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Chapter 3: Biology and Behavior
Case Study: The Brain of Phineas Gage
Section 1: The Nervous System
Section 2: The Brain: Our Control Center
Case Study: The Brain of Phineas Gage
Phineas Gage was injured in a railroad accident in 1848. He suffered a brain injury
that changed his personality.
The Accident and the Aftermath
• Gage was struck in the head by an iron bar. The bar rammed through Gage’s
brain and out the top of his head.
• Gage recovered from the physical effects of the wound, but his personality
was altered
Studies on Gage’s Skull
• After Gage’s death, his family donated his skull to a museum.
• Studies showed that the rod severely damaged an area in the brain related to
personality.
• Other studies found similar changes after injuries to the same part of the
brain.
Section 1 at a Glance
The Nervous System
• The nervous system functions as a communication system for the body.
Messages are transmitted by neurons to axons and dendrites.
• The nervous system is made up of the central nervous system and the
peripheral nervous system, which transmits messages between the central
nervous system and all parts of the body.
Main Idea: The nervous system contains billions of cells called neurons. Neurons communicate with one
another through the central and peripheral nervous systems.
Reading Focus
•
•
•
•
What are neurons, and how do they work?
How do neurotransmitters work as chemical messengers?
What does the central nervous system control?
How is the peripheral nervous system structured?
Neurons
The nervous system has two parts. The
nervous system consists of the brain
and
cord. The
nervous system is made up of nerve
cells that send messages between the central nervous system and other parts of the body.
Nerve cells are called
.
Components of a Neuron
• The
produces energy that fuels the neuron’s activity.
•
receive information from other neurons and pass the
message through the cell body.
• An
transmits information away from the cell body.
Components of a Neuron (con’t)
•
is a white, fatty substance that covers the axon, insulating
and protecting it. The myelin sheath helps to speed up the work of neurons.
• Axon
branch out at the end of the axon.
The Communication Process
• Messages are sent from the axon terminals of one neuron to the dendrites of another
neuron.
• In order for this process to happen, the message must cross a
• A synapse is a
between the axon terminals of one neuron and
the dendrites of another.
• Messages travel in only one direction. Messages
– enter the dendrites
– travel through the cell body and axon to the axon terminals
– cross the synapses to the dendrites of other neurons
Neurotransmitters: The Body’s Chemical Messengers
• Neurons send messages across synapses through the
of
neurotransmitters.
• Neurotransmitters are chemicals that are stored in
in the axon terminals.
• A neuron
, or sends a message, by releasing neurotransmitters.
– The message is converted into an electrical
that travels through
the neuron.
– The message is transmitted to the next neuron by other neurotransmitters until
the message arrives at its destination.
• There are several kinds of neurotransmitters.
– Acetylcholine is involved in the control of muscles and in learning and
memory.
–
is involved primarily in motor behavior.
The Central Nervous System
• The central nervous systems consists of the neurons of the spinal cord and the
• The spinal cord is a column of
from the brain down the back.
about as thick as a
that extends
• The spinal cord transmits messages between the brain and the muscles and glands in
the body.
• The spinal cord sends messages to specific muscles.
• The spinal cord is involved in spinal reflexes.
The Peripheral Nervous System
1. The Somatic Nervous System
 The somatic nervous system transmits
messages to the central nervous
system.
• It carries messages from the voluntary muscles and sense organs.
• It is activated by touch, pain, changes in temperature, and changes in body position
2. The Autonomic Nervous System
• The autonomic nervous system regulates the body’s
heartbeat, breathing, digestion, and blood pressure.
functions, such as
• It has two divisions.
• The sympathetic nervous system reacts to
• The parasympathetic nervous system restores peace to the body’s systems
Section 2 at a Glance
The Brain: Our Control Center
• The brain is composed of three major sections: the hindbrain, the midbrain,
and the forebrain.
