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Chapter 2
Behavioral
Neuroscience
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The Evolutionary Perspective
• stresses an organism's
adaptation to the
environment and ultimate
survival.
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Natural Selection
• natural selection most fit
organisms survive because
they adapt best to the
environment and thus pass
on their genes to future
generations.
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Behavioral Neuroscience
• describes the work of
scientists from several
disciplines who work to
understand how the nervous
system is related to behavior.
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The Brain: A Closer Look
• Early studies of brain functioning involved
stimulating or removing portions of the
cortex
• The stereotaxic instrument allowed
examination of subcortical structures
without damaging the cortex.
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The Brain: A Closer Look
• lmages of the structures of the brain can be
produced by computerized techniques such as:
– the PET (positron emission tomography- glucose
metabolism),
– the CT or CAT (computerized axial tomography = 3D
xrays),
– the MRI (magnetic resonance imaging),
– and the fMRl (functional magnetic resonance
imaging).
– SPECT scan
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The Brain
• The brain is divided
into the hindbrain,
midbrain, and
forebrain.
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The Hindbrain
• The oldest division of brain.
• Contains the medulla, pons,
and cerebellum.
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The Midbrain
• contains fibers known as
reticular formation.
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The Forebrain
• consists of subcortical
structures and two
hemispheres of cerebral
cortex joined by the corpus
collosum
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The Corpus Callosum
• Millions of myelinated axons connecting the
brain’s hemispheres
• Provides a pathway for communication between
the hemispheres
• If surgically severed (commissuratomy) for
treatment of epilepsy, hemispheres cannot
communicate directly
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The Cortex
• The cerebral cortex covers the forebrain
and is divided into four lobes:
– frontal (Motor Cortex)
– parietal (Sensory Cortex),
– temporal (Auditory Cortex),
– and occipital (Visual Cortex).
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Subcortical Structures
• A group of subcortical structures involved
in emotion, memory, eating, drinking, and
sexual behavior located beneath the
cortex.
• The limbic system, thalamus, and
hypothalamus.
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Limbic System
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The Brain
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More About the Brain
• The brain has been described as plastic,
which means it can change over time and
recover to some degree even from
removal of an entire hemisphere.
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Plasticity in Brain and Behavior
• Richer environments lead to
heavier, thicker brains, more
synapses, and better learning
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More About the Brain
• aphasias (language deficits) and apraxias
(nonverbal deficits).
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Sperry’s Split-Brain Experiment
• Split-brain subjects could not name
objects shown only to the right hemisphere
• If asked to select these objects with their
left hand, they succeeded
• The right side of the brain doesn’t control
speech
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The CNS
• The spinal cord is composed of sensory
(afferent or ascending) and motor (efferent
or descending) nerves.
• Interneurons may connect sensory and
motor neurons.
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CNS Nerves
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The Nervous System
• We use the processes of sensing,
processing, and responding to interact
with the environment.
• The nervous system is divided into the
central nervous system (CNS-brain and
spinal cord) and the peripheral nervous
system (PNS-all parts of the nervous
system outside the CNS), coordinates
these three activities.
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Divisions of the Nervous System
• Central Nervous
System
– Brain
– Spinal cord
• Peripheral Nervous
System
– Somatic
– Autonomic
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The PNS
• The PNS is composed of the somatic division
and the autonomic division.
• The somatic division consists of afferent
(sensory) nerves that run from the receptors to
the brain and efferent (motor) nerves that run to
the glands and muscles.
• The autonomic division consists of the
sympathetic division, which mobilizes the body's
resources, and the parasympathetic division
which returns the body to a normal state of
homeastasis.
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The Endocrine System
• The endocrine system affects behavior by
producing and secreting hormones, which
are chemicals that regulate body
functions.
• Among the major endocrine glands are the
pineal gland, hypothalamus pituitary gland,
the thyroid gland, the pancreas, the
gonads, and the adrenal glands.
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The Endocrine System
• Endocrine system:
– Ductless glands that
regulate growth,
reproduction,
metabolism, mood,
and some behavior
• Hormones:
– Chemical messengers
secreted into the
bloodstream
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Neurons: The Basic Cells
• The cells that make up the nervous
system are called neurons.
• Neurons are composed of:
– dendrites that receive signals from adjacent
neurons
– a cell body or soma
– an axon that transmits signals
– terminal buttons that contain
neurotransmitters.
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Structure of a Neuron
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Neurotransmitters
• Neurotransmitters enable the signal from
one neuron to be relayed to other neurons
across the synapse, a small gap that
separates neurons.
• A myelin sheath covers the axons of some
neurons to increase the speed of
transmission of the neural signal.
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The Synapse
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Key Neurotransmitters
•
•
•
•
•
•
Acetylcholine (ACh)
Dopamine
Serotonin
Endorphins
Norepinephrine
Gamma amino butryic acid (GABA)
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Neurotransmitters
• Among the key neurotransmitters,
dopamine has been implicated in the
development of Parkinson's disease.
• Acetycholine seems to play a role in
Alzheimer's disease.
• Serotonin has been implicated In a variety
of disorders, including depression and
obsessive-compulsive disorder.
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How Neurons Communicate
• Ions (electrically charged particles) are
found on the inside and outside of the
neuron's semipermeable cell membrane
• When a neuron is in a resting state, more
negative ions are on the inside of the cell
(measured at -70 mV) than on the out
side.
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How Neurons Communicate
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How Neurons Communicate
• Neurotransmitters stimulate the cell
membrane to allow ions to enter the
neuron resulting in
– depolarization (positive ions move inside the
neuron resulting in excitation) or
– hyperpolarization (additional negative ions
move inside resulting in in hibition).
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How Neurons Communicate
• If depolarization of the dendrite and soma
reaches the threshold level (-65 to -60
mV), the axon quickly reverses electrical
charge (to about +40 mV), and the signal
is transmitted to the next neuron.
• This reversal in electrical charge known as
the action potential.
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The Action Potential
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How Neurons Communicate
• Neurotransmitters must be removed from
the synapse be fore another signal can be
transmitted.
• Removal is accomplished either by
destroying the neurotransmitter
(breakdown) or by taking it back into the
terminal buttons (reuptake).
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Neuromodulators
• Neuromodulators have more widespread
and indirect effects than neurotransmitters.
• Neuromodulators also influence
transmission between cells.
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Agonists and Antagonists
• Agonists are drugs that promote the action
of a neurotransmitter.
• Antagonists are drugs that oppose or
inhibit the action of a neurotransmitter.
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Agonists and Antagonists
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Agonists and Antagonists
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