Chapter 7a, 8a, 8b

- Our nervous system is divided into 2 branches: X & X. 

CNS

- X X + X. 

PNS

- X information (X), going to the X X 

• X, receiving X could be from the internal or external environment 

- X information (X) coming out of the X 

• X nervous system

• X nervous system

        • X & X

The PNS has the X and X. So input of the PNS, Bringing X from X senses (all of the X), special senses like (X, X, X, etc), and then X coming from the X to the CNS 

- The output of the PNS is divided into X or X nervous system. The main difference is the X control, like skeletal muscles. The autonomic nervous system is X control, like the smooth muscle and the cardiac muscle. You also have the enteric nervous system which is X nervous, the X tract (the X and X). The sympathetic is the X, X muscle and X. 

- The CNS is the brain and SC, the PNS helps the CNS to X with your body. The input: X. The output: X, if it is voluntary: X, if it is involuntary: X NS (X: fight and flight; X: rest and digest)

Nervous System Cells

• 2 categories

1. Neurons

• X cells

2. Glial cells

• X cells, don’t X information, just supporting the NS. 

Soma

• Contains X and most X

Dendrites

• X of X information

Axon

• X X (X): X activity, the X activity will move down the X until it reaches the axon terminal, the AP helps with the release of X from the axon terminal.  

Axon hillock

• X is X here, the X of the axon. The AP is initiated here because this is where you have most X X. Sodium channels are important for the AP: we talked about activating a cell, you make it more positive, and if I want to make the cell more positive one of the ways is to allow X to come into the cell which carries a X charge, making the cell more positive. This is where X can easily come in to make the cell more X to create that X. 

Axon terminal

• Part that releases X

- Our nervous system is divided into 2 branches: CNS & PNS. 

CNS

- spinal cord + brain. 

PNS

- Afferent information (input), going to the integrating center 

• Senses, receiving sensation could be from the internal or external environment 

- Efferent information (output) coming out of the CNS 

• Somatic nervous system

• Autonomic nervous system

        • Sympathetic & parasympathetic

The PNS has the input and output. So input of the PNS, Bringing sensation from somatic senses (all of the body), special senses like (smell, vision, hearing, etc), and then visceral coming from the organs to the CNS 

- The output of the PNS is divided into somatic or autonomic nervous system. The main difference is responsible of the voluntary control, like skeletal muscles. The autonomic nervous system is involuntary control, like the smooth muscle and the cardiac muscle. You also have the enteric nervous system which is parasympathetic nervous, the GI tract (the rest and digest). The sympathetic is the cardiac, smooth muscle and glands. 

- The CNS is the brain and SC, the PNS helps the CNS to help the CNS to connect with your body. The input: senses. The output: movement, if it is voluntary: somatic, if it is involuntary: autonomic NS (sympathetic: fight and flight; parasympathetic: rest and digest)

Nervous System Cells

• 2 categories

1. Neurons

• Excitable cells

2. Glial cells

• Support cells, don’t transmit information, just supporting the NS. 

Components of a Neuron

Soma

• Contains nucleus and most organelles

Dendrites

• Reception of incoming information

Axon

• Action potentials (AP): electrical activity, the electrical activity will move down the neuron until it reaches the axon terminal, the AP helps with the release of neurotransmitters from the axon terminal.  

Axon hillock

• AP is initiated here, the beginning of the axon. The AP is initiated here because this is where you have most sodium channels. Sodium channels are important for the AP: we talked about activating a cell, you make it more positive, and if I want to make the cell more positive one of the ways is to allow sodium to come into the cell which carries a positive charge, making the cell more positive. This is where sodium can easily come in to make the cell more positive to create that AP. 

Axon terminal

• Part that releases neurotransmitter

Transport in Neurons

Axonal transport

• X and X

• X & X

- In the X, you transport X, X, and X. You will use X and X could be as slow as # to # millimeters per day or fast # to # millimeter per day, either X or X. If you are fast that means you use a specific specific protein called X, these are specific proteins that carry the X (protein kinesins attached to the X holding the vesicle that has the X, X, X) and move from the X to the X X going to different X and this movement will be

Anterograde transport

• X to X X, will be faster if you used those X

Retrograde transport

• X to X, X. For example, we know that in anterograde we transport the neurotransmitter from soma to the axon terminal to release the neurotransmitter. Now going backward, that could be for X, you X some of that neurotransmitter back to the soma.

