chapter 4- Neural Conduction and Synaptic transmission Flashcards
is the difference in electrical
charge between the inside and
the outside of a cell.
membrane potential
•
Position the tip of one electrode inside the neuron
and the tip of another electrode outside the neuron
in the extracellular fluid.
• The intracellular electrodes are called
microelectrodes; their tips are less than onethousandth of a millimeter in diameter.
Recording the
Membrane
Potential
• Neurons have a selectively permeable membrane
• During resting conditions membrane is;
• Permeable to Potassium (K+) (channels are open)
• Impermeable to Sodium (Na+) (channels are closed)
Resting Membrane Potential
• The resting potential is thus -70 millivolts
• The resting potential exist because positively
and negatively charged ions are distributed
unequally on the two sides of the neural
membrane: the concentration of Na+ and Clare higher outside the neuron, and the
concentration of the K+ and various
negatively charged proteins are higher inside
the neuron
Ionic Basis of the Resting
Potential
The ions in neural tissue are in
constant random motion, and particles in
random motion tend to become evenly
distributed because they are more likely to
move from areas of high concentration to areas
of low concentration than vice versa.
RANDOM MOTION
Any accumulation of
charges, positive or negative, in one area tends
to be dispersed by the repulsion among the like
charges in the vicinity and the attraction of
opposite charges concentrated elsewhere
ELECTROSTATIC PRESSURE.
Two (2) factors that act to distribute ions
equally throughout the intracellular and
extracellular fluids of the nervous system
RANDOM MOTION
ELECTROSTATIC PRESSURE
Four kinds of
ions that
contribute
significantly
to the resting
potential:
sodium
ions (Na*),
potassium
ions (K*),
chloride
ions (Cl+),
Negatively
charged
protein
ions.
are
released from buttons into
synaptic clefts, where they
induce Excitatory postsynaptic
potential or Inhibitory
postsynaptic potential in other
neurons by binding to receptors
on their postsynaptic
membranes.
Neurotransmitter molecules
is the process of
neurotransmitter release. When
a neuron is at rest, synaptic
vesicles that contain smallmolecule neurotransmitters
tend to congregate near
sections of the presynaptic
membrane that are particularly
rich in voltage-activated
calcium channels
EXOCYTOSIS
is the more common of the two deactivating mechanisms. The
majority of neurotransmitters, once released, are almost immediately
drawn back into the presynaptic buttons by transporter mechanisms.
• Other neurotransmitters are degraded (broken apart) in the synapse by
the action of enzymes proteins that stimulate or inhibit biochemical
reactions without being affected by them.
Reuptake
have been shown to release
chemical transmitters, to contain
receptors for neurotransmitters, to
conduct signals, and to participate in
neurotransmitter reuptak
Astrocytes
are narrow spaces
between adjacent neurons that are
bridged by fine tubular channels, called
connexins, that contain cytoplasm
Gap junctions
• Chemical messengers
that allow signals to
cross synapses to
transmit information
from a nerve cell or
neutron to a target cell
• Coordinate behavior by
stimulating an action or
inhibiting an impulse
Neurotransmitters
excitatory neurotransmitter
important to memory, cognition, and mood
regulation
Glutamate
