Brain Reorganization
• Hemispherectomy
– The surgical removal of an entire cerebral
hemisphere
Our Divided Brain
Our brain is divided into two hemispheres.
The left hemisphere processes reading, writing,
speaking, mathematics, and comprehension skills.
In the 1960s, it was termed as the dominant brain.
Splitting the Brain
A procedure in which the two hemispheres of the
brain are isolated by cutting the connecting fibers
(mainly those of the corpus callosum) between them.
Corpus Callosum
Split Brain Patients
With the corpus callosum severed, objects (apple)
presented in the right visual field can be named.
Objects (pencil) in the left visual field cannot.
Split Brain
“What word
did you see?”
or
“Look at the dot.”
Two words separated
by a dot are
momentarily projected.
“Point with
your left
hand to the
word you
saw.”
Brain Disorder Experiments
• The following two experiments involve people whose
brains were physically altered before beginning the
experiment
• First experiment: brain altered surgically
• Second experiment: brain damaged by disease
Roger Sperry:
Split-Brain Experiments
• Two hemispheres of our
brains are attached by
the corpus callosum,
which allows the
hemispheres to
communicate with each
other
• Split-brain patients had
their corpus collosa
severed, so their brains’
hemispheres could no
longer communicate
Sperry:
Split-Brain Experiments
• Wanted to see how
patients’ brains had
been affected and
whether they revealed
differences between
hemispheres
• What we see with our
left eye crosses over to
our right hemisphere,
and vice versa
Corpus callosum
Sperry: HEART Experiment
• Patients saw “HE” with
their left eyes and “ART”
with their right eyes
• Corpus callosum was
severed, so the
hemispheres could not
communicate
• Patients could say they saw
“ART,” but pointed to “HE”
• Shows that hemispheres
perform different functions
(speech is in left
hemisphere)
Figure 2.38 Try this!
Myers: Psychology, Eighth Edition
Copyright © 2007 by Worth Publishers
Unnumbered 2.1 Which one is happier?
Myers: Psychology, Eighth Edition
Copyright © 2007 by Worth Publishers
Non-Split Brains
People with intact brains also show left-right
hemispheric differences in mental abilities.
A number of brain scan studies show normal
individuals engage their right brain when completing
a perceptual task and their left brain when carrying
out a linguistic task.
Brain Organization & Handedness
Is handedness inherited? Yes. Archival and historic
studies, as well as modern medical studies, show that
the right hand is preferred. This suggests genes
and/or prenatal factors influence handedness.
Is it Alright to be Left Handed?
The percentage of left-handed individuals decreases
sharply in samples of older people.
Figure 2.40 The southpaw’s hazardous life
Myers: Psychology, Eighth Edition
Copyright © 2007 by Worth Publishers
Brain Structures and their
Functions
The Endocrine System
 Endocrine System
 the body’s “slow”
chemical
communication
system
 a set of glands that
secrete hormones
into the
bloodstream
Neural and Hormonal Systems
 Hormones
 chemical messengers, mostly those manufactured by
the endocrine glands, that are produced in one tissue
and affect another
 Pituitary Gland
 under the influence of the hypothalamus, the
pituitary regulates growth and controls other
endocrine glands
Pituitary Gland
Is called the “master gland.” The anterior pituitary
lobe releases hormones that regulate other glands.
The posterior lobe regulates water and salt balance.
The effects of the pituitary are clearly shown here.
Entertainer David Frost stands between the world’s
tallest and smallest man.
The tallest man in history was 8 feet 11 inches tall.
He died at the age of 22, partly as a result of this
defect. The shortest known person was 23 inches
tall when she died at the age of 19. Today’s
medicines can handle most of these problems if
caught earlier enough, but these cases show what
happen if the pituitary gland goes awry.
Neural and Hormonal Systems
• Oxytocin– stimulates contractions of the
uterus during labor and secretion of milk
during nursing.
• Growth Hormone– stimulates the physical
development of bones and muscles.
Neural and Hormonal Systems
 Adrenal [ah-DREEN-el] Glands
 a pair of endocrine glands just above the kidneys
 secrete the hormones epinephrine (adrenaline) and
norepinephrine (noradrenaline), which help to arouse the
body in times of stress
 Cortisol– regulates metabolism and response to stress.
Adrenal Glands
Adrenal glands consist of the adrenal medulla and the
cortex. The medulla secretes hormones (epinephrine
and norepinephrine) during stressful and emotional
situations, while the adrenal cortex regulates salt and
carbohydrate metabolism.
Neural and Hormonal Systems
• Pancreas Hormones
– Insulin– decreases blood sugar
– Glucagon– Increases blood sugar
Thyroid & Parathyroid Glands
Regulate metabolic and calcium rate.
Thyroxin– regulates metabolism and growth
Neural and Hormonal Systems
• Sex Glands (Gonads)
– Female Sex Hormone– Estrogen (Ovary)
– Male Sex Hormone– Androgen (Testis)
Gonads
Sex glands are located in different places in men and
women. They regulate bodily development and
maintain reproductive organs in adults.