a presynaptic axon terminal that is sensitive to the neurotransmitter released by that terminal. It stimulates a second messenger formation.
receptor agonist bind to receptors and mimic the actions of the naturally occurring neurotransmitter.
receptor antagonista inhibit neurotransmitter receptors by binding to the receptor and blocking normal action of the transmitter.
nicotinic ACh receptors a class of acetylcholine-gated ion channel found in various locations notably at the neuromuscular junction.in the CNS are responsible for the addictive effects of tobacco use.
neural computation The transformation of many synaptic inputs to a single neuronal output
synaptic integration the process by which multiple EPSPs and/or IPSPs combine within one postynaptic neuron in some cases triggering one or more action potentials.
quantal analysis of EPSP is a method of comparing the amplitudes of miniature and evoked postsynaptic potentials that can be used to determine how many vesicles release neurotransmitters during normal synaptic transmission.
miniature postsynaptic potential a change in postsynaptic membrane potential caused by the action of neurotransmitter released from a single synaptic vesicle.The size of the response can be measured electorphysiologically,
EPSP summation a simple form of synaptic integration whereby excitatory postsynaptic potentials combine to produce a larger postsynaptic depolarization.
spatial summation the combining of excitatory postsynaptic potentials generated at more than one synapse on the same cell.Adding together EPSPs generated simultaneously in different spaces.
temporal summation the combining of excitatory postsnaptic potentials generated in rapid succession at the same synapse.
shunting inhibition occurs when a neuron dendrite receives one excitatory and one inhibitory input. The depolarization current “leaks out” before it reaches the soma.
synaptic vesicles are clustered around the active zones.
inhibitory postsynaptic potential (IPSP) A transient hyperpolarization of the postsynaptic membrane potential caused by the presynaptic release of neurotransmitter. Synaptic activation of glycine-gated or GABA-gated ion channels cause an IPSP.
excitatory postsynaptic potential (EPSP). A transient postsynaptic membrane depolarization caused by the presynaptic release of neurotransmitters. Synaptic activation of ACh-gated and glutamate-gated ion channels causes EPSPs.
Describe the two types of synapses. Electrical synapses are simple in structure and function compared to chemical synapses. Electrical synapses occur at gap junctions that allow ionic current to transfer from one cell to the next.
In invertebrate species, in what kind of pathways are electrical synapses usually found? Why? found between sensory and motor neurons in neural pathways mediating escape reflexes. This mechanism allows an animal to beat a hasty retreat when faced with a dangerous situation.
In vertebrates, where are electrical synapses found? Brain
Which type of synapse is predominate in the mature human nervous system? Chemical
Describe the structural features and components of a presynaptic membrane, and a postsynaptic membrane. (Label figure 5.3) Pre- Membrane differentiations, active zones, Synaptic Vesicles Post-postsynaptic density
What are the different configurations of axon connections in the CNS, and what are the terms that describe them? axodendritic axosomatic axoaxonic dendrodendritic
Gray’s type I synapse "asymmetrical", synapses: Those in which the membrane differentiation of the postsynaptic side is thicker than that on the presynaptic side. These are usually excitatory,
Gray’s type II synapse "symmetrical", synapses: Those in which the membrane differentiations are of similar thickness. These are usually inhibitory.
Which type of postsynaptic potential is usually produced by each Gray's type? type I -excitatory type II- inhibitory
Describe the structural features and components of the neuromuscular junction. (Label figure 5.8) The NJ is one of the largest synapses in the body. The presynaptic terminal also contains a large number of active zones. The postsynaptic membrane, the motor end-plate, contains a number of folds that are packed with neurotransmitter receptors
What are the basic requirements of chemical synaptic transmission? look in notes
What are the three major molecular classes of neurotransmitters? 1) amino acids, (2) amines, and (3) peptides.
Which type of neurotransmitters are stored in synaptic vesicles, and which are stored in secretory granules? The amino acid and amine neurotransmitters are stored in and released from synaptic vesicles. Peptide neurotransmitters are stored and released from secretory granules.
Which neurotransmitters mediate fast synaptic transmission in the CNS? mediated by the amino acids glutamate (Glu), gamma-aminobutyric acid (GABA), and glycine (Gly).
Which neurotransmitter mediates fast synaptic transmisssion at the neuromuscular junction? amine acetylcholine (ACh)
How does the synthesis and storage of amino acid and amine neurotransmitters differ from peptide neurotransmitters? look at notes
Describe the process of neurotransmitter release from the presynaptic terminal.
What causes the voltage-gated calcium channels to open? The depolarization of the terminal membrane
How does the release of animo acid and amine neurotransmitters from synaptic vesicles compare to the release of peptide neurotransmitters from secretory granules? The release of peptide neurotransmitters usually occurs only in response to high-frequency trains of actin potentials.The release is a leisurely process compared to the release of neurotransmitters from synaptic vesicles.
