Download Neurons, Hormones, and the Brain

Neurons, Hormones, and the
Brain
©2002 Prentice Hall
Neurons, Hormones, and the
Brain
 The
Nervous System: A Basic Blueprint
 Communication in the Nervous System
 Mapping the Brain
 A Tour Through the Brain
 The Two Hemispheres of the Brain
 Two Stubborn Issues in Brain Research
©2002 Prentice Hall
The Nervous System: A Basic
Blueprint
The Central Nervous System
The Peripheral Nervous System
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Divisions of the Nervous System
 Central
Nervous
System
 Brain
 Spinal
cord
 Peripheral
Nervous
System
 Somatic
 Autonomic
©2002 Prentice Hall
Nervous System Organization
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The Central Nervous System
 Central
Nervous System: The portion
of the nervous system consisting of the
brain and spinal cord.
 Spinal Cord: A collection of neurons and
supportive tissue running from the base
of the brain down the center of the back,
protected by a column of bones (the
spinal column).
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The Peripheral Nervous
System
 Somatic
Nervous System: The
subdivision of the PNS that connects to
sensory receptors and to skeletal
muscles; sometimes called the skeletal
nervous system.
 Autonomic Nervous System: The
subdivision of the PNS that regulates the
internal organs and glands.
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Sympathetic and Parasympathetic
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Communication in the
Nervous System
The Structure of the Neuron
How Neurons Communicate
Chemical Messengers in the
Nervous System
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Different Kinds of Neurons

Neurons vary in size and shape, depending on
their location and function. More than 200
types have been identified in mammals.
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The Structure of the Neuron

Dendrite: Branches
that receive signals
and transmit to cell
body
 Cell Body: Controls
cell metabolism and
determines firing
 Axon: Carries
impulses away from
cell body
 Myelin Sheath: Fatty
insulation
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How Neurons Communicate
 Synapse:
Site where a nerve impulse is
transmitted from one neuron to another;
includes the axon terminal, synaptic cleft,
and receptor sites on receiving cell.
 Neurotransmitter: Chemical substance
that is released by transmitting neuron at
the synapse and alters the activity of the
receiving neuron.
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Plasticity in Brain & Behavior

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Some rats are housed
alone in empty cages
Their littermate twins are
group-housed in cages
with toys, which are
changed frequently
Richer environments led
to heavier, thicker
brains, more synapses,
and better learning
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Getting Connected

Neurons in a newborn’s brain are widely
spaced, but form connections quickly.
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Chemical Messengers in the
Nervous System

Neurotransmitters
are released into
synaptic cleft
 Bind to receptor site
on receiving neuron
 Electrical state of
receiving neuron
changes, becoming
more (or less) likely
to fire
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Major Neurotransmitters
 Acetylcholine
(ACh)
 Dopamine
 Serotonin
 Norepinephrine
 Gamma
amino butryic acid (GABA)
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Endorphins
 Chemical
substances in the nervous
system that are similar in structure and
action to opiates; they are involved in
pain reduction, pleasure, and memory,
and are known technically as
endogenous opioid peptides.
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Hormones
 Hormones:
Chemical substances,
secreted by organs called glands, that
affect the functioning of other organs.
 Endocrine Glands: Internal organs that
produce hormones and release them into
the bloodstream.
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Mapping the Brain
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Electroencephalogram
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Positron Emission Tomography

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Active areas have
increased blood flow
Radioactive isotopes
(small amounts) are
placed in the blood
Sensors detect
radioactivity
Different tasks show
distinct activity patterns
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Magnetic Resonance Imaging

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Magnetic fields align
certain ions and
compounds
When field is removed,
these molecules release
energy as radio waves
Computer calculates
tissue density from radio
waves
Provides clear, 3D images
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A Tour Through the Brain
The Brain Stem
The Cerebellum
The Thalamus
The Hypothalamus and the Pituitary Gland
The Limbic System
The Cerebrum
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The Human Brain

This view shows
the brain as if
split in half frontto-back


Inside surface of
right half of brain
Eyes on the left,
near the word
“hypothalamus”
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The Brain Stem

Brain Stem: At the top of the
spinal cord, consisting of
medulla and pons

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
Medulla: Responsible for some
automatic functions, such as
breathing and heart rate
Pons: Involved in sleep, waking,
and dreaming.
Reticular Activating System: A
dense network of neurons found
in the core of the brain stem; it
arouses the cortex and screens
incoming information.
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The Cerebellum
 Cerebellum:
Regulates movement and
balance, and is involved in learning
some simple responses.
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Thalamus and Hypothalamus

Thalamus: Relays sensory
messages to the cerebral cortex.
 Hypothalamus: Involved in
emotions and drives vital to
survival (e.g., fear, hunger, thirst,
and reproduction); it regulates the
autonomic nervous system.
 Pituitary Gland: Small endocrine
gland at the base of the brain,
which releases many hormones
and regulates other endocrine
glands.
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The Limbic System

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Limbic System: A group
of brain areas involved in
emotional reactions and
motivated behavior.
Amygdala: Involved in the
arousal and regulation of
emotion and the initial
emotional response to
sensory information.
Hippocampus: Involved in
the storage of new
information in memory.
©2002 Prentice Hall
The Cerebrum

Occipital Lobes:
Vision
 Parietal Lobes: body
sensation
 Temporal Lobes:
Hearing, language
 Frontal Lobes:
Thinking, planning,
movement
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The Case of Phineas Gage

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Gage was a railroad
construction foreman
An 1848 explosion
forced a steel tamping
rod through his head
Others said he was
“…no longer Gage…”
Lost his job, worked as a
sideshow exhibit
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The Two Hemispheres of the
Brain
Split Brains: A House Divided
A Question of Dominance
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Visual Pathways

Each hemisphere
receives information
about the opposite
side of the visual field.
 Objects to your left put
images on right side of
each retina; goes to
right side of brain
 Half of optic nerve
fibers cross at the
optic chiasm
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Split Brains: A House Divided
 Hemispheres
of brain sometimes
separated to treat severe epilepsy
 Split brain operation includes the optic
chiasm
 Optic
nerve no longer crosses
 Visual information goes only to one
hemisphere
 Different
sides of brain see different
information
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Divided Brain, Divided View
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Two Stubborn Issues in Brain
Research
Why Do We Dream?
Are There “His” and “Hers” Brains?
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Why Do We Dream?
 Rapid
Eye Movement (REM) Sleep:
Sleep periods characterized by fast eye
movement behind closed eyelids, loss of
muscle tone, and dreaming.
 Activation-Synthesis Theory: Theory
that dreaming results from cortical
synthesis and interpretation of neural
signals triggered by activity in the lower
part of the brain.
©2002 Prentice Hall
Are There “His” & “Hers” Brains?

Sex differences in the brain
have been studied for many
years.


Many findings seem to reflect
cultural bias, and change with
cultural changes
Reliable differences have been
found in activity of certain brain
areas during some tasks

♂
Example: MRI of language task,
right
©2002 Prentice Hall
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