MYTUTOR SUBJECT ANSWERS

622 views

Explain how a nerve impulse passes along a non-myelinated neuron.

Generation of a Resting Potential

▪       The sodium-potassium pump (Na+/K+ pump) maintains the electrochemical gradient of the resting potential (-70 mV)

▪       It is a membrane protein that uses active transport to exchange Na+ and K+ ions across the membrane

▪       It expels 3 Na+ ions for every 2 K+ ions admitted (in addition, some of the K+ ions will leak back out of the cell)

▪       This makes the inside of the membrane relatively negative when compared to the outside (-70 mV = resting potential)

 

 

Sodium (Na) is found in greater concentrations outside of the cell while potassium  (K) is found in greater concentrations inside the cell. Sodium-potassium pumps exist in the plasma membrane to maintain the concentration gradients and the membrane potential. 

Nerve impulses have a domino effect. An action potential in one part of the neuron causes another action potential in the adjacent part and so on. This is due to the diffusion of sodium ions between the region of the action potential and the resting potential. It is the movement of sodium and potassium that reduce the resting potential.

If the resting potential rises above the threshold level, voltage gated channels open. Voltage gated sodium channels open very fast so that sodium can diffuse into the cell down its concentration gradient. This reduces the membrane potential and results in more sodium channels opening. Sodium ions are positively charged and so the inside of the cell develops a net positive charge compared to the outside of the cell. This results in depolarization as the potential across the membrane is reversed.

A short while after this, voltage gated potassium channels open and potassium ions flow out of the cell down the concentration gradient. Since potassium ions are positively charged, their diffusion out of the cell causes a net negative charge to develop again inside the cell compared to the outside. The potential across the membrane is restored. This is called repolarization

Finally, the concentration gradients of both ions are restored by the sodium-potassium pump. Sodium is pumped out of the cell while potassium is pumped in. The resting potential is restored and the neuron is ready to conduct another nerve impulse. 

Zana Katarina L. IB Biology tutor, IB Maths tutor, IB Psychology tutor

2 years ago

Answered by Zana Katarina, an IB Biology tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist

16 SUBJECT SPECIALISTS

£22 /hr

Sharon Y.

Degree: Medicine (Bachelors) - Oxford, St Peter's College University

Subjects offered: Biology, Mandarin+ 5 more

Biology
Mandarin
Chemistry
.UKCAT.
.BMAT (BioMedical Admissions)
-Personal Statements-
-Medical School Preparation-

“About Sharon Hi! I'm a second year medic at St Peter's College in Oxford, and I can't wait to meet you all! I've been tutoring students in the Lower Sixth and below since I was at boarding school and assisted teaching an adult beginnn...”

£20 /hr

Michael J.

Degree: History (Bachelors) - University College London University

Subjects offered: Biology, History+ 1 more

Biology
History
.HAT.

“About Me: I am a History student at UCL. My interests in History are mainly modern, focusing on the Russia and the Cold War and more recently the history of political thought and tea. I also have a love of Science from my A-levels. I ...”

£20 /hr

Alice P.

Degree: Psychology (Bachelors) - Durham University

Subjects offered: Biology, Psychology

Biology
Psychology

“Hi, I'm Alice, and I'm a first year psychology undergraduate at Durham University. I enjoy psychology, biology and english, and I'm looking to tutor at GCSE and IB.”

About the author

£20 /hr

Zana Katarina L.

Degree: Psychology (Bachelors) - Durham University

Subjects offered: Biology, Psychology+ 1 more

Biology
Psychology
Maths

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

You may also like...

Posts by Zana Katarina

Describe one example of transient polymorphism.

Discuss the relative importance of genetic and cultural evolution in the recent evolution of humans.

Analyze the changes in concentration of atmospheric carbon dioxide using historical records.

Behaviour can be innate because it is genetically based and can be inherited.

Other IB Biology questions

Explain that female carriers are heterozygous for X-linked recessive alleles.

Describe the differences between the products of mitosis and meiosis.

Compare competitive and non-competitive inhibition

How does the process of blood clotting occur?

View IB Biology tutors

Cookies:

We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok