Neurophysiology Flashcards
(34 cards)
Nerve Physiology
Nerves produce ___ ___
You can record the electrical activity that the nerve produces using an____
Electricity from nerve is a ____ system.
Node: ____ inside of a membrane and the membrane has active organelles in it that are electrically ___
There is a standing (resting) potential. We can measure the difference
Its formed from the ions inside/outside the membrane and the ability of ion channels to open and close appropriately
Nerve Physiology
Nerves produce electrical pulses
You can record the electrical activity that the nerve produces using an electrode.
Electricity from nerve is a bioelectric system.
Node: electrolyte inside of a membrane and the membrane has active organelles in it that are electrically sensitive
There is a standing (resting) potential. We can measure the difference
Its formed from the ions inside/outside the membrane and the ability of ion channels to open and close appropriately
Review: Cable Properties of Nerve Membranes and Passive Potentials
- Base on “___” trans- Atlantic cable model
- The membrane can be modeled as a series of ____ ____ and ____. In such a system, the voltage ____ ____ly along the membrane.
The transmission is ____ because there are no___ elements to ___ voltage or current.
It is only effective over ___ distances.
This kind of transmission is common in ____ fields and permits ____ of thousands of voltages (from ____).
The result triggers the ___ ___ region of the cell. Some___ receptor potentials rely on ___ conductance.
There are diff kinds of electrical potentials on nerves and they all have their own fcn
Cable property: imagine wire with insulator on outside of it. Think of really long (transatlantic cable) If you put voltage at one end and measure voltage along the wire, it ____ with distance
Bc of ion channels of membrane and structure of the membrane, Nerve is like a leaky cable
As we measure down axon, the voltage decreases exponentially with distance
We can put voltages on the membrane maybe from an ___ ___ ___ or something on neurons that don’t produce AP. Just ____ membranes.
They can send the signal down _____ without a ____
Passive maintenance of the potential along the nerve for a distance.
This is the kind of transmission that often occurs with ___ ___
They don’t have to create an AP to send a signal. Signals sent passively thru leaky channel systems.
Some of the neurons in the ____ never depolarize, just send passive potentials around that trigger off axon hillock or just ___ ___ based on passive potential
This is good for ____. Passive signals close to each other in the membrane will __ __. That integrates that information.
This is basically a ___ potential.
Review: Cable Properties of Nerve Membranes and Passive Potentials
- Base on “leaky” trans- Atlantic cable model
- The membrane can be modeled as a series of
parallel resistors and capacitors. In such a system, the voltage
drops exponentially along the membrane. The transmission is passive because there are no active elements to create voltage or current. It is only effective over short distances.
This kind of transmission is
common in dendritic fields and
permits integration of thousands
of voltages (from synapses).
The result triggers the axon-hillock
region of the cell. Some sensory
receptor potentials rely on
passive conductance.
There are diff kinds of electrical potentials on nerves and they all have their own fcn
Cable property: imagine wire with insulator on outside of it. Think of really long (transatlantic cable) If you put voltage at one end and measure voltage along the wire, it decreases with distance
Bc of ion channels of membrane and structure of the membrane, Nerve is like a leaky cable
As we measure down axon, the voltage decreases exponentially with distance
We can put voltages on the membrane maybe from an ion channel opening or something on neurons that don’t produce AP. Just passive membranes.
They can send the signal down passively without a depolarization
Passive maintenance of the potential along the nerve for a distance.
This is the kind of transmission that often occurs with dendritic tress.
They don’t have to create an AP to send a signal. Signals sent passively thru leaky channel systems.
Some of the neurons in the eye never depolarize, just send passive potentials around that trigger off axon hillock or just release nt based on passive potential
This is good for integrating. Passive signals close to each other in the membrane will add up. That integrates that information.
This is basically a graded potential.
Review: Action potentials
A ____ voltage applied at (1) moves the membrane potential toward a threshold (-___ mV) (2). At threshold, the __ ___ channels snap open for a brief period greatly ____ the membrane permeability to sodium, causing the membrane potential to drive toward the Nernst equilibrium potential for sodium (___mv). (3) ____ of sodium channels is delayed by sodium channel ____ while ___ ___ channels continue to open (4). Sodium channels begin to ____ (in ____ refractory period (5)) and Em moves toward ___+ Nernst potential (6) ____ beyond the resting state, when these K channels ___ the membrane goes back to the resting potential (7).
Absolute refractory period ___ ms
relative refractory period about ___ms
Action potential: Another way we can send ___ down a neuron.
Send info down the axon as an ___ or ___ depolarization of the membrane.
Membrane potential rests around -___ mV
Put in some kind of depolarizing pulse that causes the voltage to push twd a more positive level
At some point there will be a critical threshold for depolarization (-50)
When that happens the ion channels in the membrane open up. Snap open violently.
All of the Na channels open up
Equilibrium potential, if we just had Na on the cell would be +61 mV
When AP fires, all the Na channels open up and the membrane potential drives twd +61 but it never makes it
At this point we have some K channels hyperpolarizing opening up and Na channels are deactivating.
K equilibrium is a hyperpolarizing. (more negative then resting)
Drives twd -90.
To get an AP you have to get a synchrony of these channels opening and inactivation occurring
Na channels have an inactivation component so some drugs will ____ the Na ____.
Clinically useful.
(____ drugs) slow down the whole process
The Na/K pump: pumps K in and Na out.
Inside cell has high K
Outside cell has high Na
[] gradient forces ions to move thru these channels down the gradient
Pump reestablishes the gradient if we fire the cell too much
Review: Action potentials
A depolarizing voltage applied at (1) moves the membrane potential toward a threshold (-55 mV) (2). At threshold, the fast sodium channels snap open for a brief period greatly increasing the membrane permeability to sodium, causing the membrane potential to drive toward the Nernst equilibrium potential for sodium (+61mv). (3) Recovery of sodium channels is delayed by sodium channel inactivation while slower potassium channels continue to open (4). Sodium channels begin to reactivated (in relatively refractory period (5)) and Em moves toward K+ Nernst potential (6) hyperpolarized beyond the resting state, when these K channels close the membrane goes back to the resting potential (7).
