Chapter 2 Neurons and the Action Potential Flashcards
Components of a neuron
dendrites, a cell body, an axon, and synaptic terminals
The functional subdivision of the structure of a neuron.
receiving, integrating, and transmitting compartments.
Polarization
a concept which describes that the dendrite receives, the cell-body integrated, and the axons transmit.
the outer membranes of the neurons
made of fatty substances, are draped around a cytoskeleton.
cytoskeleton
built up of rods of tubular and filamentous proteins that extend out into dendrites and axons alike.
dendritic spines
tiny protuberances that stick out from the dendrites
growth factors
molecules that the end-points of the axons also respond to. these factors are taken up inside and then transported to the cell body where they influence the expression of neuronal genes and hence the manufacture of new proteins.
synapses
the junctional spots of dendrites and neurons. most of the synapses on cells in the cerebral cortex are located on the den dendritic spines that stick out like little microphones searching for faint signals
synaptic transmission
communication between nerve cells at these contact points
excitation
currents that come into the cell
inhibition
currents that move out of the cell
action potentials
the electrical pulses that axons of neurons transmit
ion channels
contained in the axonal membrane, can open and close to let through electrically charged ions.
electrical depolarisation
When channels open, the Na+ or K+ ions flow down opposing chemical and electrical gradients, in and out of the cell
resting membrane potential
The Na+-K+ pump open, sodium and potassium channels closed. The resting membrane potential is -70. It is negative because 3 sodiums went out and 2 potassium moved in, and they are both positive ions, which causes there are more positive ions outside than inside
Failed initiations
initiation of action potential failed, unable to go to the depolarization, go back to the resting state.
Action potential - Depolarization
Start of the action potential, sodium channel opened, a pulse of sodium ions flashes into the cell and a new equilibrium is established within a millisecond. This stage is positive because there are more positive ions inside than outside.
Action potential - Repolarization
Potassium channel open. the other two are closed. There are more positive ions outside.
the refractory period
a brief period of silence
all-or-nothing
the distinctive characteristics of the action potential, they don’t vary in size, only in how often they occur. Thus, the only way that the strength or duration of a stimulus can be encoded in a single cell is by variation of the frequency of action potentials.
myelin sheath
In many axons, action-potentials move along reasonably well, but not very fast. In others, action potentials really do skip along the nerve. This happens because long stretches of the axon are wrapped around with a fatty, insulating blanket, made out of the stretched-out glial cell membranes,
