Neurons Cellular and Network Properties Figure 820 CelltoCell A Chemical Synapse Chemical synapses use neurotransmitters electrical synapses pass electrical signals Axon of presynaptic ID: 238410
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Slide1
Chapter 8b
Neurons: Cellular and Network PropertiesSlide2
Figure 8-20
Cell-to-Cell: A Chemical Synapse
Chemical synapses use
neurotransmitters; electrical synapses pass electrical signals.
Axon of
presynaptic
neuron
Postsynaptic
neuron
Axon terminal
Mitochondrion
Synaptic
vesicles
Synaptic
cleft
Receptors
Neurotransmitter
Postsynaptic
membraneSlide3
Figure 8-21
Cell-to-Cell: Events at the Synapse and Exocytosis
1
Voltage-gated
Ca
2+
channel
Postsynaptic cell
Docking
protein
Synaptic
vesicle
Action
potential
Axon
terminal
Neurotransmitter
molecules
SynapticcleftReceptor
An action potential depolarizes the axon terminal.The depolarization opens voltage-gated Ca2+
channels and Ca2+
enters the cell.
Calcium entry triggers exocytosis of synaptic vesicle contents.Neurotransmitter diffuses across the synaptic cleft
and binds with receptors on the postsynaptic cell.Neurotransmitter binding initiates a response in the postsynaptic cell.
Cellresponse
Ca2+2
3
4
5
1
2
3
4
5Slide4
Cell-to-Cell: Neurocrines
Seven classes by structure
AcetylcholineAmines
Amino acidsPurinesGasesPeptides
LipidsSlide5
Cell-to-Cell: Synthesis and Recycling of Acetylcholine at a Synapse
Figure 8-22
1
Synaptic
vesicle
Acetylcholine
Acetylcholinesterase (AChE)
Choline
Axon
terminal
Acetate
Mitochondrion
Postsynaptic
cell
Cholinergic
receptor
EnzymeCoA
Acetyl CoA
Acetylcholine (ACh) is made from choline and acetyl CoA.In the synaptic cleft ACh is rapidlybroken down by the enzyme
acetylcholinesterase.Choline is transported back intothe axon terminal and is usedto make more ACh.
1
2
3
23Myasthenia gravisSlide6
Amines
Derived from single amino acid
TyrosineDopamine
Norepinephrine is secreted by noradrenergic neuronsEpinephrine
OthersSerotonin is made from tryptophanHistamine is made from histadineSlide7
Amino Acids
Glutamate: Excitatory
CNSAspartate: Excitatory
brainGABA: Inhibitory
brainGlycineInhibitory spinal cordMay also be excitatorySlide8
Other Neurotransmitters
Purines
AMP and ATP
Gases
NO and CO PeptidesSubstance P and opioid peptidesLipids
EicosanoidsSlide9
Receptors
Cholinergic
receptorsNicotinic
on skeletal muscle, in PNS and CNSMonovalent
cation channels Na+
and K+
Muscarinic in CNS and Parsympathetic NS
Linked to G proteins to 2nd messengersAdrenergic Receptors and
Linked to G proteins and 2nd messengersGlutaminergicExcitatory in CNSMetabotropic and IonotropicSlide10
Cell-to-Cell: Postsynaptic Response
Fast and slow responses in postsynaptic cells
Figure 8-23
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+out or Cl–
in
EPSP =
excitatorydepolarizationIPSP = inhibitoryhyperpolarization
Ion channels close
LessNa+ inLess K+out
EPSP = excitatorydepolarizationAlters open
state ofion channels
Activated second
messenger pathwayInactivepathway
Modifies existingproteins or regulatessynthesis of newproteinsCoordinated
intracellularresponse
Rapid, short-actingfast synaptic potentialNeurocrine
Slow synaptic potentialsand long-term effects
Chemically gated ion channel
G protein–coupled
receptorSlide11
Cell-to-Cell: Postsynaptic Response
Figure 8-23, step 1
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationRapid, short-actingfast synaptic potential
Neurocrine
Chemically gated ion channelG protein–coupledreceptorSlide12
Cell-to-Cell: Postsynaptic Response
Figure 8-23, steps 1–2
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationRapid, short-actingfast synaptic potential
Neurocrine
Slow synaptic potentialsand long-term effectsChemically gated ion channel
G protein–coupledreceptorSlide13
Cell-to-Cell: Postsynaptic Response
Figure 8-23, steps 1–3
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationAlters openstate ofion channels
Activated second
messenger pathwayInactivepathwayRapid, short-acting
fast synaptic potentialNeurocrineSlow synaptic potentials
and long-term effects
Chemically
gated ion channelG protein–coupledreceptorSlide14
Cell-to-Cell: Postsynaptic Response
Figure 8-23, steps 1–4
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationIon channels close
LessNa+ in
Less K+outAlters openstate ofion channels
Activated secondmessenger pathwayInactive
pathway
Rapid, short-acting
fast synaptic potentialNeurocrineSlow synaptic potentialsand long-term effects
Chemically gated ion channelG protein–coupledreceptorSlide15
Cell-to-Cell: Postsynaptic Response
Figure 8-23, steps 1–5
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationIon channels close
LessNa+ in
Less K+outEPSP = excitatorydepolarization
Alters openstate ofion channels
Activated secondmessenger pathway
Inactive
pathwayRapid, short-actingfast synaptic potential
NeurocrineSlow synaptic potentialsand long-term effectsChemically
gated ion channel
G protein–coupledreceptorSlide16
Cell-to-Cell: Postsynaptic Response
Figure 8-23, steps 1–6
Postsynaptic
cell
Presynaptic axon
terminal
Ion channels open
More
Na
+
in
More K
+
out or Cl– in
EPSP = excitatory
depolarization
IPSP = inhibitoryhyperpolarizationIon channels close
LessNa+ in
Less K+outEPSP = excitatorydepolarization
Alters openstate ofion channels
Activated secondmessenger pathway
Inactive
pathwayModifies existingproteins or regulatessynthesis of newproteins
CoordinatedintracellularresponseRapid, short-actingfast synaptic potential
Neurocrine
Slow synaptic potentialsand long-term effectsChemically gated ion channel
G protein–coupled
receptorSlide17
Cell-to-Cell: Inactivation of Neurotransmitters
Figure 8-24
Synaptic
vesicle
Postsynaptic cell
Enzyme
Axon
terminal of
presynaptic cell
Glial
cell
Blood
vessel
Neurotransmitters can be returned
to axon terminals for reuse or
transported into glial cells.
Enzymes inactivate neurotransmitters.Neurotransmitters can diffuseout of the synaptic cleft.
1
23
12
3
Rapid termination of NTs