presynaptic ending portion of the axon conveying information to the next neuron Some terms presynaptic ending the portion of the axon that is conveying information to the next neuron ID: 297951
Download Presentation The PPT/PDF document "What about communication between neurons..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
What about communication between neurons?Slide2Slide3
presynaptic ending –
portion of the
axon
conveying information to the next neuron
Some terms…….Slide4Slide5
presynaptic ending –
the portion of the axon that is conveying information to the next neuron
synapse or synaptic cleft
the space between neurons where communication occurs
Some terms…….Slide6Slide7
presynaptic ending –
the portion of the axon that is conveying information to the next neuron
synapse or synaptic cleft
the space between neurons where communication occurs
postsynaptic membrane
the portion of the neuron (usually dendrite) that receives information
Some terms…….Slide8Slide9
presynaptic
ending –
the portion of the axon that is conveying information to the next neuron
synapse or synaptic cleft
the space between neurons where communication occurs
postsynaptic membrane
the portion of the neuron (usually dendrite) that receives information
pre and postsynaptic receptors
proteins in both the
presynaptic
and postsynaptic ending that allow for information to be transferred
Some terms…….Slide10Slide11
synaptic vesicles --small enclosed membranes that contain neurotransmitter - found in presynaptic ending
neurotransmitter – substance in vesicles that are released in synapse and convey info to the next neuronSlide12
Presynaptic
ending
Postsynaptic ending
synapseSlide13
AP reaches presynaptic ending-
Ca+2 channels in presynaptic ending open and Ca+2 enters
What happens at level of synapse?Slide14
Ca
+2
entry into the presynaptic ending
critical for neurotransmitter release
Why are Ca
+2
ions important?Slide15Slide16
drugs that block Ca
+2
channels…….Slide17
protein embedded in membrane
mechanism for neurotransmitter to influence postsynaptic activity by binding to receptor
postsynaptic receptorsSlide18
NT binds to postsynaptic receptors and causes
small local changes
in electrical potential (
depolarizations or hyperpolarizations)-
Called graded potentials
SummarySlide19
increase
or decrease the likelihood of the neuron receiving info to generate an action
potential
graded potentials that increase the likelihood of an action potential are called EPSPs (excitatory postsynaptic potentials)
Graded PotentialsSlide20Slide21
increase
or decrease the likelihood of the neuron receiving info to generate an action
potential
graded potentials that increase the likelihood of an action potential are called EPSPs (excitatory postsynaptic potentials)
graded potentials that decrease the likelihood of an action potential are called IPSPs (inhibitory postsynaptic potentials)
Graded PotentialsSlide22Slide23
NT binding to postsynaptic receptors cause local ion channels to
open
chemically
dependent ion channels (in contrast with electrically dependent ion channels in the axon)
How does the neurotransmitter
cause EPSPs and IPSPs?
Slide24
postsynaptic receptors open ion channels –
ion channels in postsynaptic membrane (that we need to worry about) include Na+,
Cl
- and K+
How does the neurotransmitter
cause EPSPs and IPSPs?
Slide25
EPSPs – excitatory postsynaptic potentials
- increase the likelihood of an AP
- opening of
IPSPs – inhibitory postsynaptic potentials
decrease
the likelihood of an AP
- opening of
Two kinds of Graded Potentials
Slide26
http://www.blackwellpublishing.com/matthews/neurotrans.htmlSlide27
Axon hillockSlide28
graded potentials are summed at axon
hillock and……if the sum is a great enough depolarization….
How do graded potentials result in an action potential? Slide29Slide30
action potential or
spikeSlide31
Graded Potentials and AP differ in a number of ways
AP – occurs at the axon
GP – occurs anywhere the neuron receives info from another neuron (usually dendrite although NOT ALWAYS)
action potentials are “all or none”
graded
potentials decrease over space and time Graded potentials are localized – has impact in limited region; AP travels down the axon
Graded potentials vs action potentials Slide32
Graded potentials can either increase or decrease the likelihood of an action potential
Graded vs Action PotentialsSlide33Slide34
Postsynaptic receptor and NT – think about a lock and key!
