Section 1, Lecture 3 - Survey in Biopsychology Class Notes

Notes - Survey in Biopsychology

Action Potential
(lecture 3)

action potential (AP) - a rapid depolarization of the cell memb
+30~+50mV
Basic Properties of the Action Potential
1. threshold of excitation - the membrane potential that mus
potential to occur: PSPs adding together (summation)
2. all or none phenomena - APs happen or they don't, there
(diwerent than PSPs)


Ionic Basis Of The Action Potential
1. vhen threshold is reached, Noltage-gated ;a+ channels o
i. ;a+ ions are pushed into the cell by both electros
2. ;a+ ions rush into the neuron4 the membrane depolarize
i. depolari/ationkrising phase - membrane potential
3. ;a+ channels snap shut at the peaK of the action potentia
z. Noltage-gated 6+ channels open (potassium channels op
i. 6+ ions are nov pushed outside the cell by both e
diyusion
5. 6+ channels open as ;a+ channels close4 membrane repo
polari/ed Nalue - depolari/ation)
T. 6+ channels start to close near the resting membrane po
close)
7. the membrane hyperpolarizes as 6+ channels close
i. hyperpolari/ationkfalling phase - short period of tim
tial is more negatiNe than it is at rest


Blocked Sodium Channels
tetrodotoxin (XX?) - a potent neurotoxin that blocKs sodium ch
potential e.g. noNocaine is a sodium channel blocKer