Structure and Functions of Neurons

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56 Terms

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Cell body (Soma) contains the
nucleus
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The Axon
sends messages
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Dendrites
receives messages from adjoining cells
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Terminal Buttons
contain neurotransmitters
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Resting membrane potential
the difference in voltage between the inside and outside of \n the axon membrane
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Axon Voltage measures___ inside
\-70 mV
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What determines membrane \n potential?
\n Balance between Diffusion and Electrostatic pressure
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Diffusion
molecules diffuse from regions of high concentration to low concentration (high → low)
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Electrostatic pressure
force exerted by attraction or repulsion of ions
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Cations
positive charge (+)
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Anions
negative charge (-)
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4 important ions:
* Organic ions (A-)
* Chloride ions (Cl-)
* Potassium ions (K+)
* Sodium ions (Na+)
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Sodium potassium pump in membrane kicks out ___ and takes in __.
\- Kicks out 3 Na+ ions

\- Takes in 2 K+ ions
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Sodium potassium pump in membrane keeps-
Na+ located outside cell at rest
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depolarization
Reversal of membrane potential from negative \n to positive (neg. → pos.)
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Ionic basis of the Action Potential:
NA+ in: (upswing of spike)

K+ out: (downswing of spike) \n Return to resting potential
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The action potential is a
“all or none” event
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Cable properties of the axon:
Give sub-threshold stimulation → decremental conduction
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myelinated neurons (neurons with a myelin shealth) allows:
\- Action potential (AP) to jump from node-to-node

\- Speeds up conduction

\- Energy efficient
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“synapse”:
a physical gap between pre- and post-synaptic membranes of neurons
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Communication between neurons:
Action potential → Terminal button (contains synaptic vesicles) → Synaptic vesicles (contain neurotransmitter) → Synapse
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Neurotransmitter Release Process:
\- Vesicles “docked” near presynaptic membrane \n - Action potential at the terminal opens CA++ channels \n - CA++ ions open a fusion pore \n - Vesicles release transmitter into the synapse \n - Transmitter diffuses across gap to the postsynaptic membrane receptors
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\- Vesicles “docked” near __*?* __ \n *- Action potential at the* terminal opens CA++ channels \n - CA++ ions open a fusion pore \n - Vesicles release transmitter into the synapse \n - Transmitter diffuses across gap to the postsynaptic membrane receptors
presynaptic membrane
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\- Vesicles “docked” near presynaptic membrane \n - Action potential at the terminal opens __?__ \n - CA++ ions open a fusion pore \n - Vesicles release transmitter into the synapse \n - Transmitter diffuses across gap to the postsynaptic membrane receptors
CA++ channels
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\- Vesicles “docked” near presynaptic membrane \n - Action potential at the terminal opens CA++ channels \n - CA++ ions open a __ ? __ \n - Vesicles release transmitter into the synapse \n - Transmitter diffuses across gap to the postsynaptic membrane receptors
fusion pore
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\- Vesicles “docked” near presynaptic membrane \n - Action potential at the terminal opens CA++ channels \n - CA++ ions open a fusion pore \n - Vesicles release transmitter into the __ ? __ \n - Transmitter diffuses across gap to the postsynaptic membrane receptors
synapse
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\- Vesicles “docked” near presynaptic membrane \n - Action potential at the terminal opens CA++ channels \n - CA++ ions open a fusion pore \n - Vesicles release transmitter into the synapse \n - __ __?__ *diffuses across gap to the* __ ? receptors.
\- transmitter, postsynaptic membrane
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Postsynaptic Receptors
\- Neurotransmitter “binds” to post-synaptic \n receptors (“lock and key”) \n - Receptor activation opens ion channels \n - Ions enter, producing depolarization or \n hyperpolarization \n - Ions create a “post-synaptic potential”
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\- Neurotransmitter “binds” to __?_ (“lock and key”) \n - Receptor activation opens ion channels \n - Ions enter, producing depolarization or \n hyperpolarization \n - Ions create a “post-synaptic potential”
Postsynaptic receptors
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\- Neurotransmitter “binds” to post-synaptic receptors (“lock and key”) \n - Receptor activation opens __?_ \n - Ions enter, producing depolarization or hyperpolarization \n - Ions create a “post-synaptic potential”
ion channels
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\- Neurotransmitter “binds” to post-synaptic receptors (“lock and key”) \n - Receptor activation opens ion channels \n - Ions enter, producing __?_ or __?_ \n - Ions create a “post-synaptic potential”
depolarization or hyperpolarization
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\- Neurotransmitter “binds” to post-synaptic receptors (“lock and key”) \n - Receptor activation opens ion channels \n - Ions enter, producing depolarization or hyperpolarization \n - __?_ create a “__?_ potential”
* Ions, post-synaptic
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Postsynaptic receptors control ion channels in 2 ways:
* directly, indirectly
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Directly
(ionotropic receptors)
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Indirectly
using second messenger systems (metabotropic receptors)
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Ionotropic Receptors:
The ion channel opens when a molecule of neurotransmitter attaches to the binding site.
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Post syaptic Potentials (PSP)’s are either-
excitatory (EPSP) or inhibitory (IPSP)
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Opening NA+ ion channels is-
(EPSP) *Excitatory* post synaptic potential
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Opening Cl- ion channels is-
(IPSP) *Inhibitory* Post synaptic potential
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Termination of Synaptic Transmission is accomplished via:
Reuptake or Enzymatic deactivation
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Reuptake:
Molecules of a neurotransmitter that has been released into the synaptic cleft are transported back into the terminal button

(transmitter is transported back into the presynaptic neuron)
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Enzymatic deactivation:
an enzyme destroys the transmitter molecule

\- Acetylcholine (ACh) \n - AChE – enzyme, destroys ACh
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EPSP →
depolarization
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IPSP →
hyperpolarization
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Effects of excitation or inhibition on behavior?
Need details on the neural circuits to predict \n effects on behavior
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Excitation of excitatory neurons can →
increase behavior
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Excitation of inhibitory neurons can →
decrease behavior
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Inhibition of inhibitory neurons can →
increase behavior
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Autoreceptors are located
pre-synaptically
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Autoreceptors respond to the neuron’s __?_
OWN transmitter
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Autoreceptors regulate amount of __?_ a neuron __?_.
\- transmitter \n - releases (feedback mechanism)
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To Activate autoreceptor →
decrease transmitter release
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To Block autoreceptor →
\n increase transmitter release
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(AP) Stimulate resting neuron →

__?_channels open →

Na+ enters cell →

cell is depolarized →

impulse travels down axon
Na+
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(AP) Stimulate resting neuron →

Na+ channels open →

Na+ enters cell →

cell is __?_ →

impulse travels down axon
depolarized
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(AP) Stimulate resting neuron →

Na+ channels open →

Na+ enters cell →

cell is depolarized →

impulse travels down __?_
axon