Transport in Neurons

Axonal transport

• Microtubules and neurofilaments

• Slow 0.5–40 mm/day

• Fast 100–400 mm/day

• Vesicles & kinesins

- In the axonal transport, you transport ions, chemicals, and neurotransmitters. You will use microtubule and neurofilaments could be as slow as 0.5 to 40 millimeters per day or fast 100 to 400 millimeter per day, either slow or fast. If you are fast that means you use a specific or utilizing a specific protein called kinesins, these are specific proteins that carry the vesicle (protein kinesins attached to the microtubule holding the vesicle that has the ion, chemical, neurotransmitter) and move from the soma to the axon terminal going to different kinense and this movement will be allied 

Anterograde transport

• Soma to axon terminal, will be faster if you used those proteins kinesins

Retrograde transport

• Axon to soma, backward. For example, we know that anterograde we transport the neurotransmitter from soma to the axon terminal to release the neurotransmitter. Now going backward, that could be for recycling, you recycle some of that neurotransmitter back to the soma

Ion Channels: Neurons

Leak channels

• Always X

• Will be found X the neuron

• Responsible for the X X X (-75), the cell is always negative because potassium has the most leak channel it is positive

- Not a X that opens or closes, 

Ligand-gated channels

• X or X

• Will find these ligand-gated channels in the X and cell X

• Will be used for the X or X X

Voltage-gated channels

• X or X

• The most important voltage-gated channels are the X and X and X voltage-gated channels

• The X and X voltage-gated channels are throughout, but more in the X, especially in the X X, we talked about the sodium channels found there. 

• These are the channels used for X X, the sodium channels found in the X X will be important for X the X X. 

Calcium voltage-gated channels

• Found in the X X, which means they are important for releasing the X, for the neurotransmitter to be released from the axon terminal, you need the calcium voltage-gated channel. If there are no calcium voltage gated channels, the X that has the neurotransmitter will stay X and will not be released outside.

on Channels: Neurons

Leak channels

• Always open

• Will be found throughout the neuron

• Responsible for the resting membrane potential (-75), the cell is always negative because potassium has the most leak channel it is positive so when it leaves it will make the cell more negative, sodium comes in, but potassium moves out more 

- Not a gate that opens or closes, 

Ligand-gated channels

• Open or close

• Will find these logan-gated channels in the dendrites and cell body

• Will be used for the synaptic or graded potentials

Voltage-gated channels

• Open or close

• The most important voltage-gated channels are the Sodium and potassium and calcium voltage gated channels

• The sodium and potassium voltage gated channels are throughout, but more in the axon, especially in the Axon hillock, we talked about the sodium channels found there 

• These are the channels used for action potentials, the sodium channels found in the axon hillock will be important for initiating the action potential. 

Calcium voltage gated channels

• Found in the axon terminal, which means they are important for releasing the neurotransmitter, in order for the neurotransmitter to be released from the axon terminal, you need the calcium voltage-gated channel. If there are no calcium voltage gated channels, that vesicle that has the neurotransmitter will stay inside and will not be released outside.

Types of neurons 

Bipolar neuron 

• Located in X & X

Pseudo-unipolar neuron 

• Most X neurons 

• X axon (in X)

• Modified X process

• Some X axon ( in X)

Multipolar neuron 

• Multiple projections from the X X, most X

Functional Classes of Neurons

Afferent neurons

• They mostly are X-X

• Carrying from X to X, going to the X carrying the message from the X (interoreceptors and exteroreceptors), the receptor will send a X that message will be sent to the X using the afferent neuron 

• Ganglia: clusters of nerve X X outside the X

Efferent neurons

• X shape

• Coming from the X out to the X X organ, X information 

Interneurons

• Most X type of neuron 

- X shape

• They are found in the X

• #% of neurons

CNS

• X: cell X 

• X, X, X

PNS

• X: clusters of X X outside the CNS

• X

Types of neurons 

Bipolar neuron 

• Located in olfaction & vision

Pseudo-unipolar neuron 

• Most sensory neurons 

• Peripheral axon (in PNS)

• Modified dendritic process

• Some central axon ( in CNS)

Multipolar neuron 

• Multiple projections from the cell body, most common

Functional Classes of Neurons

Afferent neurons

• They mostly are Pseudo-unipolar

• Carrying from PNS to CNS, going to the CNS carrying the message from the receptors (interoreceptors and exteroreceptors), the receptor will sent a sensation that message will be sent to the CNS using the afferent neuron 

