This is a comprehensive and detailed note on neuron and electrical transmission, endocrine system, organization of the nervous system for Psy 627.
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There are three ways that nerve cells communicate with each other
- Electrical
- Chemical
o Neurotransmitters
- Hormonal
Neuron
- Soma
o Or cell body, contains the cell’s nucleus, which contains DNA and all
chromosomal information
o The soma produces energy, manufactures neurotransmitters, and works to
remove intracellular waste
- Dendrites
o Protrude out from the soma and contain receptors
o The main responsibility of the dendrites is to receive electrical and chemical
signals and to alert the soma that a signal has been received so that the soma
can respond to the signal
- Axon
o The tubular structure extends out from the soma that transmits signals from the
soma to the terminal buttons
- Myelin sheath
o Some axons are surrounded by an insulating factor known as a myelin sheath
Myelinated axons transmit signals more rapidly
Myelinated axons appear white when imaged on MRI, thus the term
white matter
- Nodes of Ranvier
o Myelinated axons transmit signal from the soma much more rapidly, because of
the signal being able to jump from node of Ranvier to node of Ranvier.
o Myelinated axons are present in neurons that are responsible for rapid
transmission of signal like in cognitive processing and moving.
- Terminal buttons
o Located at the end of the axon
o Terminal buttons contain synaptic vesicles, which are filled with neurotransmitter
molecules
o When signaled to do so, the terminal buttons will facilitate the release of a
specific neurotransmitter into active circulation within the CNS
o Contained within these buttons are synaptic vesicles which are filled with
neurotransmitter substances and are ready to release into the CNS when the
soma is stimulated to release them.
, Electrical transmission within a neuron
- All neuros have an electrical charge, which is negative 70 millivolts
o The negative 70 mV state (inactive state) of a neuron is referred t as the resting
potential
- When a neuron is stimulated to generate and release, an electrical discharge known as
an action potential is created and released into the CNS.
o The action potential stimulates other neurons within the CNS to also generate
and release Action Potential
o In order for this electrical signal to be generated, we have to switch around the
chemicals that are outside of the cell, the chemicals that are inside of the cell,
and we have to change this negative 70 millivolts up to positive 40 millivolts in
order for this neuron to generate a burst of electricity that makes its way into the
central nervous system.
o Outside of the cell the fluid contains Na and Cl and is positively charged. Inside
the cell, the fluid contains K and negative anions (-A)
o Within your eyes, you have millions of little what are referred to as
photoreceptors, rods and cones. Rods allowing you to see black and white and
cones to see color. When light falls on one of those million photoreceptors, all of
which are neurons, it changes the resting potential of that little photoreceptors
to +40 millivolts and then the neuron generates a burst of electricity that
ultimately travels back through the optic nerve allowing you to see.
o This is the grand concept of how when you change the resting potential from
negative 70 to positive 40 mV of a neuron, you will see a whole ability of that
neuron to generate a burst of electricity in the form of an action potential.
- Fluid outside of the soma is referred to as the extracellular fluid, which contains large
volumes of Na+ and Cl- and is overall negatively charged.
- Fluid inside of the soma is referred to as the intracellular fluid and contains large
volumes of K+ and negative anions (A-) and is positively charged.
- Diffusion: molecules within a solution naturally work to diffuse evenly throughout the
solution.
- Electrostatic pressure: molecules with the same electrical charge repel each other.
o Electrostatic pressure keeps Na+ and Cl- molecules outside of the soma and
maintains K+ and A- molecules inside of the soma.
- When the threshold of excitation of a neuron is reached, an action potential is generated
by the soma of the neuron.
- The resting potential of the neuron rapidly changes from -70 Mv to +40 Mv, at which
point a bust of electricity is generated by the soma.
- When the threshold of excitation is reached, Na+ channels on the soma’s membrane
open and positively charged. Na+ rushes into the soma, causing the cellular charge to
change from -70 Mv to +40 Mv, at which point the electrical burst is generated by the
soma.
- Next K+ channels on the soma membrane open to allow for K+ to leave the cell: this
occurs in order to return the cell to its -70 Mv resting potential.
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