Absolute refractory period .5-.8 ms relative refractory period about 2 ms
Action potential: Another way we can send information down a neuron.
Send info down the axon as an all or none depolarization of the membrane.
Membrane potential rests around -70 mV
Put in some kind of depolarizing pulse that causes the voltage to push twd a more positive level
At some point there will be a critical threshold for depolarization (-50)
When that happens the ion channels in the membrane open up. Snap open violently.
All of the Na channels open up
Equilibrium potential, if we just had Na on the cell would be +61 mV
When AP fires, all the Na channels open up and the membrane potential drives twd +61 but it never makes it
At this point we have some K channels hyperpolarizing opening up and Na channels are deactivating.
K equilibrium is a hyperpolarizing. (more negative then resting)
Drives twd -90.
To get an AP you have to get a synchrony of these channels opening and inactivation occurring
Na channels have an inactivation component so some drugs will prolong the Na inactivation. Clinically useful.
(Anticonvulsive drugs) slow down the whole process
The Na/K pump: pumps K in and Na out.
Inside cell has high K
Outside cell has high Na
[] gradient forces ions to move thru these channels down the gradient
Pump reestablishes the gradient if we fire the cell too much
Notes on Action Potentials
The action potential is “___ or ___”, you get the whole thing or you don’t get it (unlike passive potential in this respect and AP‘s are __ ___ for ____ information)
The action potential is like a ____ of light from a flash light.
You can flash many times before recharging the “battery”. _______ is the “battery” recharger and usually contributes ___ to the membrane potential during the ___ ___
Also, it is an ___-____ ____. Very few ions really cross the membrane during the potential changes but do create significant membrane potentials which ___ further____ of ions (at the Nernst potential).
The brain runs on ___ , most of the energy used by the brain is for ___.
The refractory period at the end of the AP may serve to help keep the action potential going the __ ___down the nerve.
They are all or none. For that reason we don’t really integrate other potentials with AP. This is the final firing of the integrated message.
Once it reachs -50, the rest of it will happen no matter what.
Na K atpase maintains the conc grad
One AP wont get rid of this gradient on its own.
Electrochemical equiliibrium. That means that you don’t completely diffuse conc gradient on single AP. You get a bunch of them out of a single charge.
Brain runs on glucose and most of that energy
Na/K atpase uses ATP from glucose
We can monitor the fcn of the brain but looking at ___ ___
Notes on Action Potentials
The action potential is “all or none”, you get the whole thing or you don’t get it (unlike passive potential in this respect and AP‘s are not useful for integrating information)
The action potential is like a flash of light from a flash light.
You can flash many times before recharging the “battery”. Na-K ATPase is the “battery” recharger and usually contributes little to the membrane potential during the action potential.
Also, it is an electro-chemical equilibrium. Very few ions really cross the membrane during the potential changes but do create significant membrane potentials which oppose further transfer of ions (at the Nernst potential).
The brain runs on glucose, most of the energy used by the brain is for messaging.
The refractory period at the end of the AP may serve to help keep the action potential going the right way down the nerve.
They are all or none. For that reason we don’t really integrate other potentials with AP. This is the final firing of the integrated message.
Once it reachs -50, the rest of it will happen no matter what.
Na K atpase maintains the conc grad
One AP wont get rid of this gradient on its own.
Electrochemical equiliibrium. That means that you don’t completely diffuse conc gradient on single AP. You get a bunch of them out of a single charge.
Brain runs on glucose and most of that energy
Na/K atpase uses ATP from glucose
We can monitor the fcn of the brain but looking at glucose utilization
Electric Potentials on the Nerve
Threshold-the membrane potential where a____ increase in ____ to ions occurs.
Action potential-an all or nothing nerve signal that ___ travels___ distances.
Passive Potential-Changes in membrane potential that do __ ____ result in an ___ ___ and are ___ potentials effective over a ___ distance.
EPSP-___ __ ___ ___
IPSP-___________
Most CNS drug effects are mediated through changes in ___ ___ ___. Drugs can increase or decrease ____ mediated by ___ ___ or via ____ or ohm’s law changes in nerve membrane function.
A few drugs may alter brain function by acting at other sites such as ___ or through actions on neuronal ___ or ____.
This puts together idea of passive potentials and action potentials.
In order to fire an action potential you may need a number of ___ ___
EPSP (Excitatory Post Synaptic Potential): one nerve talking to another and sending nt. Nt in little packets. Each packet results in a __ __ of depolarization. If you send enough packets you can get up to___. Then automatic Na channels open and boom you get AP. Then we start to deactivate Na channels and the whole thing comes back down.
If you are in the brain and you have multiple controls (say on a dendrite for firing a particular AP) then we might have IPSPs. They ____ the neuron. One way to do that is change K conductance.Open up K conducatnce. Drives twd -90
If cell is in hyperpolarized state, it takes more of an ____ tone to signal off
Patients who are already taking stimulants tend to be more hyperexcitable, more crazy than other patients. If you are trying to depress there nerves, it takes more treatment to get them into a calm state
EPSP is generallly a ___ ___ often created by __ ___
These EPSPs and IPSPs can add up. One right after another,,,they will cancel each other out.
You might be able to suppress neuron firing if you put enough IPSPs in time
Electric Potentials on the Nerve
Threshold-the membrane potential where a nonlinear increase in permeability to ions occurs.
Action potential-an all or nothing nerve signal that quickly travels long distances.
Passive Potential-Changes in membrane potential that do not necessarily result in an action potential and are graded potentials effective over a short distance.
EPSP-Excitatory Post Synaptic Potential
IPSP-Inhibitory Post Synaptic Potential
Most CNS drug effects are mediated through changes in neruonal action potentials. Drugs can increase or decrease processes mediated by action potentials or via passive or ohm’s law changes in nerve membrane function.
A few drugs may alter brain function by acting at other sites such as glia or through actions on neuronal stability or existence.
This puts together idea of passive potentials and action potentials.