So what about these NT? Slide35
Neurotransmitter represents a key
Receptor represents the lockSlide36
directly opening the ion channel
occurs and terminates very quickly
2 ways that neurotransmitter exert these effects Slide37Slide38
http://www.blackwellpublishing.com/matthews/nmj.htmlSlide39
directly opening the ion channel
occurs and terminates very quickly
more indirect
ultimately opens ion channel via stimulating a chemical reaction
takes longer but lasts longer
2 ways that neurotransmitter exert these effects Slide40Slide41
http://www.blackwellpublishing.com/matthews/neurotrans.htmlSlide42
1. reuptake - most common
protein on
presynaptic
ending transports it back into the neuron that released itMeans of recycling NTsaving energy (neurons have to synthesize or produce their own NT)
a common way for drugs to alter normal communication
2 main ways for getting the neurotransmitter out of the synapseSlide43
cocaine, amphetamine, methylphenidate (Ritalin) – block
reuptake of a number of NT – particularly
dopamine
(reward)many of the newer antidepressants are SSRIs (selective serotonin reuptake inhibitors)
Examples of reuptake inhibitorsSlide44
enzyme degradation
enzyme - speeds up a reaction
ex. acetylcholine (
ACh)is a neurotransmitter is broken down by
acetylcholinesterase
(
AChE
) For ACh – this is done in the synapseSlide45
probably 100s of “putative” neurotransmitters – more being discovered all the time
role that the novel NTs play still being determined
Neurotransmitters Slide46
acetylcholine (ACh) –
Some classic NTSlide47
acetylcholine (
ACh) – found in CNS and PNS
receptor subtypes –
nicotinic and muscarinic
Some classic NTSlide48
acetylcholine (
ACh
) – found in CNS and PNS
receptor subtypes – nicotinic and
muscarinic
nicotinic receptors –
muscles
acetylcholine also important for various behaviors including learning and memory
alzheimers
disease, REM sleep, among other things…
Some classic NTsSlide49
Monoamines
dopamine (DA)
important for reward circuits
schizophrenia and Parkinsons disease
Neurotransmitters (cont)Slide50
Monoamines
dopamine (DA)
norepinephrine (NE)
important for arousal
altered activity implicated in depression
Neurotransmitters (cont)Slide51
Monoamines
dopamine (DA)
norepinephrine (NE)
serotonin (5HT)
aggression, anxiety, depression
Neurotransmitters (cont)Slide52
Peptides- really large neurotransmitters
Neurotransmitters (cont)Slide53
Peptides
substance P
important for pain
2. endorphins and enkephalins (endogenous opiates)
pain relievers!
Neurotransmitters (cont)Slide54
4. amino acids (tiny neurotransmitters)
glutamate
ALWAYS EXCITATORY (IE always causes EPSPs
)
2. GABA
–
always
inhibitory ( always causes IPSPs)
-
Neurotransmitters (cont)Slide55
almost any aspect of the NT function can be affected by drugs!
How
can drugs affect a neurotransmitter? Slide56
synthesis of NT
storage of NT release of NTbinding of NT
breakdown of NT
So….Slide57
agonist – mimics the neurotransmitter’s effect
antagonist – blocks the neurotransmitter’s effect
What are possibilities?Slide58Slide59
acting like a receptor agonist
nicotine
ionotropic
potent poisonacting like a receptor antagonistcurare
ACh as an example Slide60
con’t
alter breakdown of
ACh
blocks breakdown
mustard gases, insecticides,
nerve gases
Sarin
- estimated to be over 500 times more toxic than cyanideGulf War Syndrome?other current syndromes??Slide61
con’t
alter breakdown of ACh
blocks breakdown
mustard gases, insecticides, physostigmine
Gulf War Syndrome?
alter release of ACh
block release – botulismSlide62Slide63
con’t
alter release of
ACh
block release –
botulism
botox
stimulate release – black widow spider venom