• Ganglia: clusters of nerve cell bodies outside the CNS

Efferent neurons

• Multipolar

• Coming from the CNS out to the PNS effector organ, motor information 

Interneurons

• Most common type of neuron 

- Multipolar

• They are found in the CNS

• 99% of neurons

Structural Organization of Neurons

CNS

• Nuclei: cell body 

• Pathways, tracts, commissures

PNS

• Ganglia: clusters of cell bodies outside the CNS

• Nerves

Glial Cells

• 90% of all cells in the nervous system

• Glia: Latin, meaning "glue"

Five types:

1. Astrocytes – create the blood brain barrier

2. Microglia - phagocytic cell of the CNS 

3. Ependymal cells – create cerebral spinal fluid ( in the CSF)

4. Oligodendrocytes - myelinate the neuron, CNS 

5. Schwann cells - myelinate the neuron, PNS

Glial Cells

• #% of all cells in the nervous system

• Glia: Latin, meaning "X"

Five types:

1. X – create the blood brain barrier

2. X - phagocytic cell of the X 

3. X cells – create cerebral spinal fluid ( in the X)

4. X - myelinate the neuron, X 

5. X cells - myelinate the neuron, X 

Myelin-Forming Cells

CNS: Oligodendrocytes

• # oligodendrocyte:

• X myelin sheaths

• X axons

- The X is more protected than the X, # oligodendrocyte can myelinate X axons, just need one cell, parts in between with no myelination called X of X.  

PNS: Schwann cell

- They can be X easily, need X than # schwann cell to myelinate # axon terminal, also have nodes of ranvier. 

- Myelin is made of #/#, color is X, fat cannot conduct X, but the main function of myelin is to X the X and to protect the X activity becomes more X instead of X it. 

Synapses

- A connection between a X and another X, or a X and an X X. 

Two types of synapses

1. Electrical: X connection, X 

2. Chemical: X connection, X

Glial Cells

• 90% of all cells in the nervous system

• Glia: Latin, meaning "glue"

Five types:

1. Astrocytes – create the blood brain barrier

2. Microglia - phagocytic cell of the CNS 

3. Ependymal cells – create cerebral spinal fluid ( in the CSF)

4. Oligodendrocytes - myelinate the neuron, CNS 

5. Schwann cells - myelinate the neuron, PNS 

Myelin-Forming Cells

CNS: Oligodendrocytes

• One oligodendrocyte:

• Multiple myelin sheaths

• Multiple axons

• Nodes of Ranvier

- The CNS is more protected than the PNS, one oligodendrocyte can myelinate multiple axons, just need one cell, parts in between with no myelination called nodes of ranvier.  

PNS: Schwann cell

• One Schwann cell:

• One myelin sheath

• One section of an axon

• Nodes of Ranvier

- They can be damaged easily, need more than one schwann cell to myelinate one axon terminal, also have nodes of ranvier. 

- Myelin is made of fat/lipid, color is white, fat cannot conduct electricity but the main function of myelin is to protect the axon and to protect the electrical activity becomes more powerful instead of losing it. 

Synapses

- A connection between a neuron and another neuron, or a neuron and an effector organ. 

Functional association of a neuron

       • With another neuron

       • With effector organs (muscle or gland)

Two types of synapses

1. Electrical: direct connection, faster 

2. Chemical: indirect connection, slower

Electrical Synapses

X transfer of X, what is the AP? A X receives a X could be pain, smell, touch, that sensation will travel through the neuron from the X to reach your X in a form of X which can be X or X

• Neurons will be linked by X X, a connection between both, so AP on one side that could travel X and activate the other other cell, activating both cells.

Functions in the nervous system:

• Allow for X communication

• Allows X activity

• X communication, could go either way

• You can X or X at the X synapse

• Some always X, some X

• Electrical synapses found in the X, X, X (X), and X (X neurons)

- So we have a resting membrane potential around -75 millivolts at rest, the threshold is around -55 mv, it depends on the strength of the X, some stimulus will make the cell, or the receptors of the cell positive but it did not reach the threshold yet, if that stimulus was weak, did not change the X X X of the cell up to that X of -55, you will not make X X, and you wont feel it as a X because it is not traveled to your X saying something happened. However if the stimulus was strong enough to reach the -55, you will create X. In order to create AP, the X should be strong enough to reach that X -#. The X X are those stimuli that were not strong enough to create an X. To create a AP, you have to X the cell, to activate the cell you make it more X.

Chemical Synapses

• X neuron

• Synaptic X (30–50 nm wide)

• X neuron

• X, mostly from X X to the X

- Using a X to pass from one side to another.

- What part sends the signal? X X. The X receives.

• X, most of our synapses will be this, comes from axon to dendrite.

