L8+9 - Neuronal Excitation and Dendritic Integration Flashcards
What is the K2p channel?
A background channel which is not voltage dependent therefore leaks potassium
Give the Nernst Equation
E= Rt/ZF log([X]o/[X]i)
Give the law of Weber Fechner
E=kln R/Ro
What happens in Hyperkalaemia?
Depolarisation of excitable cells –> neuromuscular symptoms, parasthesias and arrythmias
What happens in hypokaleamia?
Hyperpolarisation of excitable cells –> neuromuscular symptoms, arrythmias
What happens if one is extremely hyperkalaemic?
Strong depolarisation leads to inactivation of Nav channels therefore the heart is no longer excitable
What is the reversal potential?
the equilibrium potential for an ion channel
What is the equation for driving force?
Vm-Erev
What are the types of conduction?
Electrotonic
Continuous
Saltatory
Give the equation for the length constant
Lamda = root of aRm/Ri
What are the 3 neurite filtering effects?
Attenuation of amplitude
Slowing of kinetics
Delay
What is the equation for the time constant?
tau m = RmCm
What is the conduction velocity proportional to?
length constant/time constant
What is dendritic input impedence?
Reduces current as it travels towards the soma
What is synaptic scaling?
Homeostatic plasticity that allows single neurons to regulate their overall AP firing rate
What is synaptic democracy?
Equalization of synaptic efficacies so that all synapses of a neuron have the same potential for affecting the post synaptic response regardless of their locations across the dendritic tree
What is the name of the mathematical model that models APs
The hodgkin Huxley model
Outline the features of AP conduction in dendrites
They are known as dendritic spikes
They usually travel backwards, carrying information towards the post-synaptic membrane.
When travelling forwards it is usually for a signal that would not reach the soma through passive conduction.
What are the types of dendritic spikes?
Na Ca LTS Ca spike and Na burst Rhythmic bursting
What are the functions of dendritic spines?
Chemical compartmentalization
Space for more synapses
Electrical compartmentalization
How do dendrtic spines from electrical compartments?
they have spine neck resistance which is greater flowing from the spine to the dendrite, this could be to prevent dendritic saturation.
What is shunting inhibition?
It reduces the excitatory potential by division rather than subtraction by reducing the resistance locally.
Outline the details of Hippocampal LTP
It is triggered by tetanic innervation by CA3 axons, causing Em to rise above -30mV thus removing the Mg ion blocking the NMDA receptor.
Outline the signalling process for LTD
GPCR Glu receptors –> IP3–> Ca release from the ER –> No synthase activation –> NO –> GC activation –> cGMP –> G-kinase activation –> phosphorylation of Glu ionotropic recemptors –> receptor internalization
What is the Bienenstock Cooper Munro theory?
That the concentration oc calcium tunes the synaptic weights. So low [Ca] causes LTD and high [Ca] causes LTp.
Give Hebb’s rule regarding STDP
When an axon of cell A is near enough to excite cell B and repeatedly does so, some growth process or metabolic change takes place in one or both cells so that A’s efficency as one of the cells firing B is increased.
Outline the basic rules of STDP
if Input before output –> LTP
If output before input –> LTD
