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4. BIOL257 > Neuronal communication I > Flashcards

Neuronal communication I Flashcards

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1
Q

debate btw:

A
  • reticulists

- neuronists

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2
Q

debate: reticulists

A
  • Golgi

- said nervous system was diffuse network of continuous tissue (reticulum) from fused branches of dendrites/ axons

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3
Q

debate: neuronists

A
  • Cajal
  • neurons were discreet elements
  • cytoplasm not continuous
  • observed neurons had tiny gaps btw basket cell axons and Purkinje cell bodies
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4
Q

debate: who won?

A
  • Cajal and used Golgi stain
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5
Q

4 major signalling mechanisms to allow cells to communicate:

A
  • juxtacrine
  • paracrine
  • autocrine
  • endocrine
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6
Q

signalling mechanisms: juxtacrine signalling

A
  • membrane bound proteins (MBP) interact w other membrane proteins on adjacent cells
  • MBP interact w ligands in extracellular matrix of adjacent cells
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7
Q

signalling mechanisms: paracrine signalling

A
  • local communication btw cells that are in close proximity
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8
Q

signalling mechanisms: autocrine signalling

A
  • chemical signalling released by cell bind to receptors on same cell
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9
Q

signalling mechanisms: endocrine signalling

A
  • chemical signals released by endocrine cells into circulatory system to communicate w distant target organs
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10
Q

signalling mechanisms: juxtacrine travel

A
  • travel via hydrophilic membrane channels/ pores (gap junctions) btw cells
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11
Q

signalling mechanisms: paracrine travel

A
  • neurotransmitters released by one cell diffuse through the extracellular space to contact adjacent cells
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12
Q

cell-cell contracts may be:

A
  • axodendritic
  • axosomatic
  • axoaxonic
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13
Q

neuron to neuron synapses:

A
  • juxtacrine and/or paracrine signalling
  • location of contact important functionally
  • synaptic connections create neural circuits
  • circuits trigger physiological or cognitive changes
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14
Q

synaptic delay:

A
  • neural pathway has several synapses for signal to cross

- the more synapses= slower response time, more delay

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15
Q

name types of synapse:

A
  • chemical

- electrical

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16
Q

define synapse

A
  • specialised junction btw two neurons/ neuron + effector organ
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17
Q

electrical synapses: features

A
  • cytosol of neighbouring cells linked via small pores/ channels = gap junctions
  • electrical charge diffuses passively into adjacent cell
  • no neurotransmitters required
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18
Q

electrical synapses: eg

A
  • some neurons
  • cardiac mm
  • smooth muscle (single unit)
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19
Q

electrical synapses: properties

A
  • juxtacrine signalling
  • v rapid communicaion
  • uni/ bidrectional communication
  • can transmit excitatory/ inhibitory signals at same synapse
  • signal transmission is always ‘sign conserving’ = preserves polarity passed from pre-synaptic to post-synaptic
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20
Q

electrical synapses: gap junctions large enough for

A
  • small molecules not proteins/ DNA to diffuse

- allows secondary messengers to coordinate intracellular signalling processes across coupled cells

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21
Q

electrical synapses: conductance

A
  • can be affected by secondary messengers (cAMP) in response various neuromodulators (eg. dopamine)
  • complex/ dynamic mode of intracellular communication
22
Q

electrical synapses: function

A
  • sync electrical activity among neuronal populations
  • info transfer/ signal processing
  • rapid escape response circuitry
23
Q

electrical synapses: sync electrical activity eg

A
  • eg. electrical coupling of cardiac mm cells -> synchronised contraction of heart
24
Q

electrical synapses: rapid escape eg

A
  • tail flip escape response in crayfish
25
Q

chemical synapses: significant parts

A
  • presynaptic cell
  • synaptic cleft
  • postsynaptic cell
26
Q

chemical synapses: presynaptic cell

A
  • neuron
  • axon terminal/ button/ synaptic knob
  • synaptic vesicles contain neurotransmitter molecules
  • voltage gated calcium ion channels
  • neurotransmitter re-uptake molecule
27
Q

chemical synapses: synaptic cleft

A
  • gap btw presynaptic and postsynaptic neuron
28
Q

chemical synapses: postsnynaptic cell

A
  • neuron, muscle or gland
  • receptor
  • enzyme (neurotransmitter degradation)
29
Q

