PSY 201 Lecture Notes - Lecture 2: Cognitive Deficit, Neuroglia, Basal Ganglia
1 Jun 2018
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3.1 How Does the Nervous System Operate?
• Neurons: receive, integrate, and transmit information in the nervous system
o Complex networks of neurons sending and receiving signals are the functional basis
of all psychological activity
o Do not communicate randomly or arbitrarily. They communicate selectively with
other neurons to form circuits, or neural networks
The Nervous System Has Two Basic Divisions
• Central nervous system (CNS): consists of the brain and the spinal cord, both of which
contain massive numbers of neurons
o Organizes and evaluates the information and then directs the PNS to preform specific
behaviors or make bodily adjustments.
• Peripheral nervous system (PNS): consists of all the other nerve cells in the rest of the
body
o Sends a variety of information to the CNS.
o Includes the somatic and autonomic nervous systems.
• Somatic: involved in voluntary behavior
• Automatic: less voluntary actions of body such as controlling heart rate and
other bodily functions
The Neurons are Specialized for Communication
• Nerve cells are powered by electrical impulses and communicate with other nerve cells
through chemical signals
• Reception Phase: neurons take in the chemical signals from neighboring neurons
• Integration Phase: incoming signals are assessed
• Transmission Phase: they pass their own signals to yet another receiving neuron
TYPES OF NEURONS
• Sensory neurons: detect information from the physical world and pass that info along to
the brain through the spinal cord
o Somatosensory nerves: sensory nerves that provide information from the skin and
muscles
• Motor Neurons: direct muscles to contract or relax, thereby producing movement.
• Interneurons: communicate within the local ore short-distance- circuits
o Integrate neural activity within a single area rather than transmitting information to
other brain structures or to the body organs
NEURON STRUCTURE
• Dendrites: short, branchlike appendages that detect chemical signals from neighboring
neurons
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• Cell body: information received via the dendrites from thousands of other neurons is
collected and integrated
• Axon: long narrow outgrowth where electrical impulses are transmited along once the
incoming info has been integrated in the cell body
o Longest axons reach from the spinal cord to the big toe
• Terminal buttons: knoblike structures at the end of the axon
• Synapse: the site where chemical communication occurs between neurons
o The structure at the end of the axon where information is represented as a chemical
signal between neuron
• Neurotransmitter: molecule that carries the neuronal signal across the synaptic
cleft
• Receptor: neurotransmitter-dependent ion channel
• Chemicals leave one neuron, cross they synapse, and pass signals along to other neurons'
dendrites
• Neuron covered with a membrane
o Membrane: fatty barrier that doesn’t dissolve in the water environment inside and
outside the neuron
• Semipermeable: some substances move in and out and others do not
• Ion channels: pores located on the cell membrane that allow ions to pass in and
out of the cell when the neuron transmits signals down the axon
• Regulates the concentration of electrically charged molecules
The Resting Membrane Potential is Negatively Charged
• Resting membrane potential: the difference in the electrical charge inside and outside the
membrane when a neuron is resting
o Occurs because the ration or negative to positive ions is greater inside the neuron than
outside it.
o The electrical charge inside the neuron is slightly more negative than the charge out
side
o Polarized: when a neuron has more negative ions inside than outside
• Polarized state of resting neuron creates the electrical energy necessary to power
the firing of the neuron
• Three forces maintain resting potential:
o Diffusion: ions move from areas of high concentration to areas of low concentration
o Electrostatic pressure: ions of opposite charge attract
o Sodium potassium pump: pumps 2 Na+ out, 2 K+ in
• drives the cell to be negatively charged
• requires energy from the neuron
• functions to make a cell more polarized
THE ROLES OF SODIUM AND POTASSIUM IONS
• Each ion channel matches a specific type of ion
o Sodium channels allow ONLY sodium to pass through the membrane
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o Potassium channels allow ONLY potassium to pass through the membrane
o Different ion channel means different postsynaptic results
• Gating mechanism:
o open gate: ions flow in and out of the membrane.
o Closed gate: prevents passage
• Selective permeability:
o The membrane allows some types of ions to cross more easily than others
• there is often more potassium in the neuron than sodium
• Sodium-potassium pump: increases and decreases sodium inside the neuron and helps
maintain the resting membrane potential
o pumps 2 Na+ OUT…..and…..2 K+ IN
o drives the cell to be negatively charged
o requires energy from the neuron
o functions to make a cell more polarized
Action Potentials Cause Neural Communication
• Action potential (neural firing): the electrical signal that passes along the axon which
causes terminal buttons to release chemicals that transmit signals to other neurons
CHANGES IN ELECTRICAL POTENTIAL LEAD TO ACTION
• A neuron receives chemical signals from nearby neurons through its dendrites
• By affecting polarization, these chemicals tell the neuron where to fire
• Excitatory signals: depolarize the cell membrane
o Decrease polarization by decreasing the negative charge inside the cell
o With the decrease in polarization, it is more likely that neurons will fire
• Inhibitory signals: hyperpolarize the cell
o Increase polarization by increasing the negative charge in the cell
o Decrease likelihood of neurons of firing
• If the total amount of excitatory input surpasses the neuron's firing threshold, an action
potential is created
• When a neuron fires…
o SODIUM gates open and allow sodium ions to rush into the neuron
causing the inside to be slightly more positive than the outside
o A Fraction of a second later, POTASSIUM channels open to allow
potassium ions to flow out of the membrane
o A change from a negative charge to a positive one
a. The electrical charge inside the cell starts out negative in it's initial
resting state
b. As the cell fires and allows more positive ions inside, the charge
becomes more positive
c. Through the sodium potassium pump and natural restoration,
membrane becomes negative again
ACTION POTENTIALS SPREAD ALONG THE AXON
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
They communicate selectively with other neurons to form circuits, or neural networks. Includes the somatic and autonomic nervous systems: somatic: involved in voluntary behavior, automatic: less voluntary actions of body such as controlling heart rate and other bodily functions. Interneurons: communicate within the local ore short-distance- circuits. Integrate neural activity within a single area rather than transmitting information to other brain structures or to the body organs: dendrites: short, branchlike appendages that detect chemical signals from neighboring neurons. Ion channels: pores located on the cell membrane that allow ions to pass in and out of the cell when the neuron transmits signals down the axon: regulates the concentration of electrically charged molecules. Action potentials cause neural communication: action potential (neural firing): the electrical signal that passes along the axon which causes terminal buttons to release chemicals that transmit signals to other neurons. Increase polarization by increasing the negative charge in the cell: decrease likelihood of neurons of firing.
