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Neuroscience > Neuronal signalling > Flashcards

Neuronal signalling Flashcards

1
Q

describe the general structure of a neurone

A

cell body + dendrites

axon

terminal branches of axon

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2
Q

what are the 2 types of synapses?

synapses are between..?

A

electrical
chemical (more common + complex)

2 neurones
OR
a neurone + an effector

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3
Q

define synapse

A

the point where electrical conduction is converted to chemical conduction

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4
Q

what is all activity within a neurone based on?

what is does this generate?

A

changes in electric charge of the cytoplasm
- due to movement of + or - ions across the cell membrane

membrane potential

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5
Q

what type of potential occurs in the dendrite/cell body region?

what about in the axon?

A

graded potential
= changes in charge are variable in amount

action potential
= changes in charge are always identical

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6
Q

what are the types of electrical responses?

A

intrinsic:

  • silent
  • beating
  • brusting

reposes to external:

  • sustained response
  • accommodation
  • delay
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7
Q

how is neuronal activity measured?

what are the 2 methods?

A

treat membrane as part of a circuit

electrodes placed to make contact with nerves

impalement
= charge movement

patch clamping
= channel activity

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8
Q

describe the experimental set-up for measuring neuronal activity

A

e.g. giant squid axon

an electrical stimulator is connected to an electrode in sea water and an electrode in the axon

an oscilloscope is connected to the sea water and axons via electrodes

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9
Q

what are the 2 types of clamping?

why is it important?

A

if current clamping occurs
= change in pd

if voltage clamping occurs
= change in current

important to keep 1 variable constant so that another can be measured

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10
Q

what are the features of electrical synapses?

A

gap-junctions between cells
= continuity

ions can diffuse directly

no delay

ions can move bidirectionally

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11
Q

what are the features of chemical synapses?

A

no continuity
-> slight delay

associated with neurotransmitters released from vesicles

unidirectional propagation of signals

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12
Q

describe the process which occurs at a chemical synapse

A
  1. AP invades
  2. Ca2+ influx
  3. depolarisation -> release of NT via exocytosis
  4. NT diffusion
  5. ligand binding results in opening of ligand-gated ion channels
  6. depolarisation
  7. transmitter recycling
  8. vesicular membrane recycling
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13
Q

describe fast chemical transmission

A

NT is released directly into the cleft

ligand binding directly stimulates opening of Na+ channels

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14
Q

describe slow chemical transmission

A

large vesicles release NT

release may not be towards postsynaptic cell

ligand binding functions via GPCR
-> causes ion channels to open via intracellular signalling pathways

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15
Q

give an example of a fast chemical synapse

A

motor-end plate

neurones surrounded by Schwann cells, directly contact muscle

active zones of neurone are in close contact with junctional folds of muscle
- contain ACh receptors

ACh binds to receptors which are ionotropic
-> allows entry of Na+

-> current travels through muscle

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16
Q

what is the equation for pd?

how do changes in membrane potential (pd) occur?

A

V = current x resistance

due to the changes in resistance by the closing of channels
-> prevents ion movement (=current)

17
Q

how are post-synaptic potentials generated?

A

quanta of NTs cross the synapse

NTs bind to receptors
-> opens channels
-> charge movement
= change in potential

18
Q

what are the 2 types of postsynaptic potentials?

A

excitatory

  • related to Na+
  • makes membrane more +ve

inhibitory

  • related to K+
  • makes membrane more -ve
19
Q

how do membranes enforce selective permeability?

A

neuronal membranes contain ion channels:

  • some are non-gated
    = stay open all the time
  • some are gated
    = open when action potential is present
    -> causes change in permeability of membrane
20
Q

describe the features of ion channels and ion movement

A

facilitated diffusion (no ATP)

selective
- only 1 type of ion

dynamic
- can be open or closed (gated)

21
Q

what are the 2 types of channels in a typical neurone?

A

voltage-gated
= if membrane potential changes -> channel opens

ligand-gated
= if NT binds to receptor -> channel opens

22
Q

give 3 examples of voltage-gated ion channels are their effects

A

Na+
- depolarisation
= makes membrane potential more +ve

K+
- depolarisation
= makes membrane potential more -ve

Ca2+
- causes NT release

23
Q

what does charge separation result from?

give an example

A

the different permeability of the membrane to +ve and -ve ions

K+ is free to move out of the cell but will eventually stop when -ve K+ charges outside the cell repel
(even if conc grad favours this movement)
= equilibrium potential

24
Q

what is the Nernst potential?

what does it assume?

A

membrane potential at which there is no net flow of that ion from one side of the membrane to the other

  1. there’s a difference in conc of an ion across a membrane
  2. the membrane is selectively permeable to 1 type of ion only
25
Q

what is the reversal potential?

what does this value give a clue to?

A

membrane potential at which there is no ionic current

the ion responsible for a current/ AP
- based on the varying [out]/[in] ratios of ions

determining is a postsynaptic current will be excitatory (more+) or inhibitory (more-)

26
Q

what does the Goldmann equation calculate?

A

the membrane potential when considering the opening of the 3 main ion (Na+, K+ and Cl+) channels

27
Q

what is the standard resting potential?

what must occur for an action potential to be generated?

A

-40 to -90 mV

potential must get more +ve

sum of excitatory inputs» inhibitory inputs
to exceed threshold

28
Q

what does opening Na+ channels result in?

what about K+?

what about Cl-?

A

positive ions enter
= depolarisation
= excitatory PSPs

negative ions exit
= repolarisation
= inhibitory PSPs

negative ions enter
= hyperpolarisation
= IPSPs

29
Q

what does opening of Ca2+ ligand-gated ion channels result in?

what type of PSP is this?

A

NT release

EPSP
Ca2+ is a positive ion

30
Q

give 2 examples of receptors that lead to Na+ channel opening

A

ACh

glutamate

Neuroscience (17 decks)

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