Transcript Chapter 2: Brain and Behavior

Course
Introduction to Psychology
Brain and Behaviour
Prof. BARAKAT
Summer Term
Nerves and Neurons
Nerves: Large bundles of axons and dendrites
Myelin: Fatty layer that coats some axons

Multiple Sclerosis (MS) occurs when myelin layer is
destroyed; numbness, weakness, and paralysis occur
Neurilemma: Thin layer of cells wrapped around
axons outside brain and spinal cord; forms a
tunnel that damaged fibers follow as they repair
themselves
Neuron and Its Parts
Neuron: Individual nerve cell; 100 billion in
brain




Dendrites: Receive messages from other neurons
Soma: Cell body; body of the neuron. Receives
messages and sends messages down the axon
Axon: Carries information away from the cell body
Axon Terminals: Branches that link the dendrites
and somas of other neurons
Fig. 1 An example
of a neuron, or
nerve cell, showing
several
of
its
important features.
The
right
foreground shows a
nerve cell fiber in
cross section, and
the upper left inset
gives
a
more
realistic picture of
the
shape
of
neurons. The nerve
impulse
usually
travels from the
dendrites and soma
to the branching
ends of the axon.
The neuron shown
here is a motor
neuron.
Motor
neurons originate in
the brain or spinal
cord and send their
axons
to
the
muscles or glands of
the body.
The Nerve Impulse
Resting Potential: Electrical charge of an
inactive neuron
Threshold: Trigger point for a neuron’s firing
Action Potential: Nerve impulse
Ion Channels: Axon membrane has these tiny
holes or tunnels
Fig. 2 Activity in an axon can be measured by placing electrical probes inside and outside the
axon. (The scale is exaggerated here. Such measurements require ultra-small electrodes, as
described later in this chapter.) At rest, the inside of an axon is about –60 to –70 millivolts,
compared with the outside. Electrochemical changes in a nerve cell generate an action
potential. When positively charged sodium ions (Na+) rush into the cell, its interior briefly
becomes positive. This is the action potential. After the action potential, an outward flow of
positive potassium ions (K+) restores the negative charge inside the axon. (See Figure 2.3 for
further explanation.)
Fig. 4 The inside of an axon normally has a negative electrical charge. The fluid surrounding an
axon is normally positive. As an action potential passes along the axon, these charges reverse, so
that the interior of the axon briefly becomes positive.
Fig. 5 Cross-sectional views
of an axon. The right end of
the top axon is at rest, with a
negatively charged interior.
An action potential begins
when the ion channels open
and sodium ions (Na+) enter
the axon. In this drawing the
action potential would travel
rapidly along the axon, from
left to right. In the lower
axon the action potential has
moved to the right. After it
passes, potassium ions (K+)
flow out of the axon. This
quickly renews the negative
charge inside the axon, so it
can fire again. Sodium ions
that enter the axon during an
action potential are pumped
back out more slowly. Their
removal restores the original
resting potential.
Fig.3 A highly magnified view of the synapse. Neurotransmitters are stored in tiny sacs
called synaptic vesicles. When a nerve impulse arrives at an axon terminal, the vesicles
move to the surface and release neurotransmitters. These transmitter molecules cross the
synaptic gap to affect the next neuron. The size of the gap is exaggerated here; it is actually
only about one millionth of an inch. Transmitter molecules vary in their effects: Some excite
the next neuron and some inhibit its activity.
Neurotransmitters
Chemicals that alter activity in neurons; brain
chemicals



Acetylcholine: Activates muscles
Dopamine: Muscle control
Serotonin: Mood and appetite control
Messages from one neuron to another pass over
a microscopic gap called a synapse
Receptor Site: Areas on the surface of neurons
and other cells that are sensitive to
neurotransmitters
Neural Regulators
Neuropeptides: Regulate activity of
other neurons

Enkephalins: Relieve pain and stress;
similar to endorphins

Endorphins: Released by pituitary gland;
also help to relieve pain
Neural Networks
Central Nervous System (CNS): Brain and spinal
cord
Peripheral Nervous System: All parts of the
nervous system outside of the brain and spinal
cord


