Transcript Unit III - The Independent School

The Biology of Mind
 The axiom: Everything
psychological is
simultaneously
biological.
 Since 1839, major leaps
in understanding the
brain and its relation to
the body, behavior and
feelings have been made.
 Biological Psychologists
Neural Communication
Neurons
 The building block of the nervous system is the neuron, or
nerve cell. They conduct impulses through the NS.
 Sensory (afferent): Body to NS
 Motor (efferent): NS to body (glands and muscles)
 Interneurons: Within the NS
 The Construction of Neurons
 Cell Body (or soma)
 Dendrites – back propagating
 Axon
 Axon hillock, myelin sheath, nodes of Ranvier, axon terminals
Potential and the Neuron
 Neurons have selective permeability of their cell membranes; this can
be altered to allow ions (chiefly sodium and potassium) to flow into or
out of axons through special ion channels.
 When at rest, an axon is negatively charged (about -70 millivolts), and
is surrounded with positively charged ions. This is called resting
potential (potential energy).
 When a neuron fires a signal, sections of the axon near the axon
hillock begin allowing positive sodium ions to enter the axon. This
depolarization starts a chain reaction of ion channel openings through
the length of the neuron. The charge in the axon is now around 50
millivolts.
 This electrical impulse is called the action potential, and can move
between 2 and 200 mph.
 A refractory period (1-2 milliseconds) occurs as the positive ions are
pumped out of the axon, resetting it for future firings.
Impulsive Characteristics
 Speed
 How myelin sheaths help
 “Extravert v. Introvert”
and thresholds
 The Neuronal gun and
the strength of impulses
Communication is Key
 Synapse
 The basic communication process
 Neurotransmitters: Know functions and malfunctions
 Acetylcholine
 Monoamines
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Dopamine (DA)
Serotonin
Epinephrine (Epi)
Norepinephrine (NE)
 Gamma-aminobutyric acid (GABA)
 Glutamate
 Endorphins
The Agonist and the Ecstasy
 Chemicals (such as drugs)
change brain chemistry at the
synaptic level. A drug that
mimics neurotransmitters may
change the brain’s ability to
produce or receive them.
 Agonists: Mimics the effects of
neurotransmitters, or blocks
reuptake.
 Examples: Endogenous
agonists (n.t.), morphine
 Antagonists: Block the effects
of neurotransmitters, either by
blocking release or blocking
receptor sites.
 Examples: Botulin, Curare,
beta-blockers, Ecstasy
The Nervous System
 The Electrochemical
communication system
for the body.
 Contains two major
systems:
 Central Nervous System
 Peripheral Nervous
System
 The nervous system
transmits signals via
bundles of axons called
nerves.
The Peripheral Nervous System
(PNS)
Somatic (SNS)
Autonomic (ANS)
 Motor nerves
 Operates without
conscious control or
awareness – involuntary.
 Generally, this allows you
to sense and respond to
your environment.
 Communicates with CNS
and glands, heart and
smooth muscles.
 Mostly conscious
processes – voluntary.
 Divides into sympathetic
and parasympathetic
nervous systems.
 Sensory nerves
The ANS
Sympathetic Nervous
System (SNS)
 Arouses, excites and
expends energy.
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Heart rate increases
Pupils dilate
Blood pressure increases
Digestion is inhibited
Glucose is released
Epi / NE are released
Sweat glands activate
Parasympathetic
Nervous System (PSNS)
 Calms, inhibits and
conserves energy.
See other side…
and think the opposite.
The Central Nervous System
(CNS)
 Comprised of the brain
and the spinal cord.
 General brain info (more
will come later)
 General size and scope
of CNS
 Neural Networks
 Spinal Cord
 Function
 Reflexes
 Malfunctions
The Endocrine System
 Definition
 Primary differences:
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Chemical only
Uses bloodstream
Reaction time is slower
Effects last longer
 Hormones influence
metabolism, growth
reproduction, and mood.
In the Gland Scheme of Things
 Pituitary Gland

Considered the “master gland”. Releases hormones that activate the other glands as
well as growth hormones. Controlled by the hypothalamus.
 Adrenal Gland
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Produces epinephrine and norepinephrine, as well as coticoids
 Thyroid
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Produces thyroxine, which controls metabolism
 Pineal
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Produces melatonin (derived from serotonin) to regulate sleeping and waking
patterns.
 Pancreas

