Summary
Summary OCR -A, A-level Biology Notes: Neuronal Communication
- Course
- Institution
Summary notes for the Neuronal Communication module of the OCR A specification for A-level biology. Helped obtain A* in A-level 2022.
[Show more]
Seller
Follow
poppybladon
Content preview
Nervous TransmissionResting Potentials
• When there is no transmission of nervous impulse, the potential di erence is known as the
resting potential- outside the axon is more positive than inside. The membrane is polarised with
a potential di erence of -70mV
• The charge comes from sodium and potassium ions. They cannot travel through the membrane
so are transported via voltage gated ion channels. There are also permanently open channels.
• 3 Na+ are pumped out of the axon and 2 K+ are pumped in via sodium-potassium pumps. This
results in more sodium outside the axons and more potassium inside the axon producing an
electrochemical gradient. This allows Na+ to di use back into the axon and k+ di use out of
the axon. However, most of the gated Na+ channels are closed, but K+ channels are open
allowing K+ to di use out leading to more positive ions outside the axon creating a resting
potential of -70mV with the inside negative relative to the outside.
Action Potentials
• Temporary reversal of charges on the membrane, the charge becomes +40mV, this is
depolarisation. As the neurone’s charge returns to resting, it is repolarised.
1. The stimulus excites the neurone cell membrane,
causing sodium ion channels to open so the membrane
becomes more permeable to sodium and sodium ions
di use into the neurone down the sodium ion
electrochemical gradient, making the inside of the neurone
less negative.
2.Depolarisation- the potential di erence reaches the
threshold (around -55mV) and voltage gated sodium ion
channels open and more sodium ions di use into the
neurone through positive feedback.
3.Repolarisation- at a potential di erence of around +30mV,
the sodium ion channels close and the voltage gated
potassium ion channels open. Potassium ions di use out of
the neurone and down the concentration gradient. This starts to get the membrane back to
the resting potential through negative feedback.
4. Hyperpolarisation- potassium ion channels are slow to close so there is a slight ‘overshoot’
where too many potassium ions di use out of the neurone. The potential di erence becomes
more negative than the resting potential.
5. Resting potential- the ion channels are reset, the sodium-potassium pump returns the
membrane to its resting potential by pumping sodium ions out and potassium ions in,
maintaining the resting potential until the membrane is excited by another stimulus.
ff
ff ff ffff ff ff ff ff ff ff ff
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller poppybladon. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.16. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
66475 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now