Download Unit 2, the Brain

Neuroscience and
Consciousness
Chapter 2
Neural Communication
The body’s information system is built from
billions of interconnected cells called neurons.
3 Main Types
• Sensory-information to the brain
• Motor- information from the brain
• Interneurons- communication b/w neurons
Neuron
A nerve cell, or a neuron, consists of many
different parts.
Parts of a Neuron
Cell Body: Life support center of the neuron.
Dendrites: Branching extensions at the cell body.
Receive messages from other neurons.
Axon: Long single extension of a neuron, covered with
myelin [MY-uh-lin] sheath to insulate and speed up
messages through neurons.
Terminal Branches of axon: Branched endings of an
axon that transmit messages to other neurons.
Action Potential
A neural impulse. A brief
electrical charge that
travels down an axon and
is generated by the
movement of positively
charged atoms in and out
of channels in the axon’s
membrane.
Action Potential Properties
All-or-None Response: A strong stimulus can
trigger more neurons to fire, and to fire more
often, but it does not affect the action potentials
strength or speed.
Intensity of an action potential remains the
same throughout the length of the axon.
Synapse
Synapse [SIN-aps] a junction between the axon
tip of the sending neuron and the dendrite or
cell body of the receiving neuron. This tiny gap
is called the synaptic gap or cleft.
Neurotransmitters
Neurotransmitters
(chemicals) released
from the sending
neuron travel across the
synapse and bind to
receptor sites on the
receiving neuron,
thereby influencing it to
generate an action
potential.
How Neurotransmitters Influence Us
Serotonin pathways are
involved with mood
regulation.
Linked to Depression
From Mapping the Mind, Rita Carter, © 1989
University of California Press
Dopamine Pathways
Dopamine pathways
are involved with
diseases such as
schizophrenia and
Parkinson’s disease.
Responsible for
motivation, interest,
and drive
From Mapping the Mind, Rita Carter, © 1989
University of California Press
Norepinephrine
• Helps control alertness and arousal
• It regulates attention, mental focus,
arousal, and cognition
• High levels have been linked to sleep
problems, anxiety and ADHD
Neurotransmitters
Nervous System
Central
Nervous
System
(CNS)
Peripheral
Nervous
System
(PNS)
The Nervous System
Nervous System: Consists of all the nerve cells. It
is the body’s speedy, electrochemical
communication system.
Central Nervous System (CNS): the brain and
spinal cord.
Peripheral Nervous System (PNS): the sensory and
motor neurons that connect the central nervous
system (CNS) to the rest of the body.
Kinds of Neurons
Sensory Neurons carry incoming information from the
sense receptors to the CNS. Motor Neurons carry
outgoing information from the CNS to muscles and
glands. Interneurons connect the two neurons.
Motor Neuron
(Multipolar)
Peripheral Nervous System
Somatic Nervous System: The division of the
peripheral nervous system that controls the body’s
skeletal muscles.
Autonomic Nervous System: Part of the PNS that
controls the glands, organs, and other muscles.
The Nerves
Nerves consist of neural “cables” containing many
axons. They are part of the peripheral nervous
system and connect muscles, glands, and sense
organs to the central nervous system.
Autonomic Nervous System (ANS)
Sympathetic Nervous System: Division of the
ANS that arouses the body, mobilizing its
energy in stressful situations.
Parasympathetic Nervous System: Division of
the ANS that calms the body, conserving its
energy.
Autonomic Nervous System (ANS)
Sympathetic NS
“Arouses”
(fight-or-flight)
Parasympathetic NS
“Calms”
(rest and digest)
The Nervous System
The Endocrine System
The Endocrine
System is the body’s
“slow” chemical
communication
system.
Communication is
carried out by
hormones
synthesized by a set
of glands.
Hormones
Hormones are chemicals synthesized by the
endocrine glands that are secreted in the
bloodstream. Hormones affect the brain and many
other tissues of the body.
