Transcript Behavioral Neuroscience

Neurons, Hormones, and the Brain
Chapter 4
Neurons, Hormones, and the Brain
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The central nervous system
The peripheral nervous system
Communication in the nervous system
Neurotransmitters
Mapping the brain
A walk through the brain
The two hemispheres of the brain
Where is the self?
Are there “his” and “hers” brains?
The Central Nervous System
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Brain
Spinal cord
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A collection of neurons and
supportive tissue running
from the base of the brain
down the center of the back.
Protected by spinal column.
The Withdrawal Reflex
Peripheral Nervous System
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Somatic
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Includes the nerves that are connected to sensory
receptors and skeletal muscles.
Autonomic
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The sympathetic nervous system mobilizes bodily
resources and increases the output of energy
during emotion and stress.
The parasympathetic nervous system operates
during relaxed states and that conserves energy.
Organization of the Nervous System
Communication in the Nervous System
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The structure of the neuron
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How neurons communicate
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Different kinds of neurons
Action potential
Chemical messengers in the nervous system
 Neurotransmitters
Major neurotransmitters
 Endorphins
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Endocrine system
Hormones
Structure of a Neuron
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Dendrites
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Cell body
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receive information from other neurons
and transmit towards the cell body.
keeps the neuron alive and determines
whether it will fire.
Axon
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extending fibre that conducts impulses
away from the cell body and transmits
to other cells.
Structure of a Neuron
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Myelin Sheath
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Fatty insulation that may surround the axon of a
neuron.
Different Kinds of Neurons
Neurons in the News
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Canadian research has provided evidence
for neurogenesis: the production of new
neurons from immature stem cells.
Stem cells are immature cells that renew
themselves and have the potential to
develop into mature cells; given
encouraging environments, stem cells from
early embryos can develop into any cell
type.
How Neurons Communicate
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Axon terminals release
neurotransmitter.
Neurotransmitter enters
synaptic gap.
Neurotransmitter binds
to receptors that it fits.
Action Potential
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A brief change in electrical voltage which occurs
between the inside and outside of an axon when a
neuron is stimulated. It produces an electrical
impulse.
Neurotransmitter
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A chemical substance that is released by a
transmitting neuron at the synapse and that
alters the activity of a receiving neuron.
Major Neurotransmitters
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Serotonin
Dopamine
Acetylcholine (ACh)
Norepinephrine
Gamma amino butryic acid (GABA)
Glutamate
Endorphins
Opioids and Substance P
The Endocrine System
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Endocrine glands
release hormones into
the bloodstream.
Hormones regulate
growth, metabolism,
sexual development
and behaviour, and
other functions.
Hormones: Long Distance Messengers
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Melatonin
Adrenal Hormones
 Cortisol, epinephrine, and norepinephrine.
Sex Hormones
 Androgens, estrogens, and progesterone.
Mapping the Brain
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Lesion method
Electroencephalogram (EEG)
Transcranial magnetic stimulation (TMS)
Positron-Emission tomography (PET)
Magnetic resonance imaging (MRI)
Mapping the Brain
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Lesioning
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Involves damaging and removing sections of
brain in animals, then observing their effects.
Transcranial magnetic stimulated (TMS)
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Stimulates brain cells using a powerful
magnetic field produced by a wire coil placed
on the head.
Can be used to temporarily inactivate neural
circuits.
Electroencephalogram (EEG)
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A recording of neural activity detected by
electrodes.
Positron Emission Tomography (PET)
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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.
Magnetic Resonance Imaging (MRI)
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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.
A Walk Through the Brain
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The brain stem
The cerebellum
The thalamus
The hypothalamus and the pituitary gland
The amygdala
The hippocampus
The cerebrum and lobes of the cerebral cortex
The Brain Stem
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Pons
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Medulla
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involved in sleeping, waking
and dreaming.
responsible for certain
automatic functions such as
breathing and heart rate.
Reticular activating system
(or formation)
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arouses cortex and screens
incoming information.
The Cerebellum
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Regulates movement and
balance.
Involved in remembering
simple skills and acquired
reflexes.
Plays a part in analyzing
sensory information,
solving problems and
understanding words.
The Thalamus
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Relays sensory messages to the cerebral cortex.
Includes all sensory messages except those from
olfactory bulb.
Hypothalamus and Pituitary Gland
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Involved in emotions and
drives vital to survival
including fear, hunger,
thirst, and reproduction.
Also regulates autonomic
nervous system.
Pituitary Gland
The pituitary gland is a
small endocrine gland
which releases hormones
and regulates other
endocrine glands.
The Amygdala
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Responsible for arousal
and regulation of emotion
and the initial emotional
response to sensory
information.
Plays important role in
mediating anxiety and
depression.
The Hippocampus
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Responsible for the
storage of new
information in memory.
Compares information
with what the brain has
come to expect about
the world.
“Gateway to memory”
because it enables us to
navigate through the
environment.
The Cerebrum
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Largest brain structure.
Consists of upper part of brain and divided into
two cerebral hemispheres which 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 (gray matter).
Lobes of the Cerebral Cortex
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Occipital lobes
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Parietal lobes
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Somatosensory cortex.
Temporal lobes
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Visual cortex.
Memory, perception, emotion and auditory cortex.
Left lobe, Wernicke’s area.
Frontal lobes
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Emotion, planning, creative thinking and motor cortex.
Left lobe, Broca’s area.
Lobes of the Cerebral Cortex
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
The Corpus Callosum
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Millions of myelinated
axons connecting the
brain’s hemispheres.
Provides a pathway for
communication between
the hemispheres.
If surgically severed for
treatment of epilepsy,
hemispheres cannot
communicate directly.
Split-Brain Experiment
Split-Brain Experiment
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Subjects were presented information to one or the
other side of their brains.
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.
Where Is the Self?
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Most scientists assume that what we call “mind,”
“consciousness,” self-awareness,” or “subjective
experience” can be explained in physical terms as a
product of the brain.
Some contend that the brain consists of
independent modules and that the self is an
illusion.
No one understands yet how subjective experience
is linked to physical processes in the brain.
Are There “His” and “Hers” Brains?
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After analyzing 49 studies of sex differences in
brain anatomy, Canadian researchers found small
differences between the two groups and larger
differences within groups.
There does appear to be sex differences in
lateralization of language. Males show left
hemisphere activation only. Females, left and
right.
There also appears to be differences in amounts
of grey matter. Females have more.
3 Ways to Interpret These Findings
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These supposed differences are stereotypes.
A biological difference does not necessarily
have implications for behaviour or
performance.
Sex differences in the brain could be the result
rather than the cause of behavioural
differences.