Saltatory conduction and the all-or-nothing principle Flashcards

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1
Q

What is different about myelinated axons?

A

because depolarisation of the axon membrane can only occure at the nodes of Ranvier where no myelin is present

sodium ions can pass through the protein channel in the membrane here

longer localised circuits therefore arise between adjacent nodes

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2
Q

How does the action potential jump?

A

its jumps from one node to another in a proces known a salatory conduction

much faster than a wave of depolarisation along the whole length of the axon membrane

every time channels open and ions move it takes time, so reducing the number of places where this happens speeds up the action potential transmission

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3
Q

How is saltatory conduiction more energy efficient?

A

repolarisation uses ATP in the sodium pump, so by reducing the amount of repolarisation needed, saltatory conduction makes the conduction impulses more efficient

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4
Q

How does axon diameter affect the speed at which an action potential travels?

A

the larger the axon diameter, the faster the impulse is transmitted

this is because there is less resistance to the flow of ions in the cytoplasm, compared with those in a smaller axon

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5
Q

How does temperature affect the speed at which an action potential travels?

A

the higher the temperature, the faster the nerve impulse

this is because the ions diuffuse faster at higher temperature

however, this only occurs up to 40ºC, as higher temperature cause the proteins, such as the sodum-potassium pump, to become denatured

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6
Q

Why are nerve impulses said to be all-or-nothing responses?

A

a certain level of stimulus - the trheshold value - always triggers a response

if this threshold is reached an action potential will always be created

no matter how large the stimulus is, the same sized action potential will always be triggered

fi the threshold is not reached, no action potential will be triggered

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7
Q

What does the size of a stimulus affect?

A

the number of action potentials that are generated in a given time

the larger the stimulus the more frequently the action potentials are generated

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