How Nerves Work 4

Question 1

What does a diagram of an action potential look like?

Answer 1

Question 2

<p>What is the threshold to fire an action potential?</p>

Answer 2

<p>-55mV</p>

Question 3

<p>Explain the ionic basis of the firing of an action potential?</p>

Answer 3

<ol> <li>Leaky K⁺channels bring the cell to threshold (graded potential)</li> <li>Voltage gated channels open allowing Na⁺to flow in and bring the cell to +40mV</li> <li>More K⁺channels open and bring the cell down to -90mV</li></ol>

Question 4

<p>What channel is faster, and which is slower, out of Na⁺and K⁺?</p>

Answer 4

<p>Na⁺channels open faster and K⁺stay open for longer</p>

Question 5

<p>Explain how the excitability of a cell changes?</p>

Answer 5

<p>The greater the membrane potential, the greater the excitability of a cell</p>

Question 6

<p>What does excitability of a cell mean?</p>

Answer 6

<p>How easy it is to fire an action potential</p>

Question 7

<p>What is the absolute refractory period?</p>

Answer 7

<p>When all gates are opened and the action potential fires (low excitability)</p>

Question 8

<p>What is the relative refractory period?</p>

Answer 8

<p>Gates are closing and recovering (excitability increasing)</p>

Question 9

<p>Is the size of an action potential proportional to the size of the stimulis?</p>

Answer 9

<p>No, they are all the same size</p>

Question 10

<p>How does the size of a stimulis impact an action potential?</p>

Answer 10

<p>The bigger the stimulis, the more action potentials are fired (increased frequency) but the size is the same (same amplitude)</p>

Question 11

<p>Are action potentials self-propogating or decremental?</p>

Answer 11

<p>Self propogating</p>

Question 12

<p>What does self propogating mean?</p>

Answer 12

<p>Keep making new ones for themselves</p>

Question 13

<p>How does the self propogation of action potentials work?</p>

Answer 13

<p>Depolarisation spreads across a membrane decrementally, opening more channels</p>

Question 14

<p>Why do action potentials technically not spread backwards?</p>

Answer 14

<p>They do, but the gates are not opened so nothing happens and it decremenates into nothing</p>

Question 15

<p>How can you increase conduction velocity?</p>

Answer 15

<p>Larger axons</p>

<p>Myelination</p>

Question 16

<p>Why do larger axons increase conduction velocity?</p>

Answer 16

<p>They decrease conduction resistance</p>

Question 17

<p>What two cells form myelin sheath?</p>

Answer 17

<p>Schann cells (PNS)</p>

<p>Oligodendrocytes (CNS)</p>

Question 18

<p>Where are the voltage gates on a myelinated axon?</p>

Answer 18

<p>Not in the myelinated section, but in the gaps between (nodes)</p>

Question 19

<p>How does depolarisation spread along a myelinated axon?</p>

Answer 19

<p>Spreads from node to node without decaying much to to the high insulation</p>

Question 20

<p>What are some diseases that de-myelination causes?</p>

Answer 20

<p>Multiple scerosis</p>

<p>Gwillain-Barre syndrome</p>

Question 21

<p>Why does de-myelination cause disease?</p>

Answer 21

<p>Signal decays quicker and doesn't reach threshold at the next node</p>

Question 22

<p>What is a nerve?</p>

Answer 22

<p>A bundle of axons</p>

Question 23

<p>What varies within the axons of a nerve?</p>

Answer 23

<p>The size and extent of myelination</p>

Question 24

<p>What is the compound action potential?</p>

Answer 24

<p>Signal recorded extracellularly from large populations of axons</p>

Question 25

<p>What does each bump in the graph of a compound action potential represent?</p>

Answer 25

<p>An action potential going past at that point in time, each one being from the same stimuli</p>

Question 26

What are the different waves and speeds in a compount action potential?

Answer 26

A compound action potential (CAP) is a signal recorded from a nerve trunk made up of numerous axons. It is the result of summation of many action potentials from the individual axons in the nerve trunk.

Question 27

<p>Which end of the spectrum of waves is most sensitive to anoxia and local anaesthetic?</p>

Answer 27

<p>Aa is most sensitive to anoxia</p>

<p>C is most sensitive to local anaesthetic</p>

Question 28

<p>What is anoxia?</p>

Answer 28

<p>An absence of oxygen</p>