This document discusses the structure and function of neurons and the nervous system. It describes how neurons communicate via electrical and chemical signals. The basic parts of neurons are identified as the cell body, dendrites, axon, and terminal buttons. Action potentials and neurotransmitters are discussed as the means by which neurons signal one another. The central and peripheral nervous systems are described along with their roles in voluntary and involuntary functions. Key parts of the brain like the cortex, limbic system, and motor/sensory areas are also outlined.

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Essentials of
Understanding
Psychology
RobertS. Feldman| TwelfthEdition

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Chapter 2
Neuroscience and Behavior

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MODULE 5 - Neurons: The Basic Elements
of Behavior
• Why do psychologists study the brain and the
nervous system?
• What are the basic elements of the nervous
system?
• How does the nervous system communicate
electrical and chemical messages from one part
to another?

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The Structure of the Neuron
• Neurons: Nerve cells; the basic elements of the nervous
system
• Consist of a cell body that contains a nucleus
• Physically held in place by glial cells which:
• Provide nourishment to neurons
• Insulate neurons
• Help repair damage
• Support neural functioning

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The Structure of the Neuron
• Distinctive feature of neurons
• Ability to communicate with other cells
• Transmission of information across relatively long
distances

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The Structure of the Neuron
• Cluster of fibers at one end of a neuron that receives messages from
other neurons
Dendrite
• Part of the neuron that carries messages destined for other neurons
Axon
• Small bulges at the end of axons that send messages to other
neurons
Terminal buttons
• Protective coat of fat and protein that wraps around the axon
Myelin sheath

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Figure 1: The Primary Components of the Neuron

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How Neurons Fire
• Neurons follow an all-or-none law
• Rule that neurons are either on or off
• Resting state: State in which there is a negative electrical
charge of about -70 millivolts within a neuron
• Before a neuron is triggered
• Action potential: Electric nerve impulse that travels
through a neuron’s axon when it is set off by a “trigger”
• Positive electrical charge of about +40 millivolts within
a neuron

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Figure 2: Movement of an Action Potential along an Axon

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Figure 3: Changes in the Voltage in a Neuron
During the Passage of an Action Potential

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Speed of Transmission
• Speed at which an action potential travels along an axon is
determined by the:
• Axon’s size
• Thickness of the myelin sheath
• Neurons differ in terms of:
• Quickness of an impulse moving along the axon
• Potential rate of firing
• Intensity of a stimulus determines how much of a neuron’s
potential firing rate is reached

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Mirror Neurons
• Specialized neurons that fire, when a person:
• Enacts a particular behavior
• Observes another individual carrying out the same
behavior

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Mirror Neurons
• Discovery of mirror neurons suggests that humans’
capacity to imitate others may be an inborn behavior
• Helps in explaining how and why humans have the
capacity to understand others’ intentions
• Possible basis for:
• Empathy feelings
• Development of language in humans

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Where Neurons Meet: Bridging the
Gap
• Synapse: Space between two neurons where the axon of a
sending neuron communicates with the dendrites of a
receiving neuron by using chemical messages
• Neurotransmitters: Chemicals that carry messages across the
synapse to the dendrite (and sometimes the cell body) of a
receiving neuron

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Where Neurons Meet: Bridging the
Gap
• Every neuron is not capable of receiving the chemical message
carried by a particular neurotransmitter
• Successful chemical communication is possible only when a
neurotransmitter fits precisely into a receptor site

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Where Neurons Meet: Bridging the
Gap
• Types of chemical message delivered by neurotransmitters:
• Excitatory message: Makes it more likely that a receiving neuron
will fire and an action potential will travel down its axon
• Inhibitory message: Prevents or decreases the likelihood that a
receiving neuron will fire

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Figure 4: A Synapse is the Junction Between an Axon and a Dendrite

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Where Neurons Meet: Bridging the
Gap
• Neurotransmitters remaining at the site of the synapse lead
to:
• Receiving neurons awash, in a continual chemical bath
• Producing constant stimulation or constant inhibition of the
receiving neurons
• Effective communication across the synapse will no longer be
possible

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Where Neurons Meet: Bridging the
Gap
• Reuptake: Reabsorption of neurotransmitters by a
terminal button
• Understanding of reuptake has led to the development
of certain drugs that treat psychological disorders
• SSRIs (selective serotonin reuptake inhibitors): permit certain
neurotransmitters to remain in synapses for a longer period of
time
• Reduces the symptoms of depression

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Figure 5: Major Neurotransmitters

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MODULE 6 - The Nervous Systemand the Endocrine
System:CommunicatingWithin the Body
• How are the structures of the nervous system linked?
• How does the endocrine system affect behavior?

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Central and Peripheral Nervous
Systems
• Central nervous system (CNS): Part of the nervous system
that includes the brain and spinal cord
• Spinal cord: Bundle of neurons that leaves the brain and runs
down the length of the back
• Main means for transmitting messages between the brain
and the body
• Controls simple behaviors on its own, without any help
from the brain

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Central and Peripheral Nervous
Systems
• Reflex: Automatic, involuntary response to an incoming
stimulus
• Kinds of neurons involved in reflexes:
• Sensory (afferent) neurons: Transmit information from the
perimeter of the body to the central nervous system
• Motor (efferent) neurons: Communicate information from the
nervous system to muscles and glands

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Figure 1: A Schematic Diagram of the Relationship of the Parts of the Nervous
System

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Figure 2: Central Nervous System

