Neuronal Communication

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What is a sensory receptor?
A sensory nerve endings that detects and repsonds to a stimulus and can create action potentials
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What are sensory receptors adapted to do?
Detect and respond to different types of energy. E.g. thermoreceptors detect temperature changes
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What is a transducer?
A cell that converts one form of energy to another
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What are pacinian corpuscles?
Pressure receptors in the skin that dectect changes in pressure
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What happens when pacinian corpuscles detect pressure changes?
This causes the rings of connective tissue to deform and push against the nerve ending
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What is a neurone?
A specialised nerve cell that transmits electrical impulses
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What is a nerve?
A discrete bundle of several thousand neurone axons
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What is myelin sheath made of?
Schwann cells wrapped around the dendron/axon of a neurone
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What are nodes of Ranvier?
Gaps in the myelin sheath
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What's the difference between a myelinated and non-myelinated neurone?
The speed of transmission of the impulse is increased in myelinated neurones
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What is the perineurium?
An insulating layer around the perimeter of a neurone
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What is resting potential?
The potential difference across the membrane when its at rest (-6o to -70mV)
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What is an action potential?
The brief reversal of potential across the membrane of a neurone from -70mV to +40mV
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What causes depolarisation?
When Na+ voltage gated channels open, and sodium ions diffuse in
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What is depolarisation?
When the inside the neurone becomes less negatively charged compared with the outside
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What is the threshold value?
-50mV
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What is repolarisation?
When K+ voltage gated channel open, and K+ ions diffuse out of the neurone. This makes the neurones interior more negative compared to the outside.
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What is hyperpolarisation?
The membrane potential the value is more negative than at rest
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What is the refractory period?
A period where the neurone recovers after an action potential
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Why is the refractory period important?
It allows the neurones to recover and ensures the transmission is one direction
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Are all action potentials the same size?
Yes, regardless of the strength of the stimulus
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What is the 'all or nothing' law?
If the stimulus passes the threshold value (-55mV) you get an action potential.
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What is the strength of the stimulus determined by?
The frequency of the action potentials and the number of neurones carrying the action potential
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What are local currents?
Currents in the cytoplasm of a neurone, due to depolarisation caused by the influx of sodium ions
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What is saltatory conduction?
When the action potential jumps from node to node of a myelinated neurone
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What is the advantage of saltatory conduction?
The speed of transmission of the impulse is increased
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What is the synaptic cleft?
A small gap between neurones
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What transmits information from the AP across the synaptic cleft?
Neurotransmitters
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What is a neurotransmitter?
A chemical signalling molecule between two neurones in a synpase
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What is a cholinergic synapse?
A synapse that uses acetylcholine as its neurotransmitter
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Why does the pre-syaptic neurone have lots of mitochondria?
Because exocytosis and the recombining of ethanoic acid and choline requires energy from ATP
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Why does the pre-syaptic neurone have lots of vesicles?
They contain the neurotransmitter
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Why does the pre-syaptic cell membrane have lots of calcium ion voltage gated channels?
Because the influx of calcium ions causes the vesicles to move
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Why does the pre-syaptic neurone have lots of SER?
To package the neurotransmitter into vesicles
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What happens when vesicles fuse to the pre-synaptic cell surface membrane?
They release ACh by exocytosis using ATP
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What happens if ACh remains bound to the receptors on the post-synaptic neurone?
The sodium ion channels remain open + there will be constant action potentials
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How is this prevented?
Acetylcholinase hydrolyses acetylcholine into ethanoic acid and choline
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What recombines ethanoic acid and choline?
Energy from ATP
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What is an excitatory post-synaptic potential?
A potential that makes the post-synaptic neurone more likely to fire an action potential
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What is summation?
The combined effect of several EPSP's (reaches the threshold potential and generates an AP)
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What is temporal summation?
Summation that results from several action potentials in the same pre-synaptic neurone
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What is spatial summation?
Summation that results from action potentials arriving from several different neurones
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What are inhibitory post-synaptic potentials?
A potential that reduces the effects of summation and the generation of action potentials in the post-synaptic neurone
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Card 2

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What are sensory receptors adapted to do?

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Detect and respond to different types of energy. E.g. thermoreceptors detect temperature changes

Card 3

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What is a transducer?

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Card 4

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What are pacinian corpuscles?

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Card 5

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What happens when pacinian corpuscles detect pressure changes?

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