Somatic System: Carries messages to and from
skeletal muscles and sense organs; controls voluntary
behavior
Autonomic System: Serves internal organs and
glands; controls automatic functions such as heart
rate and blood pressure
The Spinal Cord
Spinal Nerves: 31 of them; carry sensory and
motor messages to and from the spinal cord
Cranial Nerves: 12 pairs that leave the brain
directly; also work to communicate messages
Subparts of the Nervous System
Two Divisions of the Autonomic
System
Sympathetic: Arouses body; emergency
system
Parasympathetic: Quiets body; most
active after an emotional event
Fig. 6 (a) Central and peripheral nervous systems. (b) Spinal nerves, cranial nerves, and
the autonomic nervous system.
Fig.7
Sympathetic
and parasympathetic
branches
of
the
autonomic
nervous
system.
Fig.
8
A
simple
sensory-motor (reflex)
arc. A simple reflex is
set in motion by a
stimulus to the skin (or
other
part
of
the
body).
The
nerve
impulse travels to the
spinal cord and then
back out to a muscle,
which
contracts.
Reflexes provide an
“automatic” protective
device for the body.
How is the Spinal Cord Related to
Behavior?
Reflex Arc: Simplest behavioral pattern; occurs when a stimulus
provokes an automatic response
Sensory Neuron: Nerve cell that carries messages from the senses
toward the CNS
Connector Neuron: Nerve cell that links two others
Motor Neuron: Cell that carries commands from the CNS to muscles
and glands
Effector Cells: Cells capable of producing a response
Researching the Brain
Ablation: Surgical removal of parts of the brain
Deep Lesioning: A thin wire electrode is lowered into a
specific area inside the brain; Electrical current is then
used to destroy a small amount of brain tissue
Electrical Stimulation of the Brain (ESB): When an
electrode is used to activate target areas in the brain
Electroencephalograph (EEG): Detects, amplifies, and
records electrical activity in the brain
Fig. 9 The functions of brain structures are explored by selectively activating or removing
them. Brain research is often based on electrical stimulation, but chemical stimulation is also
used at times.
Fig.
10
recording.
An
EEG
Researching the Brain (cont.)
Computed Tomographic Scanning
enhanced X-ray of the brain or body
(CT):
Computer-
Magnetic Resonance Imaging (MRI): Uses a strong
magnetic field, not an X-ray, to produce an image of the
body’s interior
Functional MRI: MRI that makes brain activity visible
Positron Emission Tomography (PET): Computergenerated color image of brain activity, based on glucose
consumption in the brain
© Huntington Magnetic Resonance Center, Pasadena, California
Fig 11. An MRI scan of the brain.
Washington University School of Medicine, St.
Fig 12. PET scans.
Louis
Washington University School of Medicine, St. Louis
Fig.13.The bright spots you see here were created by a PET scan. They are similar to the
spots in Fig.12 However, here they have been placed over an MRI scan so that the brain’s
anatomy is visible. The three bright spots are areas in the left brain related to language. The
spot on the right is active during reading. The top-middle area is connected with speech. The
area to the left, in the frontal lobe is linked with thinking about a word’s meaning
(Montgomery, 1989).
Courtesy of Richard Haier, University of California, Irvine
Fig. 14 In the images you see here, red, orange, and yellow indicate high consumption of
glucose; green, blue, and pink show areas of low glucose use. The PET scan of the brain
on the left shows that a man who solved 11 out of 36 reasoning problems burned more
glucose than the man on the right, who solved 33.
Fig. 19 This simplified drawing shows the main structures of the human brain and describes
some of their most important features. (You can use the color code in the foreground to
identify which areas are part of the forebrain, midbrain, and hindbrain.)
Central Cortex Lobes
Occipital: Back of brain; vision center
Parietal: Just above occipital; bodily sensations
such
as
touch,
pain,
and
temperature
(somatosensory area)
Temporal: Each side of the brain; auditory and
language centers
Frontal: Movement, sense of smell, higher mental
functions
 Contains
motor
cortex;
controls
motor
movement
Forebrain
Structures are part of the Limbic System: System
within forebrain closely linked to emotional
response and motivating behavior
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Thalamus: Relays sensory information on the
way to the cortex; switchboard
Hypothalamus: Regulates emotional behaviors
and motives (e.g., sex, hunger, rage, hormone
release)
Amygdala: Associated with fear responses
Hippocampus:
Associated
with
storing
permanent memories; helps us navigate through
space
Right Brain/Left Brain
About 95 percent of our left brain is used for language
Left hemisphere better at math, judging time and rhythm,
and coordinating order of complex movements

