neuroscience test 2
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| electrical synapse | an electric current that flows from one neuron to the next
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| chemical synapse | information is transferred from one neuron to the next by chemical neurotransmitters;
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| presynaptic | The first neuron
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| postsynaptic | target cells
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| 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
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| connexon | formed by six connexins
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| connexins, | a cluster of special proteins that span the narrow gap that separates the membranes of two cells.
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| 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.
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| 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.
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| 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
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| presynaptic element | the presynaptic side of the synapse, is usually an axon terminal. The terminal contains synaptic vesicles.
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| neurotransmitters | the chemicals that communicate with postsynaptic neurons
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| secretory granules | larger vesicles in axon terminal. Contains peptides intended for secretion by exocytosis.
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| membrane differentiations | are dense accumulations of protein adjacent to and within the membrane on either side of the synaptic cleft.
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| active zones | the presynaptic side, proteins form pyramids at the active zones, the sites of neurotransmitter release.
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| postsynaptic density | is the accumulation of proteins along the postsynaptic membrane. It contains the neurotransmitter receptors.
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| axodendritic | Axon to dendrite
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| axosomatic | Axon to Soma
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| axoaxonic | Axon to axon
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| dendrodendritic | Dendrite to dendrite
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| 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.
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| motor end-plate | contains a number of folds that are packed with neurotransmitter receptors.
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| glutamate | amino acids that are the building blocks of proteins, and are abundant in all types of cells, including neurons. (AMINO ACID)
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| GABA | are made only by neurons that release them.(AMINO ACID)
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| glycine | amino acids that are the building blocks of proteins, and are abundant in all types of cells, including neurons. (AMINO ACID)
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| acetylcholine (ACh) | mediates fast synaptic transmission at all neuromuscular junctions.(AIMES)
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| transporters | special proteins in the vesicle membrane, are responsible for uptaking and accumulating these neurotransmitters inside the vesicles
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| voltage-gated ion channels | a membrane protein forming a pore that is permeable to ___ ions and gated by depolarization of the membrane.
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| transmitter-gated ion channels | a membrane protein forming a pore that is permeable to ions and gated by neurotransmitter.
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| G-protein-coupled receptors | a membrane protein that activates G-proteins when it binds neurotransmitter
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| metabotropic receptors | a G-protein coupled receptor whose primary action is to stimulate an intracellular biochemical response
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| 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.
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| receptor agonist | bind to receptors and mimic the actions of the naturally occurring neurotransmitter.
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| receptor antagonista | inhibit neurotransmitter receptors by binding to the receptor and blocking normal action of the transmitter.
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| 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.
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| neural computation | The transformation of many synaptic inputs to a single neuronal output
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| 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.
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| 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.
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| 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,
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| EPSP summation | a simple form of synaptic integration whereby excitatory postsynaptic potentials combine to produce a larger postsynaptic depolarization.
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| 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.
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| temporal summation | the combining of excitatory postsnaptic potentials generated in rapid succession at the same synapse.
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| shunting inhibition | occurs when a neuron dendrite receives one excitatory and one inhibitory input. The depolarization current “leaks out” before it reaches the soma.
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| synaptic vesicles | are clustered around the active zones.
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| 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.
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| 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.
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| 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.
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| 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.
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| In vertebrates, where are electrical synapses found? | Brain
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| Which type of synapse is predominate in the mature human nervous system? | Chemical
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| 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
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| What are the different configurations of axon connections in the CNS, and what are the terms that describe them? | axodendritic axosomatic axoaxonic dendrodendritic
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| 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,
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| Gray’s type II synapse | "symmetrical", synapses: Those in which the membrane differentiations are of similar thickness. These are usually inhibitory.
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| Which type of postsynaptic potential is usually produced by each Gray's type? | type I -excitatory type II- inhibitory
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| 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
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| What are the basic requirements of chemical synaptic transmission? | look in notes
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| What are the three major molecular classes of neurotransmitters? | 1) amino acids, (2) amines, and (3) peptides.
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| 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.
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| Which neurotransmitters mediate fast synaptic transmission in the CNS? | mediated by the amino acids glutamate (Glu), gamma-aminobutyric acid (GABA), and glycine (Gly).
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| Which neurotransmitter mediates fast synaptic transmisssion at the neuromuscular junction? | amine acetylcholine (ACh)
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| How does the synthesis and storage of amino acid and amine neurotransmitters differ from peptide neurotransmitters? | look at notes
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| Describe the process of neurotransmitter release from the presynaptic terminal. |
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| What causes the voltage-gated calcium channels to open? | The depolarization of the terminal membrane
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| 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.
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| What are the two basic classes of neurotransmitter receptors? | transmitter-gated ion channels and G-protein-coupled receptors
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| 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
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| 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
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| 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.
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| 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
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| What two types of effectors are activated by G-proteins? |
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| Why are G-protein-coupled receptors referred to as metabotropic receptors? | Because G-protein-coupled receptors can trigger widespread metabolic effects,
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| How can one transmitter have different postsynaptic actions? | The same neurotransmitter can have different postsynaptic actions, depending on what receptors it binds to.
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| What is the function of an autoreceptor? | that stimulate second messenger formation. The
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| 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
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| How is neuropharmacology used to distinguish neuroreceptor classes? |
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| Describe the quantal analysis of EPSPs. |
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| What is a “mini”, and what role does in play in quantal analysis? |
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| 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.
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| 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
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| What mechanism do dendrites use to amplify small postsynaptic potentials? |
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| 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.
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| 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
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| 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
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| generator potential, |
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| threshold, | the critical level of depolarization that must be crossed in order to trigger an action potential.
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| absolute refractory period, | the period of time measured from the onset of action potential during which another action potential CAN NOT be triggered
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| relative refractory period, | the period of time following action potential during which MORE deoplarizing current than usual is required to achieve threshold.
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| channelopathy, | a human genetic disease caused by alterations in the structure and function of ion channels.
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| tetrodotoxin, | a toxin that blocks Na+ permeation though voltage gated sodium channels, there by blocking action potential
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| saxitoxin, | channel blocking toxin produced by dinoflagellates of the genus gonyaulax. (clams, muscles and other shell fishthat feed on these marine protozoa)
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| 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.
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| veratridine and aconitine, | Veratridine- toxins produced by lilies aconitine- toxins produced by buttercups
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| 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.
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| orthodromic, | action potential only conduct only in one direction
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| myelin, | allows increased action potential conduction velocity. it is wrapped aroudnt he axon. serves as insulation.
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| salutatory conduction, | in myelinated axons, the action of action potential is skipping from node to node.
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| axon hillock, | a swelling of the axon where it joins the soma.
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| spike-initiation zone | part of the neuron where an axon origionates from the soma (axon hillock)
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| 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). |
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| 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"
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| 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.
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| 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.
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| 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.
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| 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
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| What accounts for the weird configuration of a sensory neuron (figure 4.14b)? |
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