In order to fire an action potential you may need a number of depolarizing pulses
EPSP (Excitatory Post Synaptic Potential): one nerve talking to another and sending nt. Nt in little packets. Each packet results in a small amt of depolarization. If you send enough packets you can get up to threshold. Then automatic Na channels open and boom you get AP. Then we start to deactivate Na channels and the whole thing comes back down.
If you are in the brain and you have multiple controls (say on a dendrite for firing a particular AP) then we might have IPSPs. They hyperpolarize the neuron. One way to do that is change K conductance.Open up K conducatnce. Drives twd -90
If cell is in hyperpolarized state, it takes more of an excitatory tone to signal off
Patients who are already taking stimulants tend to be more hyperexcitable, more crazy than other patients. If you are trying to depress there nerves, it takes more treatment to get them into a calm state
EPSP is generallly a graded potential often created by synaptic release
These EPSPs and IPSPs can add up. One right after another,,,they will cancel each other out.
You might be able to suppress neuron firing if you put enough IPSPs in time
Peripheral Fibers
•The speed of neuron transmission increases with:
–Increased ___ ___ (reduces intracelluar ___).
–Increased ___ of the myelin sheath (decreases __ ___across the nerve membrane, which saves ___ because preserves the ____ over ____ distances)
Increase the lumen that decreases the resistance within the neuron.
Giant squid neurons are used in neurophysiology all the time. They have huge lumens so fire off really fast
Myelin: insulator on outside of membrane
Peripheral Fibers
•The speed of neuron transmission increases with:
–Increased axon diameter (reduces intracelluar resistance).
–Increased thickness of the myelin sheath (decreases current loss across the nerve membrane, which saves energy because preserves the voltage over longer distances)
Increase the lumen that decreases the resistance within the neuron.
Giant squid neurons are used in neurophysiology all the time. They have huge lumens so fire off really fast
Myelin: insulator on outside of membrane
Myelinated Fiber Conduction.
- In myelinated fibers the myelin acts as an ____ with Nodes of Ranvier where the membrane is ___.
- The action potential jumps down the nerve from node to node, ____ only occurs at the nodes so its more ___,
Myelinated nerve is efficient and its fast.
We only ____ at points along the nerve called nodes of ranvier
When we fire the nerve this one may depolarize and its graded potential. If its high enough here it will be able to depolarize this node.
If the graded potential isn’t ____ too much, it can trigger off ___ in this one
That one fires off, we got a big pulse and then the next one fires and fires and fires
Instead of going down the nerve in a fuse, its ____
Myelinated Fiber Conduction.
- In myelinated fibers the myelin acts as an insulator with Nodes of Ranvier where the membrane is exposed.
- The action potential jumps down the nerve from node to node, repolarization only occurs at the nodes so its more efficient.
Myelinated nerve is efficient and its fast.
We only depolarize at points along the nerve called nodes of ranvier
When we fire the nerve this one may depolarize and its graded potential. If its high enough here it will be able to depolarize this node.
If the graded potential isn’t degraded too much, it can trigger off firing in this one
That one fires off, we got a big pulse and then the next one fires and fires and fires
Instead of going down the nerve in a fuse, its hopping
Myelinated Fibers.
•Myelination of peripheral axons.
–Coated by ____ sheaths (____), remnants of ___ ___ ___.
–Node of Ranvier – those areas ____ the areas of myelin produced by different Schwann cells.
–___ __ are clustered at the nodes and do not exist____ the myelination. The nodes act like ____ stations for the axon signal to move it ___ the nerve.
(d) The alignment of proteins subdomains in relation to morphological features of the axoglial apparatus in the PNS demonstrates that sodium channels (red in the second panel) are restricted to the node of Ranvier and are flanked by the caspr paranodal domain (red in the third panel). Potassium channels (green in the third panel) are localized distal to the caspr “collar” in the juxtaparanodal region. Schmidt-Lanterman incisures contain the myelin associated glycoprotein (green in the second panel). Adapted from Arroyo and Scherer (2000).
Liliana Pedraza, Jeffrey K. Huang,and David R. Colman1
The Corinne Goldsmith
Organizing Principles Viewpoint of the Axoglial Apparatus
Neuron, Vol. 30, 335–344, May, 2001, Copyright 2001 by Cell Press
Here is myelinated nerve
Look for Na channels with a new dye
Na channels only exist in ___ of ____
K channels are pretty much only around the nodes of ranvier too.
The only place that has these electrically active Na/K channels is at NOR
The purpose of those channels is to generate a ____ voltage that can then send the signal to the next NofR
Myelinated Fibers.
•Myelination of peripheral axons.
–Coated by Schwann sheaths (neurolemma), remnants of Schwann cell membrane.
–Node of Ranvier – those areas between the areas of myelin produced by different Schwann cells.
–Ion channels are clustered at the nodes and do not exist under the myelination. The nodes act like booster stations for the axon signal to move it down the nerve.
(d) The alignment of proteins subdomains in relation to morphological features of the axoglial apparatus in the PNS demonstrates that sodium channels (red in the second panel) are restricted to the node of Ranvier and are flanked by the caspr paranodal domain (red in the third panel). Potassium channels (green in the third panel) are localized distal to the caspr “collar” in the juxtaparanodal region. Schmidt-Lanterman incisures contain the myelin associated glycoprotein (green in the second panel). Adapted from Arroyo and Scherer (2000).
Liliana Pedraza, Jeffrey K. Huang,and David R. Colman1
The Corinne Goldsmith
Organizing Principles Viewpoint of the Axoglial Apparatus
Neuron, Vol. 30, 335–344, May, 2001, Copyright 2001 by Cell Press
Here is myelinated nerve
Look for Na channels with a new dye
Na channels only exist in nodes of ranvier
K channels are pretty much only around the nodes of ranvier too.
The only place that has these electrically active Na/K channels is at NOR
The purpose of those channels is to generate a booster voltage that can then send the signal to the next NofR
Action Potential Conduction
Action potential on unmyelinated nerve
-like a ___ ___. Ion channels ___ ___ the fiber.
Action potential on myelinated nerve
____ from Node of Ranvier to the next node of Ranvier, called “____ ____”.
Dendrites usually conduct by ____ potentials but in this example a “___ ___” sits at a ____ with active ion Na+ channels that boost the signal to __ __ and __ ___ (which has many active sodium ion channels).