Processes information sequentially and is involved with
analysis
Right hemisphere good at perceptual skills, and at
expressing and detecting other’s emotions

Processes information simultaneously and holistically
Split Brains
Corpus Callosum is cut; done to control severe
epilepsy (seizure disorder)
Result: The person now has two brains in one
body
This operation is rare and is often used as a last
resort
Fig.15 Corpus Callosum
Fig. 16 Basic nerve
pathways
of
vision.
Notice that the left
portion of each eye
connects only to the left
half
of
the
brain;
likewise,
the
right
portion of each eye
connects to the right
brain. When the corpus
callosum is cut, a “split
brain”
results.
Then
visual information can be
directed
to
one
hemisphere or the other
by flashing it in the right
or left visual field as the
person stares straight
ahead.
Fig. 18 The left
and right brain
have
different
information
processing
styles. The right
brain gets the
big pattern; the
left focuses on
small details.
When the Brain Fails to Function
Properly
Association Cortex: Combine and process information from
the five senses
Aphasia: Language disturbance resulting from brain
damage
Broca’s Area: Related to language and speech production

If damaged, person knows what s/he wants to say but can’t say the
words
Wernicke’s Area: Related to language comprehension; in
left temporal lobe

If damaged, person has problems with meanings of words, NOT
pronunciation
When the Brain Fails to Function
Properly (cont.)
Agnosia: Inability to identify seen
objects
Facial Agnosia: Inability to perceive
familiar faces
Subcortex: Reticular Formation (RF)
Reticular Formation: Inside medulla and
brainstem
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
Associated with alertness, attention, and
some reflexes (breathing, coughing,
sneezing, vomiting)
Reticular Activating System (RAS): Part of
RF that keeps it active and alert
 RAS
acts like the brain’s alarm clock
 Activates and arouses cerebral cortex
Endocrine System
Glands that pour chemicals (hormones) directly into
the bloodstream or lymph system
Pituitary Gland: Regulates growth via growth
hormone
Too little means person will be smaller than
average

Hypopituitary Dwarfs:
proportioned but tiny
As
adults,
perfectly
Treatable by using human or synthetic growth
hormone; will add a few inches
 Treatment is long and expensive

Fig. 20 Parts of the
limbic system are
shown in this highly
simplified drawing.
Although only one
side is shown, the
hippocampus
and
the
amygdala
extend out into the
temporal lobes at
each side of the
brain. The limbic
system is a sort of
“primitive core” of
the brain strongly
associated
with
emotion.
Endocrine System (cont.)
Too much growth hormone leads to giantism
(Excessive body growth)
Acromegaly: Enlargement of arms, hands, feet,
and facial bones

Caused by too much growth hormone secreted
late in growth period
Pituitary also governs functioning of other glands,
especially thyroid, adrenals, and gonads
Endocrine System (cont.)
Pineal Gland: Regulates body rhythms and sleep cycles.

Releases hormone melatonin, which responds to daily
variations in light
Thyroid: In neck; regulates metabolism

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Hyperthyroidism: Overactive thyroid; person tends to be
thin, tense, excitable, nervous
Hypothyroidism: Underactive thyroid; person tends to
be inactive, sleepy, slow, obese
The Adrenal Glands
Adrenals (located on top of kidneys) :

Arouse body,

Regulate salt balance,

Adjust body to stress,

Regulate sexual functioning,

Release epinephrine and norepinephrine (also
known as adrenaline and noradrenaline)


Epinephrine arouses body; is associated with fear
Norepinephrine arouses body; is linked with anger
The Adrenal Glands (cont.)
Adrenal Medulla: Inner core of adrenals; source of
epinephrine and norepinephrine
Adrenal Cortex: Produces hormones known as corticoids

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Regulate salt balance
Deficiency in some types will cause powerful salt
cravings
Help body to adjust to stress
Secondary source of sex hormones
Oversecretion of adrenal sex hormones can cause virilism:
exaggerated male characteristics (Bearded woman)
Neurogenesis and Plasticity
Neurogenesis: Production of new brain
cells
Plasticity: Brain’s ability to change its
structure and functions
Fig.
21
Neuroscientists
are
searching for ways to repair
damage caused by strokes and
other brain injuries. One promising
technique involves growing neurons
in the laboratory and injecting them
into the brain.
These immature
cells are placed near damaged
areas, where they can link up with
healthy neurons.
The technique
has proved successful in animals
and is now under study in humans.
Thank you