Action Potentials and Synaptic Transmission

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What are the 2 components that make up the Nervous System?
Central Nervous System (CNS) and Peripheral Nervous System (PNS).
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What 2 things make up the CNS?
Brain and spinal cord.
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What makes up the PNS?
Nerves outside the brain and spinal cord.
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What is the brain and spinal cord (CNS) protected by?
Skull and spinal collumn.
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What are the 2 types of cells in the nervous system?
Neurons and Glial Cells.
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What do neurons do?
Transmit signals and process information.
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What do Glial cells do?
Supportive functions. Involved in repair of brain tissue.
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What sends out the communication (chemiccal) to other neurons?
Buttons.
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What determines the name of the neuron?
Number of projections it has.
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What is different about a multipolar interneuron?
Does not have a long axon. Can only communicate in the given area.
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What is the advantage of the other neurons having a long axon?
Can communicate between different areas of the brain. Can stimulate a completely different area of the brain.
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How are signal transmitted within a neuron?
Electrical signals. AP travels from axon to buttons.
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How are signals transmitted between neurons?
Chemical transmission. Neurotransmitters.
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Where do most drugs have their effect?
On Neurotransmission.
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Is the cell membrane of a neuron permeable?
No.
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What allows ions to move in about out of a cell?
Ion channels.
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At rest, what is the charge inside a neuron?
Negatively charged. -70MV.
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At rest, what is the charge outside a neuron?
Positively charged.
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What ions make the outside of a neuron positively charged?
Sodium ions.
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What else is on the outside of the cell?
Chloride ions.
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What makes the neuron negatively charged?
Negatively charged proteins.
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What else is high in concentration on the inside of the neuron?
Potassium ions.
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What is the term used for the neuron at rest and being negative on the inside?
The cell is POLARISED.
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What is the term used when the neuron becomes less negative?
Depolarisation.
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What is the term used when the neuron becomes more negative on the inside?
Hyperpolarisation.
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Do negatively charged proteins move? Where are they made?
No and within the neuron.
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What is a process which tries to even out the charge?
Homogenising.
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What processes make up the term homogensing?
Random motion (through diffusion) - move from high conc to low conc. Electrostatic pressure - opposites attract.
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What factors try to keep the cell polarised?
Cell membrane being selectively permeable. Sodium potassium pump. For every 2 potassium ions that come in, 3 sodium get pumped out.
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What ions move readily?
Potassium and chloride.
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What does not move readily?
Sodium and negatively charged proteins.
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What is an AP?
Signal within a neuron?
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When is an AP triggered?
When a neuron gets excited.
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What is the threshold that needs to be met for an AP to fire?
-65MV - becomes depolarised.
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What is the region an AP gets generated?
Axon hillock.
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What happens when the neuron becomes depolarised to -65MV?
Voltage gated sodium ion channels open & sodium rushes in.
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When an AP is generated, what is the charge of the neuron?
+50MV.
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Why does hyperpolarisation occur?
K+ voltage gated ion channels are slower to close.
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What charge does repolarisation happen at?
+50MV.
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What stimulates a neuron?
EPSP.
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What inhibits a neuron?
IPSP.
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What is the refractory period?
Makes it harder for an AP to be generated. Need more stimulation than initially required. Stops AP from going backwards and limits rate of firing.
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What excites a neuron?
Depolarisation around the axon hillock.
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What causes this depolarisation?
Neurotransmitters.
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How do neurons communicate between each other?
Neurotransmitters.
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Are NT's excitatory or inhibitory?
Both.
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What determines whether an AP will be generated?
Whether the summation of EPSP's and IPSP's are enough to depolarise the membrane potential at the axon hillock.
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What are the steps from NT transmission to depolarisation?
NT released. Binds to post synaptic receptor. Sodium influx, k+ leaves. If enough sodium to cause depolarisation = AP
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What do NT's do to the post synpatic receptor?
Produce electrical changes = causes a post synaptic potential. Determines whether an AP is generated or not.
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What is a ligand?
Molecule that binds to a receptor. NT is a ligand for its receptor.
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What does it mean that post synaptic potentials are graded?
Vary in size. Get less and less as they get to axon hillock.
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What two types of receptors are there?
Ionotropic or metabotropic.
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What are ionotropic receptors?
Associated with ligand activated ion channels. Depending on which ion channel is opened will determine whether an AP is generated.
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Why are EPSP's and IPSP's decremental?
Get smaller as they travel.
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What is temporal summation?
Summation of events happening at the same time
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What is spatial summation?
Summation of events happening in different places.
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Card 4

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Card 5

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