Diifferent kinds of neurons in the brain
Some are unmyelinated
These have Na/K channels all along the nerve
Electric potential is like a fuse and just rolls down the nerve
If its mylenated nerveà soltatory conduction
Jumps from one node to the next
We now know that in CNS, even on dendritic trees, if you want to boost up a signal in dendritic tree so that it makes it to the axon hillock (part of nerve that ___ the ___), you can have ___ in the ___ ___ which creates a ___ and allows the signal to get down to the axon hillock
This can occur anywhere you want AP to occur
Action Potential Conduction
Action potential on unmyelinated nerve
-like a burning fuse. Ion channels all along
the fiber.
Action potential on myelinated nerve
hop from Node of Ranvier to the next node
of Ranvier, called “Saltatory conduction”.
Dendrites usually conduct by passive
potentials but in this example a “booster station” sits at a junction with active ion Na+ channels that boost the signal to cell body and axon hillock (which has many active sodium ion channels).
Diifferent kinds of neurons in the brain
Some are unmyelinated
These have Na/K channels all along the nerve
Electric potential is like a fuse and just rolls down the nerve
If its mylenated nerveà soltatory conduction
Jumps from one node to the next
We now know that in CNS, even on dendritic trees, if you want to boost up a signal in dendritic tree so that it makes it to the axon hillock (part of nerve that makes the AP), you can have channels in the dendritic tree which creates a boost and allows the signal to get down to the axon hillock
This can occur anywhere you want AP to occur
Axon Hillock Initiates the Axonal Action Potential
- Cerebellar Purkinje Cell
- NaV=Red, voltage gated ___ ___
- DAPI Stains __ __ ___
- Green=KCNQ3 type ____channels
- Merge: Cell body with axon initial segment decorated with ion channels. This is where the action potential ____. (Note: cell bodies usually have depolarizing ____ channels.)
nucleic acid-binding dye 4,6-diamidino-2-phenylindole dihydrochloride (DAPI)
F: Na channels red
Q3: K channels green
Blue: Nucleus
You can see there are a lot of K channel binding in the nucleus but its also seen densely in the axon hillock region
Axon hillock has the ___ ___ for depolarization anywhere on the cell.
What we have to do is ____ all the information of dendrites and the final soln gets sent down the ___ ___ and that triggers off ___ down the cell
The cell bodies can actually____ as well.
The positive potential carrier on cell bodies is ____
More extracellular than intracellular 1000:1
Theres a couple places we see these Ca mediated currents. One is in the cell body. Other is at the ___ ___
The currents at the synaptic jcns are carried by Ca instead of Na
Axon Hillock Initiates the Axonal Action Potential
- Cerebellar Purkinje Cell
- NaV=Red, voltage gated sodium channel
- DAPI Stains cell bodies blue
- Green=KCNQ3 type potassium channels
- Merge: Cell body with axon initial segment decorated with ion channels. This is where the action potential initiates. (Note: cell bodies usually have depolarizing Ca++ channels.)
nucleic acid-binding dye 4,6-diamidino-2-phenylindole dihydrochloride (DAPI)
F: Na channels red
Q3: K channels green
Blue: Nucleus
You can see there are a lot of K channel binding in the nucleus but its also seen densely in the axon hillock region
Axon hillock has the lowest threshold for depolarization anywhere on the cell.
What we have to do is integrate all the information of dendrites and the final soln gets sent down the axon hillock and that triggers off AP down the cell
The cell bodies can actually depolarize as well.
The positive potential carrier on cell bodies is Ca.
More extracellular than intracellular 1000:1
Theres a couple places we see these Ca mediated currents. One is in the cell body. Other is at the synaptic ending
The currents at the synaptic jcns are carried by Ca instead of Na
Axonal Transport
Materials from the __ __ can be transported to various locations on the cell through multiple ___
An important process is ____ transport of materials along ____. This schematic depicts endosomes produced near the cell soma being transported by the____ protein toward the end of the ___. Also, material ___ ___ of the membrane at the end of the ____ can be retrogradely transported toward the ____ by ____ motors.
Neurons are ____ manufacturing engines
It synthesizes the proteins from DNA/RNAà Golgi
Problem: Neurons are ___ ___
Have to get those proteins down the axon.
They have little ___s and little ___
Proteins are made and turned into little cargo vesicles
These use ___ for there E source
Motors walk the cargo down the axon tubule.
2 types of motors:
____: carries stuff from ___ to ___
___: ___ to ___
Axonal Transport
Materials from the cell body can be transported to various locations on the cell through multiple processes.
An important process is biomotor transport of materials along neurotubles. This schematic depicts endosomes produced near the cell soma being transported by the kinesin protein toward the end of the axon. Also, material pinched off of the membrane at the end of the axon can be retrogradely transported toward the nucleus by dynein motors.
Neurons are protein manufacturing engines
It synthesizes the proteins from DNA/RNAà Golgi
Problem: Neurons are really long
Have to get those proteins down the axon.
They have little tracks and little engines.
Proteins are made and turned into little cargo vesicles
These use ATP for there E source
Motors walk the cargo down the axon tubule.
2 types of motors:
Kinases: carries stuff from cell body to synapsis
Dynein: periphery to cell body.
Axoplasmic Transports
•What is transported?
–___(isoform parts)
–___
–__ ___
–___ __ ___
–___ __ ___
–Stuff from ___ ___ to ____ (____ transport) example= ____ or rabies viruses.
We have axon transport mechanisms in the cell that are important for maintence of the cell but also for repair of damage
Cell surface elementsà stuff from cell surface to the nuclues. That would be like damage control or garbage collecting
Sometimes stuff from gaps bw the cells, synapses or areas where there isn’t any structure, there is virus hanging out out there and these transport mechanism can…bc the membrane is always pinching off membrane and bringing it ___ the cell so that stuff gets picked up from the transport processes and gets transported back to the ____ where sometimes it can cause disease
Axoplasmic Transports
•What is transported?
