Synaptic Integration & Plasticity Flashcards
What is the modality of a circuit?
Connectivity of neurones
What is the intensity of an electrical signal determined by?
Patterns of activity / number of action potentials
What perceptual function is linked to the skin stimulus of light touch?
Skin movement
Which receptor gives information about skin movement?
Hair follicles
What perceptual function is linked to the skin stimulus of dynamic deformation?
Slipping objects
Which receptor gives information about slipping objects?
Meissner corpuscle
What perceptual function is linked to the skin stimulus of vibration?
Contact with objects
Which receptor gives information about contact with objects?
Pacinian corpuscle
What perceptual function s linked to the skin stimulus of indentation depth?
Fine tactile dicrimination
Which receptor gives information about form and texture (fine tactile discrimination)?
Merkel cell/neurite complex
What perceptual function is linked to the skin stimulus of stretch?
Direction of object motion and finger position
Which receptor gives information about hand shape and direction of object motion?
Ruffini corpuscle
What perceptual function is linked to the skin stimulus of touch?
Pleasant contact and social interaction
Which receptor gives information about pleasant contact and social interaction?
C-fibre LTM
What perceptual function is linked to the skin sensation of injurious force?
Skin injury and pain
Which receptor gives information about skin injury and pain?
Nociceptor
What do cochlear implants do?
Electrically stimulate the auditory nerve
How is an electrical current generated by ions?
Flow of ions between compartments down electrochemical gradient
What is the capacitance of a system?
Ability to store an electrical charge
Why does membrane potential increase quickly then slowly when current is applied?
Current builds up as capacitance then flows through resistance pathway
Why does membrane potential decrease quickly then slowly when applied current is halted?
Built-up capacitance is released via the resistance pathway
Why does the voltage effect of a membrane current take time?
Membrane capacitance
When is membrane potential proportional to applied current?
Below-threshold potentials
When is membrane potential no longer proportional to applied current?
Active electrical action potential propagation
Why doesn’t an action potential diminish over long distances?
Action potentials regenerate themselves
What equipment is used when measuring the electrical properties of neurones?
Glass pipette, model cell, electrode connected to amplifier (resistor and capacitor)
How do model cells differ from real ones?
No active neuronal properties and sit at 0mV
V = ?
I x R
Time constant =
Rm x Cm
What is the length constant a measurement of?
Rate of decay of passive membrane potential changes against distance travelled
I = ?
V x G
What is conductance measured in?
G in Siemens
What is a voltage clamp used for?
Measuring isolated currents within a larger current
What is a patch clamp used for?
Measure membrane potential using a tight seal between membrane and pipette
How does a voltage clamp allow separation of components of membrane current?
Negating the capacitative current
What are the three neuronal membrane currents?
Potassium, sodium and leak
Which direction is the spike caused by depolarisation of neuronal membranes?
Downwards
Which direction is the spike caused by an action potential depolarisation?
Upwards
What are the glutamate receptors?
GABA and NMSA
What is the Nernst equation?
Ek = (RT/zf) log ([x+]out/[x+]in)
Why is the equilibrium potential of a cation channel zero?
Equal concentrations of cations in and out of the neurone (between Na and K)
What are GABA(A) receptors selective for?
Cl-
During early development, where is Cl- concentrated?
Inside neurones
What is achieved by the expression of KCC2 transporters as neurones mature?
Lower intracellular Cl- concentration, very negative reversal potential for Cl-
What determines the current carried by an ion?
Conductance multiplied by driving force for that ion
Where in the brain is the cerebral cortex?
Grey matter on the outside
Which neurones can receive back-propagated action potentials?
Cortical neurones
When is signal summation linear?
When the threshold has not been reached
Which neurone properties cause non-linear summation of signals?
Active
What is the specialisation of interneurones at the axon hillock?
To modulate and shut down certain signals
What is temporal summation?
Successive synaptic inputs that occur before the neurone fully recovers
What is spatial summation?
Multiple synaptic inputs onto different parts of a neurone
How is coincidence detection produced in central synapses?
Requirement of summation of many inputs to generate an action potential
What are detonator synapses?
No summation required, presynaptic input always leads to postsynaptic output
Name three examples of detonator synapses
Peripheral NMJs, Calyx of Held, Mossy fibre in hippocampus
What causes mossy fibre synapses to be converted from sub-detonation into full-detonation mode?
Short-term plasticity after high frequency stimulation
How is long-term plasticity expressed in mossy fibres?
Changes in neurotransmitter release
What is often needed for development of synaptic plasticity?
Communication between pre- and post-synaptic terminals
How do cannabinoids cause synaptic plasticity?
Retrograde signalling
What makes NMDA receptors voltage-dependent?
Mg2+ blockade near resting membrane potential
How do NMDA receptors act as coincidence detectors?
They only open when there is both glutamate release and post-synaptic depolarisation
What is the result of repetitive activation of AMPA and NMDA receptors?
More AMPA receptors expressed, synaptic plasticity
What often accompanies synaptic plasticity?
Structural remodelling and spine growth
What receptor mediates synaptic plasticity?
NMDA receptors
What receptor causes synaptic plasticity?
AMPA receptors