Produces insulin and glucagon to regulate blood sugar.
 Gonads
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Produce sex hormones: androgens (male) and estrogen and progesterone (female)
The Brain
Brain Games
 Imagine the wrinkled brain of Edward Titchener on the
shelf at Cornell University. Is “he” still there?
 The feedback loops from the brain to the body allow for
the sensations of living to reach us. But they also allow for
our feelings about those sensations to change our
behavior and alter our local environment.
 The ways in which the CNS impacts the release of
hormones, leading to a hormonal effect on the CNS, point
to the need for a brain and a body to create our conscious
experience.
 First, we must determine how we study the brain.
Tools of the Trade
 Early clinical experiences
 Brain lesions
 Electroencephalograms (
electroencephalograph)
 CT Scans
 MRI
 PET Scans
 fMRIs
 SQUID and MEG
An fMRI scan
Older Brain Structures
 Ratio of body weight to brain size is a poor predictor of
innate intelligence. Instead – brain structures provide
clues.
 These are often automatic, involuntary processes.
 The Brainstem: Medulla, Pons, Reticular Formation
 Thalamus
 Cerebellum
 Limbic System: Hippocampus, Amygdala, Hypothalamus
Robo Rat
 Research by John Chapin, stimulating whisker sensors in
rats to “steer” them.
 www.youtube.com/watch?v=EvOlJp5KIY&feature=related
The Cerebrum and
The Cerebral Cortex
 The Cerebrum: Largest structure in the human brain; composed
of left and right hemispheres.
 More on this left/right duality later.
 The Cerebral cortex is a gray outer cover on the cerebrum,
about an eighth of an inch thick.
 This is the center of motor, sensory and thinking activity.
 The cortex is rather large – about 2’X3’. It wrinkles and folds over
the cerebrum. These are convolutions.
 The presence of billions of neurons gives this area its grayish
appearance – hence “gray matter”.
 “White matter” lies below this layer, comprised of whiter, myelincovered axons that connect the cortex to other brain areas.
The Structure of the Cortex
 Besides nerves, nine times as many glial cells support the
neurons. Technically called oligodendrocytes in the CNS.
 Provide food and myelin, direct connections and clean
waste. Glia make up more than 50% of the brain’s volume.
 Four lobes: Divided by fissures, we find the frontal,
parietal, occipital and temporal.
 Three primary functions of the cortex:
 Motor: Controls voluntary movement
 Sensory: Where sensory input registers
 Association: Memory, language, perception and thought
Functions of the Cortex
 Motor Cortex
 At the back of the frontal lobe, running from ear to ear in an arch
across the brain.
 Foerster and Penfield experiments and conclusions
 www.youtube.com/watch?v=bkxuJwlquuQ&feature=related
 Sensory Cortex (or somatosensory cortex)
 At the front of the parietal lobe, parallel to the motor cortex.
 The more sensitive a region of the body, the more space it occupies.
 Other Sensory locations
 Occipital Lobe: Visual cortex
 Frontal Lobe: Broca’s area; Broca’s Aphasia
 Temporal Lobe: Auditory Cortex; Wernicke’s Area; Auditory Aphasia
 Association Areas
A Representation of the Motor
and Somatosensory Cortexes
The Brain’s Plasticity
 The brain can repair and
adapt itself: it retains some
plasticity throughout a life
time.
 Some functions – severed
nerves or damaged brain
areas may never recover.
 Neural tissue can
sometimes reorganize to
make up for a loss of
function.
 Constraint-induced
therapy
 Lack of sensory experience
 Neurogenesis
Split Brain Research
 Each hemisphere of the brain specializes in certain functions, and each
has importance in the overall functioning of our brain.
 This fact has been demonstrated in split-brain research.
 To relieve patients of seizures, the corpus callosum was severed.
 Sperry and Gazzaniga conducted important research on split brain
patients, that suggested the uses of each hemisphere.
 Personality and intelligence were normal
 Patients could “see” one word, but point to another word as the one
they’d seen.
 Patients could not identify objects in their left visual field, but could
pick it up, without “knowing” what they’d seen.
 Patients could draw different images with each hand.
 Patients could follow orders in the right hemisphere, but be unaware
of why they begin following that order.
Drawings by Split Brain Patients
Left
vs.
Right
 Right side of body
 Left side of body
 Language
 Perception
 Mathematics
 Musical processing
 Logic
 Visual-spatial reasoning
 Complex Motion
 The “self”
 Literal interpretations of
language
 Inferential and nonverbal
interpretation
 Positive emotions
 Negative emotions
Yard Stick
The Brain Comes in Handy
 Handedness offers a clue as to hemispheric dominance.
 90% of people are right handed – left brain language function
 10% of people are left handed – 70% left brain language function
 Handedness shows genetic traits, as well as evolutionary traits.
 Right handedness predominates across cultures, and through
history (and prehistory). Even fetuses prefer their right thumbs.
 Strangely, identical twins may not share handedness
 Correlational research demonstrates:
 Southpaws are more likely to have reading disabilities, allergies
and migraines; become musicians, mathematicians, professional
baseball and cricket players, architects and artists; and may
outperform righties in academic settings.
 There may be less hemispheric specialization in lefties