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39 Cards in this Set

  • Front
  • Back
What is an ion channel?
An ion channel is a tunnel protein that lets charged atoms through that affect the charge across a membrane.
How much is the resting membrane potential in living neurons, what is the state of the K+ protein channels?
–70mV, slightly negative on the inside, a few K+ channels are open.
Which is bigger Na+ or K+?
K+
What ion has a higher concentration inside the cell Na+/K+?
K+ (potassium – banana ion). Na+ has a high concentration on the outside of the cell.
What are the two primary ions that bioelectricity is based on?
K+/Na+
How does ATPase work in respect to resting membrane potential?
It shifts 3 x Na+ cations OUT of the cell for 2 x K+ cations IN the cell, More (+) leaving contributes to membrane potential.
What does the term depolarised mean in respect to action potential in neurons.
It means that the voltage is more positive. ie –60mV this happens when the sodium channels open letting in positively charged ions.
What does the term hyperpolarised mean in respect to action potential in neurons.
The voltage gets more negative, this happens when more K+ channels open resulting in positive charges leaving the cell. This is an inhibitory response.

What are the events that occur during the propagation of an action potential in a neuron(6)?

1. A small number of stimulus-gated Na+ channels open causing the membrane potential to depolarise towards -59mV
2. As more Na+ enters the cell through, voltage–gated Na+ channels, the membrane depolarizes even further.
3. The magnitude of the action potential peaks (at +30mV) when voltage–gated Na+ channels close(absolute refractory period).
4.Repolarization begins when voltage–gated K+ channels open, allowing outward diffusion of K+(relative refractory period).
5. After a brief period of hyperpolarization, the resting potential is restored by the sodium–potassium pump and the return of ion channels to their resting state.

Name the zones and parts of a neuron(4).

Input zone (dendrites), Summation zone(axon hillock), Conduction zone(axon) and Output zone(synapse).

How many mV in the threshold potential?
–59mV
What is the refractory period in regards to action potential in a neuron?
The refractory period is charges that stop the action potential moving the wrong way. There are two types: absolute (no response), and relative (large stimulus required). This depends on the inactive state of the Na+ channels. Inactive channels do not respond to the electrical field.
How does an action potential conduct down the axons?
The movement of the action potential relies on the depolarising electric fields (these becomes more negative as the positive action potential moves through them). As the action potential moves along the axon it instantly activates the next set of voltage gated Na+ channels.
How does myelination increase the velocity of the action potential?
It cause the ion channels to be in one place which makes the electrical fields larger. Schwann cells act as an insulater between the nodes of ravier(gaps in the schwann cells). Electrical fields become big enough to span the space between nodes of ranvier. Myelinated axons are 10 times faster the unmyelinated axons.
What is a Synapse?
The junction between nerve cells, where a nerve impulse is transferred form one neuron to another.
What are the two different types of synapses?
Electric and Chemical
What are some features of electric synapses?
They are linked by gap junctions. The gap junction is a tunnel made of proteins. This provides a direct link through a physical connection. It is a very fast synapse. Direct propagation of action potential.
What function does calcium have in neurotransmitters?
Triggers the release of vesicles
What is EPSP?
Excitatory post synaptic potential.
What is IPSP?
Inhibitory post synaptic potential.

What is the process of synaptic transmission?

1. Actionpotential propagates down the axon – to thepre–synaptic bouton


2. Pre–synaptic bouton is depolarised –voltage gated Ca2+ channels open


3. Ca2+ ions TRIGGER the release of the neurotransmitterform the vesicles


4. Neurotransmitter is released INTO the synapticcleft


5. Neurotransmitter binds to its SPECIFIC receptorson the POST SYNAPSE


6. Na+ channels open – LOCALdepolarisation of postsynaptic cell


7. Net depolarisation – called the EXCITATORY POST SYNAPTIC POTENTIAL – or EPSP


or


8. Net hyperpolarisation – called the INHIBATORYPOST SYNAPTIC POTENTIAL – or IPSP

How is a synapse switched off?

The degradation(enzymic), reuptake (Bouton/glia cells) of excess transmitter to released into the synaptic cleft. This requires Atp

What are the 3 ways excess neurotransmitter can be removed from the synaptic cleft?

a. Degradation–enzymic


b. Reuptake intothe bouton


c. Reuptake (diffusion) into gliacells - This requires ATP, produced by mitochondria in the presynaptic knob.

What effect does inhibitory(IPSP) neurotransmitter have on the action potential across a neuron lipid bilayer, which ions are involved in what?

Inhibitory mean that the voltage goes down, this is caused by the influx of Cl– into the post synaptic neuron or the outflow of K+.

What effect does excitatory(EPSP) neurotransmitter have on the action potential across a neuron lipid bilayer and what ions do what?

Excitatory mean that the voltage goes up, this is caused by the influx of Na+(and sometimes Ca2+) into the post synaptic neuron. Depolarisation.

What is the most common excitatory neurotransmitter in the CNS and what channels does it activate?
Glutamine, stimulus–gated Ca2+ channels and stimulus–gated Na+ channels.

Name two excitatory neurotransmitters.

Acetylcholine and Glutamine.

What stimulus–gated channel does Acetylcholine open and where in the body are these channels.
Acetylcholine activates Na+ stimulus–gated channels in the brain and neuromuscular junctions. These channels are know as ionotropic receptors.
Name the most common inhibitory neurotransmitter in the brain.
GABA – gamma amino butyric acid.

What kind of channels does gamma amino butyric acid(GABA) and what function does this neurotransmitter have?

GABA is an inhibitory neurotransmitter, it activates Cl– channels(ionotropic receptor) and K+ channels(metabotropic receptor).

What is HYPERpolarisation in the process of neuro transmission?
Hyper polarisation is an inhibitory function. It prevents to much stimulus form the environment going into our consciousness.

What is summation in neurotransmission, what are the two types of summation?

Summation is multiple inputs contributing to the membrane potential of a neuron. Spatial summation and Temporal summation. The sum of these inputs can excite or inhibit an action potential.

What is spatial summation?
Integration of inputs from different synaptic knobs at different localisation.
What is temporal summation?
Time dependent summation – integration of inputs within a short time at the same synaptic knob.
How does temporal summation work?
The presynaptic action potential takes 3ms to discharge and inthe postsynaptic neuron it takes 4 – 5ms. This allows them to add up to makethe threshold to inhibit or excite an action potential. This could excitemultiple action potentials.Presynaptic inputs could be inhibitory signals or excitatorysignals.
What are the two types of networks neurons use to create action potential?
Divergence and convergence.

How does the neuronal divergent network work?

Information from a single neuron may diverge to different brain regions(multiple neurons) or different body parts. This provides an opportunity to amplify signals and gives us more control points for precise coordinated control of muscles.

How does the neuronal convergence work?
Information form multiple neurons may converge on one single neuron(summation) that initiates a single response. Provides redundancy. Back up route for the transmission of signals. Cut finger, pain and visual can indicate that you should do something about it! Also provides alternatives if one component fails.

Why is KCl lethal?

K+ and Cl– injected into the ECF will cause the voltage inside the cell to go down because Cl– will go into the cell and K+ wont be able to leave as levels in the ECF will not let it diffuse out.