NEUROPHYSIOLOGY - BIO&PHYSIOLOGY

Question 1

What is action potential

Answer 1

potential energy required to transmit nerve impulses

Question 2

what is needed to have a membrane potential (Vm) (2 things)

Answer 2

• ion conc gradient
• membrane has differing permeabilities do different ions

Question 3

what does Na+/K+ ATPase do

Answer 3

activley transports sodium and potassium ions in different directions across the membrane

Question 4

what ion balances Na+ outside the cell

Answer 4

cl-

Question 5

what ions balance K+ inside cell

Answer 5

organic anions (eg proteins and phosphates)

Question 6

why is resting membrane potential possible

Answer 6

K+ leak channels are always open so K+ is constantly moving out of the cell and are trasported in via Na+/K+ ATPase
there is a cycle of movement of K+ ions
there are negativley charged species that line up on the ouside of the cell membrane - local separation = resting potential maintained

Question 7

what is eqm potential

Answer 7

voltage at which the electrical force experienced by an ion is eaqul and opposite to the chemical force produced by the conc grad

Question 8

what causes depolarisation

Answer 8

K+ conc increaces = Vm becomes less nagative = depolarisation of cell

Question 9

describe the four steps of AP generation

Answer 9

1- INITIAL DEPOLARISATION: stimulus needs to reach threshold
2- DEPOLARISATION: depolarisation reaches threshold, VG Na+ channels open - Vm becomes less negative
3 - REPOLARISATION: VG K+ channels open to reverse change in Vm, VG Na+ channels close
4 - HYPERPOLARISATION: VG K+ channels remain open after Vm reaches resting, refracory perioid

Question 10

increasing stength of stimuli increases …

Answer 10

… frequency

Question 11

effect if increasing temp on conductance

Answer 11

increases conductance

Question 12

effect of inc axon diameter on conductance

Answer 12

increases conductance as longitudinal resistance is decreased

Question 13

effect of inc myelination on conductance

Answer 13

inc conductance as larger insulating layer of phospholipids allows AP impulses to transmit quicker

Question 14

how do local anesthetics work

Answer 14

inhibit VGSC - bind to intacellular side - block AP conduction
pass through membrane in unioniosed form
ionise in cell to bind to ion channel

Question 15

what are some of the side effects of LA’s if they enter systemic circulation

Answer 15

CNS effects - confusion, tremors, respiratory depression
CVS effects - myocardial depression, vasodilation, fall in bp