–Proteins (isoform parts)
–Mitochondria
–Ion channels
–Cell surface elements
–Synaptic vesicle proteins
–Stuff from cell surface to nucleus (retrograde transport) example= herpes or rabies viruses.
–
–
We have axon transport mechanisms in the cell that are important for maintence of the cell but also for repair of damage
Cell surface elementsà stuff from cell surface to the nuclues. That would be like damage control or garbage collecting
Sometimes stuff from gaps bw the cells, synapses or areas where there isn’t any structure, there is virus hanging out out there and these transport mechanism can…bc the membrane is always pinching off membrane and bringing it intot eh cell so that stuff gets picked up from the transport processes and gets transported back to the nucleus where sometimes it can cause disease
Peripheral fibers - _____ flow.
•Cellular elements for the axon originated in the____ ___ and travels by process known as axoplasmic flow of ___ ___
–Fast 100 to 400 mm /day
–Slow 0.25 to 3 mm/day
–Intermediate
There are multiple transport mechanisms in cells. You can measure ___ __.
Some fast some slow and some in bw.
Peripheral fibers - axoplasmic flow.
•Cellular elements for the axon originated in the cell body and travels by process known as axoplasmic flow of various speeds.
–Fast 100 to 400 mm /day
–Slow 0.25 to 3 mm/day
–Intermediate
•
There are multiple transport mechanisms in cells. You can measure different rates Some fast some slow and some in bw.
•The Importance of the Golgi Transports…
Endoplasmic reticulum and Golgi make, package and send materials down ___ ___.
Orthograde transport is used to ___ ___ ___ (___)
Retrograde transport used to ____ membrane elements.
Membrane ___ ___ and ____to cell or ____ . (___)
Vacher H, Trimmer J Diverse roles for auxiliary subunits in phosphorylation
dependent regulation of mammalian brain voltage-gated potassium channels.
Eur J Physiol (2011) 462:631–643
You are taking DNAà RNAà proteinsà Golgià put it on a transporter and it is transported to where it is needed.
Imagine if you take a nerve and you compress it in the middle. All the cellular elements build up on the proximal side before the constriction. Down stream there wont be any bc they can’t go down there. That can cause ___ ___ sometimes
•The Importance of the Golgi Transports…
Endoplasmic reticulum and Golgi make, package and send
materials down nerve processes. Orthograde transport is used to build membrane elements (Kinesin)
Retrograde transport used
to renew membrane elements.
Membrane pinched off and returned
to cell or nucleus . (Dynein)
Vacher H, Trimmer J Diverse roles for auxiliary subunits in phosphorylation
dependent regulation of mammalian brain voltage-gated potassium channels.
Eur J Physiol (2011) 462:631–643
You are taking DNAà RNAà proteinsà Golgià put it on a transporter and it is transported to where it is needed.
Imagine if you take a nerve and you compress it in the middle. All the cellular elements build up on the proximal side before the constriction. Down stream there wont be any bc they can’t go down there. That can cause chronic pain sometimes
Membrane Oragnelle Processing
Vacher H, Trimmer J Diverse roles for auxiliary subunits in phosphorylation
dependent regulation of mammalian brain voltage-gated potassium channels.
Eur J Physiol (2011) 462:631–643
Look at picture in red.
Pmàendocytic vesicles: sometimes we suck it back up and carry it back to the nucleus
Membrane Oragnelle Processing
Vacher H, Trimmer J Diverse roles for auxiliary subunits in phosphorylation
dependent regulation of mammalian brain voltage-gated potassium channels.
Eur J Physiol (2011) 462:631–643
Look at picture in red.
Pmàendocytic vesicles: sometimes we suck it back up and carry it back to the nucleus
Synapse.
- Presynaptic terminals with synaptic vesicles, synaptic cleft, postsynaptic membrane and receptors.
- Neurotransmitters and synaptic events.
- Excitatory vs. inhibitory transmission.
Synapse: Where these neurons ____to each other
Gap bw 2 neurons.
Synaptic vesicles have nt material
Synaptic cleft: ____
Synapse.
- Presynaptic terminals with synaptic vesicles, synaptic cleft, postsynaptic membrane and receptors.
- Neurotransmitters and synaptic events.
- Excitatory vs. inhibitory transmission.
Synapse: Where these neurons talk to each other
Gap bw 2 neurons.
Synaptic vesicles have nt material
Synaptic cleft: the space
Notes.
- When the action potential reaches the ___ ___ (___synaptic) it generally triggers an ___ ___ current that activates the machinery that ____ the neuro- transmitter.
- ____ potential can ____ neurotransmitters too, if the potential is ___ enough. This is common in ___ receptors.
Synaptic bouton at the___ of the____
In some cases it’s not an AP, it’s a passive potential
If its large enough to induce these Ca channels then a synapse can fire even though there is no AP to precipitate. Its just a matter of getting the voltage up high enough to where nt will be released
Notes.
- When the action potential reaches the synaptic bouton (presynaptic) it generally triggers an inward Ca++ current that activates the machinery that releases the neuro- transmitter.
- Passive potential can release neurotransmitters too, if the potential is large enough. This is common in sensory receptors.
Synaptic bouton at the end of the axon
In some cases it’s not an AP, it’s a passive potential
If its large enough to induce these Ca channels then a synapse can fire even though there is no AP to precipitate. Its just a matter of getting the voltage up high enough to where nt will be released
Neurotransmission
Example Cholinergic
- Vesicle ____ (From Golgi or other)
- Transmitter ____ (Presynaptic or in vesicle)
- Transmitter in ____ (Held by ___ gradient or ___ ___)
- Presynaptic ___ ___ channels – Action potential triggers ____ of CA to ____neurotransmitter
- Presynaptic auto receptors (Can___ ___)
- Presynaptic reuptake (Different in cholinergic synapses-___ only)
- Synapse- (A physical ___)
- Post synaptic receptor actions- ion channels or other. Many types, these transmit the ____ to second cell.
