PY 105 Chapter Notes - Chapter 10: Resting Potential, Active Transport, Cell Membrane
Neuronal Structure and Function
• Neurons are specialized cells that transmit and process information from one part of the body to
another
• This information takes the form of electrochemical impulses known as action potentials
• The action potential is a localized area of depolarization of the plasma membrane that travels in a
wave-like manner along an axon
• The signal is transformed into a chemical signal with the release of neurotransmitter into the
synaptic cleft, a process called synaptic transmission
Structure of the Neuron
• The basic functional and structural unit of the nervous system is the neuron
• The structure of these cells is highly specialized to transmit and process action potentials, the
electrochemical signals of the nervous system
• Neurons have a central body, the soma, which contains the nucleus and is where most of the
biosynthetic activity of the cell takes place
• Slender projections, termed axons and dendrites, extend from the cell body
• Neurons have only one axon but most possess many dendrites
• Neurons with one dendrites are termed bipolar; those with many dendrites are terms multipolar
• Neurons generally carry action potentials in one direction, with dendrites receiving signals and
axons carrying action potentials away from the cell body
• Axons can branch multiple times and terminate in the synaptic knobs that form connections with
the target cell
• Chemical messengers are released and travel across a very small gap called the synaptic cleft to
the target cell
The Action Potential
The Resting Membrane Potential
• The resting membrane potential is an electric potential across the plasma membrane of
approximately -70mV, with the interior of the cell negatively charged with respect to the exterior
of the cell
• Two membrane proteins are required to establish the resting membrane potential: Na+/K+
ATPase and the potassium leak channels
• The Na+/K+ ATPase pumps three sodium ions out of the cell and two potassium ions into the cell
with the hydrolysis of one ATP molecule (primary active transport)
• Result: sodium gradient with high sodium outside of the cell and a potassium gradient with high
potassium inside the cell
• Leak channels are channels that are open all the time, simply allow ions to "leak" across the
membrane according to their gradient
o Potassium leak channels allow potassium, but no other ions, to flow down their gradient out
of the cell
• Interior of the cell has a net negative charge than the outside of the cell with a net positive charge
• Cells can be described as polarized; negative on the inside and positive on the outside
• An action potential is a disturbance in this membrane potential, a wave of depolarization of the
plasma membrane that travels along an axon
• Depolarization is a change in the membrane potential from the resting membrane potential of
approximately -70mV to a less negative, or even positive, potential
• After depolarization, repolarization returns the membrane potential to normal
Depolarization
• Voltage-gated sodium channels
find more resources at oneclass.com
find more resources at oneclass.com
