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
