Behavioral Neuroscience, Lecture on September 24th
Introduction to Neurophysiology
Neural communication in the brain,
> between neurons, chemical.
>> happens at synapses.
> within neurons, electrical.
>> neural electrical impulse- changes in the relative charge of the inside the cell
versus the outside of the cell.
>>> how does this happen? By changing the distribution of ions along the
All about ions,
An ion is an electrically charged atom or molecule
> sometimes have unequal number of protons and electrons.
Two major types,
Anion, extra electrons (negative - Cl-)
Cation, extra protons (positive - Na+, K+)
> Anion vs. Cation defends on chemical properties of atom.
Electrical currents in neuronal membranes are caused by the movement of
electrically charged atoms (ion) in and out of the cell - through ion channels.
> Ion channels are made of proteins that span the membrane (transmembrane
proteins) have an opening that allows ions to flow through them.
> Some neurotransmitters bind to receptor sites on the outside surface of ion
channels and cause them to open or close.
The neuron at rest:
> Unequal distribution of charges, more anions inside the cell and more cations
outside of the cell.
> You can the cell has an electrical gradient, a membrane potential (there is a
potential for these ions to move), and the neuron is polarized (there is a
difference) - in this case it would be negatively polarized since there is more
negative cells in the membrane.
Measuring the resting potential
> Reference electrode - outside of the cell
> Recording electrode - inside the cell
> Oscilloscope - lets us visualize the cell
> Usually the resting voltage of neurons is around -60 to -70volts.
Graded changes in potential,
> Can be artificially applied with an electrical stimulator.
>> Another set of electrodes and the simulator pumps ions into the cell. Depolarization vs. Hyperpolarization
> Depolarization, membrane potential becomes more positive.
>> closer to zero.
> Adding more positive charge inside the cell.
> Hyperpolarization, charge inside cell becomes even more negative compared to
>> further from zero.
The effects of hyperpolarizing and depolarizing stimuli on a neuron,
> after pumping negative ions in, there is a greater change at the sight of
injection but the effects fade across the neuron. (Hyperpolarizing)
> if we add a few positive ions there is minimal changes. If we add more positive
ions there are drastic spike chan