Psychology Chapter #3 Notes
(Starting from page 87)
Reviewing the Principles – What is the Genetic Basis of Psychological
•Human behavior is influenced by genetic processes.
•People inherit both physical and personality traits from parents.
•Methods have been developed to either enhance, or interrupt gene
•Scientist are looking at how to modified RNA can be used to silence
gene expression entirely.
How does the Nervous System Operate?
•The nervous system takes in a variety of information from the external
world, evaluates the information, and produces behaviors, or makes
bodily adjustments to adapt to the environment.
Neurons are specialized for Communication
•Neurons – the basic unit of the nervous system that operates through
electrical impulses, which communicate with other neurons through
chemical signals. Neurons receive integrate, and transmit information
on the nervous system.
oCells that specialize in communication
o3 functions, 1) take in information (reception) 2) integrate those
signals (conduction) 3) pass signals to other neurons
•Neurons can take all different shapes and sizes, but typically share 4
oDendrites – branchlike extensions of neurons that detect
information from other neurons. (Short out growths that
increase the neurons receptor field.) – the branch like
appendages detect chemical signals from neighboring neurons
oCell body- In the Neuron, where information from thousands of
other neurons is collected and processed. – Also the site of
metabolism and genetic action.
oAxon – a long narrow outgrowth of a neuron by which
information is transmitted to other neurons. (This region varies
a lot in length)
The longest Axons go from your spinal cord, to big toe.
oTerminal Button – small nodules at the end of axons that
release chemical signals from the neuron to an area called
oSynapse – the site for chemical communication between neurons
•The boundary of a neuron is defined by its membrane (double layer of
fatty molecules called lipids)
Types of Neurons
•3 basic types – sensory, motor and interneuron.
•Sensory – detect information from the physical world and pass that
information to the brain. Often called afferent neurons, b/c. They send
their signals from the body to the brain
•Motor – direct muscles to contract or relax. (Produce movement)
efferent neurons because they travel signals from the brain to the
•Interneuron - communicate within local or short distance (typically
within a specific brain region)
•The nerves that provide information from muscles are referred to as
somatosensory (which is the general term for sensations experienced
from within the body
•Even the smallest movements require the coordination and integration
of several brain and body systems.
Action Potentials Cause Neuronal Communication
•Neural communication depends on the neuron to respond to incoming
stimulations by changing electrically and subsequently passing along
signals to other neurons
•Action potential (neuronal firing) – neural impulse that passes along
the axon and subsequently causes the release of chemicals from the
The Resting Membrane Potential is Negatively Charged
•The resting membrane potential – the electrical charge of a neuron
when it is not active.
•(Important pg 90)
•Scientist measure a neuron’s resting membrane potential with
microelectrodes, small devices that register electric current.
The roles of sodium and potassium ions
•Two types of ion that contribute to a neurons resting membrane
potential are sodium ions and potassium ions. (Ions pass through the
cell membrane through special pores called ion channels.
•The passing of ions is through a gate mechanism.
•The flow of ions is also affected by the fact that the cell membrane is
•Partially as a result of the selective permeability of the cell membrane,
there is more potassium inside the neuron than sodium, this
contributes to polarization.
Changes in Electrical Potential lead to action
•“Firing” refers to passing a signal along the axon and releasing
chemicals from the terminal buttons.
•Signals arrive at the dendrites by the thousands, and are
oExcitatory - signals stimulate the neurons to fire. (Excitorty
depolarize the neurons) Or
oInhibitory – reduce the likelihood of neurons firering.
(Hyperpolarize the neuron)
•Signals work by polarization.
Depolarization and Hyperpolarization
•Cells fire when they are depolarized past a certain threshold.
Depolarization causes a change in the permeability of the cell
membrane, which opens the gates for sodium, the influx of sodium
causes the inside of the neuron to be slightly more positive charged
than the outside. (This change is the basis of the action potential)
•When a neuron Hyperpolarizes it makes it more difficult for the
sodium to come through, thus it doesn’t fire.
Action Potentials Spread Along the Axon
•An action potential is generated when there are more excitatory
signals that inhibitory signals, thus the total amount of depolarization
surpasses the neurons threshold.
•When the neuron is fires, the depolarization of the cell membrane
moves along the axon, like a wave, which is called propagation
•Like toppling dominos, sodium rushing through its ion channels leas to
further depolarization, causing adjacent sodium channels to open.
•At any point along the axon, the sudden influx of sodium repels
•This continues until a equilibrium is reached, and other forces work to
close the sodium gate (this all happens in about 1/1,000 of a second.
Absolute and Relative Refractory Periods
•The gate stops the flow of sodium, potassium stops leaving (this take 1-
2 milliseconds) in this time, a decreased amount of potassium in the
cell body momentarily creates a state of hyperpolarization.
•This brief period is referred to as ‘absolute refractory period’ – it is
impossible for the neuron to fire, (which keeps from a ripple effect
•Each section of the axon depolarizes, the preceding section enters its
absolute refractory state. (the signal cant travel backwards)
•As potassium stops leaving the neuron, and the cell membrane is
returning to its resting membrane potential, the neuron can fire. (But
only in response to a very strong signal)
• - This period of time is called relative refractory period.
Psychology chapter #3 notes (starting from page 87) Reviewing the principles what is the genetic basis of psychological. How does the nervous system operate: the nervous system takes in a variety of information from the external world, evaluates the information, and produces behaviors, or makes bodily adjustments to adapt to the environment. Neurons are specialized for communication: neurons the basic unit of the nervous system that operates through electrical impulses, which communicate with other neurons through chemical signals. The branch like appendages detect chemical signals from neighboring neurons: cell body- in the neuron, where information from thousands of other neurons is collected and processed. Also the site of metabolism and genetic action: axon a long narrow outgrowth of a neuron by which information is transmitted to other neurons. (this region varies a lot in length) Types of neurons: 3 basic types sensory, motor and interneuron, sensory detect information from the physical world and pass that information to the brain.