Transcript The Brain - Gordon State College

Chapter 2
The Brain
The Brain
Technology to Study the Brain
• Electroencephalograph (EEG):
•
records “waves” of electrical activity in the brain using metal electrodes
• Computerized axial tomograph (CAT):
•
thousands of X-ray photos of the brain are combined to form a crosssectional picture
• Magnetic resonance imaging (MRI):
•
produces three-dimensional images of the brain’s soft tissues by
detecting magnetic activity from nuclear particles in brain molecules
Technology to Study the Brain
• Positron emission tomography (PET):
measures neural activity in different brain regions
over several minutes by monitoring sugar glucose
consumption
• Functional magnetic resonance imaging
(fMRI): measures neural activity in different brain
regions averaged over seconds by monitoring
blood oxygen levels
PET Scan
MRI Scan
Three Major Brain Regions
• Their names come from their physical
location in the human embryo.
– Hindbrain: Located above the spinal
cord,
– Midbrain: Located above the hindbrain
– Forebrain: Located above the midbrain
Development of the Brain
Three Major Brain Regions:
Hindbrain
• Hindbrain consists of:
– Medulla: controls breathing, heart rate,
swallowing, digestion, and posture
– Pons: associated with sleep and arousal
– Cerebellum: regulates and coordinates body
movement and may play a role in learning
The Cerebellum
Midbrain
Reticular formation: regulates and
maintains consciousness
– plays an important role in
controlling arousal
Forebrain
Controls complex emotional reactions, cognitive
processes, and movement patterns. Consists
of:
– Thalamus: the brain’s sensory relay station
– Limbic system: influences fear, aggression, and
new memories
– Cerebral cortex: located on top of these structures;
the most complex part of the brain
Thalamus
• Brain’s Sensory Switchboard
• Directs incoming information from the
sensory systems (except smell) to the
appropriate location on the cortex.
The Brainstem and
Thalamus
Limbic System
• a doughnut-shaped system of neural structures at the
border of the brainstem and cerebral hemispheres
• associated with emotions such as fear and aggression
and drives such as those for food and sex
• includes the hypothalamus, hippocampus and amygdala
The Limbic
System
Hypothalamus
• neural structure lying below (hypo) the
thalamus
• directs several maintenance activities
• eating
• drinking
• body temperature
• helps govern the endocrine system via the
pituitary gland
• linked to emotion
Hippocampus
• Structure linked to the
processing/formation of new explicit
memories
• Manufactures new neurons
Amygdala [ah-MIG-dah-la]
– two almond-shaped neural clusters
that are components of the limbic
system and are linked to emotion,
especially rage and fear
The Limbic System
• Electrode implanted in reward center
Main Parts of the Human Brain
Lobes of the Cerebral
Cortex
• The cerebral cortex is divided into two
rounded halves, called the cerebral
hemispheres.
– These hemispheres are connected
together at the bottom by the corpus
callosum.
– Both hemispheres are divided into four
major sections called lobes:
The Brain
The Cerebral Cortex
Cortical Localization
• Occipital Lobes
– include the visual areas, each of which
receives visual information from the
opposite visual field
• Temporal Lobes
– include the auditory areas, each of
which receives auditory information
primarily from the opposite ear
Visual Cortex
• Functional MRI
scan of the
visual cortex
activated by
light shown in
the subject’s
eyes
Visual and Auditory
Cortex
Cortical
Localization
• Frontal Lobes
– involved in speaking and muscle
movements and in making plans and
judgments
• Parietal Lobes
– include the sensory cortex
The Cerebral Cortex
The Cerebral Cortex
• Motor Cortex
– area at the rear of the frontal lobes
that controls voluntary movements
• Sensory Cortex
– area at the front of the parietal lobes
that registers and processes body
sensations
Association Areas
• Areas of the cerebral
cortex that are not involved
in primary motor or sensory
functions
• Involved in higher mental
functions such as learning,
remembering, thinking, and
speaking
Cerebral Cortex Speech
• Aphasia
– impairment of language, usually caused by left hemisphere
damage either to Broca’s area (impairing speaking) or to
Wernicke’s area (impairing understanding)
• Broca’s Area
– an area of the frontal lobe that directs the muscle movements
involved in speech
• Wernicke’s Area
– an area of the left temporal lobe involved in language
comprehension and expression
Specialization and Integration
Brain Activity when Hearing,
Seeing & Speaking Words
Cortical Lateralization: Right and Left
Hemispheres Function Differently
• Right hemisphere: superior to the left hemisphere
in visual and spatial tasks, recognizing
nonlinguistic sounds, identifying faces, and
perceiving and expressing emotions
• Left hemisphere: superior to the right hemisphere
at language, logic, and providing explanations for
events
• Women may be more likely than men to use both
hemispheres for language (their brains are more
bilateralized).
Left-Handers are Different
• 65% have speech on the left (95 % RH)
• Weak correlations:
– + gifted & creative
– - reading disabilities, epilepsy, alcoholism,
schizophrenia, allergies, MR
Brain
Reorganization
• Corpus Callosum
– large bundle of neural fibers connecting the
two brain hemispheres and carrying
messages between the hemispheres
Brain Reorganization
Corpus Callosum
Brain
Reorganization
– Split Brain
– a condition in which the two hemispheres of
the brain are isolated by cutting the
connecting fibers (mainly those of the corpus
callosum) between them
Brain
Reorganization
• The information
highway from the
eyes to the brain
Testing the Split Brain
The Brain Can Alter Its Neural
Connections
– Plasticity: the flexibility of the brain to alter its neural
connections following injury
– Hemispherectomy: a radical surgical procedure in
which one of the cerebral hemispheres is removed to
control life-threatening epileptic seizures. The
remaining healthy hemisphere takes over many of the
functions of the removed hemisphere.
– Plasticity is highest in childhood, but it also occurs in
older adults.
Brain
Reorganization
-- the brain’s capacity for modification
as evident in brain reorganization
following damage (functional plasticity)
--and in experiments on the effects of
experience on brain development
Structural Plasticity)
Use it or Lose It
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1.
2.
3.
4.
5.
Avoid Harmful Substances
Exercise
Eat Sensibly
Challenge Yourself Mentally
Wear Your Helmet/Seat Belt.
Blood-Brain Barrier
• A semipermeable wall of tiny blood vessels
that prevent certain chemicals in the
bloodstream from reaching the brain
-
Protects the brain from many “foreign substances” in the
blood that may injure the brain,
Protects the brain from hormones and neurotransmitters
in the rest of the body, and
Maintains a constant environment for the brain.
Blood-Brain Barrier
– Beneficial substances allowed to enter the brain
through the blood-brain barrier are blood gases,
such as oxygen, and small nutritional
molecules.
– An important nutritional molecule transported
out of the bloodstream in this way is glucose.
– Scientists have learned how to trick the bloodbrain barrier into accepting therapeutic drugs
through the bloodstream to the brain.
Blood-Brain BarrierBa