• X

• X

• X

Electrical Synapses

Direct transfer of AP, what is the AP? A receptor receives a sensation could be pain, smell, touch, that sensation will travel through the neuron from the dendrite to reach your CNS in a form of AP which can be electrical or chemical 

• Neurons will be linked by gap junctions, a connection between both, so AP on one side that could travel directly and activate the other other cell, activating both cells, that is a direct synapse 

• Also neurons and glial cells

Functions in the nervous system:

• Allow for rapid communication

• Allows synchronous activity

• Bidirectional communication, could go either way 

• You can excite or inhibit at the same synapse

• Some always open, some gated

• Electrical synapses found in the retina, cortex, brainstem (breathing), and hypothalamus (neuroendocrine neurons)

- So we have a resting membrane potential around -75 millivolts at rest, the threshold is around -55 mv, as a sensation that affects the receptor, it depends on the strength of the stimulus, some stimulus will make the cell, or the receptors of the cell positive but it did not reach the threshold yet, if that stimulus was weak, did not change the resting membrane potential of the cell up to that threshold of -55, you will not make action potential, and you wont feel it as a sensation because it is not traveled to your brain saying something happened. However if the stimulus was strong enough to reach the -55, you will create AP. In order to create AP, the stimulus should be strong enough to reach that threshold -55. The graded potential are those stimuli that were not strong enough to create an AP. To create a AP, you have to activate the cell, to activate the cell you make it more positive. 

Chemical Synapses

Functional anatomy of chemical synapses

• Presynaptic neuron

• Synaptic cleft (30–50 nm wide)

• Postsynaptic neuron

• Unidirectional, mostly from axon terminal to the dendrite 

- Using a chemical to pass from one side to another. 

Location of synapses

- What part sends the signal? Axon terminal. The dendrite receives. 

• Axodendritic, most of our synapses will be this, comes from axon to dendrite. 

• Axosomatic

• Axoaxonic

• Dendrodendritic

Anatomy of a Synapse

Presynaptic axon terminal

• Will have X-containing X that you will release

• Will have X-gated X+ channels, which is required to have in order to release that X

• X molecules, sometimes when you are done with the X, you can X it down and either send it away from the X or you can X it to use it to make more X

Postsynaptic neuron

• X

• X

- You have the action potential that is initiated in X X because it has more X-gated X channels, these sodium-voltage gated channels are needed because after the threshold you go up in charge becoming more X that upward deflection is because X is coming in so the action potential is initiated at the axon hillock and it will travel through the X to reach the X X. The action potential has to first reach the X voltage-gated channel where it is going to stimulate that voltage-gated X channel to open it. Outside the action potential has that channel to open, X comes in, and that X ion will help the vesicles X into the X of the axon terminal, then X of the neurotransmitter, will help the vesicle get to the X and X what is inside that vesicle. 1. X X 2. Voltage-gated X channel opens 3. X enters triggering X X and X 4. Releasing that X through X and it will bind to the X, creating another X X, causing a X in the cell.

- As long as that X found in that X, you will always have a X, a binding on the receptor, you can help stop that through the X on the X cell, the enzyme there is to X the action of the X, X the X, and it will no longer function on that X and cannot cause a X on the other side. For that reason, that enzyme is a target for a lot of X, if a patient has a problem stimulating the muscle, then you get a drug that stops the X, allowing more acetylcholine at the synapse, more action to cover for the X acetylcholine. The enzyme that degrades the neurotransmitter is a site that is used for X to either X or to X.

- After the neurotransmitter finishes its action, it has 3 choices: X, X and X to go to a neighboring area to X that response on the other side , or X.

Anatomy of a Synapse

Presynaptic axon terminal

• Will have neurotransmitter-containing vesicles that you will release

• Will have Voltage-gated Ca2+ channels, which is required to have in order to release that neurotransmitter 

• Reuptake molecules, sometimes when you are done with the neurotransmitter, you can break it down and either send it away from the synapse or you can recycle it to use it to make more neurotransmitters 

Synaptic cleft

Postsynaptic neuron

• Receptors

• Enzymes

- First you have the action potential that is initiated in axon hillock because it has more voltage-gated sodium channels, these sodium-voltage gated channels are needed because after the threshold you go up in charge becoming more positive that upward deflection is because sodium is coming in so the action potential is initiated at the axon hillock and it will travel through the axon to reach the axon terminal. The action potential has to first reach the calcium channel where it is going to stimulate that voltage-gated calcium channel to open it, is calcium high outside or inside? outside the action potential has that channel to open, calcium comes in, and that calcium ion will help the vesicles dock into the edge of the axon terminal, then exocytosis of the neurotransmitter, will help the vesicle get to the edge and releasing what is inside that vesicle. 1. Action potential 2. Voltage-gated calcium channel opens 3. Calcium enters triggering vesicle docking and secretion 4. Releasing that neurotransmitter through diffusion and it will bind to the receptor, creating another action potential causing a response in the cell. 

