Nervous System Flashcards
The Spread of Action Potentials
The size (diameter) of an axon influences how fast the action potentials can spread. The speed is a rate.
Sciatic Nerve
Largest Nerve in the Body
What size axons conduct FASTER signals?
Larger Axons
How fast can Action Potential’s be?
0.04 m/sec-100 m/sec
What produces the Myelin Sheets?
Schwann Cells & Oglio dendritic cells
Where can we generate Action Potentials?
There can only be Action Potentials in myelinated axons in specific sights
What is clustered in the Breaks of the Nodes of Ranvier?
Ion channels are clustered : Sodium Channels, and Potasium Chnnels
What is Saltatory Conduction?
The jumping of Action Potential s
What is the speed of unmyelinated vertebrate axons?
-1 m/sec
What is the top speed of Myelinated Vertebrate acons ?
up to 120 m/sec
What diseases causes demyelination?
MS, immune system attacks Glial cells that make myelin
What is the Acute phase of MS?
The current decays because there is no myelin sheets, but the cluster of ions are still present.
What is the Chronic Phase of MS?
Ion channels are now being spread though out the axon. This causes information to move at a slower pace. (e.g. slower movement)
For a graded postsynaptic response, stimulus intensity is reflected in terms of the ______ of the change in membrane potential/
Amplitude , stronger stimuli produce a larger change in Vm than weaker stimuli.
What is Synaptic Transmission?
Cell to Cell communication in the nervous system. (Interneuron specialize in such transmission)
What is a Synapse?
How the information is passed from one cell to another
Electrical Synapses (Gap Junctions) are formed by what type of proteins?
Connexons, and they must be present in both cells.
What are the Benefits of Electrical Synapses (Gap Junctions)
-Very Fast, Very Reliable, and Limited Flexibility.
It is the fastest kind of way to connect cells. EX. Tail flips, the behavior of crustaceans like cray fish or lobsters.
What are the limitations of Electrical Synapses (Gap Junctions)
They are inflexible, the response can not be changed or modified.
What type of synapse are most common?
Chemical Synapses
What is the process of Chemical Synapses transferring action potentials?
Electrical to chemical and chemical to electrical.
What is the advantage of Chemical Synapses?
It sums up all the information and the decision making of sending the action potential further is simple. You also have 2 different kind of responses, Inhibitory and Excitatory.
How many cells can synapse to Purkinje cells?
100,000 Cells
What is the name of the synapse between nerve and muscle?
Nueromuscularjunction (NMJ)
The first step of Chemical Synaptic Transductions?
Action potential travels down to the presynaptic terminal. OPENS VOLTAGE GATED Ca2 Channels.
The second step of Chemical Synaptic Transductions?
The depolarization opens voltage -gated Ca2 channels. Ca2 enter the cell and is very positive (180 mV) (CALCIUM will always enter the cell)
What is Calcium’s equilibrium potential ?
Very Positive, high concentration the outside relative to in.
Cells maintain calcium at very low levels inside the cells.
What is the 3rd step of Chemical Synaptic Transductions?
The Influx of Ca2 leads to the fusion of synaptic vesicles containing neurotransmitter with the presynaptic membrane.
Releases neurotransmitters from vesicles when fused.
What is the 4th step of Chemical Synaptic Transductions?
The vesicles release their neurotransmitter into the synaptic cleft, where it diffuses toward the postsynaptic cell.
What is the 5th step of Chemical Synaptic Transductions
The Neurotransmitter(ligand) binds to ligand-gated channel allows both Na and K to cross the membrane, depolarizing the cell.
What is a non-specific monovalent Cation Channel
Non-Specific: Lets any biological ion that has 1 positive charge in it,
What is the 6th step of Chemical Synaptic Transductions
The neurotransmitter diffuses away or is enzymatically degraded, ending the signal.
What happens when action potential stops?
Signaling Stops.
How does a cation-selective channel lead to cell depolarization?
Positive Charge going out and one coming in.
*Na and K are equally permeable and therefore the sum would b 0 millivolts.
Does the cell care about charge and ions?
No
What is Driving Force?
The power of Na overpowers Vm (-70) and therefore Na influx dominates K efflux. A lot more Sodium is going to come in then Potassium leave.
What is the Driving Force formula for K and Na
|Vm-Ex|
For K–> 22mV
For Na–> 132mV
What drives membrane potential (Vm) toward 0 mV( depolarization above threshold)
Opening a cation-selective ion channel from Rest causes Cell Activation.
What are the two ways to look at making an Action Potential?
The Nernst Equation and Driving Force Equation.
What is the Nernst Equation?
Adding up all the Sodium and Potassium from both sides and put into the equation.
Define Direct Synaptic Transmission
The activation of Ligand Gated Channels by Neurotransmitters.
Direct; because the binding of the chemical to ion channel causes a change of conformation to open.
What do postsynaptic effect?
Depolarization/hyperpolarization of membranes.
What does Excitatory Do?
Depolarize
What does Inhibitory Do?
Hyperpolarize
What does the Purkinje Cell primarily deal in?
Inhibitory signals in movement.
What do Na and Ca channels do to Selective Channel?
Moves the cell closer to threshold. (Excitatory)
What does K and Cl channels do?
Move the cell further from threshold (Inhibitory)
Where do Cation-Selective channels Rest?
at 0 mV
What is Summation?
Excitatory Postsynaptic Potential (EPSP ) and Inhibitory Postsynaptic Potential (IPSP)
Post synaptic cell is summing up all the information that it is receiving.
Explain Synaptic Integration
Temporal (TIME) and Spatial summation (SPACE)
How is stimulus intensity coded as for Action Potential?
Frequency
Explain Indirect Synaptic Transmission
Neurotransmitter that binds to and activates a receptor that is not directly coupled with an ion channel. (Activation of 2nd messenger pathways).
What can the 2nd messenger do (Intracellular)?
Activate a ligand gated channel and other intermediates. Receptors, transporters, Ion channels. It took time to make the second messenger.
Metabotropic Receptor is inline with?
G Protein Coupled Receptors (GCPR)
How does LTP function?
The change of synapse function by repeated stimulation .
How doe we generate a larger postsynaptic response?
- Presynaptic terminal releases glutamate
- Glutamate binds to two types of Ligand Gated Channels (AMPA & NMDA) (Both are Cation)
- Ca influx through NMDA receptors
AMPA activates ?
Cation-selective channel (Na, K)
NMDA activates?
Cation Selective Channel.Permeable to Na, K, & Ca. Ca adds phosphorylation, which makes receptor work better.
- Increases responsiveness of AMPA receptors
- Increase # of AMPA receptors available
- Leads to retrograde release of nitric oxide, a gaseous neurotransmitter, that enhances presynaptic release of glutamate.
