L2 - Action Potential Flashcards
T/F neurones are classified as non-excitable tissue
FALSE - neurones are excitable tissues
In an undisturbed neurone, the plasma membrane is polarized - what does this mean?
there is an uneven distribution of positive and negative charge across the membrane
is the inside of the plasma membrane more positively or negatively charged?
negatively
what is the value of resting membrane potential?
70mV
how does the membrane potential change?
the movement of certain ions in and out of the neurone through specific voltage gated ion channel proteins in the plasma membrane
how does nerve action potential begin?
arrival of a stimulus to a neurone causes a change in permeability of the plasma membrane to Na+ and K+
explain the process of depolarization
the polarity is reversed (neg->pos) as Na+ ions diffuse into the cell through sodium in channels
explain the process of repolarization
the sodium ion channels and K+ channels open allowing K+ to diffuse out of the cell - this causes the membrane potential to revert back to the resting state
how does the sodium-potassium exchange pump help to maintain the RMP
using ATP to pump Na+ out of the cell while simultaneously pumping K+ into the cell
does active transport require ATP?
yes - produced in the mitochondria in the presence of oxygen
what is the all-or-nothing principle?
action potential can only occur if the membrane potential reaches a certain threshold - no half action
an action potential must complete before another can generate
what is the refractory period?
extends from the time the neurone reaches threshold until it returns to the RMP
explain action potential propagation with continuous conduction?
occurs in unmyelinated neurones - continuous propagation as each section of the axon is sequentially depolarized
slow conduction (heel to toe)
explain action potential propagation with saltatory conduction?
axons are wrapped in a myelin sheath which is sectioned by intervals called nodes of Ranvier
action potentials are conducted only at the nodes
fast conduction (big steps)
what is a synapse?
a functional connection between a neurone and either another neurone or a muscle or gland cell (electrical or chemical)