- As long as that neurotransmitter found in that synapse, you will always have a response, a binding on the receptor, you can help stop that through the enzyme on the postsynaptic cell, the enzyme there is to degrade the action of the neurotransmitter, degrade the neurotransmitter, and it will no longer function on that receptor and cannot cause a response on the other side. For that reason that enzyme is a target for a lot of drugs, if a patient has a problem stimulating the muscle, then you get a drug that stops the enzyme allowing more acetylcholine at the synapse, more action to cover for the weak acetylcholine. The enzyme that degrades the neurotransmitter is a site that is used for drugs to either stop or to increase. 

- After the neurotransmitter after it finished its action, it has 3 choices: recycle, diffuse and leave to go to a neighboring area to stop that response on the other side , or degrade. 

As a neurotransmitter you bind to the receptor.

Synaptic Delay

• #–# msec between the ariiva; of an X x and change in X X X

• Delay: X entry, vesicle X, and release of X

• X of neurotransmitter across the X X is almost X

- Since we are using a X that is released from one side to another, you have a delay of #-# X between an arrival of an X and the change in the X-X X X, delays because you have X entry, X X, and releasing X. The delay is due to X synapse, due to the X 

- Action potential started at the X X because you have a lot of X voltage gated channels, creating an X X that travels down the X to reach the X X, activating the X X opening, X comes in, calcium will do X and X of X into the X, the neurotransmitter will bind to the X on the X cell. Once it binds to the receptor, you will create a X on the other side, to stop the response you need an X to X the X. After the neurotransmitter is done, it can X out of the X X, X only, or X and X back to use 

Signal Transduction at Chemical Synapses: Channel-linked

• Channel-linked or X receptors, a neurotransmitter will bind onto the X-X channel and it will either X or X. If the neurotransmitter opens the sodium channel, do you think you inhibit or activate the other side? When the channel opens and sodium rushes in because it is high on the outside, the other side will become more X, so you X the other side. After the neurotransmitter binds to the channel it will close the X channel, is that activating or inhibiting the cell? Potassium tends to leave outside because higher inside, when there is a channel the potassium it will tend to leave, so if you close the channel the potassium is stuck inside, will the other side be positive or negative? X, because you keep potassium, which is X inside. A neurotransmitter binds to the channel and it opens a potassium channel and potassium leaves, leaving the other side more X so x the other side. 

• X-X channels

• X change in X X X

• Channel X as soon as X leaves

Signal Transduction at Chemical Synapses

G protein–coupled or metabotropic receptors 

• X acting

• Two types

1. X coupling: neurotransmitter binds to that X receptor, activating the X-X, which will activate a X, that channel could be X or X 

2. Second messenger. You will have like X, X binds to the receptor, activating X-X, activating an enzyme X X, activating cAMP, producing a cell response or opening or closing a channel.

Synaptic Delay

• 0.5–5 msec between arrival of an action potential and change in postsynaptic Vm

• Delay: Ca2+ entry, vesicle docking, and release of neurotransmitter

• Diffusion of neurotransmitter across the synaptic cleft is almost instantaneous

- Since we are using a chemical that is released from one side to another, you have a delay of 0.5-5 millisecond between an arrival of an AP and the change in the post-synaptic membrane potential, delays because you have calcium entry, vesicle docking, and releasing neurotransmitter. The delay is due to chemical synapse, due to the steps 

- Action potential started at the axon hillock because you have a lot of sodium voltage gated channels, creating an action potential that travels down the axon to reach the axon terminal, activating the calcium channel opening, calcium comes in, calcium will do docking and secretion of neurotransmitters into the synapse, teh neurotransmitter will bind to the receptor on the postsynaptic cell. Once it binds to the receptor you will create a response on the other side, to stop the response you need an enzyme to degrade the neurotransmitter. After the neurotransmitter is done, it can diffuse out of the synaptic cleft, degrade only, or degrade and recycle back to use 

Signal Transduction at Chemical Synapses

• Channel-linked or ionotropic receptors,

 neurotransmitter will bind onto the ligand-gated channel and it will either open or close. If the neurotransmitter opens the sodium channel, do you think you inhibit or activate the other side? When the channel opens and sodium rushes in because it is high on the outside, the other side will become more positive so you activate the other side. After the neurotransmitter binds to the channel it will close the potassium channel, is that activating or inhibiting the cell? Potassium tends to leave outside because higher inside, when there is a channel the potassium it will tend to leave, so if you close the channel the potassium is stuck inside, will the other side be positive or negative? Positive, because you keep potassium, which is positive inside. A neurotransmitter binds to the channel and it opens a potassium channel and potassium leaves, leaving the other side more negative inhibiting the other side. 

