Chapter 48 (4)

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Chapter 48 (4)
2011-04-03 15:19:49
Section Four

AP Bio
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  1. In most cases, actio potentials are not transmitted from eurons to other cells. However, info is transmitted and this trasmission occurs at the synapses. Some synapses, called __, contain gap junctions, which do allow electrical current to flow irectly from one neuron to another.
    electrical synapses
  2. In both vertebrates and invertebrates, __ synnchronize the activity of neurons responsibe for certain rapid, unvarying behaviors. There are also many __ in the brain.
    electrical synapses x2
  3. The majority of synapses are __, which involve the release of achem neurotransmitter by the __ neuron. The cell body and dendrites of one __ neuron may receive inuputs from chemical synapses with hundred or even thousands of synaptic terminals.
    • chem synapses
    • presynaptic
    • postsynaptic
  4. At each terminal, the __ neuron synthesize shte neurotransmitter and packages it in multiple membrane bound compartments called __. The arrival of an action potential at a synaptic terminal depolarizes the plasma membrane, opening voltage gated channels that allow Ca2+ to diffuse into the terminal. THe resulting rise in Ca2+ concentration in the terminal causes some the synaptic vesicles to fuse with the terminal membrane, releasing hte neurotransmitter. The neurotransmitter then diffuses across the __, the narrow gap that separates the presynaptic neuron from the postsynaptic cell.
    • presynaptic
    • synaptic vesicles
    • synaptic cleft
  5. Information transfer is much more readily modified at __ synapses than at __ synapses. A variety of factors can affect the amt of neurotransmitter that is release dor the responsivemenss of the postsynatic cell. Such modifications underlie an animal's ability to alter its behavior in rsponse to change and form the basis of learning and memory.
    • chemical
    • electrical
  6. At many chem synapses, __ ion channels capable of binding to the neurotransmitter are clustered int eh membrane of the postsynaptic cell, directly opposite the synaptic terminal. Dinding of the neurotransmitter to a particular part of the channel opens the channlel and allows specific ions to diffuse across the posystmaptic membarne.
    ligand gated
  7. The result is generally a __, a change in the membrane potential of hte postsynaptic cell. At synapses, the neurotransmitter binds to a type of channle through which both K+ and Na+ can diffuse.
    When thos channels open, the postsynaptic membrane depolarizes as the membrane potential approaches a value roghly midway between EK and ENa.
    postsynaptic potential
  8. BEcause these depolarizations bring hte membrane potential toward threshold, they are called __. At other synapses, a different neurotransmitte rbidns to channels that are selectively permeable for only K+ or Cl-.
    - When those channels open, the postsynaptic membrane hyperpolarizes. __ produced n htis manner are caled __ because they move the membrane potential farhter from threshold.
    • excitatory postsynaptic potentials (EPSPs)
    • Hyperpolarizations
    • inhibitory postsynaptic potentials (IPSPs)
  9. Various mechanisms rapidly clear neurotransmitters from the __, terminatign their effect on postsynaptic cells. Certain neurotransmitters may be actively transported into the presynaptic neuron, to b e repackaged into synaptic vesices, or they may be transported into __, to be metabolized as fuel. Other neurotransmitters are removed from the __ by simple diffuion or by an enzyme that catalyzes hydrolysis of hte neurotransmitter.
    • synaptic cleft
    • glia
    • synaptic cleft
  10. Unlike action potentials. which are __ events, __ are graded: their magnitude varies with a # of factors, includining amt of neurotransmitter released by the presynaptic neuron. Furhtermore, __ usually do not regenrate as they spread along the membrane of a cell; they become smaller with distance from the synapse.
    o Recall that most synapses on a neuron are located on its dendrites or cell bod,y whereas action potentials are generally initiated at hte axon hillock. There fore, a single __ is usually too small to trigger an action potential in a postsynaptic neuron.
    • all- or- none
    • postsynaptic potentials x2
    • EPSP
  11. O some occasions, two EPSPs occur at a single synapse in such rapid succession that the postsynaptic neuron's membrane potential has not returned to the resting potential before hte arrival of the second EPSP. When that happens, the EPSPs add together. an effect called __.
    temporal summation
  12. oreover, EPSPs producued nearly simultaneously by different synapses on the same postsynaptic neuron can also add together, an effect called __. Through __ and __, several EPSPs can depolarize the membrane at the axon hillock to the threshold, causing the postsynaptic neuron to produce an action potential.
    • spatial summation
    • spatial an d temporal summation
  13. __ applies as well to IPSPs: Two or more IPSPs occcuring nearly simultaneously or in rapid successon have a larger hyperpolarizig effect than a single IPSP. Through __, an IPSP can also counter the effect of an EPSP.
    summation x2
  14. Th einterplay between multiple excitatory and inhibitory inputs is the essence of integration in the NS. The __ is the neuron's integrating center, the region where hte membrane potential at any instant represents the summed efffect of alll EPSP and IPSPs. Whenever hte membrae potential at the __ reaches hte threshold, an action potential is generated and travels along hte axon to its synaptic terminals. After the refractory period., the neuron may produce another action potential, provided hte membrane potential at hte __once again reaches the threshold.
    axon hillock x3
  15. There are synapses in which the receptor for the neurotransmitter is not part of an ion channel. Instead, binding of the neurotransmitter to its receptor in the postsynaptic cell activates a STP involving a __.
