sinapsis_Rizki Fauziah_3415110139.ppt

8/10/2019 sinapsis_Rizki Fauziah_3415110139.ppt

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SYNAPSE

Rizki Fauziah3415110139


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What is a synapse?

A synapseis the junction between 2 neurones. There is a very narrow gap of about 20nm

between neurones called the synaptic cleft.

An action potential cannot cross the synapticcleft, so nerve impulses are carried by

chemicals called neurotransmitters.


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http://glencoe.mcgraw-

hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapse

The synapse is where the nerve impulsepasses from one cell to the next

The electrical signal (the action potential)stops and a chemical signal takes over to

cross the gap between the cells The chemical messenger is called aneurotransmitter

The neurotransmitter crosses the gap bydiffusion, which creates a small delay

2008 Paul Billiet ODWS
http://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.htmlhttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapsehttp://glencoe.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::530::530::/sites/dl/free/0076611841/930317/Chemical_Synapse.swf::Chemical%20Synapse


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Neurotransmitter

Neurotransmitter is made by thepre-synaptic neuroneand is stored

in synaptic vesselsat the end of the

axon. The membrane of thepost-synaptic

neuronehas chemical-gated ionchannels called neuroreceptors.

These have specific binding sites

for neurotransmitters.


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Designer signals

The advantage of using neurotransmitteris that the nerve impulse can be givensome more specificity

Neurotransmitters can also control theoperation of the nervous system by

inhibition orexcitation Many drugs that try to cure problems in

the nervous system operate at synapses

http://www.saburchill.com/IBbiology/bio_hp.htmlhttp://www.saburchill.com/IBbiology/bio_hp.html


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Neurotransmitters and hormones

In many ways neurotransmitters arehormonesworking over a very shortdistance (about 20 nm)

Some of them work both at synapsesand in the circulatory system



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A Synapse

Pre-synaptic neurone = neurone sending impulse

Post-synaptic neurone = neurone receiving impulse


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Cholinergic Synapses

Acetylcholine is acommon transmitter.

Synapses that haveacetylcholine transmitterare called cholinergicsynapses.

Some neurones formmore than 1 synapse. This is an electron

micrograph of synapsesbetween nerve fibres anda neurone cell body.


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1. Action potential arrives at

terminal button

Membrane receptor

for neurotransmitter

Ca2+

channel

Vesicle storing

neurotransmitter



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Dept of Biology, Saint Louis University
http://starklab.slu.edu/neuro/Cumulative.htmhttp://starklab.slu.edu/neuro/Cumulative.htm


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Ca2+ Ca2+ Ca2+Ca2+

2.Depolarisationopens Ca2+channels

Ca2+enters terminal

button

3.Ca2+stimulates

vesicles to fuse

with membrane

4.Exocytosis of

neurotransmitter

It diffuses 20nm across

the synaptic cleft



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The passage across the synapse

An action potential travels down an axon to theterminal buttonsor synaptic knobs at the end The action potential depolarises the membrane of a

terminal button causing voltage-gated Ca2+channels

to open Ca2+ions flood into the terminal button This stimulates hundreds of synaptic vesicles, packed

with neurotransmitter, to fuse with the membrane ofthe terminal button

By exocytosis The Ca2+ions are then pumped out again



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6.Localised

depolarisation as

ions leak in or out

of membrane.

5.Neurotransmitter

receptor sites on the

postsynaptic membrane

are ion channels.They open when the

neurotransmitter binds



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The passage across the synapse

The neurotransmitter diffusesacross cleftto postsynaptic membrane The neurotransmitter molecules bind with

specific receptor siteson postsynapticmembrane

The receptor sites are part of a ligand-gated ion channel

These channels let Na+ions in or K+ions outcausing localised depolarisationof themembrane



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8.Neurotransmitter

destroyed by

enzymes in the cleft.

Stops signal being

perpetuated.

7.Action potential

generated which

travels down the

postsynaptic cell.



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A new action potential

If the localised depolarisations build up tothe nerve cell threshold, a full actionpotentialwill be produced

This will travel away, down the postsynapticneurone

The action of the neurotransmitters stops:(i) as they dilute by diffusionin the synapticcleft(ii) by hydrolysisthrough the action ofenzymesthere

Important:The signal must not beperpetuated indefinitely 2008 Paul Billiet ODWS

Figure 48 15


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Presynapticcell

Postsynaptic cell

Axon

Presynapticmembrane

Synaptic vesiclecontainingneurotransmitter

Postsynapticmembrane

Synaptic

cleft

Voltage-gatedCa2 channel

Ligand-gatedion channels

Ca2

Na

K

2

1

3

4

Figure 48.15

Figure 48 16


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Figure 48.16

Postsynapticneuron

Synapticterminalsof pre-synaptic

neurons

5

m


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Neuromuscular Junctions

Same stages ascholinergic synapses but in this case the

postsynaptic membraneis the muscle fibremembrane,(Sarcolemma).

Depolarisation of thesarcolemma leads tocontraction of musclefibre.


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The neuromuscular junction is asynapse

The motor end plateis the terminal button

of a motor neuronethat makes contact witha muscle cell

The motor end plate releases the

neurotransmitter acetylcholinethatultimately causes the muscle cell to contract



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Motor end plates

David B. Fankhauser, Ph.D., Professor of Biology and Chemistry, University of Cincinnati Clermont College
http://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/Nerve_Histology/Nervous_Tissue_Histology.htmhttp://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/Nerve_Histology/Nervous_Tissue_Histology.htmhttp://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/Nerve_Histology/Nervous_Tissue_Histology.htmhttp://biology.clc.uc.edu/fankhauser/Labs/Anatomy_&_Physiology/A&P202/Nerve_Histology/Nervous_Tissue_Histology.htm


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Drugs

Drugs which have molecules ofsimilar shape to transmittersubstances can affect protein

receptors in postsynapticmembranes.

Drugs that stimulate a nervoussystem are called AGONISTS

Drugs that inhibit a nervous systemare called ANTAGONISTS.


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Various effects of drugs on

synapses:DRUG ACTION EFFECT

Mimic a neurotransmitter Switch on a synapse

Stimulate the release of a

neurotransmitter

Switch on a synapse

Open a neuroreceptor channel Switch on a synapse

Block a neuroreceptor channel Switch off a synapse

Inhibit the breakdown enzyme Switch on a synapse

Inhibit the Na+K+ATPase pump Stop action potentials

Block the Na+or K+channels Stop action potentials


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Effect of nicotine and atropine


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Thank

You

sinapsis_Rizki Fauziah_3415110139.ppt

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