chemical synapses: properties

A
  • paracrine signalling
  • gap is wide to prevent action potentials electrically passing
  • mostly unidirectional
  • synapses either excitatory (Type I) or inhibitory (Type II)
  • slower than electrical synapses
30
Q

chemical synapses: conversion

A
  • electrical (as AP) - chemical - electrical
31
Q

chemical synapses: pathway

A
  1. AP arrives at nerve terminal
  2. depolarisation causes voltage gated calcium channels open - calcium influx
  3. influx Ca triggers exocytosis of neurotransmitter
  4. neurotransmitter diffuses across cleft and binds to receptors on postsynaptic cell
  5. response triggered in postsynaptic cell
32
Q

chemical synapses: pathway response terminated by removing neurotransmitter from synaptic cleft

A
  1. degradation/ inactivation of NT
  2. reuptake of NT
  3. diffusion of NT
33
Q

neurotransmitters: features

A
  • chemical messengers carry signals across chemical synapse from neuron -> postsynaptic neurons/ mm cells/ effector cells (glands)
34
Q

neurotransmitters: criteria to be one

A
  • present (and usually synthesised within) presynaptic neuron
  • released in regulated fashion (usually exocytosis) following stimulation of presynaptic neuron
  • receptors for substance must be present on postsynaptic target cell
  • mechanisms must be present to remove/ inactivate substance
35
Q

neuromodulator:

A
  • messenger may/ not be released at synaptic sites

- tend to affect groups of neurons w appropriate receptors often w longer-lasting effects

36
Q

neurohormone:

A
  • messenger released into circulation that exerts an effect on distant target cells
37
Q

neurotransmitters: name catagories

A
  • classical
  • neuropeptides
  • purines
  • others
38
Q

neurotransmitters: classical NT

A
  • single amino acids (glutamate)
  • biogenic monamines (derived from aa. eg. GABA)
  • acetylcholine
39
Q

neurotransmitters: neuropeptides

A
  • short chains of aa.

- eg. substance P -> central/ peripheral pain pathways

40
Q

neurotransmitters: purines

A
  • ATP
41
Q

neurotransmitters: others

A
  • endocannabinoids (appetite, mood, pain sensation)
42
Q

neurotransmitters: most common excitatory NT in CNS

A
  • glutamate

- excitatory over 90% synapses

43
Q

neurotransmitters: most common inhibitory NT in CNS

A
  • GABA (inhibitory at 90% synapses that do not use glutamate)
  • glycine
44
Q

neurotransmitters: synthesis

A
  • in synaptic terminal from precursors transported from site of manufacture in cell body
45
Q

drugs that affect synapses: name them

A
  • drugs
  • agonist
  • antagonists
46
Q

drugs that affect synapses: drugs features

A
  • exogenous ligands

- similar chemical structure to endogenous neurotransmitter

47
Q

drugs that affect synapses: agonist features

A
  • similar enough to endogenous neurotransmitter that it binds to receptors on pre/post synaptic membrane and activates them (eg. morphine) mimic natural effect of natural endorphins
48
Q

drugs that affect synapses: antagonists features

A
  • similar enough to neurotransmitter binds to receptor site and blocks it (not enough to activate receptor)
  • curare binds/ blocks nicotinic ACh receptors = muscle paralysis
49
Q

inhibitory drugs: function

A
  • mimic inhibitory NTs (hyperpolarise postsynaptic cell, decrease firing APs)
  • eg. alcohol mimic GABA
  • block receptors for excitatory NTs (prevent generation of AP in postsynaptic neuron)
  • eg. heroin blocks synaptic transmission in pain pathways
  • block release of excitatory NTs (prevent generation of AP in postsynaptic neuron)
  • eg. botulinum toxin (botox) block release of ACh
50
Q

excitatory drugs:

A
  • mimic excitatory NTs (increase depolarisation, increase firing AP)
  • eg. nicotine at autonomic ganglia
  • block receptors for inhibitory NTs (prevent inhibition of AP in postsynaptic neuron)
  • eg. caffeine inhibits inhibitory NT adenosine
  • block NT reuptake pumps (NT remains in synaptic cleft longer)
  • eg. cocaine blocks dopamine uptake
  • block autoreceptors (no modulation of NT release)
  • eg. clonidine blocks norepinephrine alpha2 autoreceptors

4. BIOL257 (18 decks)

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