• Ligand-gated channels

• Postsynaptic potential (PSP)

• Fast change in Vm

• Channel closes as soon as neurotransmitter leaves

Signal Transduction at Chemical Synapses

G protein–coupled or metabotropic receptors 

• Slow acting

• Two types

1. Direct coupling: neurotransmitter binds to that metabotropic receptor, activating the G-protein, which will activate a channel, that channel could be sodium or potassium 

2. Second messenger. You will have like cAMP, neurotransmitter binds to the receptor, activating G-protein, activating an enzyme adenylate cyclase, activating cAMP, producing a cell response or opening or closing a channel. We also have IP3 and DAG.

Postsynaptic Potential (PSP)

- What happens on the other side, will you excite or inhibit. Excite=more X inhibit=more X

• Graded potential: Change in X X in response to X-X binding, if that graded potential is strong enough to reach the X it will create x, if the graded potential did not reach threshold, no X, no x on other side. 

Excitatory postsynaptic potential (EPSP): exciting, means making the other side more X 

• X

Inhibitory postsynaptic potential (IPSP): making the other side more X 

• X/X. Both making the cell on the other side more X. Reporalization means you make it more X and stop at the X X X which is -#, don’t go X that. Hyperpolarize negative beyond the X X X -#. 

Excitatory Post Synaptic Potential (EPSP)

Fast Response

X channel opened

• Both X and X

• X

• X duration

• Removal of X

The resting membrane potential is -70 millivolts. Which ion has the higher electrochemical gradient? X because the electrical and chemical X direction, so when you open the channel and let both sodium and potassium ions leave, more X will leave than X. This is a X-gated channel, more X comes in than X leaving, making cell more positive, even though potassium and sodium are moving, but potassium has X electrochemical gradient. This is X excitation, X duration. 

Excitatory Post-Synaptic Potential (EPSP)

Slow Response

- Excitation using X receptors. 

• Activation of X receptor with X X and X X messenger

• The X channel X

• Meaning X no longer leaks out, cannot leave, cannot make the cell more negative so it will be X. 

• X due to X-X

• X duration

• Seconds to hours

• Breakdown of X

Postsynaptic Potential (PSP)

- What happens on the other side, will you excite or inhibit. Excite=more +; inhibit=more -

• Postsynaptic cell

• Graded potential: Change in membrane potential in response to receptor-neurotransmitter binding, if that graded potential is strong enough to reach the threshold it will create AP, if the graded potential did not reach threshold, no AP, no response on other side. 

Excitatory postsynaptic potential (EPSP): exciting, means making the other side more positive 

• Depolarizing

Inhibitory postsynaptic potential (IPSP): making the other side more positive 

• Hyperpolarizing/repolarize. Both making the cell on the other side more negative. Reporalization means you make it more negative and stop at the resting membrane potential which is -75, don’t go below that. Hyperpolarize negative beyond the resting membrane potential -75. 

• Membrane stabilization

Excitatory Post Synaptic Potential (EPSP)

Fast Response

Cation channel opened

• Both Na+ and K+

• At resting Vm = -70mV, which ion has a higher electrochemical gradient?

• EK = -94 mV

• ENa = +60 mV

• Fast

• Short duration

• Few to several hundred msec

• Removal of ligand

The resting membrane potential is -70 millivolts, which ion has the higher electrochemical gradient? Sodium because the electrical and chemical same direction, so when you open the channel and let both sodium and potassium ions leave, more sodium will leave than potassium. This is a voltage-gated channel, more sodium comes in than potassium leaving, making cell more positive, even though potassium and sodium are moving, but potassium has less electrochemical gradient. This is fast excitation, short duration.

Excitatory Post-Synaptic Potential (EPSP)

Slow Response

- Excitation using metatropic receptors. 

• Activation of metabotropic receptor with G protein and cAMP second messenger

• The K+ channel closed

• Meaning K+ no longer leaks out, cannot leave, cannot make the cell more negative so it will be positive. 

