Transcript PSY110 Week 2 Biology and Behavior

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 Discovering
the Mysteries of the Nervous
System
 The
Neurons and the Neurotransmitters
 The
Human Nervous System
A
Closer Look at the Thinking Part of the Brain
 Age,
Gender, and the Brain
 Beyond
the Nervous System
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
Electrical activity detected by electrodes placed on the
scalp

Produces record of brain-wave activity
• beta wave: pattern associated with mental or physical activity
• alpha wave: associated with deep relaxation
• delta wave: slow-wave (deep) sleep

Shows epileptic seizure in progress, neural activity of
other disorders

Microelectrode
• monitors or stimulates activity of a single neuron
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 CT
Scan (Computerized Axial Tomography)
• uses a rotating, computerized X-ray tube
• produces cross-sectional images of brain structures
 MRI
(Magnetic Resonance Imaging)
• produces clearer and more detailed images without exposure to
potentially dangerous X-rays of a CT scan
• can be used to find abnormalities in the central nervous system
and in other systems of the body
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 PET
Scan (Positron Emission Tomography)
• used to study normal brain activity and identify
malfunctions
• maps patterns of blood flow, oxygen use, and glucose
consumption
 glucose: food of the brain
• allows for the study of the action of drugs and other
biochemical substances in the brain and other organs
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 functional
MRI (fMRI)
• advantages over PET:




Provides images of both brain structure and brain activity
Requires no injections (of radioactive or other material)
Can identify locations of activity more precisely than PET
Detects changes that take place in less than a second,
compared with about a minute for PET
 SQUID
(Superconducting Quantum Interference
Device)
• measures magnetic changes produced by electric current that
neurons discharge when they fire
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 Most
neurons are made of three parts:
• cell body
 contains the nucleus
 carries out the metabolic functions of the neuron
• dendrites
 primary receivers of signals from other neurons
• axon
 slender, tail-like extension of the neuron
 sprouts into branches, each ending in a bulbous axon terminal
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 Glial
Cells
• located in the brain and spinal cord
• support neurons, remove waste products
• perform other manufacturing, nourishing, and cleanup
tasks
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 Axon
terminals are separated from the receiving
neurons by fluid-filled gaps: synaptic clefts.
 Synapse
• junction where axon terminal of sending neuron
communicates with receiving neuron
• There may be as many as 100 trillion synapses in the
human nervous system.
• A single neuron may form synapses with thousands of
other neurons.
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

A measurable electrical
impulse is present with every
move or thought.
Permeability of cell membrane
changes
• allows ions to move into and out of
the axon

Body fluids contain ions.
• Ions have positive or negative
electrical charges.
• There are normally more negative
than positive ions.
• An axon at rest carries about 70
millivolts (relative to the fluid
outside the cell).
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
Resting Potential
• slight negative electrical
potential of the axon membrane
of a neuron at rest

Action Potential
• sudden reversal of the resting
potential, initiates firing of
neuron

“All or None” Law
• A neuron either fires completely
or does not fire at all.

Refractory Period
• short resting period after firing
during which a neuron cannot
fire again
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 Influenced
by the
myelin sheath
• white, fatty coating on some
axons
• makes action potential
travel up to 100 times faster
 Nodes
of Ranvier
• gaps in the myelin sheath
• Neural impulse is
regenerated at each node.
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
Neurotransmitters
• chemical substances that
transmit messages
between neurons
• released into synapse by
axon terminals of sending
neuron
• bind to receptor sites on
dendrites of receiving
neuron
• taken back into axon
terminal by the process of
reuptake
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
How do synaptic vesicles continue to pour out
neurotransmitters yet maintain a ready supply of
neurotransmitter?
• The cell body of the neuron is always working to manufacture more of
the neurotransmitter.
• Unused neurotransmitters in the synaptic cleft may be broken down into
components and reclaimed by the axon terminal to be recycled.
• Reuptake: the neurotransmitter is taken back into the axon terminal,
intact and ready for immediate use.
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 The
peripheral nervous system consists of
two subdivisions.
• somatic nervous system
 consists of all sensory nerves and motor nerves
• autonomic nervous system
 transmits messages between the central nervous
system and glands, cardiac muscle, and smooth
muscles
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 Sympathetic
Nervous
System
• mobilizes the body’s
resources during stress and
emergencies
 Parasympathetic
Nervous System
• brings heightened bodily
responses back to normal
following an emergency
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 Spinal
Cord
• best thought of as
extension of the brain
• transmits messages
between the brain and
the peripheral nervous
system
• can act without help
from the brain to
protect the body from
injury
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• Withdrawal or
Spinal Reflex
 triggered by a painful
stimulus
 involves 3 types of
neurons:
 sensory-afferent
 motor-efferent
 interneuron
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

Structures control vital
functions.
Brainstem
•

begins at the site where the spinal
cord enlarges as it enters the skull
Medulla
• controls heartbeat, blood pressure,
breathing, coughing, swallowing

Reticular Formation
• plays a crucial role in arousal and
attention
• screens sensory messages
entering the brain
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
Pons
• plays a role in body
movement
• influences sleep and
dreaming

Cerebellum
• helps the body execute
smooth, skilled movements
• regulates muscle tone and
posture
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
The midbrain links the
physiological functions of
the hindbrain to the
cognitive functions of the
forebrain.

