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NEURAL SIGNAL TRANSMISSION - Coggle Diagram
NEURAL SIGNAL TRANSMISSION
RMP
DEFINE:
Difference of charge creates a voltage difference across the cell membrane.
RESTING NEURON CHARGE
: The neuron has a negative membrane potential when it's polarized
Positive charge on the outside
Negative charge on the inside.
IONS
Sodium (Na+) ions are mostly outside of the cell
Potassium (K+) ions are mostly on the inside of the cell.
PASSIVE CHANNELS:
Aka leak channels; Passages on cell membrane that are always open and allow ions to move from areas of high concentration to low concentration areas (aka diffuse).
K+ LEAK CHANNELS
: Since there is a higher concentration of K+ ions inside of the neuron, K+ ions leave through these leak channels.
There are more K+ leak channels than Na+ leak channels in the membrane of the cell.
Na+ LEAK CHANNELS:
Since there is a higher concentration of Na+ ions outside of the neuron, Na+ ions leave through these leak channels.
Since there are less Na+ leak channels on the cell membrane than K+ leak channels, the cell membrane is less permeable to Na+ ions.
ACTIVE PUMPS:
Actively transport Na+ out of the neuron and K+ ions into the neuron. Important in the rarefaction stage of AP.
WHAT HAPPENS IF A NEURON LEAVES THE RESTING STATE?
When Vm becomes more negative or more positive due to a signal.
GRADED POTENTIAL
: Small changes in the Vm that do not lead to neural transmission.
ACTION POTENTIALS:
Large changes in Vm that leads to neural transmissions.
ACTION POTENTIAL
DEFINE:
Aka nerve impulse; all or none event;
CAUSE:
Starts when pressure or other sensory input disturbs the cells plasma membrane to the point where the potential difference reaches the threshold voltage of -45 to -55mV.
WHERE?
Initiated in the axon hillock of the cell and once triggered moves along the axon of the until it reaches the axon terminal
Along the axon the AP is regenerated at multiple locations (Axon hillock, nodes of Ranvier).
These ate places of voltage gated channels which contribute to the generation and regeneration of AP at every stop.
PHASES:
DEPOLARIZATION
:Once the cell reaches -45- -55 threshold, the voltage gated Na+ channels open quickly, causing the cell to depolarize. this results in more Na+ channels opening, which depolarizes the cell further (cell becomes more positive).
REPOLARIZATION
:When the action potential is peaked (+40mV), Na+ channels begin to inactivate, and K+ channels open up and K+ ions leave the cell. This causes the cell to reduce in the positive charge of the neuron, leadingn to repolarization (cell becomes more negatively charged).
HYPERPOLARIZATION
:The K+ channels close near the cells resting potential but the close slowly. This causes hyperpolarization (cell becomes more negatively charged than it was at RMP) RMP is restored using passive ion channels and ion pumps.
INTEGRATION
DEFINE:
Process by which a post synaptic neuron combines all incoming synaptic potentials (EPSPs and IPSPs).
TEMPORAL:
PSPs received and summated from a single nueron, multiple times.
SPATIAL:
When PSPs are received from multiple neurons.
VOTES EXPLAINATION:
Neuron recieves thousands of synaptic inputs (votes) with each input representing either EPSPs (yes vote) or IPSPs (no vote).
To generate an AP, the total number of EPSPs versus IPSPs needs to combine to produce a net charge that crosses the firing threshold of the axon hillocks.
ADJACENT NEURON TRANSMISSION
PRE-SYNAPSE NEURON
STEPS
The AP reaches the axon terminal after traveling along the axon.
When the AP reaches the axon terminal, Calcium voltage-gated channels open and Ca ions flow into the presynaptic terminal.
Ca ions cause the vesicles to move toward the membrane of the presynaptic terminal, and proceed to fuse with the membrane.
Chemical neurotransmitters are released into the synaptic space.
neurotransmitters bind to protein receptors on the post synaptic neuron.
POST SYNAPSE NEURON
STEPS
The neurotransmitters bind with the receptors.
Receptors are ligand gated channels
This binding triggers ion channels to open and ions flow in and out of the cell.
Ion channels open and allow negative chloride ions and/or positive Na+ ions into the post-synaptic neuron.
PSPs (Post synaptic potential) create EPSPs and IPSPs
Summation of these PSPs occursand determines if an AP fires or not.
Neurotransmitters are released from the receptors back into the synaptic space.
Some of the neurotransmitters are degraded by enzymes, while others return to the presynaptic terminal to be repackaged into vesicles, which will fire with the next AP.
SALTATORY CONDUCTION
DEFINE:
Conduction through myelinated nerve fiber.
HOW SALTATORY CONDUCTION INCREASES THE RATE OF PROPAGATION OF AP
Conserves energy for the axon, because depolarization only occurs at the nodes.
100x less movement of ions that would otherwise be necessary.
Conserving energy to re-establish Na+ and K+ concentration differences across the membrane.
Increases the speed of impulse transmission.
Depolarization can only occur at the Nodes of Ranvier. Myelin acts as insulation for the axon so depolarization cannot occur at the myelinated regions.
COMPARING AP AND PSP
AP
All or nothing responses that happen quickly.
Always same amplitude and always excitatory .
PSP
Can be depolarizing and excitatory, or hyperpolarizing and inhibitory.
Post synaptic potentials are gradient responses; meaning they vary in amplitude depending on the strength of the signal.
CLINICAL IMPLICATIONS
WHEN MYELIN SHEATH IS NOT PRESENT
Action potentials need to happen at each node of Ranvier because they contributes to its regeneration. If there is not myelin sheathing along the axon, and the action potential takes longer to reach the axon terminal. This leads to slow response times.
Multiple Sclerosis is associated with myelin sheath problems.
AXONS ARE DEGENERATED
Characteristic of Alzheimer Disease or could also be healthy aging. Maybe signs of synaptic pruning.
Causes reduction of communication and reaction time, as well as a lack of alertness.
WHEN NEUROTRANSMITTERS ARE NOT BEING PRODUCED
Electrical transmissions can communicate quickly without neurotransmitters, but chemical information needs to be carried by neurotransmitters.
A characteristic of Parkinson's Disease is the lack of Dopamine neurotransmitters being produced.
This disease can cause tremors, slow movements, and a change in walking patterns.