• Slow due to G-protein

• Longer duration

• Seconds to hours

• Breakdown of cAMP

Inhibitory Post-Synaptic Potential (IPSP)

• A X binds to receptor

• Channels for either X or Xwill open

• If K channels open: K+ moves out, making the cell more X

• If Cl– channels open: it is X outside will move X, so Cl– moves X, making cell X Or Cl– stabilizes membrane potential

Inhibitory Post Synaptic Potential Are X Potentials

1. Higher X of action potentials

2. More X released

3. More X binds to X to X (or X) X

4. Greater increase (or decrease) in ion X

5. Greater (or lesser) ion X

6. Greater X, more X

Inhibitory Post Synaptic Potential (IPSP)

Fast Response

• The ligand binds to X channel

- K+ channel X

• K+ leaks out

• Making the cell more X, that is X, X

Inhibitory Post Synaptic Potential (IPSP)

Fast Response

• Cl- channel opened

• Cl- diffuses in

• Cells with Cl- leak channels & no Cl- X X

- membrane stabilization, which means you are going to be X, but you will stabilize it in the membrane, like X. Inhibitory, will use a X, so X movement, even though chlorine is high outside the pump will get chloride X of the cell, when it gets the chlorine X, there will be even more X chlorine X, and so when the ligand bind to the channel the chloride channel will X, more chloride will come in, making it even more X, X it, but you need that pump to create a X to push it further. To get that chloride to come in.

• Cl- channel & excitatory channel opened, the chloride diffuses in, but there is no X X to keep creating the X, so you are not X, and at the same time, at X, no X for chloride, will get membrane X. Having a X that will create more X which means more X will keep coming in, X not stopping at the X X X potential. So in order to hyperpolarization, you need the X of X and chloride channel to open. In order to stablize the membrane you just need chloride X to open, no X.

Opening sodium voltage channel: sodium comes X, making it more X, X, X. Blocking the potassium channel: that is X, X. Inhibiting could use more X or opening the channel for X to leave, to make the cell more X, inhibiting, hyper polarization. Inhibiting means more X and there is a difference stopping at resting membrane potential: X, or more negative than the vM which is X,

Inhibitory Post-Synaptic Potential (IPSP)

• A Neurotransmitter binds to receptor

• Channels for either K+ or Cl– will open

• If K channels open: K+ moves out, making the cell more negative IPSP

• If Cl– channels open: it is higher outside will move inside, so Cl– moves in, making cell negative Or Cl– stabilizes membrane potential

Inhibitory Post Synaptic Potential Are Graded Potentials

1. Higher frequency of action potentials

2. More neurotransmitter released

3. More neurotransmitter binds to receptors to open (or close) channels

4. Greater increase (or decrease) in ion permeability

5. Greater (or lesser) ion flux

6. Greater hyperpolarization, more inhibition 

Inhibitory Post Synaptic Potential (IPSP)

Fast Response

• The ligand binds to potassium channel

- K+ channel opened

• K+ leaks out

• Making the cell more negative, that is inhibiting, Hyperpolarization

Inhibitory Post Synaptic Potential (IPSP)

Fast Response

• Cl- channel opened

• Cl- diffuses in

• Cells with Cl- leak channels & no Cl- ATPase pump

• At equilibrium

• No gradient for Cl-

• Membrane stabilization

-  membrane stabilization which means you are going to be negative, but you will stabilize it the membrane, like repolarization. Inhibitory, will use a pump, so active movement, even though chlorine is high outside the pump will get chloride out of the cell, when it gets the chlorine out, there will be even more higer chlorine outside, and so when the ligand bind to the channel the chloride channel will open, more chloride will come in, making it even more negative, hyperpolarizing it, but you need that pump to create a difference to push it further. To get that chloride to come in. 

• Cl- channel & excitatory channel opened, the chloride diffuses in, but there is no ATPase pump to keep creating the difference, so you are not hyperpolarizing, and at the same time, at equilibrium, no gradient for chloride, will get membrane stabilization. Having a pump that will create more difference which means more chloride will keep coming in, hyperpolarizing not stopping at the repolarizing resting membrane potential. So in order to inhibit hyperpolarization, you need the pump of chloride and chloride channel to open. In order to stablize the membrane you just need chloride channel to open, no pump.  

Opening sodium voltage channel: sodium comes in, making it more positive, exciting, deporalization. Blocking the potassium channel: that is exciting, depolarization. Inhibiting could use more chloride or opening the channel for potassium to leave, to make the cell more negative, inhibiting, hyper polarization. Inhibiting means more negative and there is a difference stoping at resting membrane potential: repolarization, or more negative than the vM which is hyperpolarization, 

Threshold reminder

• X stimulus

• X & X stimulus

- -70 is where the X X X is, the threshold is -#, below the threshold is the X, no X X. 

