Lecture 3

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  • Created by: The Shrew
  • Created on: 20-02-16 12:21
Temporal summation
Several impulses from one neurone over time before neurone reaches baseline- reaches threshold, can be hyperpolarising as well (anaesthetics)
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Spatial summation
Impulses from several places to one neurone
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Many neurones don't have AP or they're very short
Conduction is passive or decremental
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Based on squid motor neurone
Not all like this- can fire automatically even when no input, don't display AP, dendrites can activity transmit AP
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Mylinated axons/ Non mylinated
224mph (cats)/ 2.24mph
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Can't all be mylinated
Too thick, only essential things (quick pain= mylinated/ long term ache= non-mylinated)
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Electrical synapse
Bidirectional- some plasticity
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0.2ms from neurone to neurone/ connect large group of neurones/ Evolution
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Controls brain as a whole
Keeps between coma and seizure
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Cerebral cortex
Allow network of inhibitory neurones to fire in a highly coordinated way
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2ms from neurone to neurone/ can only go one way- two sides different
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Directed synapse
Site of NT release and receptor are in close proximity
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Non-directed synapse
Distance between release and receptor- can go several places at the end of an axon
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Depolarization of pre-synaptic membrane
Ca2+ goes in through voltage gates- facilitated diffusion
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NT produce signals by
binding to receptors (proteins) that are specific for given NT
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Molecule that binds to another
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Multiple receptor subtypes
for one given NT
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2 biochemical features that receptors have in common
Membrane spanning proteins/ region exposed to external environment recognises and binds transmitters
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Ion channels/ ligand gated channels/ Ionotropic receptors
Need key to open/ excititary or inhibitory
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Excitatory Ionotropic receptors
NT binds to ionotropic receptor, associated channel opens or closes inducing immediate post-synaptic potential
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Can let K+ out (with conc gradient but not polar gradient) or let Cl- in- Inside of cell more negative
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binds to GABA receptors and makes them stay open- more Cl- in cell= inhibited in cerebellum which messes up balance and speech
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G protein linked/ Metabotropic
key changes inside of membrane slightly- wave of positivity/ excitatory or inhibitory
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Slower to develop but
longer lasting, more diffusion and more variables/ some in presynaptic receptors and autoreceptors
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Don't control ion channels/ always metabotropic/ bind to neurones own neurotransmitter/ located in presynaptic membrane/ control internal processes- synthesis and release of NT
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Neurotransmitters (5 assumptions)
Produced within a neurone/ Released when neurone is stimulated/ Acts on post-synaptic receptor and causes biological effect/ must be inactivated once released/ chemical is applied on post-synaptic membrane
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4 small molecule NT
Amino acids, Monoamines, Acetylcholine, Unconventional Small-NT
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Amino acids
Molecular building blocks of proteins
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Obtained through
Proteins we eat or protein synthesis
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Found at
Fast acting direct synapses
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Most prevelent excitatory NT
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Most prevalent inhibitory NT
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Monoamine synthesized from
single amino acid
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Synpases tend to be
Non-direct= effects are variable
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Acetylcholine synthesised by
Adding an acetyl group to chlorine
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Fast acting/ direct
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Two types of receptors distributed differently in nervous system
Nicotinic (ionotropic, activates muscles)/ Muscarinic (metabotropic, memory)
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Unconventional small NT
Soluble gases= exist only briefly/ easily pass through cell membranes/ involved in retrograde transmission (regulate activity of presynaptic cells)
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Similar to THC/ inhibit release of NT
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Large- need nucleus/ 100 identified/ more and more being discovered/
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Released at
Non-direct synapses
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Neurotransmitter Pharmacology
Agonist- facilitate activity/ Antagonist- inhibit activity
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Termination of NT action
Receptors need a rest or they stop responding, exposure must be limited
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let NT diffuse away- not quick enough
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Enzymatic breakdown
Enzyme breaks down NT and recycles
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Protein in presynaptic neurone brings it back in and recycles- prozac stops this from happening with dopamine
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Glial uptake
Glia wraps around terminal and reuptakes and recycles
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Aid release of NT/ inhibit reabsorbsion of NT/ delay NT breakdown/ determines mental state- moods long lasting
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Released at
non-direct synapses
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Colocalization/ Coexistence
Many neurones contain more than one NT (usually one small and one neuropeptide)
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Axoaxonic synapse
axon of a neurone synapses with the presynaptic terminal of another
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Presynpatic inhibition
Reduction in amount of NT released, lessen voltage sensitivity of Ca2+ channels/ Open Cl- channels on postsynaptic terminal (don't feel pain under stress- evolution)
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Presynaptic facilitation
Classical conditioning- increases Ca2+ entry on postsynaptic terminal
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Other cards in this set

Card 2


Spatial summation


Impulses from several places to one neurone

Card 3


Many neurones don't have AP or they're very short


Preview of the front of card 3

Card 4


Based on squid motor neurone


Preview of the front of card 4

Card 5


Mylinated axons/ Non mylinated


Preview of the front of card 5
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