What are the two basic classes of neurotransmitter receptors? transmitter-gated ion channels and G-protein-coupled receptors
What is the basic structure of a transmitter-gated ion channel? These are membrane spanning proteins consisting of five subunits that come together to form a pore between them
What determines whether the postsynaptic potential is excitatory (EPSP) or inhibitory (IPSP)? channels are permeable to Na+=depolarizes postsynaptic cell-EXCITATORY Permeable to Cl- =hyperpolarize- inhibitory
Which types of ion channels and neurotransmitters cause EPSP vs. IPSP? (Compare Figures 5.14 and 5.15.) Synaptic activation of ACh-gated and glutamate-gated ion channels causes EPSPs. Synaptic activation of glycine-gated or GABA-gated ion channels cause an IPSP.
What are the three general steps involved in transmitter activation of G-protein-coupled receptors? Bind to receptor proteins Activate small G-proteins G-proteins activate “effector” proteins
What two types of effectors are activated by G-proteins?
Why are G-protein-coupled receptors referred to as metabotropic receptors? Because G-protein-coupled receptors can trigger widespread metabolic effects,
How can one transmitter have different postsynaptic actions? The same neurotransmitter can have different postsynaptic actions, depending on what receptors it binds to.
What is the function of an autoreceptor? that stimulate second messenger formation. The
Describe two mechanisms that clear neurotransmitters from the synaptic cleft to terminate their action. 1)Diffusion: Away from the synapse. Reuptake: Neurotransmitter re-enters presynaptic axon terminal 2)Enzymatic destruction inside terminal cytosol or synaptic cleft - AChE cleaves Ach to inactive state
How is neuropharmacology used to distinguish neuroreceptor classes?
Describe the quantal analysis of EPSPs.
What is a “mini”, and what role does in play in quantal analysis?
What are two types of EPSP summation? 1. spatial summation is the adding together of the EPSPs generated simultaneously at many different synapses on a dendrite. 2. temporal summation is adding together of EPSPs generated at the same synapse if they occur in rapid succession.
What determines the effectiveness of an excitatory synapse in triggering an action potential? (1) how far the synapse is from the spike-initiation zone and (2) the properties of the dendrite membrane
What mechanism do dendrites use to amplify small postsynaptic potentials?
How is shunting inhibition achieved by IPSPs? occurs when a neuron dendrite receives one excitatory and one inhibitory input. The depolarization current “leaks out” before it reaches the soma.
What are two important differences between inhibitory postsynaptic receptors and excitatory postsynaptic receptors? Excitatory synapses Gray’s type I morphology Use glutamate Inhibitory synapses Gray’s type II morphology Use GABA Many are clustered on soma and near axon hillock
action potential, a brief fluctuation in membrane potential caused by the rapid opening and closing of voltage gated ion channels (aka spike, nerve impulse or discharge)Sweep like a wave along axons to transfer info from 1 place to another in the nervous system
generator potential,
threshold, the critical level of depolarization that must be crossed in order to trigger an action potential.
absolute refractory period, the period of time measured from the onset of action potential during which another action potential CAN NOT be triggered
relative refractory period, the period of time following action potential during which MORE deoplarizing current than usual is required to achieve threshold.
channelopathy, a human genetic disease caused by alterations in the structure and function of ion channels.
tetrodotoxin, a toxin that blocks Na+ permeation though voltage gated sodium channels, there by blocking action potential
saxitoxin, channel blocking toxin produced by dinoflagellates of the genus gonyaulax. (clams, muscles and other shell fishthat feed on these marine protozoa)
batrachotoxin, a toxin isolated from the skin of the columbian frog. it causes channels to remain opened longer than usual. this causes the info encoded by action potentials to be scrambled.
veratridine and aconitine, Veratridine- toxins produced by lilies aconitine- toxins produced by buttercups
delayed rectifier, K+ gates dont open immediately upon depolarization, like Na+ gates do. it takes them 1msec for them to open. K+ conductance serves to rectify (reset) the membrane potential, and there is a delay.
orthodromic, action potential only conduct only in one direction
myelin, allows increased action potential conduction velocity. it is wrapped aroudnt he axon. serves as insulation.
salutatory conduction, in myelinated axons, the action of action potential is skipping from node to node.
axon hillock, a swelling of the axon where it joins the soma.
spike-initiation zone part of the neuron where an axon origionates from the soma (axon hillock)
Know the chart shown in figure 4.1b. Be able to identify the different parts of the curve, and describe the events in each stage (page 91).
What is meant by “all-or-none”, referring to the generation of an action potential? applying increaded depolarization to a neuron has no effect until it crosses the threshold, when it does that then an action potential can be formed. "all or none"
How is sodium ion selectivity accomplished? (figure 4.8) water is needed for Na+ to pass through the channel. the ion water complex can be used to select Na+ and exclude K+. when Na+ is hydrated it can fit through the channel. When K+ is hydrated it cant fit through the cannel-that channel Na+ selective.
What is a channelopathy, and know the example given in the text. a human genetic disease caused by alterations in structures and functions in ion channels. Examples : generalized epilepsy with febrile seizures.
Why are some substances that interfere with sodium channels toxic? What are some of the toxins? some substances that interfere with sodium channels are toxic bc they inhibit with functions of channel to not function properly.
What structural feature of vertebrate axons increases action potential conduction down the axon? Myelin- it is insulation that is wrapped on the axon. Schwann- PNS, Oligodendroglia-CNS
What accounts for the weird configuration of a sensory neuron (figure 4.14b)?
Created by: katie.nelson8