1.Notes: Synapse 2.Reading: Anatomy of Nervous...
Transcript of 1.Notes: Synapse 2.Reading: Anatomy of Nervous...
Wednesday - 1/9
1.Notes: Synapse2.Reading: Anatomy of
Nervous System
Synapse ModelMust include:
• presynaptic cell
• postsynaptic cell
• vesicles
• molecules: neurotransmitters + calcium
• protein channel receptors
• synaptic cleft This will be a working model that can demonstrate the steps that take place at the synapse
Tuesday - 1/20
1. Notes: Synapse2. Model Synapse w/Questions
The Synapse
What happens when a nerve impulse gets to the end of a neuron?
1. The Synapse (greek = to clasp)
A. Physical Description1. Place where axonal end of one
neuron interfaces with another cell
• Other cell may be another neuron or an effector cell
2. Point of contact where signals are passed on
II.Chemical Synapse
A. Nerve impulse arrives at pre-synaptic terminal
B. Special Ca+ gates open for a split second and let Ca+ rush into cell.
C.Ca+ promote the fusion of synaptic vesicles w/presynaptic membrane and neurotransmitters are released into synaptic cleft
II.Chemical Synapse (cont’d)
D. Neurotransmitter diffuse across synaptic cleft and attach to protein receptors on post-synaptic membrane
• Receptor specific to neurotransmitterE. Ion channels allowing Na+ to rush into
cell causing action potential• Nerve impulse is passed on
F. Neurotransmitter is reabsorbed or destroyed by enzymes, causing action potential to stop (ion channels close)
III.NeurotransmittersA.The “language” of the nervous
system is considered electrochemical
• electro- = nerve (electrical) impulse
• -chemical = neurotransmitters
B.Neurons communicate with each other using neurotransmitters, chemical messengers
Questions to Answer1. What is a synapse? 2. What is the purpose of a neurotransmitter? 3. How does a neurotransmitter affect the post synaptic
cell? 4. What is the role of calcium at the synapse? What
causes it to rush into the pre-synaptic cell? 5. How do neurotransmitters get into the synaptic cleft? 6. What do neurotransmitters do after they diffuse across
the synaptic cleft? 7. Neurotransmitters are only present in the synaptic cleft
for a few milliseconds. What happens to them after this time?
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin CummingsFigure 8-11 2 of 5
An action potential arrives and depolarizes the synaptic knob
Action potential
EXTRACELLULAR FLUID
Synaptic knob
PRESYNAPTIC NEURON
Synaptic vesiclesER
AChE
POSTSYNAPTIC NEURONCYTOSOL
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin CummingsFigure 8-11 3 of 5
An action potential arrives and depolarizes the synaptic knob
Action potential
Extracellular Ca2+ enters the synaptic cleft triggering the exocytosis of ACh
EXTRACELLULAR FLUID
Synaptic knob
PRESYNAPTIC NEURON
Synaptic vesiclesER
AChE
POSTSYNAPTIC NEURONCYTOSOL
ACh
Ca2+
Ca2+ Synaptic cleft
Chemically regulated sodium channels
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin CummingsFigure 8-11 4 of 5
An action potential arrives and depolarizes the synaptic knob
Action potential
Extracellular Ca2+ enters the synaptic cleft triggering the exocytosis of ACh
ACh binds to receptors and depolarizes the postsynaptic membrane
EXTRACELLULAR FLUID
Synaptic knob
PRESYNAPTIC NEURON
Synaptic vesiclesER
AChE
POSTSYNAPTIC NEURONCYTOSOL
ACh
Ca2+
Ca2+ Synaptic cleft
Chemically regulated sodium channels
Initiation of action potential
if threshold is reached
ReceptorNa2+
Na2+Na2+Na2+Na2+
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin CummingsFigure 8-11 5 of 5
An action potential arrives and depolarizes the synaptic knob
Action potential
ACh is removed by AChE (acetylcholinesterase)
Extracellular Ca2+ enters the synaptic cleft triggering the exocytosis of ACh
ACh binds to receptors and depolarizes the postsynaptic membrane
EXTRACELLULAR FLUID
Synaptic knob
PRESYNAPTIC NEURON
Synaptic vesiclesER
AChE
POSTSYNAPTIC NEURONCYTOSOL
ACh
Ca2+
Ca2+ Synaptic cleft
Chemically regulated sodium channels
Initiation of action potential
if threshold is reached
ReceptorNa2+
Na2+Na2+Na2+Na2+
Propagation of action potential (if generated)
Synapse Clay Models1.Using clay you will design a model of the synapse
with the follow parts:
• pre-synaptic neuron (terminal)• Ca++ gates and molecules• pre-synaptic vesicles • neurotransmitters• synaptic cleft• post-synaptic neuron (membrane)• protein receptors on post-synaptic membrane
3.This is a working model and you will be asked to demonstrate the process that takes place at the synapse when passing on a nerve impulse
Neurotransmitters
• There are 50 different neurotransmitters
• Neurons vary in the # they produce
• Some produce one
• Some produce several
• Their release depends on frequency of a stimulation
• Allows nervous system to control release of specific neurotransmitters when needed
Common
• Acetylcholine
• Found mainly @ neuromuscular junction w/skeletal muscles
• Stimulate skeletal muscle contraction
• Norepinephrine
• found in CNS + PNS
• “feeling good” neurotransmitter
• Removal from synapse blocked by cocaine
• Eventual removal causes depression
During normal communication between nerve
cells, or neurons, the transmitting neuron releases neurotransmitter molecules that stimulate the receiving
neuron by binding to receptor molecules on its surface. After
this communication has occurred, transporter
molecules collect the released neurotransmitters and
transport them back into the transmitting neuron for later
release. When cocaine is present, the drug blocks the
transporter, preventing neurotransmitter reuptake so
that the neurotransmitters continue to stimulate the
receiving neuron.
Common
• Dopamine
• Found in CNS(mainly) + PNS
• “feeling good” neurotransmitter
• Reuptake blocked by cocaine
• Body gets used to high levels; once cocaine wears off, not enough to cause pleasure; instead depression
• Serotonin
• Found in CNS
• May play a role in sleep, appetite, nausea, and regulation of mood
• Drugs that block its uptake relieve anxiety and depression
Common
• Endorphins
• Found in CNS
• Natural opiates, mimicking effects of morphine and heroin; bind to opiate receptors
• Inhibits pain: prevents pain signal from reaching brain