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Trinity Term 1 > Neuronal signalling > Flashcards

Neuronal signalling Flashcards

1
Q

Electrical properties of membranes can be measured using

A
  • a black-lipid bilayer
  • membrane acts as a capacitor
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2
Q

Capacitance

A

C = Q/V

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3
Q

How to measure the conductance of purified ion channels or vesicle preparations?

A

reconstituted into black-lipid bilayers

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4
Q

Channels act as conducters

A

allowing ion flow across the membrane

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5
Q

conductance (g)

A
  • reciprocal of resistance
  • 1/R
  • unit = Siemens, S
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6
Q

Give the circuit analogue view of a channel

A
  • pump
  • membrane capacitance
  • channel conductance
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7
Q

The average current-voltage relationship of open channels follows

A

Ohm’s Law

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8
Q

The convention for ion currents is that

A

positive charge flowing out of the cytoplasm is a positive current

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9
Q

Conductance is measured graphically as

A

the gradient (m)

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10
Q

A concentration gradient of an ion establishes

A

a diffusion potential

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11
Q

Give the The Nernst Equilibrium potential for K+:

A

2.3 (𝑅𝑇/𝑧𝐹) 𝑙𝑜𝑔^10 ([𝐾^+ ]𝑜𝑢𝑡/[𝐾^+ ]𝑖𝑛)

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12
Q

The equilibrium potential shifts

A

the average current-voltage relationship along the axis

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13
Q

Give the equilibrium potential for chloride

A

-70mV

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14
Q

Give the equilibrium potential for potassium

A

-90mV

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15
Q

Give the equilibrium potential for sodium

A

+60mV

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16
Q

Give the equilibrium potential for calcium

A

+130mV

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17
Q

The activity of single ion channels can be measured using

A

patch-clamp techniques

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18
Q

Describe the effect of patch clamp configuration

A
  • different patch-clamp configurations give access to either side of the membrane
  • pulling without suction = inside-out patch
  • pulling with gentle suction = outside-out patch
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19
Q

Time-averaged current depends on

A

frequency and duration of channel opening events

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20
Q

Membrane potential affects

A

the open probability of the channel: voltage-gating

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21
Q

Describe the KcsA channel from Streptomyces lividans

A
  • four subunits, each with 2 membrane helices (outer and inner) and a pore loop
  • surround a central pore cavity
  • turret
  • K+ ion and crystal water
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22
Q

Ion selectivity is determined by

A
  • ionic radius
  • hydration energy
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23
Q

Ionic radius is measured in

A

angstrom

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24
Q

Hydration energy is measured in

A

kcalmol-1

25
Q

Describe Li+ and Na+ trying to pass through a K+ channel

A
  • small enough
  • only if sufficient energy is recouped from interactions with pore residues to overcome the hydration energy required to strip off the associated water molecules
26
Q

Describe the selectivity filter in KcsA

A

created by juxtaposition of the four P-loop chains

27
Q

Describe the S4 membrane spanning domain

A
  • inward Kirs have four subunits
  • each subunit has six MSDs
  • Na+ and Ca2+ channels have four domains, each with six-membrane spanning alpha-helices, including four copies of the S4 voltage sensor
  • positively charged arginine or lysine amino acids every third residue
  • helix moves in response to the membrane potential; affects the conformation of the channel protein opening (or closing) the pore
28
Q

Kirs

A

rectifying K+-channels

29
Q

MSDs

A

membrane spanning domains

30
Q

Voltage gating is associated with

A

movement of charges within the protein

31
Q

Channels may show

A

time-dependent kinetics

32
Q

Describe delayed-rectifier channels

A
  • delay before full conductance due to recruitment of channels from an inactive form
  • time-dependent inactivation
  • e.g. K+
33
Q

Describe a voltage-gated Na+ channel

A
  • activates rapidly
  • followed by rapid decrease in conductance due to channel inactivation
34
Q

Describe time-dependent inactivation

A

via pore occlusion

35
Q

Describe chemical coupling via synapses

A
  • pre-synaptic axon
  • synaptic cleft
  • post-synaptic dendritic spine
36
Q

Describe the initiation of an action potential via nAChR

A
  • acetylcholine released from the pre-synaptic membrane activates the receptor
  • a low conductance K+ ‘leak’ channel sets the resting membrane potential close to Ek
  • although the ACh receptor will conduct both Na+ and K+, only Na+ moves initially as Na+ is far from equilibrium
  • influx of Na+ causes membrane depolarisation
37
Q

nAChR

A

nicotinic acetylcholine receptor

38
Q

Describe a channel conductance graph

A
  • foot
  • rising phase
  • falling phase
  • refractory period
39
Q

List the types of synapse

A
  • neuromuscular junctions
  • synapses with another neurone
  • neuroglandular synapses
40
Q

Describe neuromuscular junctions

A
  • neurone
  • collateral branch
  • telodendria
  • synaptic terminals
  • neuromuscular junctions
  • skeletal muscle fibres
41
Q

Describe synapses with another neurone

A
  • dendrites
  • collateral branch
  • synapses with another neurone
  • axolemma
  • neurone 2
42
Q

Describe neuroglandular synapses

A

gland cells

43
Q

The motor end-plate is

A

a modified synapse

44
Q

Describe the sarcomere

A
  • fibrils
  • outer vesicles of SR
  • PM
  • longitudinal tubules of SR
  • transverse tubule
  • Z line
  • I band
  • thin filament
  • H zone
  • M line (bare zone)
  • overlap region
  • A band
  • triad
45
Q

SR

A

sarcoplasmic reticulum

46
Q

How can sarcomeres be visualised?

A

X-ray crystallography

47
Q

Describe EPSPs

A
  • increase the likelihood of a post-synaptic action potential occurring
  • typically mediated by glutamate receptors
  • allow influx of Na+ or Ca2+
48
Q

EPSPs

A

Excitatory Post-Synaptic Potentials

49
Q

Describe InhibitoryPSPs

A
  • decrease the likelihood of a post-synaptic action potential
  • typically mediated by GABA receptors
  • allow influx of Cl-
50
Q

Describe optogenetics

A
  • bringing neurons under experimental control in intact organisms
  • modulate targeted neurone activity using light
51
Q

List some light-activated channels and pumps

A
  • blue-light dependent depolarisation using ChR2
  • yellow-light hyperpolarisation using Halorhodopsin chloride pumping
52
Q

ChR2

A
  • Channel Rhodopsin 2
  • K+ out
  • Na+ + Ca2+ in
  • controls neuronal activity
  • visualised in nematode mobility
53
Q

Six steps to optogenetics

A
  • piece together genetic construct of promotor (to drive expression) and gene encoding opsin
  • insert construct into virus
  • inject virus into animal brains (opsin expressed in targeted neurones)
  • insert optrode
  • laser light of specific wavelength opens membrane ion channel in neurones (sodium influx)
  • record electrophysiological and behavioural results
54
Q

opsin

A

light-sensitive ion channel

55
Q

oprtode

A

fibre-optic cable plus electrode

56
Q

Describe optogenetics and aggression

A

pptogenetic stimulation of neurons in VMHvl

57
Q

VMHvl

A

ventromedial hypothalamus, ventrolateral subdivision

58
Q

What happens if you touch and optogenetic nematode’s body muscles?

A

forward locomotion

59
Q

What happens if you touch and optogenetic nematode’s neck muscles?

A

head movements

Trinity Term 1 (38 decks)

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