- Transmitter action termination- Several processes- ____, _____, destruction by ___-depends on ___ and ____. For acetylcholine almost exclusively ___
Neurotransmission on a model system (Chollinergic)
This is a bad model system because Handles nt differently than all the rest of the cells
But it’s a very commmon type of sys
First need to Form vesicles and synthesize nt that needs to go into the vesicle
In the case of Ach, the action of Ach is almost entirely terminated by catabolism of Ach. In most transmitter systems you actually take the nt back up. What you reuptake in this system is actually choline. Choline has Acetyl coA molecule attached to it to form Ach.
Then there are pumps in the ____ wall
Sometimes its an antiporter. H for Ach to go into the vesicle.
There are more than one kind of pump. This is just an ex
We’ve got the nt in the vesicle
AP comes down and causes Ca current to come into presynaptic nerve ending and then various molecules on the presynaptic nerve membrane begin to combine with molecules on the synaptic vesicles
These bind and fuse and contents of synaptic vesicle is released onto the gap (synaptic cleft)
Then the nt will diffuse to the receptors on post synaptic cell.
Nt activates some kind of events in the post synaptic cell
For Ach, we have enzyme, _____. Rips the acetyl group off of choline. Choline is not a good transmitter. Wipes out the transmitter action when it does that.
In most neurons you have these catabolic enzymes around
Many neurons have presynaptic receptors for the ____ nt they release. They are called ____
The autoreceptors regulate the ___ and ___ of nt release.
Sometimes they have ____. Like a recptor for an opiate on a chollinergic neuron. Some___ nt system can regulate the ____ of nt from this particular cell
Transporter for choline: those are called reuptake transporters. All cells have those for different nt. There are in the central part of this whole synaptic depolarization process.
Neurotransmission
Example Cholinergic
- Vesicle formation (From Golgi or other)
- Transmitter Synthesis (Presynaptic or in vesicle)
- Transmitter in Vesicles (Held by H+ gradient or active pumps)
- Presynaptic Calcium ion channels – Action potential triggers influx of CA to release neurotransmitter
- Presynaptic auto receptors (Can regulate release)
- Presynaptic reuptake (Different in cholinergic synapses-choline only)
- Synapse- (A physical gap)
- Post synaptic receptor actions- ion channels or other. Many types, these transmit the action to second cell.
- Transmitter action termination- Several processes- Catabolism, reuptake, destruction by glia-depends on cell and neurotransmitter. For acetylcholine almost exclusively catabolism.
Neurotransmission on a model system (Chollinergic)
This is a bad model system because Handles nt differently than all the rest of the cells
But it’s a very commmon type of sys
First need to Form vesicles and synthesize nt that needs to go into the vesicle
In the case of Ach, the action of Ach is almost entirely terminated by catabolism of Ach. In most transmitter systems you actually take the nt back up. What you reuptake in this system is actually choline. Choline has Acetyl coA molecule attached to it to form Ach.
Then there are pumps in the vesicle wall
Sometimes its an antiporter. H for Ach to go into the vesicle.
There are more than one kind of pump. This is just an ex
We’ve got the nt in the vesicle
AP comes down and causes Ca current to come into presynaptic nerve ending and then various molecules on the presynaptic nerve membrane begin to combine with molecules on the synaptic vesicles
These bind and fuse and contents of synaptic vesicle is released onto the gap (synaptic cleft)
Then the nt will diffuse to the receptors on post synaptic cell.
Nt activates some kind of events in the post synaptic cell
For Ach, we have enzyme, achesterase. Rips the acetyl group off of choline. Choline is not a good transmitter. Wipes out the transmitter action when it does that.
In most neurons you have these catabolic enzymes around
Many neurons have presynaptic receptors for the same nt they release. They are called autoreceptors.
The autoreceptors regulate the rate and degree of nt release.
Sometimes they have heteroreceptors. Like a recptor for an opiate on a chollinergic neuron. Some other nt system can regulate the release of nt from this particular cell
Transporter for choline: those are called reuptake transporters. All cells have those for different nt. There are in the central part of this whole synaptic depolarization process.
Synapse-The Place Where Neurons
Communicate with Each Other
A prototype synapse diagram is in the middle. To the left is an electron micrograph showing the corresponding structures indicated in the figure.
In the presynaptic terminal vesicles (little vessels) containing the transmitter substances are held, waiting for an action potential to depolarize the presynaptic nerve ending.
Depolarization of the presynaptic ending permits ___ ___ to enter the presynaptic ending, activating a ____ of proteins that pull the ____ into the presynaptic membrane and release its contents into the synaptic ___.
The transmitters diffuse across the synaptic cleft. On the postsynaptic membrane are receiver molecules. These may be ___ ___ ion channels or other kinds of receptors.
Once the message is received a wide variety of changes in the post synaptic nerve can occur from ____ of the post synaptic nerve to initiating a sequence of steps that lead to a ____ of the postsynaptic nerve. The figure in the lower right is from a review discussing how certain drugs can lead to ____ of the nerves in the brain to relieve ___ ___.
Südhof TC., The presynaptic active zone.
Neuron. 2012 Jul 12;75(1):11-25.
Postsynaptic receptor density: that’s the receptor tissue
Synaptic vesicles have a variety of different proteins and machinery associated with them which allows them to be dragged into the presymaptic membrane, opened up and contents released into synaptic cleft
Highly regulated process.
There are a bunch of different proteins here that are modulating maintaining the process of delivering the nt.
Post synaptic side is also fairly complex.
There are several postsynaptic receptors on the postsynaptic side.
Nt will active some of them
These nt can cause a series of biochemical changes to occur in the cell.
We call those ___ ___ ____: Rxns that occur inside the cell following the arrival of the nt onto the post synaptic cell
Synapse-The Place Where Neurons
Communicate with Each Other
A prototype synapse diagram is in the middle. To the left is an electron micrograph showing the corresponding structures indicated
in the figure. In the presynaptic terminal vesicles (little vessels) containing the transmitter substances are held, waiting for an action potential to depolarize the presynaptic nerve ending. Depolarization of the presynaptic ending permits calcium ions to enter the presynaptic ending, activating a synaptosome of proteins that pull the vesicles into the presynaptic membrane and release its contents into the synaptic cleft. The transmitters diffuse across the synaptic cleft. On the postsynaptic membrane are receiver molecules. These may be ligand gated ion channels or other kinds of receptors. Once the message is received a wide variety of changes in the post synaptic nerve can occur from depolarization of the post synaptic nerve to initiating a sequence of steps that lead to a remodeling of the postsynaptic nerve. The figure in the lower right is from a review discussing how certain drugs can lead to remodeling of the nerves in the brain to relieve psychiatric depression.
