Psych Chapter 3
• Communication in the Nervous System
o Nervous Tissue: The Basic Hardware
o The Neural Impulse: Using Energy to Send Information
o The Synapse: Where Neurons Meet
o Neurotransmitters and Behaviours
• Organization of the Nervous System
o The Peripheral Nervous Systems
o The Central Nervous System
• Looking Inside the Brain: Research Methods
o Electrical Recordings
o Electrical Stimulation of the Brain
o Transcranial Magnetic Stimulation
o Brain-Imaging Procedures
• The Brain and Behaviour
o The Hindbrain
o The Midbrain
o The Forebrain
o The Plasticity of the Brain
• Right Brain/Left Brian: Cerebral Laterality
o Bisecting the Brain: Split-Brain Research
o Hemispheric Specialization in the Intact Brain
www.notesolution.com • The Endocrine System
• Heredity and Behaviour: Is it All In The Genes?
o Basic Principles of Genetics
o Investigating Hereditary Influence
o The Interplay of Heredity and Environment
• The Evolutionary Bases of Behaviour:
o Darwin’s Insights
o Subsequent Refinements to Evolutionary Theory
o Behaviours as Adaptive Traits
Communication in the Nervous System
Nervous Tissue: The Basic Hardware
• Cells in nervous system fall into two major categories:
• Neurons: The individual cells in the nervous system that receive, integrate, and
o Neurons permit communication within the nervous system.
o Soma: Soma, or cell body, contains the cell nucleus and much of the chemical
machinery common to most cells. Soma is Greek for body.
o Dendrites: Part of the neuron that are specialized to receive information.
Greek word for tree. Each branch is a dendrite.
www.notesolution.com o Axon: Long, thin fibre that transmits signals away from the soma to the
other neurons or to muscles or glands.
o Myelin Sheath: Insulating material derived from glia cells. They encase
o Terminal Buttons: Small knobs that secrete chemicals called
o Synapse: Junction where information is transmitted from one neuron to
another. Greek for junction.
o Information is received at the dendrites, passed through the soma along the
axon, and transmitted to the dendrites of other cells at meeting points called
• Glia: Cells found throughout the nervous system that provide various types of
support for neurons. Greek for glue.
o Smaller than the neurons, but outnumber them 10 to 1.
o Supply nourishment to neurons, help remove thee neurons’ waste products,
provide insulation around many axons (Myelin sheath).
The Neural Impulse: Using Energy to Send Information
• The Neuron at Rest: A Tiny Battery
www.notesolution.com o Inside and outside the neuron, there are fluids containing electrically ions.
o Positively charged sodium and potassium flow at a slower rate than
negatively charged chloride, thus there is a slightly larger rate of negative
charge ions (meaning the cell is at rest)
o The resting potential of a neuron is its stable, negative charge when the cell
• The Action Potential
o When the voltage is constant, the cell is quiet and there are no messages
o When the neuron is stimulated, the channels in its cell membrane open,
allowing positively charged sodium ions to rush in. Thus, the neuron either
becomes less negative, or even positive creating action potential.
o Action Potential is a very brief shift in a neuron’s electrical charge that
travels along an axon.
o When charged with action potential, the neuron fires the action potential
down the axon and the cell membrane closes off.
o The absolute refractory period is the minimum length of time after an
action potential during which another action potential cannot begin.
• The All-or-None Law
o The firing of action potential is a gun, you fire everything and there is no
o A neuron fires or it doesn’t, all action potential is the same size.
o However, neurons can convey information about the strength of a stimulus by
varying the rate at which they fire the action potential (stronger = faster
volley of neural impulses)
www.notesolution.com The Synapse: Where Neurons
• Sending Chemicals: Chemicals as Couriers
o Two neurons don’t actually touch. Separated by the synaptic cleft.
o Synaptic Cleft: A microscopic gap between the terminal button of one
neuron and the cell membrane of another neuron.
o The neuron that sends the signal is the presynaptic neuron, and the one that
receives is called the postsynaptic neuron.
o The arrival of an action potential at an axon’s terminal buttons triggers the
release of neurotransmitters – chemicals that transmit information from
one neuron to another
o In the terminal buttons, the chemicals are stored in small sacs, called
o These neurotransmitters spill into the synaptic cleft, and may bind with
special molecules in the postsynaptic cell membrane at various receptor
sites. These sites are specifically “tuned” to recognize and respond to some
neurotransmitters and not others.
• Receiving Signals: Postsynaptic Potentials
o When a neurotransmitter and a receptor molecule combine, it causes a
postsynaptic potential (PSP)
o Postsynaptic Potential: Voltage change at a receptor site on a postsynaptic
o Postsynaptic potential doesn’t follow the all-or-none law.
www.notesolution.com o Instead they are graded (vary in size, increase/decrease probability of a
neural impulse in the receiving cell in proportion to the amount of voltage
o Two types of messages can be sent from cell to cell:
o An excitatory PSP is a positive voltage shift that increases the likelihood that
the postsynaptic neuron will fire an action potential. An inhibitory PSP is a
negative voltage shift that decreases the likelihood that the postsynaptic
neuron will fire action potentials.
o Reuptake: Process in which neurotransmitters are sponged up from the
synaptic cleft by the clef by the presynaptic membrane allowing the synapses
to recycle their materials.
• Integrating Signals: Neural Networks
o Neurons fire together/sequentially in the millions to perform certain
o The nervous system eliminates old synapses which are no longer being used
and tends to create an abundance of new synapses. This is called synaptic
o Donald Hebb called these neuron networks cell assemblies.
o Hebb also created the Hebbian Learning Rule. “When an axon of cell A is
near enough to excite a cell B and repeatedly or persistently take part in
firing it, some growth process or metabolic change take place in one or both
cells such that A’s efficiency, as one of the cells firing B, is increased”. Thus
one neuron stimulating another neuron repeatedly produces learning.
Neurotransmitters and Behaviour
• Agonist: Chemical that mimics the actions of a neurotransmitter.
• Antagonist: Chemical that opposes the action of a neurotransmitter.
Neurotransmitt Functions and Characteristics
www.notesolution.com Acetylcholine Activates motor neurons controlling skeletal muscles
(ACh) Contributes to the regulation of attention, arousal, and memory
Some ACh receptors stimulated by Nicotine
Only transmitter between motor neurons and voluntary muscles
Dopamine (DA) Contributes to control of voluntary movement, pleasurable emotions
Decreased levels associated with Parkinson’s Disease
Overactivity at DA synapses associated with schizophrenia
Cocaine and amphetamines elevate activity at DA synapses
Norepinephrine Contributes to modulation of mood and arousal
(NE) Cocaine and amphetamines elevate activity at NE synapses
Serotonin Involved in regulation of sleep and wakefulness, eating, aggression
Abnormal levels may contribute to depression and obsessive compulsive
Prozac and similar antidepressant drugs affect serotonin circuits.
GABA Serves as widel