Transmitters and Excitability Flashcards
What is needed to transmit and control signals?
Transmitters
Receptors
Extracellular matrix eg glial cells also have a role in controlling the ion concentration in the extracellular matrix
What happens to the resting potential fall during development?
Resting potential falls and is more negative
What other changes occur in development?
Input resistance falls - ability of current in the cell to flow
Membrane time constant falls - how quickly the potential can fall
Why does MTC change during development?
The neurons get bigger so they store more charge
What does MTC depend on?
Resistance and capacitance
capacitance is the ability to store charge
What are the two principal routes of action potential development?
Long calcium dependent then short sodium dependent ( tetrodotoxin resistance, eg mouse DRG, Rohan-Beard cells
Short sodium dependent (eg mouse spinal cord)
What are rohan beard cells?
Mechanosensory cells of lower vertebrate dorsal spinal cord
They are found in the spinal cord before DRGs become functional
What are the first action potentials characteristics?
Like a cardiac action potential as it is calcium driven
Elongated profile
10ms
After development what happens to the action potential?
It shortens to 2.5 ms
There are two factors which cause this - volatage gated sodium channels shut very quickly and voltage gated potassium channels are triggered for depolarisation
What is a rectifier?
A channel that only allows current through one way
What is a delayed rectifier? Give an example
A channel that only opens some time after its threshold has been reached
Eg outward delayed potassium rectifiers allow positive charge out of neurons after an action potential
These shorten the action potentials
What are the three types of spiking in development?
Fast spiking (FS) Regular spiking (RS) Immature multiple spiking (IMS)
Calcium channels appear as what?
Low voltage activated (Iva) T-currents
What are N and L currents?
N = axon terminals L = used to control transcription
Spontaneous calcium waves can influence what?
Growth of processes
Differnetiation
Neuronal development involves changes in receptor….
populations
subunits
localisation
efficacy
GABAa receptors are what type of receptors?
Ionotropic
GABAb receptors are what type of receptors?
Metabotropic
What is the structure of a GABAa receptor?
2 alpha, 2 beta and 1 gamma
Describe GABA receptor development?
In GABAa development they depolarise
Immature neurons have increased Cl- inside
Cl- efflux causes sodium and calcium influx via VAC’s
What changes between immature CNS and mature CNS neurons?
Immature neurons have an increased expression of NKCC1 and decreased expression of KCC2
The mature neurons have increased expression of KKC2 and decreased expression of NKCC1
