Graded Potentials And Action Potentials Flashcards
What are excitable tissues?
Nerve and muscle cells are excitable tissues, they produce rapid changes to their RMP which produce electrical signals
-Neuron’s use these signals to receive and transmit messages
-Muscles respond to the electrical signals by contracting
Ion channels
Ion channels is the fastest ways ions move across a cell membrane
They are pores in cell membranes and selective for one ion and passive so no energy is required as ions go down the electrochemical gradient
Leak channels so they are open all the time
But can be gated
Graded potential
Short distance signals, changes in the RMP occur often
It has a triggering stimuli - where neurotransmitters act on the ligand ion gated channels
Can be hyper of depolarised
Action potential
Long distance signals , large changes in the RMP as it reverses (becomes positive)
Voltage gated channels
Na+ channel has two voltage gates- must stay open for na+ to enter.
Gate 1= activation gate- closes at RMP and opens quickly in response to depolarization
Gate 2= inactivation gate- opens at RMP and closes quickly in response to depolarisation
K+ channel has a single voltage gate which closes at RMP and opens slowly in response too depolarization
Restoration of RMP
Concentration of ICF and ecg is restored using na/k/ atpase pump
3Na+ pumped into the ECF
2K+ pumped into ICF
Two types of AP propagation
Contiguous conduction is conduction in unmyelinated fibers
Saltatory conduction is rapid conduction in myelinated fibers
Absolute refractory period
During the absolute refractory period , a neuron cannot respond to another
stimulus as it is already generating an AP - total inability for the new AP to be generated
Relative refractory period
During the relative refractory period the neuron’s threshold is elevated because repolarization is ongoing - second AP can be generated by a triggering response much higher than the usual
