The brain: The source of mind and self
4Overview
The nervous system- central and peripheral
Neurons
Neuron Communication
Chemical messengers
Inside the brain
Parts of the brain
Split Brain Patients
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Organization of the nervous system
4The withdrawal reflex (automatic, does not involve the brain)
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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 center
of the back. Actually and extension
of the brain.
Protected by spinal column
4Structure of a neuron
Dendrites
Receive information from other
neurons and transmit toward the
cell body
Cell body
Keeps the neuron alive and
determines whether it will fire
Axon
Extending fiber that conducts
impulses away from the cell body
and transmits to other cells.
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4Structure of a neuron Your turn
Which part of a neuron is tree-like or “branchy”?
1. Dendrites
2. The axon
3. The cell body
4. The nucleus
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Your turn
Which part of a neuron is tree-like or “branchy”?
1. Dendrites
2. The axon
3. The cell body
4. The nucleus
4How neurons communicate
Axon terminals release
neurotransmitters.
Neurotransmitter enters 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.
4Neurotransmitter
Chemical released by a transmitting neuron at the synapse and capable of affecting the activity of a receiving neuron
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Major neurotransmitters
Serotonin--sleep, mood, eating
Dopamine--movement, learning, emotion
Acetylcholine (Ach), muscle action, memory
Norepinephrine- heart rate, learning, memory
(GABA)-inhibitory
4Endorphins-brain’s natural opiates, reduce pain promote pleasure
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The endocrine system
Endocrine glands release hormones into the bloodstream…
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…Hormones regulate
growth, metabolism,
sexual development
and behavior, and other
functions.
The endocrine system
Hormones
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
4Mapping the brain
1.! Researchers study brains that have experienced disease or injury
2. Some Animal Studies Involves damaging and removing sections of animals’ brain and observing the effects.
3. EEG
4. TMS
5. PET
6. MRI
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Electroencephalogram (EEG)
A recording of neural activity detected by needle electrodes
4Transcranial magnetic stimulation (TMS)
Involves delivering a large current through a wire coil on a person’s head
Can be used to
Produce motor responses
Temporarily inactivate an area of the brain
Treat depression
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Positron emission tomography (PET Scan)
Active areas have increased blood flow.
Sensors detect radioactivity.
Different tasks show distinct activity patterns. Diagnose abnormalities or just learn about normal brain
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A method for analyzing biochemical changes in the brain as they occur, using injections of a glucose-like substance containing a radioactive element
Magnetic resonance imaging (MRI)
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 nice clear 3D images
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Method for studying body and brain tissue
A tour through the brain
Brain stem
Cerebellum
Thalamus
Hypothalamus and pituitary gland
Amygdala
Hippocampus
Cerebrum and lobes of the cerebral cortex
4The brain stem
Pons Involved in sleeping, waking, and dreaming
Medulla Responsible for certain automatic functions such as breathing and heart rate
Reticular activating system Arouses cortex and screens incoming information
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The cerebellum
Regulates movement and balance
Involved in remembering simple motor skills and acquired reflexes
Plays a small part in Analyzing sensory information
Understanding words
4The 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
4The amygdala
Responsible for
Arousal
Regulation of emotion
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
4The cerebrum(also called”the
cortex” or the “Modern Brain”
Largest brain structure
Two cerebral hemispheres 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)
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Lobes of the cerebral cortex
Occipital lobes (visual cortex)
Parietal lobes (somatosensory cortex)
Temporal lobes Memory, language perception, emotion, and auditory cortex
Frontal lobes Planning, creative thinking, language: also emotional regulation and complex motor movements
4Lobes of the cerebral cortex
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Your turn
Omar bumps his head and is suddenly unable to see, although
the doctor says there is nothing wrong with her eyes? Which
part of his brain did Omar damage?
1. The amygdala
2. The hippocampus
3. The occipital lobe of the cerebral cortex
4. The parietal lobe of the cerebral cortex
4Your turn
Omar bumps his head and is suddenly unable to see, although
the doctor says there is nothing wrong with his eyes? Which
part of his brain did Omar damage?
1. The amygdala
2. The hippocampus
3. The occipital lobe of the cerebral cortex
4. The parietal lobe of the cerebral cortex
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Phineas Gage-1848
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
4The corpus callosum
Millions of myelinated axons connecting the brain’s hemispheres
Provides a pathway for communication
If surgically severed to treat epilepsy, hemispheres cannot communicate directly
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Split-brain experiment
4Split-brain experiment
Subjects were presented information to one or the other side of their brains.
Patients identified verbally the pictures to the right (e.g., boy’s face). Right side goes to left brain, the verbal side.
BUT, When patients were asked to POINT to the face seen, the patients pointed to the left (man’s) picture.
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Research on split-brain patients shows us that…
1.! Nearly all right-handed and the majority of left-handed individuals process language mainly in the left hemisphere.
2.! Many researchers believe in left-hemisphere dominance because cognitive skills originate here.
3.! Others insist right-hemisphere is just as important for spatial visual problem solving, art & music appreciation and is more intuitive.
4. The two hemispheres are more allies than opposites
Finally….for all you philosophy lovers….where is “The Self”?
Brain scientists explain the mind and the soul in physical terms as mainly a product of the cerebral cortex, and then frontal lobes critical. But when you say, “My mind is playing tricks on me” who is the “me” being tricked? Can we leave out that me?
Cognitive Scientist Daniel Dennett says that Mind is a series of independent brain parts dealing with different aspects of thought and perception constantly getting together to meet and “revise their drafts” of reality.
Interestingly the idea that the self is an illusion is consistent with the teachings of many spiritual eastern traditions. Buddhism teaches us that our “self” is really a collection of thoughts and feelings that shift and change from moment to moment.
But even today, with modern neuroscience and technology no one has a clear picture of how the inner life of the mind is linked to the physical processes of the brain.
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Closing Wise Words
“I used to think that the brain was the
most wonderful organ in my body. Then
I realized…… well, look what's telling me
this!”-Emo Phillips, Actor & Comedian)