Substantia Nigra
• controls unconscious motor
movements
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
Forebrain
• largest part of the brain
• functions include memory,
logic, and self-awareness

Thalamus
• relay station for information
flowing into or out of the brain

Hypothalamus
• regulates hunger, thirst, sexual
behavior, body temperature,
and a variety of emotional
behaviors
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
Amygdala
• part of the limbic system
• plays important role in
emotion

Hippocampus
• part of the limbic system
• central role in storing
new memories,
responses to new or
unexpected stimuli, and
navigational ability
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
Cerebral Hemispheres
• left and right halves of
cerebrum

Corpus Callosum
• connects the two
hemispheres

Cerebral Cortex
• thin outer covering of
cerebrum
• responsible for higher
mental processes of
language, memory, and
thinking
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 The
•
cerebral cortex contains 3 types of areas.
Sensory Input Areas
 vision, hearing, touch, pressure, and temperature register
• Motor Areas
 control voluntary movement
• Association Areas
 house memories and are involved in thought, perception, and
language
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 Left
Hemisphere
• controls the right side
of the body
• handles most language
functions
• specialized for
mathematics and logic
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 Right
Hemisphere
• controls left side of
body
• processes music
• interprets emotional
messages conveyed by
tone of voice and
gestures
• is specialized for
visual-spatial relations
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
Corpus callosum is absent or has been surgically modified.

Only the verbal left hemisphere can report what it sees.

The left hemisphere does not see what is flashed to the right hemisphere;
the right hemisphere is unable to report verbally what it has viewed.
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Frontal Lobes
 Motor Cortex

• controls voluntary body
movement

Broca’s Area
• located in frontal lobe
• usually in the left
hemisphere
• controls speech production

Association Areas
• areas involved in thinking,
planning for the future,
impulse control
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A Closer Look at the Thinking Part of the Brain:
The Four Cerebral Lobes
 Parietal
Lobes
• somatosensory cortex
 located at the front of the
parietal lobes
 where touch, pressure,
temperature, and pain
register in the cortex
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 Occipital
Lobes
• involved in reception
and interpretation of
visual information
 Primary
Visual Cortex
• area at the rear of the
occipital lobes where
vision registers in the
cortex
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Temporal Lobes
 Primary Auditory Cortex

• area in each temporal lobe
where hearing registers in
the cortex

Wernicke’s Area
• language area in the left
temporal lobe involved in
comprehending spoken
language and formulating
coherent speech and written
language
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

The brain grows in spurts from conception until well into adulthood.
Each growth spurt also seems to involve a different brain area.
• The spurt that begins around age 17 and continues into the early 20s
mainly affects the frontal lobes.

Synaptogenesis
•

occurs in spurts throughout the life span
Pruning
• process through which the developing brain eliminates unnecessary or
redundant synapses follows periods of synaptogenesis

Myelination
• development of myelin sheaths around axons
• begins prior to birth but continues well into adulthood

Plasticity
• The capacity to adapt to changes is maintained throughout life.
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WOMEN’S BRAINS

Equal proportions of gray and
white matter in the left and right
hemispheres

More gray matter in the area of the
brain that controls emotions
• may explain women’s superior
ability to perceive emotions

MEN’S BRAINS

Lower proportion of white matter in
the left hemisphere than in the
right
• may explain men’s superior ability
in spatial tasks

Navigational Information
• use left hippocampus
Navigational Information
• use right parietal cortex and right
frontal cortex
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 System
of Ductless
Glands
• manufacture hormones
• secretes hormones into
bloodstream

Endocrine Glands
• pituitary gland
 “master gland”
 releases hormones that activate
other endocrine glands
• pineal gland
 secretes melatonin, which
controls sleep/wakefulness cycle
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
Thyroid Gland
• located below the voice box
• produces thyroxine
 regulates rate of food
metabolization

Thymus Gland
• produces thymosin
• regulates immune system

Parathyroid Gland
• produces parathyroid
hormone
 helps the body absorb minerals
from the diet
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
Thymus Gland
• produces hormones
essential to immune system
functioning

Adrenal Gland
• releases hormones that
prepare the body for
emergencies and stressful
situations

Gonads
• ovaries in females
• testes in males
• produce sex hormones
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 Genes
• segments of DNA located on chromosomes
• transmit all heredity traits
 Chromosomes
• 46 chromosomes (23 pairs) contain 20,000 to 25,000 genes
• 22 matching pairs called autosomes; 23rd pair are sex
chromosomes
 Polygenetic
Inheritance
• Many genes influence a particular characteristic.
• multifactorial inheritance
 influenced by genes and environmental factors
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 Dominant-Recessive
Pattern
• dominant
 It is only necessary that one gene be present on
chromosome pair for a given trait to be expressed.
• recessive
 Two genes are required on the chromosome pair for trait
expression.
 Sex-Linked
Inheritance
• involves genes on the X and Y chromosomes
 example: red-green color blindness
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 Behavioral
Genetics
• investigates the effects of heredity and environment on
behavior
 Twin
Studies
• examine identical (monozygotic) and fraternal
(dizygotic) twins
 compare similarities and differences in twin pairs
 Adoption
Studies
• compare adopted children’s abilities and traits to those
of adoptive parents and biological parents
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