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Flashcards

Synapses & Information

Amy Walker Neuroscience and Behaviour Inglês 71 flashcards

Flashcards do conjunto (71)

  1. 1What are synapses?points of contact and communication between nerve cells or between nerve cells and muscle cells
  2. 2What are the pre and postsynpatic membranes located?Presynaptic: terminal boutons
    Postsynaptic: dendrites
  3. 3What is the synaptic cleft?the gap between the pre- and postsynaptic membranes containing filaments to keep the membranes in alignment
  4. 4What are the two major types of synapses?- Electrical Synapses
    - Chemical Synapses
  5. 5What are some fundamental mechanisms of electrical synapses?- simple molecular machinery
    - instantaneous transmission
    - bidirectional
    - direct current (ion) flow
    - limited plasticity
    - junctures between adjacent cell's PM for ion flow
  6. 6What are some fundamental mechanisms of chemical synapses?- complex molecular machinery
    - delayed transmission
    - unidirectional
    - excitatory and inhibitory transmission
    - more plasticity
    - synaptic cleft between two cells uses neurotransmitter release
  7. 7How are neurotransmitters released at chemical synapses?NTs stored in presynaptic vesicles which are activated by voltage-gated calcium channels
  8. 8What is the mechanism for neurotransmitter release?1. AP arrives
    2. voltage-gated Ca2+ channel opens
    3. calcium enters & triggers vesicles to move to presynaptic membrane
    4. vesicles "dock" and release NT to synaptic cleft
    5. NT diffuses across cleft & bind to receptor
    6. receptor produces response
  9. 9How are neurotransmitters generally removed from the synaptic cleft?1. degraded by an enzyme
    2. some subject to re-uptake
    3. small amounts diffuse away
  10. 10What is an ionotropic receptor?a receptor with a direct link to an ion channel
  11. 11How do ionotropic receptors elicit a response?binding of NT opens the ion channel allowing the ion through
  12. 12What is a PSP?Post-Synaptic Potential: local current change, has fast onset and ends within a few milliseconds
  13. 13What determines the nature of the PSP?- can be either excitatory (causing depolarisation) or inhibitory (causing hyperpolarisation)
    - determined by nature of the synapse (what channels they open)
  14. 14What is an EPSP?Excitatory Post-Synaptic Potential: moves membrane potential closer to threshold
  15. 15What is an IPSP?Inhibitory Post-Synaptic Potential: causes stabilisation or hyperpolarisation of membrane potential
  16. 16What determines how large the PSP is?Graded potentials: amplitude depends on strength of stimulus
  17. 17What is summation?- the process by which PSPs are "summed" to determine their net action on the cell
    - a single EPSP is rarely sufficient to bring the membrane potential up the threshold
  18. 18How many inputs can a neuron receive?hundreds
  19. 19What is temporal summation?- multiple inputs at the same synapse in rapid succession
    - IPSPs can detract from EPSPs
    - EPSPs & IPSPs are graded potentials so can be "summed"
  20. 20What is spatial summation?Integration of PSPs from multiple synapses
  21. 21How does a neuron encode information about a stimulus?- Frequency Coding: more stimuli can generate more APs at a higher frequency
    - Information about the sensory stimulus is encoded in the frequency and pattern of APs
    - The size of the stimulus is encoded in the frequency of firing
  22. 22How does summation link to frequency coding?summation can affect the frequency of firing of APs in the postsynaptic cell to transmit a message
  23. 23What is a neurotransmitter?chemicals that are released by one neuron and interact its ligand with the binding site of a receptor on the synaptic partner of that neuron
  24. 24What does the action of the NT depend on?the receptor
  25. 25What are the main groups of NT?- acetyl choline
    - biogenic amines
    - amino acid NTs
    - purines
    - neuropeptides
    - gases
  26. 26How do chemicals other than neurotransmitters work in the brain?- any medical or recreational chemical has to have similarity to the native signal (NT) in order to interact with the receptor
    - external signals can mimic or counteract the action of the normal signal
  27. 27What is an agonist?- chemical mimic
    - can be precursors (increase amount of NT synthesised & released into synapse)
    - can bind with proteins that cause docked vesicles to fuse with presynaptic membrane causing NT release
    - can deactivate terminal membrane transporters responsible for reuptake
  28. 28What is an antagonist?- Chemical counteract-er
    - can deactivate enzymes which produce the NT, preventing its release
    - can block vesicle transporters which pump NT across the vesicle membrane leaving vesicle empty
    - can deactivate proteins that cause docked vesicles to fuse with membrane
  29. 29Where is acetylcholine released?CNS & PNS
  30. 30What is the function of acetylcholine?CNS: role in REM sleep, facilitating perceptual learning, modulation of hippocampus (memories)
    PNS: role at neuromuscular junctions for muscle contraction
  31. 31What are the two main types of acetylcholine receptor?Ionotropic: nicotinic (nAChRs)
    Metabotropic: muscarinic (mAChRs)
  32. 32What are some typical agonists and antagonists of acetylcholine receptors?nAChRs agonist: nicotine
    nAChRs antagonist: curare
    mAChRs agonist: muscarine
    mAChRs antagonist: atropine
  33. 33How is ACh removed from the synapse?deactivated by the enzyme acetylcholinesterase (AChE)
