Download Chapter 3 Section 2 The Brain

Chapter 3 Section 2
The Brain: Our Control Center
Obj: Identify the major structures
of the brain, and explain the
functions of each structure.
Parts of the Brain
The brain is divided into three sections: the
hindbrain, the midbrain, and the forebrain.
The hindbrain is the lower portion of the
brain and is involved in many vital
functions such as heart rate, respiration,
and balance. The midbrain includes areas
that are involved in vision and hearing.
The forebrain, the front area of the brain,
is involved in complex functions such as
thought and emotion.
The Hindbrain
The medulla is involved in
vital functions such as
heart rate, blood pressure,
and breathing. The pons
is located in front of the
medulla and is involved in
regulating body
movement, attention,
sleep, and alertness. The
cerebellum is involved in
balance and coordination.
(if it gets injured, the
person could walk
unsteadily or occasionally
fall down)
The Midbrain
It’s located between the
hindbrain and the
forebrain, and is involved in
vision and hearing.
Contains the reticular
activating system, which
is important for attention,
sleep, and arousal.
Stimulation makes us alert.
Some drugs reduce the
activity of this system, thus
affecting alertness and
reaction time.
The Forebrain
Four key areas are the
thalamus, the
hypothalamus, the limbic
system, and the
cerebrum. All are
involved in complex
thinking processes.
• Thalamus – (Relay station) transmits
sensory information, such as pain and
input from the eyes, to the areas of the
brain that interpret the information.
• Hypothalamus – vital to the regulation of
body temperature, the storage of nutrients,
and various aspects of motivation and
emotion.
• Limbic system – involved in learning and
memory, emotion, hunger, sex, and
aggression. Damage can cause short-term
memory loss, passivity, or severe
aggression.
• Cerebrum – comprises
70% of the weight of the
brain. The wrinkled
surface is the cerebral
cortex, the outer layer of
the brain. This is the part
that thinks, deals with
memory, language,
emotions, complex
motor functions,
perception, and much
more.
The Cerebral Cortex: What
Makes Us Unique
The cerebral cortex is
composed of two sides – a
left hemisphere and a
right, with the corpus
callosum dividing them.
Information received by
one side is transmitted to
the opposite hemisphere
of the brain. Each
hemisphere is divided into
four parts, or lobes: frontal,
parietal, temporal, and
occipital.
Senses and Motor Behavior
The occipital lobe contains the primary
visual area of the cerebral cortex. When
light strikes the eye, neurons in this lobe
fire, enabling us to see. Damage to this
area can create the inability to recognize
objects, or being unable to differentiate it
from another object that is similar.
The hearing, or auditory, area is in the
temporal lobe. Sounds are relayed from
the ears to the thalamus to the auditory
area. When this occurs, we hear sounds. if
this area gets damaged, people may not
recognize common sounds.
Messages received from the skin go to the
parietal lobe. Different neurons fire,
depending on whether you have scratched
your nose, touched a hot stove, etc.
Neurons in the motor cortex fire when we
move certain parts of our body.
Association Areas
Much of the cerebral cortex is composed of areas
that involve sensory and motor functions. Other
areas, called association areas, shape
information into something meaningful. They
take information and put it all together to make
sense. Example-take bunch of lines and turn it
into a car.
They are connected with sensory areas in the
brain and can tap whatever sensory information
is needed or desired; visual, auditory, and other
kinds of memories and manipulates them.
Language Abilities
Language functions are based in the left
hemisphere of most people, whether left or
right handed. Two key language areas are
Broca’s area (controls the areas of the
face used for speaking) and Wernicke’s
area (pieces together sounds and sights).
Damage to either area is likely to cause an
aphasia, a difficulty with specific aspects
of understanding or producing language.
Left Versus Right Hemisphere
Left hemisphere is usually more involved in logic,
problem solving, and math. The right is
associated with imagination, art, feelings, and
spatial relations. Although some differences do
exist between the two, the hemispheres do not
act independently of each other. Most of what
we know about the two hemispheres is the result
of a surgery that splits the two halves for severe
cases of epilepsy. The surgery can have strange
effects. Example; people may be able to
describe verbally the objects they hold in their
right hand but not what they hold in the left. This
is due to the language side of the brain being on
the opposite side of the body.
Methods of Studying the Brain
• Accidents – brain damage from head
injuries and other accidents. We’ve learned
that which particular area is damaged may
have a greater effect than the amount of
the damage.
• Electrical Stimulation of the Brain – This
has shown that specific areas are
associated with specific types of
sensations (such as seeing light or feeling
a tap on the arm) or motor activities ( such
as walking).
• Electroencephalogram – the
electroencephalogram (EEG) is a device
that records the electrical activity of the
brain. Electrodes attached to the scalp
with tape or paste detect small amounts of
electrical activity called brain waves.
• Scans – techniques where computers
generate images of the brain from various
sources of information.
– CAT scans, a moving ring passes X-ray
beams around and through the head.
Computers measure the amount of radiation
and piece together a 3-dimensional view.
– MRI scan, a person lies in a very powerful
magnetic field. Radio waves then cause parts
of the brain to give off extra energy. This
energy is measured from multiple angles and
is translated by computer into a visual.
– PET scan shows the activity of the brain
rather than a snapshot of the brain at a given
time. The person is injected with radioactive
sugar. As the sugar reaches the brain, more
of it is used where brain activity is greater. A
computer image is generated based on the
activity.