Lecture 7 - Measuring Neural Signals

Question 1

single unit recording

Answer 1

– Microelectrodes are made of pulled glass (or metal) with a conductive
solution inside.
– Recording electrode is inside the nerve fiber (axon).
– Reference electrode is placed outside the fiber
– Difference in charge between them
is (typically) -70 mV

Question 2

resting potential

Answer 2

the negative charge of the neuron relative to its surroundings

-70mV

Question 3

action potentials

Answer 3

the neuron is responding to some form of stimulation

are the primary means of transmitting signals to other
neurons.

They are the voltage changes that travel the length of the neuron
to the terminal button, where a neurotransmitter is released – possibly
causing an action potential in the next neuron(s).

Question 4

action potentials are discrete

Answer 4

they come through one at a time

Question 5

morphology of action potential

Answer 5

Actively propagated down 
the axon.
• Will fire spontaneously
without stimulation 
(baseline rate).
• Remains the same size, 
regardless of intensity.
• Increasing signal intensity 
can increase the rate of 
firing

Question 6

baseline rate

Answer 6

neurons are never “off” - unless strongly inhibited or dead

the baseline activity - they pop off every now and then

Question 7

always a relative measure

Answer 7

it’s always going to be in reference to whatever the base-rate is before and after the activity

Question 8

excitatory post synaptic potential (EPSP)

Answer 8

When neurotransmitter binds to a receptor, ion channels open:

An influx of positively charged ions
(e.g. Na+) pushes the neuron toward depolarization (increases the charge inside)

Question 9

inhibitory post-synaptic potential

Answer 9

When neurotransmitter binds to a receptor, ion channels open:

An efflux of positively charged ions (e.g. K+) makes the neuron more polarized (hyperpolarized) - going further away from its threshold of excitation

Question 10

EPSPs and IPSPs can
summate on the same
neuron.

Answer 10

they “fight” over whether that neuron is excited or inhibited

An action potential is only 
triggered if the EPSPs can 
push the neuron to 
depolarization faster than 
the IPSPs pull it toward 
hyperpolarization.

all about changing the rate of those spikes

Question 11

When excitation is stronger…

Answer 11

…you get more action

potentials.

Question 12

When inhibition is stronger,

Answer 12

you get fewer action
potentials, sometimes to the point of going below the
spontaneous resting rate.