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Synapses & Information
Fichas del conjunto (71)
- 1What are synapses?points of contact and communication between nerve cells or between nerve cells and muscle cells
- 2What are the pre and postsynpatic membranes located?Presynaptic: terminal boutons
Postsynaptic: dendrites - 3What is the synaptic cleft?the gap between the pre- and postsynaptic membranes containing filaments to keep the membranes in alignment
- 4What are the two major types of synapses?- Electrical Synapses
- Chemical Synapses - 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 - 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 - 7How are neurotransmitters released at chemical synapses?NTs stored in presynaptic vesicles which are activated by voltage-gated calcium channels
- 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 - 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 - 10What is an ionotropic receptor?a receptor with a direct link to an ion channel
- 11How do ionotropic receptors elicit a response?binding of NT opens the ion channel allowing the ion through
- 12What is a PSP?Post-Synaptic Potential: local current change, has fast onset and ends within a few milliseconds
- 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) - 14What is an EPSP?Excitatory Post-Synaptic Potential: moves membrane potential closer to threshold
- 15What is an IPSP?Inhibitory Post-Synaptic Potential: causes stabilisation or hyperpolarisation of membrane potential
- 16What determines how large the PSP is?Graded potentials: amplitude depends on strength of stimulus
- 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 - 18How many inputs can a neuron receive?hundreds
- 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" - 20What is spatial summation?Integration of PSPs from multiple synapses
- 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 - 22How does summation link to frequency coding?summation can affect the frequency of firing of APs in the postsynaptic cell to transmit a message
- 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
- 24What does the action of the NT depend on?the receptor
- 25What are the main groups of NT?- acetyl choline
- biogenic amines
- amino acid NTs
- purines
- neuropeptides
- gases - 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 - 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 - 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 - 29Where is acetylcholine released?CNS & PNS
- 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 - 31What are the two main types of acetylcholine receptor?Ionotropic: nicotinic (nAChRs)
Metabotropic: muscarinic (mAChRs) - 32What are some typical agonists and antagonists of acetylcholine receptors?nAChRs agonist: nicotine
nAChRs antagonist: curare
mAChRs agonist: muscarine
mAChRs antagonist: atropine - 33How is ACh removed from the synapse?deactivated by the enzyme acetylcholinesterase (AChE)
- 34What is a biogenic amine?- NT derived from amino acids
- all posses an amine group - 35What are the 3 main classes of biogenic amine?1. Catecholamines
2. Indolamines
3. Ethylamines - 36What are some of the catecholamines?1. dopamine
2. epinephrine
3. norepinephrine - 37What is an example of an indolamine?serotonin (5-HT)
- 38What is an example of an ethylamine?histamine
- 39What types of receptors do biogenic amines typically have?- typically metabotropic
- generally act via G-proteins - 40Where is dopamine released?CNS
- 41What is the role of dopamine?- produces either EPSPs or IPSPs depending on the postsynaptic receptor
- implicated in movement, attention, learning and drug-reinforcement - 42What types of receptor does dopamine have?- 5 types all metabotropic
- D1 & D5 increase production of cAMP
- D2-D4 decrease production of cAMP - 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 - 44Where is (Nor)Epinephrine released?CNS & PNS
- 45What are the roles of (Nor)Epinephrine?CNS: vigilance
PNS: autonomic nervous system regulation - 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 - 47How do Nor(Epinephrine) receptors work?receptors coupled to G-proteins that control the production of second messengers
- 48How is (Nor)Epinephrine removed from the synapse?norepinephrine transporter removes excess NT from the synapse & then is deactivated by MAO
- 49Where is serotonin released?CNS & PNS
- 50What is the role of serotonin?CNS: mood regulation, eating, sleep, dreaming, arousal, impulse control
PNS: enteric nervous system (digestive tract) - 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 - 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 - 53Where is histamine released?CNS & PNS
- 54What is the role of histamine?CNS: wakefulness
PNS: immune response - 55What types of receptor does histamine have?4 types all metabotropic: H1-H4
- 56What are some examples of the amino acid neurotransmitters?Excitatory: glutamate & aspartate
Inhibitory: GABA & glycine
- GABA is derived from glutamate - 57Where is glutamate released?CNS
- 58What are the types of glutamate receptors?Ionotropic: kainate, NMDA, AMPA (most common)
Metabotropic: mGluR - 59What do the AMPA and kainate receptors do?control a sodium channel & produce EPSPs
- 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 - 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) - 62How is glutamate removed from the synapse?by excitatory AA transporters and borken down into glutamine by glutamine synthase
- 63Where is GABA released?CNS
- 64What types of GABA receptors are there?3 types: GABA-A, GABA-B & GABA-C
- GABA-A receptor is ionotropic and controls chloride channels - 65How is GABA removed from the synapse?by GABA transporters and broken down by GABA aminotransferase
- 66What happens at an ionotropic receptor?- NT binds which opens the channel
- NT can then freely move across the membrane - 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 - 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 - 69What happens when a second messenger is used?- has a slower activation than ionotropic receptors
- longer lasting effects - 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 - 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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- (The brain) Neuroscience and Behaviour Fichas sobre Synapses & Information, creado por Amy Walker el 27/01/2020.
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- Amy Walker
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