Studied by 2 peopleCell body (Soma) contains the
nucleus
The Axon
sends messages
Dendrites
receives messages from adjoining cells
Terminal Buttons
contain neurotransmitters
Resting membrane potential
the difference in voltage between the inside and outside of \n the axon membrane
Axon Voltage measures___ inside
-70 mV
What determines membrane \n potential?
\n Balance between Diffusion and Electrostatic pressure
Diffusion
molecules diffuse from regions of high concentration to low concentration (high → low)
Electrostatic pressure
force exerted by attraction or repulsion of ions
Cations
positive charge (+)
Anions
negative charge (-)
4 important ions:
Organic ions (A-)
Chloride ions (Cl-)
Potassium ions (K+)
Sodium ions (Na+)
Sodium potassium pump in membrane kicks out ___ and takes in __.
- Kicks out 3 Na+ ions
- Takes in 2 K+ ions
Sodium potassium pump in membrane keeps-
Na+ located outside cell at rest
depolarization
Reversal of membrane potential from negative \n to positive (neg. → pos.)
Ionic basis of the Action Potential:
NA+ in: (upswing of spike)
K+ out: (downswing of spike) \n Return to resting potential
The action potential is a
“all or none” event
Cable properties of the axon:
Give sub-threshold stimulation → decremental conduction
myelinated neurons (neurons with a myelin shealth) allows:
- Action potential (AP) to jump from node-to-node
- Speeds up conduction
- Energy efficient
“synapse”:
a physical gap between pre- and post-synaptic membranes of neurons
Communication between neurons:
Action potential → Terminal button (contains synaptic vesicles) → Synaptic vesicles (contain neurotransmitter) → Synapse
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
- 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
- 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
- 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
- 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
- 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
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”
- 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
- 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
- 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
- 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
Postsynaptic receptors control ion channels in 2 ways:
directly, indirectly
Directly
(ionotropic receptors)
Indirectly
using second messenger systems (metabotropic receptors)
Ionotropic Receptors:
The ion channel opens when a molecule of neurotransmitter attaches to the binding site.
Post syaptic Potentials (PSP)’s are either-
excitatory (EPSP) or inhibitory (IPSP)
Opening NA+ ion channels is-
(EPSP) Excitatory post synaptic potential
Opening Cl- ion channels is-
(IPSP) Inhibitory Post synaptic potential
Termination of Synaptic Transmission is accomplished via:
Reuptake or Enzymatic deactivation
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)
Enzymatic deactivation:
an enzyme destroys the transmitter molecule
- Acetylcholine (ACh) \n - AChE – enzyme, destroys ACh
EPSP →
depolarization
IPSP →
hyperpolarization
Effects of excitation or inhibition on behavior?
Need details on the neural circuits to predict \n effects on behavior
Excitation of excitatory neurons can →
increase behavior
Excitation of inhibitory neurons can →
decrease behavior
Inhibition of inhibitory neurons can →
increase behavior
Autoreceptors are located
pre-synaptically
Autoreceptors respond to the neuron’s _?
OWN transmitter
Autoreceptors regulate amount of _? a neuron __?_.
- transmitter \n - releases (feedback mechanism)
To Activate autoreceptor →
decrease transmitter release
To Block autoreceptor →
\n increase transmitter release
(AP) Stimulate resting neuron →
__?_channels open →
Na+ enters cell →
cell is depolarized →
impulse travels down axon
Na+
(AP) Stimulate resting neuron →
Na+ channels open →
Na+ enters cell →
cell is _? →
impulse travels down axon
depolarized
(AP) Stimulate resting neuron →
Na+ channels open →
Na+ enters cell →
cell is depolarized →
impulse travels down _?
axon
Note
Flashcard