    -- Compared with th epostsynaptic ptentials produced by __-gated ion channels, the effects of these __ systems have a slower onset but last longer.
    o __ modulate the responsiveness of postsynaptic neurons to inputs in diverse ways, like altering the # of open K channels.
    • second mesengers
    • ligand
    • 2nd messengers x2
  16. A variety of STPs play a role in modulating synaptic transmission. One of the best is __.
  17. There ar emore than 100 known neurotransmitters. However, nearly all of these fal into one of a few groups based on che structure.
    - The major classes of neurotransmitters are __, __, __, __, and __.
    • acetylcholine
    • biogenic amines
    • amino acids
    • neuropeptides
    • gases
  18. True or False:
    A single neurotransmitter may have more than a dozen different receptors. Furthermore, the receptors for a specific neurotransmitter can vary significantly in their efffects on postsynaptic cellls.
    - THis is why drugs are targeted to receptors instead of neurotransmitters.
  19. ONe of the most common neurotransitters in both in and vertebrates is __. Except in the heart, vertebrate neurons that form a synapse with muslce cells release __ as an excitatory transmitter. __ binds to receptors on ligand-gated ion channels in the muscle cell, producing an EPSP.
    acetylcholine x3
  20. __ bidns to the same reeptors, whicha re also found elsewhere in the PNS and in the CNS. __ effects as a physiological and psychological stimulate result from its affinity for this typ eof __ receptor. __ activity is terminated by __, an enzzyme in the synaptic cleft that dydrolyzes the neurotransmitter.
    • nicoine x2
    • acetylcholine x2
    • acetylcholinesterase
  21. Certain bacteria produce a toxin that specifically inhibits presynaptic release of __. this toxin hte cause of rare but severe form of food poisoning called __.
    • acetylcholine
    • botulism
  22. Inr egulating vertebrate cardiac (heart) muscle, __ has inhibitroy rather htan excitatory effects. In hte heart, __ released by neurons activates a STP. The G proteins in the pathway inhibit __ and open potassium channels in the muscle cell membranne. Both effects reduce the rate at which cardiac msucle cells contract.
    • acetylcholine x2
    • adenylyl cyclase
  23. __ ar eneurotransmitter derived from amino acids. The __ is synthesized from tryptophan. SEveral other __, the __ are derived from tyronsine.
    - One __,- __, acts only as a neurotrasnmititer.
    Two others- __ and __- act both as neurotrasmitters and as hormones.
    • biogenic amines
    • biogenic amine serotonin
    • biogenic amines
    • catecholamines x2
    • dopamine
    • epinephrine
    • norepinephrine
  24. Int he PNS of vertebrates, __ is one of tw major neurotransmitters, the other being __. Acting through a G protein coupled receptor, __ generates EPSPs in the __, a branch of the PNS.
    • norepinephrine
    • acetylcholin e
    • norepinephrine
    • autonomic NS
  25. Int eh CNS, the __ are often involed in modulating synaptic transmission. __ and __ are released at many sites int he brain and affect sleep, mood, attention and learning. SOme psychoactive drugs, like LSD and mescaline, apparentl y produce their hallucinatroy effects by binding to brain receptors for __ and __.
    • biogenic amines
    • dopamine and seratonin x2
  26. __ have a central role in a # of NS disorders and treatments.
    biogenic amines
  27. Two amino acids serve as the major neurotransmitters in hte vertebrate CNS: __ and __.
    • gamma-aminobutyric acid (GABA)
    • glutamate
  28. __, which appears to be hte neurotransmitter at msot inhibitory synapses in the brain, produces IPSPs by increasing hte permeabbility of hte postsynaptic membrane to Cl-. In clontrast, __, the most common neurotransmitter in the brain, is always excitatory.
    • GABA
    • glutamate
  29. A third amino acid, __ acts as inhibitory synapses in parts of hte CNS that lie outside the brain.
  30. Several __, relatively short chains of amino acids serve as neurotransmitters that operate via STPs. Such pepetides are typically produced by cleaveage of much larger protein precursors.
  31. The neuropeptide __ is a key excitatory neurotransmitter that meditates our erception of pain, while other neuropeptides, called __, function as natural analgeesics, decreasing pain perception.
    • substance P
    • endorphins
  32. painkilling drugs such as morphine and heroin
  33. __ are produced int eh brain during tiems of physical or emotional stress, like childbirth. In addition to relieving pain, they decrese urine output, depress respiration, and produce __, as well as other emotional effects. Because __ bind to the same receptor proteins as __, __ mimic __ and produce many of hte same physiological effects.
    • endorphins
    • euphoria
    • opiates
    • endorphins
    • opiates
    • endorphins
  34. In common with many other types of cells, some neurons in vertebrates release disssolved gas, notably __, taht act as local regulators.
    nitric oxide
  35. Unlike most neurotransmitters, __ is not stored in cytoplasmic vesicles but is instead synthesize don demand. __ diffuses into neighboring target cells, produces a change, and is broken down- all within a few secodns. In many of its targets including sommth muscle cells, __ works like many hormones, stimulating an enzyme to synthesize a second messenger that directly affects cell metabolism
    NO x3
  36. Althoug inhaling air containg the gas __ can be deadly, the verberate body produces samll amts of __, some of which act as neurotransmitters. __ is generated by the enzyme __, one form of which is found in certain populations of neurons in the brain and PNS. In the brain, __ regulates the release of hypothalamic hormoes. In the PNS, it acts ans an inhibitory neurotransmitter htat hyperpolarizes interstinal smooth musscle cells.
    carbon monoxide (CO) x all