Südhof TC., The presynaptic active zone.
Neuron. 2012 Jul 12;75(1):11-25.
Postsynaptic receptor density: that’s the receptor tissue
Synaptic vesicles have a variety of different proteins and machinery associated with them which allows them to be dragged into the presymaptic membrane, opened up and contents released into synaptic cleft
Highly regulated process.
There are a bunch of different proteins here that are modulating maintaining the process of delivering the nt.
Post synaptic side is also fairly complex.
There are several postsynaptic receptors on the postsynaptic side.
Nt will active some of them
These nt can cause a series of biochemical changes to occur in the cell.
We call those secondary metabolism cascades: Rxns that occur inside the cell following the arrival of the nt onto the post synaptic cell
Synaptic Vesicle Proteins
Proteins for ____ - e.g VGlut1/2 loads glutamate (___ anti-porter)
Proteins for _____ - (cATPase a hydrogen ion transporter)
Proteins for ____ (VAMP, synaptotagmin)
SV2- binds ____ (target for an ____ drug)
VAMP-vesicle associated membrane protein
SV2-synaptic vesicle glycoprotein (target for Botulinum toxin and anticonvulsant levitriacetam)
Synaptotagmin- a calcium binding protein involved in release of synaptic vesicles
Synaptophysin, synaptogyrin- help regulate vesicle exocytosis but functions not clear yet
vATPase- ATP drive proton pump that ____ the vesicle contents.
CSP-cystiene string protein
vGlut-vesicular Glutamate ____ protein
Composition of isolated synaptic boutons reveals the amounts of vesicle trafficking proteins.
Wilhelm BG, Mandad S, Truckenbrodt S, Kröhnert K, Schäfer C, Rammner B, Koo SJ, Claßen GA, Krauss M, Haucke V, Urlaub H, Rizzoli SO.
Science. 2014 May 30;344(6187):1023-8. doi: 10.1126/science.1252884.
Wen-Pin Chang1 and Thomas C. Südhof1,2,3,4
SV2 Renders Primed Synaptic Vesicles Competent for Ca2+-Induced Exocytosis
The Journal of Neuroscience, 28 January 2009, 29(4): 883-897
Synaptic vesicle proteins. There is quite a few.
Some to get nt into the vesicle
Most nt are amines (base). Some proteins are there to create an environment to acidify the inside of the vesicle.
That traps the nt inside bc its ___
There are porteins for fusion
SV2 is the one that botox binds to. It’s a ____ of synaptic transmission. If you want to paralyze someone, tie up their SV2 youre wrinkles will go away and you’ll stop breathing
Migraines from temporallis muscle being hyperpolarized. Shoot those muscles with botox to relieve headaches.
Synaptic Vesicle Proteins
Proteins for loading - e.g VGlut1/2 loads glutamate (hydrogen anti-porter)
Proteins for acidification - (cATPase a hydrogen ion transporter)
Proteins for fusion (VAMP, synaptotagmin)
SV2- binds Botox, (target for an anticonvulsant drug)
VAMP-vesicle associated membrane protein
SV2-synaptic vesicle glycoprotein (target for Botulinum toxin and anticonvulsant levitriacetam)
Synaptotagmin- a calcium binding protein involved in release of synaptic vesicles
Synaptophysin, synaptogyrin- help regulate vesicle exocytosis but functions not clear yet
vATPase- ATP drive proton pump that acidifies the vesicle contents.
CSP-cystiene string protein
vGlut-vesicular Glutamate uptake protein
Composition of isolated synaptic boutons reveals the amounts of vesicle trafficking proteins.
Wilhelm BG, Mandad S, Truckenbrodt S, Kröhnert K, Schäfer C, Rammner B, Koo SJ, Claßen GA, Krauss M, Haucke V, Urlaub H, Rizzoli SO.
Science. 2014 May 30;344(6187):1023-8. doi: 10.1126/science.1252884.
Wen-Pin Chang1 and Thomas C. Südhof1,2,3,4
SV2 Renders Primed Synaptic Vesicles Competent for Ca2+-Induced Exocytosis
The Journal of Neuroscience, 28 January 2009, 29(4): 883-897
Synaptic vesicle proteins. There is quite a few.
Some to get nt into the vesicle
Most nt are amines (base). Some proteins are there to create an environment to acidify the inside of the vesicle.
That traps the nt inside bc its ionized
There are porteins for fusion
SV2 is the one that botox binds to. It’s a modulator of synaptic transmission. If you want to paralyze someone, tie up their SV2 youre wrinkles will go away and you’ll stop breathing
Migraines from temporallis muscle being hyperpolarized. Shoot those muscles with botox to relieve headaches.
Synaptosome Proteins
There around ____ synaptic related proteins. The functions of synapses are highly ____ yet may fail, resulting in ____
The images developed by Wilhelm et al 2014 demonstrate some of this complexity. You can see a video on Youtube
Composition of isolated synaptic boutons reveals the amounts of vesicle trafficking proteins.
Wilhelm BG, Mandad S, Truckenbrodt S, Kröhnert K, Schäfer C, Rammner B, Koo SJ, Claßen GA, Krauss M, Haucke V, Urlaub H, Rizzoli SO.
Science. 2014 May 30;344(6187):1023-8. doi: 10.1126/science.1252884.
It’s a complex process
Synaptosome Proteins
There around 300,000 synaptic related proteins. The functions
of synapses are highly regulated, yet may fail, resulting disease.
The images developed by Wilhelm et al 2014 demonstrate some of this complexity. You can see a video on Youtube
Composition of isolated synaptic boutons reveals the amounts of vesicle trafficking proteins.
