Electrical Signals of Nerve Cells

Question 1

Resting membrane potential

Answer 1

neurons generate a constant voltage across their membranes at rest (this is negative - as their a big negatively charged proteins in the cell)

Question 2

receptor potentials

Answer 2

result of the activation of sensory neurons by external stimuli (light, sound, head) - these receptors change the resting potential momentarily

Question 3

synaptic potentials

Answer 3

activation of synapses allow transmission of info from one neuron to another

Question 4

action potentials

Answer 4

type of electrical signal that travels along axons: responsible for long range transmission of information
- hyperpolarzation: membrane potential becomes more negative
- depolarization: current becomes more positive
this is generated by selective changes in the permeability of the neuronal membrane

intensity is encoded in FREQUENCY rather than amplitude

Question 5

Long distance transmission of electrical signals

Answer 5

• axons are not good electrical conductors
• progressive decrease in amplitude of induced potential change occurs because the injected current leaks out across the axonal membrane

Question 6

Initial ion concentrations

Answer 6

Inside: 
K+ (many) 
Na+ (few) 
Cl- (few) 
A- (many) 

Outside: 
K+ (few)
Na+ (many) 
Cl- (many) 
A- (few)

Question 7

Ion concentration gradients are established by

Answer 7

active transporters (which move against their concentration gradients using ATP) and ion channels (passive movement)

Question 8

Diffusion:

Answer 8

process resulting from random motion of molecules by which there is a net flow of matter from a region of high concentration to a region of low concentration

diffusive forces depend on concentration gradient and channel permeability

Question 9

Electrical forces

Answer 9

what is the charge on the inside relative to the charge on the outside?

Question 10

Forces that create membrane potentials

Answer 10

Equilibrium potential: the electrical potentail generated across the membrane at electrochemical equilibrium

Predicted by the Nernst equation

Equ. potential is affected by the concentration and electrical gradients of one ion; membrane potential is affected by gradients of all ions

Question 11

Electrochemical equilibrium in an environment with > 1 permanent ion

Answer 11

• equilibrium of electric force is most determined by the ion with the most permability
• K is more permeable than Na at rest
• Goldman Equation

Question 12

Phases of the action potential

Answer 12

• rising phase (open Na channels)
• overshoot phase (inactivation of Na, opening of K)
• declining phase (efflux of K)
• undershoot phase (too many K ions exit cell, becomes hyperpolarised)
• baseline phase (return to resting potential)

Question 13

Clinical applications : anaesthesia

Answer 13

Anaesthesia interferes with the electrical signalling mechanisms of neurons

• local: blocks action potential prop along peripheral nerves by blocking the Na channels
• regional: injecting local anaesthetics near the spinal cord to desensitise a larger region of the body

Question 14

That’s all

Answer 14

folks