Synapses Flashcards
Synapse
Point of communication between two neurons
What are the two kinds of synapses?
- Chemical Synapse
- Electrical Synapse
Chemical Synapse (definition)
messages that are transmitted from one neuron to another by chemical neurotransmitters
Electrical Synapse (gap junctions)
- when ions are moved to adjacent cells through channels that are touching each other
- Gap is between synapses is super small: 3.5nm
- Because of small gap special protein channels connect the two cells which allows the positive current to go directly from presynaptic neuron to post
- Super fast
- Only has excitation, not inhibition
- used for fast transmissions like stress hormones
Two basic steps of Chemical Synapses
- Release of Neurochemicals by a presynaptic cell
- Reaction of post-synaptic cell to neurochemicals
9 Steps of Chemical Synapses
- We have vesicles filled with neurotransmitters that are carried by the microtubules
- AP reaches the presynaptic terminal
- Depolarization allows ion channels to open which allows Ca2+ into the cell as the calcium channels open
- Ca2+ causes vesicles to release from microtubules
- Exocytosis -Fusion of sacks of vesicles that have neurotransmitters with membranes/protein of presynaptic cell. When that happens, the neurotransmitters released and go to the synaptic gap
- Once it gets to the gap the postsynaptic receptors receive it and binds
- Neurotransmitters arrive, bind to the receptors, which opens an ion channel, which causes a change in postsynaptic potential when the ions from the surrounding environment enters
- An action potential is fired through the next cell as a result of opening of ion channels
- When u have sodium ions, they can go inside the cell and make it depolarized. If u have lots of sodium channels now being opened so I might reach threshold an action potential can be generated
- Neurotransmitter is inactivated or transported back into presynaptic terminal via retrograde support
Exocytosis
Fusion of sacks of vesicles that have neurotransmitters with membranes/protein of presynaptic cell. When that happens, the neurotransmitters released and go to the synaptic gap
Excitation and Inhibition
excitation
- happens in both electrical and chemical synapses
- increases likelihood that it will depolarize and fire an AP
inhibition
- happens only in chemical synapses
- decreases likelihood that it will fire an AP
What happens if something positive enters the post synpatic cell?
it will get closer to deploarization
What happens if something negative enters the post-synaptic cell?
it will get further away from depolarization
What happens if something positive exits the cell?
obvs it will become more negative
Auto receptors
feedback that the presynaptic neuron receives after the release of neurochemicals about its own level of activity
Receptors
special proteins embedded in the postsynaptic membrane that responds to chemical messengers
Recognition molecules
molecule inside the receptors that bind to specific types of neurochemicals
Receptors- 3D proteins- two kinds
- Ionotropic
- Metabotropic
Ionotropic
- when Ion channels open fast and directly. As soon as the receptors catches a molecule of the neurochemical the ion channel opens.
- These are also Ion channels, they bind, channels open.
Metabotropic
-
Metabotropic- indirect. Extends to extracellular protein and G proteins on the intracellular.
- Neurotransmitter binds to a receptor
- Receptor releases a g protein which binds to an ion channel
- The G-protein causes the ion-channel to open and ion passes through
- Might be slower but allows for so many more functions
- This is just a receptor. It still causes the confirmational change when neurotransmitters bind to it which will activate a nearby ion channel. The g protein on it will cause a nearby channel to open.
Second messengers
When the molecules of neurochemicals become bound at reception site the G protein separates from the receptor area and goes to another part of Postsynaptic cell which causes the ion channels to activate additional chemical messengers in postsynaptic cell which are:
Three different ways a message can be terminated:
- Diffusion- there are all those neurochemicals and astrocytes there, so it makes it go away from areas
- Deactivated by enzymes in the synaptic gap
- Reuptake- the presynaptic membrane uses its own set of receptors called transporters that takes all the neurochemicals back, packages them up, and returns them to the interior of the axon terminals
EPSP
- A small depolarization produced in the post-synaptic cell as a result from an input from a presynaptic cell
- Result from opening of ligated rather that voltage dependent sodium channels in the postsynaptic membrane. The inward travel of pos sodium ions make the depolarization happen too
- EPSP’s are not all or none rather- graded- as opposed to AP’s that last 1ms these last 5-10ms
- Open sodium channels
IPSP
- Result from opening of ligulated rather that voltage dependent sodium channels in the postsynaptic membrane
- Inward movement of Cl- and outward movement of K+
- Since the Cl- is negative and it goes into the postsynaptic cell it makes the inside negative as can be which makes it hyperpolarize
- Open either chloride (Cl-; into neuron) or potassium (K+; out of neuron) channels
- “You lose something positive, it becomes more negative”
What determines whether a post-synaptic neuron will have an EPSP or an IPSP?