Wilhelm BG, Mandad S, Truckenbrodt S, Kröhnert K, Schäfer C, Rammner B, Koo SJ, Claßen GA, Krauss M, Haucke V, Urlaub H, Rizzoli SO.
Science. 2014 May 30;344(6187):1023-8. doi: 10.1126/science.1252884.
It’s a complex process
Some Pre-Synaptic proteins
Calcium ion influx triggers ____
Voltage Gated Calcium Ion channels with ____ facilitate ____ action
Synaptotagmin-___ ___
SNARE-complex-on ____ (VAMP-synaptobrevin)
SNAP complex-on ____ (SNAP-Complexin-Syntaxin-Munc)
These proteins + calcium attach synaptic vesicles to the cell membrane and trigger dumping of the synaptic vesicle contents-which includes ___ ___ just the transmitter. Transmitter, ___, ___, ____, peptides, etc.)
VAMP-vesicle associated membrane protein
Synaptotagmin- a __ ___ protein involved in release of ___ ___
Synaptophysin, synaptogyrin- help regulate ___ ____ s but functions not clear yet
Munc-Mammal uncoordinated protein-needed for ____
Rab-Part of the Ras protein family –regulate synaptic ___ and binding to transports and processing ____ vesiciles
RIM- Rab3-interacting molecule
RIM-BP – RIM binding protein
Ca channel: allows Ca to come in and trigger off the events.
Rim proteins are _____. They interact with ____ that interacts with proteins on the synaptic vesicle
This form a commplex
Complex pulls the ____ into the cell
Some Pre-Synaptic proteins
Calcium ion influx triggers exocytosis
Voltage Gated Calcium Ion channels with RIMs facilitate Ca++ action
Synaptotagmin-Ca++ Sensor
SNARE-complex-on vesicle (VAMP-synaptobrevin)
SNAP complex-on membrane (SNAP-Complexin-Syntaxin-Munc)
These proteins + calcium attach
Synaptic vesicles to the cell membrane and trigger dumping of the synaptic vesicle contents-which includes more than just the transmitter. Transmitter, H+, ATP, proteins, peptides, etc.)
VAMP-vesicle associated membrane protein
Synaptotagmin- a calcium binding protein involved in release of synaptic vesicles
Synaptophysin, synaptogyrin- help regulate vesicle exocytosis but functions not clear yet
Munc-Mammal uncoordinated protein-needed for exocytosis
Rab-Part of the Ras protein family –regulate synaptic function and binding to transports and processing clathrin vesiciles
RIM- Rab3-interacting molecule
RIM-BP – RIM binding protein
Ca channel: allows Ca to come in and trigger off the events.
Rim proteins are modulators. They interact with munches that interacts with proteins on the synaptic vesicle
This form a commplex
Complex pulls the vesicle into the cell
The Stretching Membrane Problem
If synaptic vesicles are added to thepresynaptic membrane, why doesn’t it enlarge?
Various molecules cause parts of the membrane to __ ___ and return to the ___ of the presynaptic membrane (____).
The ___molecule (or other ___) are involved in the formation of these ___ vesicles.
What if there is something in the __ __ (e.g. viruses) when the vesicles are formed?
They may be ___ into the interior of the neuron (The neuron is ____ its environment).
If we take this vesicles and shove them in the Presynaptic membrane, the membrane will get really big.
What happens to extra membrane material. After it binds to the presynaptic membrane, there are some molecules such as clathrin and adaptin.
These pinch off chunks of membrane and pulls them inside the cell.
Constant process of pinching and pulling
Helps maintain the shape of the membrane after its depolarized a lot
The Stretching Membrane Problem
If synaptic vesicles are added to the
presynaptic membrane, why doesn’t it enlarge?
Various molecules cause parts of the membrane to pinch off and return to the inside of the presynaptic membrane (endocytosis).
The clathrin molecule (or other adaptins)
are involved in the formation of these
endocytic vesicles.
What if there is something in the synaptic gap (e.g. viruses) when the vesicles are formed?
They may be absorbed into the interior of the neuron (The neuron is tasting its environment).
If we take this vesicles and shove them in the Presynaptic membrane, the membrane will get really big.
What happens to extra membrane material. After it binds to the presynaptic membrane, there are some molecules such as clathrin and adaptin.
These pinch off chunks of membrane and pulls them inside the cell.
Constant process of pinching and pulling
Helps maintain the shape of the membrane after its depolarized a lot
Experiment on Calyx of Held-Mammalian Auditory Giant Synapse
Electrodes placed __ and ___ synaptically
Pre is fluorescent ___
Post is fluorescent ___
If ___ function is blocked, transmitter ___ is ___
Recall that in Parkinsons and Alzheimers, they get transynaptic transmission of toxic material (lipofusin)
Prions can reform cellular proteins into bad prion particles. Like a molecular infection that occurs. You can’t kill it.
Can lead to bovine spongy epelopathy.
Experiment
They looked at a neuron. The Mammalian Auditory Giant Synapse
With this system you can put an electrode in to pre and post synaptic side. Most synapses are super tiny and you could never get an electrode in. This one is big enough. They squirted dyes into one part and the other
They measured what happens when you fire off a bunch of ___
They asked: What if you prevent the cell from making nt, what happens to all that machinery involved in ____ the vesicles into the membrane and then ___ it.
Experiment on Calyx of Held-Mammalian Auditory Giant Synapse
Electrodes placed
Pre and post
synaptically
Pre is fluorescent green
Post is fluorescent red
If mitochondrial function is
blocked transmitter
release is exhausted.
Recall that in Parkinsons and Alzheimers, they get transynaptic transmission of toxic material (lipofusin)
Prions can reform cellular proteins into bad prion particles. Like a molecular infection that occurs. You can’t kill it.
Can lead to bovine spongy epelopathy.
Experiment
They looked at a neuron. The Mammalian Auditory Giant Synapse
With this system you can put an electrode in to pre and post synaptic side. Most synapses are super tiny and you could never get an electrode in. This one is big enough. They squirted dyes into one part and the other
They measured what happens when you fire off a bunch of AP
They asked: What if you prevent the cell from making nt, what happens to all that machinery involved in fusing the vesicles into the membrane and then recovering it.