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Central and Peripheral Nervous
Systems
• Peripheral nervous system: Made up of neurons with long
axons and dendrites, it branches out from the spinal cord and
brain and reaches the extremities of the body
• Includes
• Somatic division: Specializes in the control of voluntary
movements and the communication of information to and from
the sense organs
• Autonomic division: Controls involuntary movement of the heart,
glands, lungs, and other organs

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Activating the Divisions of the Autonomic
Nervous System
• Autonomic nervous system consists of:
• Sympathetic division: Acts to prepare the body for action in
stressful situations, engaging all the organism’s resources to
respond to a threat
• Parasympathetic division: Acts to calm the body after an
emergency has ended

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Figure 3: The Major Functions of the Autonomic Nervous System

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The Evolutionary Foundations of the
Nervous System
• Evolutionary psychology: Branch of psychology that seeks to
identify behavior patterns that are a result of our genetic
inheritance from our ancestors
• Behavioral genetics: Study of the effects of heredity on
behavior

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The Endocrine System: Of Chemicals
and Glands
• Endocrine system: A chemical communication network that
sends messages throughout the body via the bloodstream
• Hormones: Chemicals that circulate through the blood and
regulate the functioning or growth of the body
• Pituitary gland: Major component of the endocrine system, or
the “master gland”
• Secretes hormones that control growth and other parts of the
endocrine system

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Figure 4: Location and Function of the Major Endocrine
Glands

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MODULE 7 - The Brain
• How do researchers identify the major parts and functions of
the brain?
• What are the major parts of the brain, and for what behaviors
is each part responsible?
• How do the two halves of the brain operate interdependently?
• How can an understanding of the nervous system help us find
ways to alleviate disease and pain?

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Studying the Brain’s Structure and
Functions: Spying on the Brain
• Electroencephalogram (EEG)
• Records electrical activity in the brain through electrodes placed
on the outside of the skull
• Functional magnetic resonance imaging (fMRI)
• Provides a detailed, three dimensional computer-generated
image of brain structures and activity by aiming a powerful
magnetic field at the body

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Studying the Brain’s Structure and
Functions: Spying on the Brain
• Positron emission tomography (PET)
• Shows biochemical activity within the brain at a given moment
• Requires radioactive tracer injection
• Transcranial magnetic stimulation (TMS)
• Causes a momentary interruption of electrical activity by
exposing a tiny region of the brain to a strong magnetic field

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Figure 2: The Major Divisions of the Brain

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The Central Core: Our “Old Brain”
• Central core: “Old brain”
• Controls basic functions such as eating and sleeping and is
common to all vertebrates
• Hindbrain contains:
• Medulla: Controls a critical body functions, such as breathing and
heartbeat
• Pons: Bridge in the hindbrain
• Acts as a transmitter of motor information
• Involved in regulating sleep
• Cerebellum: Part of the brain that controls bodily balance

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The Central Core: Our “Old Brain”
• Reticular formation: Extends from the medulla through the
pons, passing through the midbrain and the forebrain
• Produces general arousal of the body
• Thalamus: Part of the brain located in the middle of the
central core that acts primarily to relay information about the
senses

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The Central Core: Our “Old
Brain”
• Hypothalamus: Tiny part of the brain, located below
the thalamus
• Maintains homeostasis
• Produces and regulates behavior that is critical to the basic
survival of the species
• Eating, self-protection, sex

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Figure 3: The Major Structures in the Brain

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The Limbic System: Beyond the
Central Core
• Limbic system: Part of the brain that controls eating,
aggression, and reproduction
• Includes the amygdala and hippocampus
• Plays an important role in emotion, learning, and memory, along
with hippocampus
• Otherwise referred as “animal brain,” due to similarities in
structures and functions to those of other mammals

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Figure 4: The Limbic System

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The Cerebral Cortex: Our “New
Brain”
• Responsible for the most sophisticated information processing
in the brain
• Lobes: Four major sections of the cerebral cortex
• Frontal
• Parietal
• Temporal
• Occipital
• Sulci: deep grooves in the cortex that physically divide the four
sets of lobes

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Figure 5: The Cerebral Cortex of the Brain

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The Motor Area of the Cortex
• Motor area: Responsible for the body’s voluntary
movement
• Well mapped: researchers have identified the amount
and relative location of cortical tissue used to produce
movement in specific parts of the body

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The Sensory Area of the Cortex
• Sensory area: Site in the brain of the tissue that
corresponds to each of the senses, with the degree of
sensitivity related to the amount of tissue
• Example: somatosensory area - in the parietal lobe;
specific locations associated with the ability to
perceive touch and pressure in a particular location on
the body
• Auditory area in temporal lobe
• Visual area in occipital lobe

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The Association Areas of the Cortex
• Association areas: Site of the higher mental processes
• Thought, language, memory, and speech
• Example: Phineas Gage, railroad worker accident
• Damage to the association area
• Aphasia: result from injuries to the association areas of
the brain, and create problems with language
• Broca’s aphasia
• Wenicke’s aphasia

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Neuroplasticity and the Brain
• Neuroplasticity
• Changes in the brain that occur throughout the life
span relating to the addition of new neurons
• New interconnections between neurons
• Reorganization of information-processing areas
• Neurogenesis - Creation of new neurons in certain areas
of the brain during adulthood

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The Specialization of the Hemispheres:
Two Brains or One?
• Brain is divided into two roughly mirror-image halves
• Hemispheres: Symmetrical left and right halves of the brain
that control the side of the body opposite to their location
• Lateralization: Dominance of one hemisphere of the brain in
specific functions
• Language

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The Split Brain: Exploring the Two
Hemispheres
• Split-brain patients
• Corpus callosum surgically cut
• Last resort treatment for severe epilepsy