Download Behavioral Neuroscience

Neurons, Hormones,
and the Brain
Chapter 4
Copyright © 2007 Pearson Education Canada
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Chapter Outline
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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
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The Nervous System:
A basic blueprint
• The central nervous system
• The peripheral nervous system
– Somatic nervous system
– Autonomic nervous system
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Organization of the Nervous System
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The Central Nervous System
• Brain
• Spinal cord
– A collection of neurons and
supportive tissue running from
the base of the brain down the
centre of the back
– Protected by spinal column
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The Peripheral Nervous System
• Somatic nervous system:
the subdivision of the peripheral
nervous system that connects to
sensory and to skeletal muscles
• The autonomic nervous system:
the subdivision of the peripheral
nervous system that that regulates
internal organs and glands
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The Autonomic Nervous System
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Communication in the nervous
system
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The structure of the neuron
Neurons in the news
How neurons communicate
Chemical Messengers
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Structure of a Neuron
• Dendrites
– receive information from other
neurons and transmit towards the cell
body
• Cell body
– keeps the neuron alive and
determines whether it will fire
• Axon
– extending fibre that conducts impulses
away from the cell body and transmits
to other cells
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Types of Neurons
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Structure of a Neuron
• Myelin Sheath
– Fatty insulation that may surround the neuron’s
axon
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Neurons in the News
• Neurogenesis
– The production of new
neurons from immature
stem cells
• Stem cells
– Immature cells that
renew themselves and
have the potential to
develop into mature
cells
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Stem-Cell Research
• Embryonic stem cells appear most promising
in developing treatments for cancers, organ
and brain diseases (e.g., Alzheimer’s)
• Currently have ethical debate over their use
• New techniques try to extract them without
harming the embryo
• McGill team has had some success in
transforming adult cells into brain tissue
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How Neurons Communicate
• Axon terminals
release
neurotransmitter
• Neurotransmitter
enters the synapse
• Neurotransmitter
binds to receptors
that it fits
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Action Potential
• A brief change in electrical voltage that
occurs between the inside and outside of an
axon when a neuron is stimulated
• This produces an electrical impulse
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Chemical Messengers
• Neurotransmitters
• Hormones
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Neurotransmitter
• Chemical substance released by a transmitting
neuron at the synapse and capable of affecting
the activity of a receiving neuron
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Major Neurotransmitters
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Serotonin
Dopamine
Acetylcholine (ACh)
Norepinephrine
Gamma amino butyric acid (GABA)
Glutamate
Endorphins
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Opioids and Substance P
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The Endocrine System
• Endocrine glands
release hormones
into the bloodstream
• Hormones regulate
growth, metabolism,
sexual development
and behaviour, and
other functions
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Hormones: Long Distance
Messengers
• Melatonin
– Regulates daily biological rhythms
• Adrenal Hormones
– Involved in emotions and stress
• Cortisol, epinephrine, and norepinephrine
• Sex Hormones
– Regulate development and functioning of
reproductive organs
• Androgens, estrogens, and progesterone
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Mapping the Brain
• Lesioning
– Involves damaging and removing sections
of brain in animals, then observing their
effects
– Some lesions are cased by accidents,
traumas, or disease
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Electroencephalogram (EEG)
• A recording of neural activity detected by
electrodes
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Transcranial magnetic stimulation (TMS)
• Involves delivering a large current
through a wire coil on a person’s head
• Also used to:
– produce motor responses
– temporarily inactivate an area of the brain
– treat depression
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Positron Emission Tomography (PET)
• A method for analyzing biochemical activity in
the brain, using injections of a glucose-like
substance containing a radioactive element
• Active areas have
increased blood flow
• Sensors detect
radioactivity
• Different tasks show
distinct activity patterns
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Magnetic Resonance Imaging
(MRI)
• Method for studying body and
brain tissue
• 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
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Brain stem
Cerebellum
Thalamus
Hypothalamus and the pituitary gland