The cerebral cortex is the part of the brain that controls thinking, memory, language,
emotions, complex motor functions, perceptions, and much more
The Brain: Our Control Center
Main Idea
The human brain has many parts that work together to coordinate body movement,
create thought and emotions, and shape behaviors.
Reading Focus
•
•
•
•
What were some of the early beliefs about the brain?
What are the parts of the brain, and how do they function?
How is the cerebral cortex divided?
Which methods do scientists use to study the brain?
Early Beliefs About the Brain
• In ancient times, people did not attribute human psychological processes such
as thinking to the working of the brain.
• Instead, people widely believed that the body was inhabited by
• Ancient Egyptians believed that a
and regulated behavior.
• The Greek philosopher
heart.
person dwelled within the skull
thought that the soul resided in the
• Today we recognize that the mind, or consciousness, dwells within the brain.
Parts of the Brain
The Hindbrain
• The
is involved in heart rate, blood pressure, and breathing.
• The
regulates body movement, attention, sleep, and alertness.
• The
is involved in balance and coordination.
The Midbrain
• Areas within the midbrain are involved in
• Contains part of the reticular activating system, which is important for
attention, sleep, arousal, and
The Forebrain
• The
serves a relay station for sensory stimulation.
• The
is vital to the regulation of body temperature,
the storage of nutrients, and various aspects of motivation and emotion. It is
also involved in hunger, thirst, sexual behavior, caring for offspring, and
aggression.
• The
system is involved in learning and memory, emotion,
hunger, sex, and aggression.
• The
makes up about
percent of the brain’s weight
and is where most conscious and intellectual activities take place.
• The
cortex is the outer layer of the brain. It is the part
that thinks, and it also deals with memory, language, emotions, complex motor
skills, perception, and more.
The Cerebral Cortex
• The cerebral cortex has a left side and right side.
• Each side is called a
• The corpus callosum is the structure that connects the two hemispheres.
• Information received by one side of the body is transmitted to the
hemisphere of the brain.
• Each hemisphere is divided into four parts:
– frontal lobe
– parietal lobe
– temporal lobe
– occipital lobe
Senses and Motor Behavior
• The
lobe is the primary visual area of the cerebral cortex.
• The
cortex.
lobe is the hearing, or auditory, area of the cerebral
• Messages received from the skin’s sensory receptors are projected to the sensory
cortex in the
lobe.
• These sensations include warmth, cold, touch, and pain.
Association Areas
• The association areas of the cerebral cortex shape information into something
• The association areas in the
center.
lobes function as the brain’s executive
• Association areas provide the core of the
memory.
• The frontal region of the brain thus retrieves visual, auditory, and other kinds of
memories.
• Other association areas make possible the psychological functions of language.
Language Abilities
• For nearly all right-handed people, language functions are based in the
hemisphere.
• Language functions are also based in the left hemisphere of about two out of three
left-handed people.
• Wernicke’s area connects sounds and sights. When this area is damaged, people find
it difficult to understand
•
area is involved in speech. When this area is damaged, people
speak slowly and use simple sentences.
Left and Right Hemispheres
• The
hemisphere is usually more involved in logic, problem solving,
and mathematical computation.
• The
hemisphere is more concerned with imagination, art, feelings,
and spatial relations.
Split-brain operations have taught psychologists much of what they know about left- and
right-hemisphere functioning
Methods of Studying the Brain
Accidents
• Researchers are able to learn how the brain is related to psychological functions
through the study of brain damage due to accidents.
Electrical Stimulation
• Electrical stimulation of the brain has shown that specific areas are associated with
specific types of sensations.
• It is not a reliable research tool
Lesions
• Scientists can study a brain by cutting, removing, or destroying parts of it.
• This method is used on laboratory animals.
Electroencephalogram
• The EEG is a device that records electrical activity of the brain.
• EEG readings can help diagnose certain psychological disorders and to help locate
tumors.
Brain Imaging
• Brain imaging can provide information about
– brain damage
– cancers
– difficult surgeries
• Brain imaging techniques include
– CAT scans
– MRI scans
– PET scans
– fMRI scans