L8+9 - Neuronal Excitation and Dendritic Integration

Question 1

What is the K2p channel?

Answer 1

A background channel which is not voltage dependent therefore leaks potassium

Question 2

Give the Nernst Equation

Answer 2

E= Rt/ZF log([X]o/[X]i)

Question 3

Give the law of Weber Fechner

Answer 3

E=kln R/Ro

Question 4

What happens in Hyperkalaemia?

Answer 4

Depolarisation of excitable cells –> neuromuscular symptoms, parasthesias and arrythmias

Question 5

What happens in hypokaleamia?

Answer 5

Hyperpolarisation of excitable cells –> neuromuscular symptoms, arrythmias

Question 6

What happens if one is extremely hyperkalaemic?

Answer 6

Strong depolarisation leads to inactivation of Nav channels therefore the heart is no longer excitable

Question 7

What is the reversal potential?

Answer 7

the equilibrium potential for an ion channel

Question 8

What is the equation for driving force?

Answer 8

Vm-Erev

Question 9

What are the types of conduction?

Answer 9

Electrotonic
Continuous
Saltatory

Question 10

Give the equation for the length constant

Answer 10

Lamda = root of aRm/Ri

Question 11

What are the 3 neurite filtering effects?

Answer 11

Attenuation of amplitude
Slowing of kinetics
Delay

Question 12

What is the equation for the time constant?

Answer 12

tau m = RmCm

Question 13

What is the conduction velocity proportional to?

Answer 13

length constant/time constant

Question 14

What is dendritic input impedence?

Answer 14

Reduces current as it travels towards the soma

Question 15

What is synaptic scaling?

Answer 15

Homeostatic plasticity that allows single neurons to regulate their overall AP firing rate

Question 16

What is synaptic democracy?

Answer 16

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

Question 17

What is the name of the mathematical model that models APs

Answer 17

The hodgkin Huxley model

Question 18

Outline the features of AP conduction in dendrites

Answer 18

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.

Question 19

What are the types of dendritic spikes?

Answer 19

Na
Ca
LTS
Ca spike and Na burst
Rhythmic bursting

Question 20

What are the functions of dendritic spines?

Answer 20

Chemical compartmentalization
Space for more synapses
Electrical compartmentalization

Question 21

How do dendrtic spines from electrical compartments?

Answer 21

they have spine neck resistance which is greater flowing from the spine to the dendrite, this could be to prevent dendritic saturation.

Question 22

What is shunting inhibition?

Answer 22

It reduces the excitatory potential by division rather than subtraction by reducing the resistance locally.

Question 23

Outline the details of Hippocampal LTP

Answer 23

It is triggered by tetanic innervation by CA3 axons, causing Em to rise above -30mV thus removing the Mg ion blocking the NMDA receptor.

Question 24

Outline the signalling process for LTD

Answer 24

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

Question 25

What is the Bienenstock Cooper Munro theory?

Answer 25

That the concentration oc calcium tunes the synaptic weights. So low [Ca] causes LTD and high [Ca] causes LTp.

Question 26

Give Hebb’s rule regarding STDP

Answer 26

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.

Question 27

Outline the basic rules of STDP

Answer 27

if Input before output –> LTP

If output before input –> LTD