To provide structural support and metabolic nourishment to other nervous system cells, maintaining tissue integrity
To produce and secrete cerebrospinal fluid, which cushions and protects the brain and spinal cord from physical trauma
Synthesizing proteins
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WhyNeurons are specialised to carry electrical impulses, transmitting information rapidly throughout the body.
2Multiple choice
What are the elongated nerve fibers that project from the cell body of a neuron called?
Axons and dendrites
Node of Ranvier
Synapses
Neurotransmitters
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WhyAxons and dendrites are the elongated nerve fibres projecting from a neuron's cell body.
3Multiple choice
What is the long, single nerve fiber of a neuron called?
Axon.
Dendrite.
Synapse.
Myelin sheath.
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WhyThe axon is the single long fibre that carries impulses away from the neuron's cell body.
4Multiple choice
What are the multiple, shorter nerve fibers of a neuron called?
Dendrites.
Axons.
Synapses.
Nodes of Ranvier.
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WhyDendrites are the multiple short fibres that receive incoming signals for the neuron.
5Multiple choice
How is the resting potential of a neuron generated?
By pumping ions to establish concentration gradients.
By osmosis.
By facilitated diffusion.
By passive transport.
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WhyThe resting potential arises as ion pumps establish concentration gradients of sodium and potassium across the membrane.
6Multiple choice
What drives the pumping of sodium and potassium ions across the neuron's plasma membrane?
The breakdown of ATP by the sodium-potassium pump
The action potential generated by ion flow
Passive diffusion down concentration gradients
Osmosis of water molecules across the membrane
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WhyThe sodium-potassium pump hydrolyses ATP to actively move ions against their gradients across the membrane.
7Multiple choice
Why is the resting potential of a neuron negative?
The action of the sodium-potassium pump (Na+/K+ pump) actively transporting less potassium ions (K + ) into the cell than sodium ions (Na + ) out of the cell
The continuous influx of sodium ions (Na + ) into the cell through always-open voltage-gated channels, creating a positive charge on the outside
The action of the sodium-potassium pump (Na+/K+ pump) actively transporting more potassium ions (K + ) out of the cell than sodium ions (Na + ) into the cell
The large number of negatively charged protein molecules that are actively pumped out of the cell, contributing to the external positive charge
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WhyThe resting potential is negative because the Na+/K+ pump exports three Na+ for every two K+ imported, leaving the interior negative.
8Multiple choice
How does the speed of nerve impulses vary?
The presence of a myelin sheath and a larger axon diameter both significantly increase impulse conduction velocity, enabling saltatory conduction in the former and reduced resistance in the latter
Nerve impulse speed is solely determined by the strength of the initial stimulus, with stronger stimuli leading to faster propagation
The speed of impulse transmission is inversely proportional to the number of synapses encountered along the pathway, as each synapse introduces significant delay.
Impulse speed primarily increases with the total length of the axon, as longer axons offer less resistance to signal flow
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WhyA myelin sheath and larger axon diameter both raise conduction velocity, enabling saltatory conduction and reducing resistance.
9Multiple choice
What is the relationship between axon diameter and nerve impulse speed?
Positive correlation.
Negative correlation.
No correlation.
Inverse correlation.
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WhyLarger axon diameter lowers internal resistance, so impulse speed shows a positive correlation with diameter.
10Multiple choice
What is the relationship between animal size and nerve impulse speed?
Negative correlation.
Positive correlation.
No correlation.
Direct correlation.
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WhyImpulse speed does not depend directly on body size, and smaller animals often have relatively faster relative conduction, giving a negative correlation.
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Neuron: A cell specialised to carry electrical impulses, with dendrites, a cell body and an axon.
Resting potential: The voltage across the membrane of a neuron that is not firing, about −70 mV, maintained mainly by the sodium–potassium pump.
Action potential: A rapid, all-or-nothing reversal of membrane potential that travels along an axon as a nerve impulse.
Depolarisation: The inflow of sodium ions that makes the inside of the membrane positive during an action potential.
Repolarisation: The outflow of potassium ions that restores the negative inside of the membrane after depolarisation.
Threshold: The level of depolarisation that must be reached to trigger a full action potential.
Saltatory conduction: The jumping of an action potential between nodes of Ranvier in a myelinated axon, greatly speeding transmission.
Synapse: The junction between two neurons, across which a signal is passed chemically by a neurotransmitter.