IB Biology Topic C2.2.9 Propagation of an Action Potential Along a Nerve Fibre/axon Revision Notes (HL)

IB Biology Topic C2.2.9 Propagation of an Action Potential Along a Nerve Fibre/axon Revision Notes (HL) | RevisionDojo

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Local Currents Spread an Action Potential Along the Axon

When one region of the axon depolarizes, local currents spread sideways and depolarize the adjacent membrane, moving the signal along.

Analogy

An action potential travels like a wave passing through a stadium crowd.
Each section triggers the next, so the wave moves along the axon without any single part travelling the whole way.

A Depolarized Region Creates Currents That Reach Its Neighbour

During depolarization, sodium ions ($Na^+$) enter the axon and reverse the charge across that patch of membrane.
This makes the inside of the depolarized region positive relative to the neighbouring resting region.
The charge difference drives local currents as ions flow between the two regions.
1. Inside the axon, positive charge flows from the depolarized region towards the adjacent resting region.

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Local Currents Spread an Action Potential Along the Axon

When one region of the axon depolarizes, local currents spread sideways and depolarize the adjacent membrane, moving the signal along.

Analogy

An action potential travels like a wave passing through a stadium crowd.
Each section triggers the next, so the wave moves along the axon without any single part travelling the whole way.

A Depolarized Region Creates Currents That Reach Its Neighbour

During depolarization, sodium ions ($Na^+$) enter the axon and reverse the charge across that patch of membrane.
This makes the inside of the depolarized region positive relative to the neighbouring resting region.
The charge difference drives local currents as ions flow between the two regions.
1. Inside the axon, positive charge flows from the depolarized region towards the adjacent resting region.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

IB Biology Topic C2.2.9: Propagation of an Action Potential Along a Nerve Fibre/axon Notes

A - Unity and Diversity9 subtopics

B - Form and Function10 subtopics

C - Interaction and Interdependence9 subtopics

D - Continuity and Change12 subtopics

Local Currents Spread an Action Potential Along the Axon

A Depolarized Region Creates Currents That Reach Its Neighbour

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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Local Currents Spread an Action Potential Along the Axon

A Depolarized Region Creates Currents That Reach Its Neighbour

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account