- Threshold or suprathreshold, create an X X, if X is strong enough to make that cell X to reach -#, then X X happens.

- X stimuli: no action potential

- X and X stimulus: action potential caused 

Divergence and Convergence

- Divergence is when you have # neuron (X-X) connecting with X neurons (X-X) 

- Convergence is X neurons (X-X) connection with # neuron (X-X)

Summation

• Add X X

- Graded potentials are X the X therefore no X X, summation is when you X those X X together to make it more X to reach that X.

- You can add X and X graded potential, so reach the X to create an X X. 

• Temporal: two X from the X neuron, neuron A and another neuron A, those two will be X together to create that X to reach that X creating an X X, in this temporal summation

• Spatial: you have neuron X and neuron X, if you added them that would be spatial summation, two X neurons, the C if you see it is inhibitory A and B are excitatory so if I add A and C that is spatial summation

Frequency Coding

- Frequency is important in X 

• Frequency of action potentials

• X influences X of action potentials

• Duration and strength of graded potential, strength: the X the X the more likely you reach that X line, creating X action potentials. Duration: duration between each X and the other, the X in between X X, there is also a refractory period

• ↑ action potentials → ↑neurotransmitter released

Modulation

The regulation of X across a X, changing the X 

• X synapses, one axon to another axon, modulation uses X communication, you can X and you can X

• X facilitation

• X inhibition

Presynaptic facilitation: helps you to release X, if you release more X, the chance of you getting that X and X X is higher

• Neuron C is secreting neurotransmitters, the modulation came from neuron E, then you will have more neurotransmitters made, this is presynaptic X

Presynaptic inhibition

• Decrease likelihood of X stimulus

• Axon H

Neural Integration

Threshold reminder

• Subthreshold stimulus

• Threshold & suprathreshold stimulus

- -70 is where the resting membrane potential is, the threshold is -55, below the threshold is the subthreshold, no action potential. 

- Threshold or suprathreshold, create an action potential, if stimulus is strong enough to make that cell positive to reach -55, then action potential happens.

- Subthreshold stimuli: no action potential

- Threshold and suprathreshold stimulus: action potential caused 

Divergence and Convergence

- Divergence is when you have 1 neuron (pre-synaptic) connecting with multiple neurons (post-synaptic) 

- Convergence is multiple neurons (pre-synaptic) connection with one neuron (post-synaptic)

Summation

• Add graded potentials

- Graded potentials are below the threshold therefore no action potential, summation is when you add those graded potentials together to make it more positive to reach that threshold.

- You can add excitatory and inhibitory graded potential, so reach the threshold to create an action potential. 

• Temporal: two stimuli from the same neuron, neuron A and another neuron A, those two will be added together to create that positivity to reach that threshold creating an action potential, in this temporal summation

• Spatial: you have neuron A and neuron B, if you added them that would be spatial summation, two different neurons, the C if you see it is inhibitory A and B are excitatory so if I add A and C that is spatial summation

Frequency Coding

- Frequency is important in time 

• Frequency of action potentials

• Summation influences frequency of action potentials

• Duration and strength of graded potential, strength: the higher the stimulus that probability that you reach that threshold line is high creating multiple action potentials. Duration: duration between each potential and the other, the space in between action potentials, there is also a refractory period: the time between each action potential and the toher, no matter if you got a stimulus if you reached the threshold 

• ↑ action potentials → ↑neurotransmitter released

• Greater IPSP or EPSP in the next neuron

Modulation

The regulation of communication across a synapse, changing the communication 

• Axoaxonic synapses, one axon to another axon, modulation uses axoaxonic communication, you can facilitate and you can inhibit

• Presynaptic facilitation

• Presynaptic inhibition

Presynaptic facilitation: helps you to release neurotransmitters, if you release more neurotransmitters, the chance of you getting that threshold and action potential is higher

• Increase likelihood of threshold stimulus

• Neuron C is secreting neurotransmitters, the modulation came from neuron E, then you will have more neurotransmitters made, this is presynaptic facilitation

Presynaptic inhibition

• Decrease likelihood of threshold stimulus

• Axon H

Synaptic Function Comparison

Axoaxonic

• X

• X or X one synapse, like X

Axodendritic and axosomatic

• X

• Affecting: Excite or inhibit postsynaptic neuron membrane potential not a specific synapse

Synaptic Function Comparison

Axoaxonic

• Selective

• Excites or inhibits one synapse, like modulation

Axodendritic and axosomatic

• Nonselective

• Affecting: Excite or inhibit postsynaptic neuron membrane potential not a specific synapse