CPG organisation and pacemakers Flashcards
what does CPG stand for
central pattern generator
where is CPG locotion
throughout NS but mostly in spinal cord
what are CPGs
network of neurons which generate a range of rhythmic movements
what are 4 factors which determine CPG output
intrinsic properties
synaptic connectivity
properties of synapses
neuromodulation
what are intrinsic properties
individual neurons in network (ion channels and neurotransmitter expression) determine their output
what are two factors which are reflected by CPG rhythmicity
oscillating networks
endogenous bursters
what are oscillating networks
simple network of neurons which generate activity of time dependent processes exist to enhance or reduce activity of neurons
what do oscillating networks utilise?
the half centre hypothesis of inhibition
what is the main driver of half centre hypothesis
reciprocal inhibition and fatigue
what are endogenous bursters
pacemaker cells
capacity to burst spontaneously
what are the three stages of rhythmic pacemaker activity
initiation - depolarisation
maintenance
termination
what are the three channels involved in initiation of depolarising phase
hyperpolarisation activated inward current (h)
low voltage activated calcium currents (ILVA)
transient potassium current (Ia)
what is the main feature of a h channel
mixed cationic ions flow (k and na)
causes depolarisation if the membrane is depolarised
what is the main feature of ILVA channels
inactivating (transient) calcium currents activated at low voltages
how do we remove inactivation caused from ILVA channels
hyperpolarisation needed
what is the main feature of Ia channels
outward current of transient hyperpolarising potassium
what are three channels associated with the maintenance of depolarisation
persistent sodium current (INaP)
high voltage activared calcium currents (IHVA)
slow non-selective cationic current (ICAN)
what is the main feature of INaP channels
non-activating, persistent current
lower activation theshhold than inactivating Na
same channels as inactivating Na channels but in different form
what is main feature of IHVA channels
activated by depolarisation from resting membrane potential
activated from resting potential
what is the main feature of ICAN channels
calcium activated current
no voltage sensitivity
what are two channels which contribute to termination
inactivating sodium currents (lna)
calcium activated potassium currents (IK(Ca))
what is the main feature of INa channels
cause progressive slow in firing- inactivate when depolarised
what is the main feature of IKCa channels
activated by calcium entry
and this drives K outflow
underlies AHP
what is AHP
post action potential afterhyperpolarisation