Amygdala
Hippocampus
Cerebrum and lobes of the cerebral cortex
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The Brain Stem
• Pons
– involved in sleeping,
waking and dreaming
• Medulla
– responsible for certain
automatic functions such
as breathing and heart
rate
• Reticular activating system
(or formation)
– arouses cortex and
screens incoming
information
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The Cerebellum
• Regulates movement and
balance
• Involved in remembering
simple skills and acquired
reflexes
• Plays a part in:
– analyzing sensory
information
– solving problems
– understanding words
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The Thalamus
• Relays sensory
messages to the
cerebral cortex
• Includes all sensory
messages except those
from olfactory bulb
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Hypothalamus and Pituitary Gland
• Involved in emotions and
drives vital to survival
– fear, hunger, thirst, and
reproduction
• Regulates autonomic
nervous system
• Pituitary gland
– small endocrine gland
which releases
hormones and regulates
other endocrine glands
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The Amygdala
• Responsible for:
– arousal
– regulation of emotion
– the initial emotional
response to sensory
information
• Plays important role in
– mediating anxiety and
depression
– emotional memory
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The Hippocampus
• Responsible for:
– storage of new
information in memory
– comparing sensory
information with what
the brain expects about
the world
– enabling us to form
spatial memories for
navigating the
environment
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The Cerebrum
• Largest brain structure
• This upper part of the brain is divided into
two cerebral hemispheres that are
connected by the corpus callosum
• In charge of most sensory, motor and
cognitive processes
• Surrounded by cerebral cortex, a collection
of several thin layers of cells (grey matter)
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Lobes of the Cerebral Cortex
• Occipital lobes (visual cortex)
• Parietal lobes (somatosensory cortex)
• Temporal lobes
– Memory, perception, emotion and auditory cortex
– Left lobe, Wernicke’s area
• Frontal lobes
– Emotion, planning, creative thinking and motor cortex
– Left lobe, Broca’s area
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Lobes of the Cerebral Cortex
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Phineas Gage
• 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 and worked as a
sideshow exhibit
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The Two hemispheres of the
Brain
• The Split Brain: a house divided
• The two hemispheres: allies or
opposites?
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The Corpus Callosum
• Millions of myelinated
axons connecting the
brain’s hemispheres
• Provides a pathway for
communication
between hemispheres
• If surgically severed to
treat epilepsy,
hemispheres cannot
communicate directly
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Split-Brain Experiment
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Split-Brain Experiment
• Subjects were presented information to one or
the other side of their brain
• Patients identified verbally the pictures to the
right (i.e., boy)
• When asked to point to the face seen, the
patients pointed to the left picture
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The Two Hemispheres:
Allies or Opposites?
• Research on split-brain patients shows us:
– Nearly all right-handed and the majority of lefthanded individuals process language mainly in the
left hemisphere
– Many researchers believe in left-hemisphere
dominance
– Others insist the right-hemisphere is important for
spatial visual problem-solving, comprehending
non-verbal sounds, and some language abilities
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Two Stubborn issues in Brain
Research
• Where is the Self?
• Are there “his” and “hers” brains?
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Where is the Self?
• Modern brain scientists explain the mind or
soul in physical terms, as a product of the
cerebral cortex
– The mind is:
• a series of independent brain parts dealing with different
aspects of thoughts (Dennett, 1991)
• a loose confederation of mental systems all working
without conscious awareness (Gazzaniga, 1998; Roser &
Gazzaniga, 2004)
• Frontal lobes may play a critical role
• Many still question the relationship between
subjective experience and physical processes
of the brain
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Are There “His” and “Hers” Brains?
• After analyzing 49 studies of sex differences in
brain anatomy, researchers found small
differences between the two groups and larger
differences within groups
• There do appear to be sex differences in
lateralization of language. Males show lefthemisphere activation only; females, left and
right
• There also appear to be differences in amounts
of grey matter: females have more
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Gender & Language Laterality
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What do “Differences” Mean for
Behaviour?
• These supposed differences are stereotypes
• A brain difference does not necessarily explain
behaviour or performance
• Sex differences in the brain could be the result
rather than the cause of behavioural differences
• Use your critical thinking skills to evaluate all of
the research!
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