Transcript What is Psychology? - Weber State University

Neurons, Hormones, and the
Brain
Chapter 4
Neurons, Hormones, and the
Brain
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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
The Nervous System: A Basic
Blueprint
The Central Nervous System
The Peripheral Nervous System
Divisions of the Nervous System
• Central Nervous
System
– Brain
– Spinal cord
• Peripheral
Nervous System
– Somatic
– Autonomic
Nervous System Organization
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).
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.
Sympathetic and
Parasympathetic
Communication in the Nervous
System
The Structure of the Neuron
How Neurons Communicate
Chemical Messengers in the
Nervous System
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.
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
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.
Plasticity in Brain & Behavior
• 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
Getting Connected
• Neurons in a newborn’s brain are widely
spaced, but form connections quickly.
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
Major Neurotransmitters
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Acetylcholine (ACh)
Dopamine
Serotonin
Norepinephrine
Gamma amino butryic acid (GABA)
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.
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.
Mapping the Brain
Electroencephalogram (EEG)
Positron Emission
Tomography
• Active areas have
increased blood flow
• Radioactive isotopes
(small amounts) are
placed in the blood
• Sensors detect
radioactivity
• Different tasks show
distinct activity patterns
Magnetic Resonance
Imaging
• 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
A Tour Through the Brain
The Brain Stem
The Cerebellum
The Thalamus
The Hypothalamus and the Pituitary
Gland
The Limbic System
The Cerebrum
The Human Brain
• This view shows the
brain as if split in
half front-to-back
– Inside surface of right
half of brain
– Eyes on the left, near
the word
“hypothalamus”
The Brain Stem
• Brain Stem: At the top of the
spinal cord, consisting of
medulla and pons
– 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.
The Cerebellum
• Cerebellum: Regulates movement and
balance, and is involved in learning
some simple responses.
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.
The Limbic System
• 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.
The Cerebrum
• Occipital Lobes:
Vision
• Parietal Lobes: body
sensation
• Temporal Lobes:
Hearing, language
• Frontal Lobes:
Thinking, planning,
movement
The Two Hemispheres of the
Brain
Split Brains: A House Divided
A Question of Dominance
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
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
Divided Brain, Divided View
Two Stubborn Issues in Brain
Research
Why Do We Dream?
Are There “His” and “Hers”
Brains?
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.
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,
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