- The type of neurotransmitter delivered to it by the pre-synaptic neurons
Neural Integration
- When the neuron decides whether or not to send an AP based on excitatory and inhibitory messages
Spatial Summation
an action potential will only be fired when it gets up to threshold which can result from a summation of many different charger from all around the cell
Temporal summation
when there is so much charge in one synapse, that post synaptic cell is triggered by that one synapse
Neuromodulation- 3 types
- Axo-axonic synapses- pre and post synaptic elements are axons
- Presynaptic facilitation- if the presynaptic neuron increases the amount of neurochemical released
- Presynaptic inhibition- of the presynaptic neuron decreases the amount of neuro chemical released
Point of communication between two neurons
Synapse
- Chemical Synapse
- Electrical Synapse
What are the two kinds of synapses?
messages that are transmitted from one neuron to another by chemical neurotransmitters
Chemical Synapse (definition)
- when ions are moved to adjacent cells through channels that are touching each other
- Gap is between synapses is super small: 3.5nm
- Because of small gap special protein channels connect the two cells which allows the positive current to go directly from presynaptic neuron to post
- Super fast
- Only has excitation, not inhibition
- used for fast transmissions like stress hormones
Electrical Synapse (gap junctions)
- Release of Neurochemicals by a presynaptic cell
- Reaction of post-synaptic cell to neurochemicals
Two basic steps of Chemical Synapses
- We have vesicles filled with neurotransmitters that are carried by the microtubules
- AP reaches the presynaptic terminal
- Depolarization allows ion channels to open which allows Ca2+ into the cell as the calcium channels open
- Ca2+ causes vesicles to release from microtubules
- Exocytosis -Fusion of sacks of vesicles that have neurotransmitters with membranes/protein of presynaptic cell. When that happens, the neurotransmitters released and go to the synaptic gap
- Once it gets to the gap the postsynaptic receptors receive it and binds
- Neurotransmitters arrive, bind to the receptors, which opens an ion channel, which causes a change in postsynaptic potential when the ions from the surrounding environment enters
- An action potential is fired through the next cell as a result of opening of ion channels
- When u have sodium ions, they can go inside the cell and make it depolarized. If u have lots of sodium channels now being opened so I might reach threshold an action potential can be generated
- Neurotransmitter is inactivated or transported back into presynaptic terminal via retrograde support
9 Steps of Chemical Synapses
Fusion of sacks of vesicles that have neurotransmitters with membranes/protein of presynaptic cell. When that happens, the neurotransmitters released and go to the synaptic gap
Exocytosis
excitation
- happens in both electrical and chemical synapses
- increases likelihood that it will depolarize and fire an AP
inhibition
- happens only in chemical synapses
- decreases likelihood that it will fire an AP
Excitation and Inhibition
it will get closer to deploarization
What happens if something positive enters the post synpatic cell?
it will get further away from depolarization
What happens if something negative enters the post-synaptic cell?
obvs it will become more negative
What happens if something positive exits the cell?
feedback that the presynaptic neuron receives after the release of neurochemicals about its own level of activity
Auto receptors
special proteins embedded in the postsynaptic membrane that responds to chemical messengers
Receptors
molecule inside the receptors that bind to specific types of neurochemicals
Recognition molecules
- Ionotropic
- Metabotropic
Receptors- 3D proteins- two kinds
- when Ion channels open fast and directly. As soon as the receptors catches a molecule of the neurochemical the ion channel opens.
- These are also Ion channels, they bind, channels open.
Ionotropic
-
Metabotropic- indirect. Extends to extracellular protein and G proteins on the intracellular.
- Neurotransmitter binds to a receptor
- Receptor releases a g protein which binds to an ion channel
- The G-protein causes the ion-channel to open and ion passes through
- Might be slower but allows for so many more functions
- This is just a receptor. It still causes the confirmational change when neurotransmitters bind to it which will activate a nearby ion channel. The g protein on it will cause a nearby channel to open.
Metabotropic
When the molecules of neurochemicals become bound at reception site the G protein separates from the receptor area and goes to another part of Postsynaptic cell which causes the ion channels to activate additional chemical messengers in postsynaptic cell which are:
Second messengers
- Diffusion- there are all those neurochemicals and astrocytes there, so it makes it go away from areas
- Deactivated by enzymes in the synaptic gap
- Reuptake- the presynaptic membrane uses its own set of receptors called transporters that takes all the neurochemicals back, packages them up, and returns them to the interior of the axon terminals
Three different ways a message can be terminated:
- A small depolarization produced in the post-synaptic cell as a result from an input from a presynaptic cell
- Result from opening of ligated rather that voltage dependent sodium channels in the postsynaptic membrane. The inward travel of pos sodium ions make the depolarization happen too
- EPSP’s are not all or none rather- graded- as opposed to AP’s that last 1ms these last 5-10ms
- Open sodium channels
EPSP
- Result from opening of ligulated rather that voltage dependent sodium channels in the postsynaptic membrane
- Inward movement of Cl- and outward movement of K+
- Since the Cl- is negative and it goes into the postsynaptic cell it makes the inside negative as can be which makes it hyperpolarize
- Open either chloride (Cl-; into neuron) or potassium (K+; out of neuron) channels
- “You lose something positive, it becomes more negative”
IPSP
- The type of neurotransmitter delivered to it by the pre-synaptic neurons
What determines whether a post-synaptic neuron will have an EPSP or an IPSP?
- When the neuron decides whether or not to send an AP based on excitatory and inhibitory messages
Neural Integration
an action potential will only be fired when it gets up to threshold which can result from a summation of many different charger from all around the cell
Spatial Summation
when there is so much charge in one synapse, that post synaptic cell is triggered by that one synapse
Temporal summation
- Axo-axonic synapses- pre and post synaptic elements are axons
- Presynaptic facilitation- if the presynaptic neuron increases the amount of neurochemical released
- Presynaptic inhibition- of the presynaptic neuron decreases the amount of neuro chemical released
Neuromodulation- 3 types