  34. 34What is a biogenic amine?- NT derived from amino acids
    - all posses an amine group
  35. 35What are the 3 main classes of biogenic amine?1. Catecholamines
    2. Indolamines
    3. Ethylamines
  36. 36What are some of the catecholamines?1. dopamine
    2. epinephrine
    3. norepinephrine
  37. 37What is an example of an indolamine?serotonin (5-HT)
  38. 38What is an example of an ethylamine?histamine
  39. 39What types of receptors do biogenic amines typically have?- typically metabotropic
    - generally act via G-proteins
  40. 40Where is dopamine released?CNS
  41. 41What is the role of dopamine?- produces either EPSPs or IPSPs depending on the postsynaptic receptor
    - implicated in movement, attention, learning and drug-reinforcement
  42. 42What types of receptor does dopamine have?- 5 types all metabotropic
    - D1 & D5 increase production of cAMP
    - D2-D4 decrease production of cAMP
  43. 43How is dopamine removed from the synapse?- removed by dopamine transporters
    - several drugs block the reuptake of dopamine, prolonging its effects, including cocaine
    - the destruction of dopamine is facilitated by the enzyme MAO
  44. 44Where is (Nor)Epinephrine released?CNS & PNS
  45. 45What are the roles of (Nor)Epinephrine?CNS: vigilance
    PNS: autonomic nervous system regulation
  46. 46What types of receptor do (Nor)Epinephrine have?4 types of adrenergic receptor sensitive to both NTs all metabotropic
    - alpha 1 & 2
    - beta 1 & 2
  47. 47How do Nor(Epinephrine) receptors work?receptors coupled to G-proteins that control the production of second messengers
  48. 48How is (Nor)Epinephrine removed from the synapse?norepinephrine transporter removes excess NT from the synapse & then is deactivated by MAO
  49. 49Where is serotonin released?CNS & PNS
  50. 50What is the role of serotonin?CNS: mood regulation, eating, sleep, dreaming, arousal, impulse control
    PNS: enteric nervous system (digestive tract)
  51. 51What types of receptor does serotonin have?at least 9 different types:
    - all are metabotropic except 5-HT3 which is ionotropic
    - 5-HT3 controls a chloride channel so produces IPSPs
  52. 52How is serotonin removed from the synapse?- removal of the synapse by the serotonin transporter
    - drugs that inhibit the reuptake of serotonin are important in the treatment of mental illness
  53. 53Where is histamine released?CNS & PNS
  54. 54What is the role of histamine?CNS: wakefulness
    PNS: immune response
  55. 55What types of receptor does histamine have?4 types all metabotropic: H1-H4
  56. 56What are some examples of the amino acid neurotransmitters?Excitatory: glutamate & aspartate
    Inhibitory: GABA & glycine
    - GABA is derived from glutamate
  57. 57Where is glutamate released?CNS
  58. 58What are the types of glutamate receptors?Ionotropic: kainate, NMDA, AMPA (most common)
    Metabotropic: mGluR
  59. 59What do the AMPA and kainate receptors do?control a sodium channel & produce EPSPs
  60. 60What does the NMDA receptor do?- controls both a sodium & calcium channel
    - sodium causes depolarisation
    - calcium acts as a second messenger to activate other enzymes
  61. 61Why are NMDA receptors different from the other ionotropic receptors?- both glutamate and glycine must bind to the site to open the calcium channel
    - magnesium must not be bound to the site (which occurs if the membrane is partially depolarised)
  62. 62How is glutamate removed from the synapse?by excitatory AA transporters and borken down into glutamine by glutamine synthase
  63. 63Where is GABA released?CNS
  64. 64What types of GABA receptors are there?3 types: GABA-A, GABA-B & GABA-C
    - GABA-A receptor is ionotropic and controls chloride channels
  65. 65How is GABA removed from the synapse?by GABA transporters and broken down by GABA aminotransferase
  66. 66What happens at an ionotropic receptor?- NT binds which opens the channel
    - NT can then freely move across the membrane
  67. 67What happens at a metabotropic receptor which is linked to an ion channel?- NT binds to receptor
    - receptor activates G-protein
    - G-protein opens or closes ion channels
  68. 68What happens are a metabotropic receptor linked to second messengers?- NT binds to receptor
    - receptor activated G-protein
    - G-protein activated or inhibits enzyme
    - enzyme produces second messenger
    - second messenger goes on to affect the cell eg. open/close ion channels or produces other cell response
  69. 69What happens when a second messenger is used?- has a slower activation than ionotropic receptors
    - longer lasting effects
  70. 70What happens at the dopamine (D1) receptor?- dopamine interacts with D1 receptor
    - D1 receptor ineracts with GPCR (activates G-protein)
    - GPCR activates adenylyl cyclase
    - AC converts ATP into cAMP
    - cAMP has downstream effects on the cell
  71. 71What happens at a muscarinic acetylcholine receptors (mAChR)- acetylcholine interacts with mAChR
    - mAChR (2 & 4) inhibit AC production and therefore cAMP
    - opens a potassium channel
    - mAChR (1, 3, 5) interferes with reaction cascades which can affect gene expression & generation of channels
    - opens a calcium channel

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Neuroscience and Behaviour (The brain) FlashCards sobre Synapses & Information, criado por Amy Walker em 27-01-2020.
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Amy Walker
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