For example, epinephrine (adrenaline) increases
heart rate, blood pressure, blood sugar, and
feelings of excitement during emergency
situations.
Pituitary Gland
Is called the “master gland.” The anterior pituitary
lobe releases hormones that regulate other glands.
Plays a role in growth.
Brainstem
The Medulla [muhDUL-uh] is the base of
the brainstem that
controls heartbeat and
breathing.
Brainstem
The Thalamus [THALuh-muss] is the brain’s
sensory switchboard,
located on top of the
brainstem. It directs
messages to the sensory
areas in the cortex and
transmits replies to the
cerebellum and
medulla.
Brainstem
Reticular Formation is a
nerve network in the
brainstem that plays an
important role in
controlling arousal.
-keeps us alert, even
while sleeping
Cerebellum
The “little brain”
attached to the rear of
the brainstem. It helps
coordinate voluntary
movements and
balance. Processes and
stores memory we
cannot consciously
recall (muscle memory).
The Limbic System
The Limbic System is a
doughnut-shaped
system of neural
structures at the border
of the brainstem and
cerebrum, associated
with emotions such as
fear, aggression and
drives for food and sex.
It includes the
hippocampus, amygdala,
and hypothalamus.
Amygdala
The Amygdala [ah-MIGdah-la] consists of two lima
bean-sized neural clusters
linked to the emotions of
fear and anger.
Hypothalamus
The Hypothalamus lies
below (hypo) the
thalamus. It directs
several maintenance
activities like eating,
drinking, body
temperature, and
control of emotions. It
helps govern the
endocrine system via
the pituitary gland.
The Cerebral Cortex
The intricate fabric of interconnected neural cells that
covers the cerebral hemispheres. It is the body’s ultimate
control and information processing center.
Structure of the Cortex
Each brain hemisphere
is divided into four
lobes that are separated
by prominent fissures.
These lobes are the
frontal lobe (forehead),
parietal lobe (top to rear
head), occipital lobe
(back head) and
temporal lobe (side of
head).
Phineas Gage? Pg.42-43
Functions of the Cortex
The Motor Cortex is the area at the rear of the
frontal lobes that control voluntary movements.
The Sensory Cortex (parietal cortex) receives
information from skin surface and sense organs.
Visual Function
The functional MRI scan
shows the visual cortex
is active as the subject
looks at faces.
Courtesy of V.P. Clark, K. Keill, J. Ma.
Maisog, S. Courtney, L.G.
Ungerleider, and J.V. Haxby,
National Institute of Mental Health
Auditory Function
The functional MRI scan
shows the auditory
cortex is active in
patients who hallucinate.
Language
Aphasia is an impairment of language, usually
caused by left hemisphere damage either to Broca’s
area (impaired speaking) or to Wernicke’s area
(impaired understanding).
The Brain’s Plasticity
The brain is sculpted by our genes but also by our
experiences.
Plasticity refers to the brain’s ability to modify
itself after some types of injury or illness.
Right-Left Differences
People show left-right hemispheric differences in
mental abilities.
A number of brain scan studies show normal
individuals engage their right brain when
completing a perceptual task and their left brain
when carrying out a linguistic task.
Right Brain vs. Left Brain
Dominance
• Left Brain- analytical, organized, would
judge objects by their relationships
• Right Brain-creative, free-thinking, would
judge objects by their physical similarities
Forms of Consciousness
AP Photo/ Ricardo Mazalan
Stuart Franklin/ Magnum Photos
Christine Brune
Bill Ling/ Digital Vision/ Getty Images
Consciousness, modern psychologists believe, is
an awareness of ourselves and our environment.
Selective Attention
Our conscious awareness processes only a
small part of all that we experience. We
intuitively make use of the information we
are not consciously aware of.
Inattentional Blindness
Daniel Simons, University of Illinois
Inattentional blindness refers to the inability
to see an object or a person in our midst.
Simons & Chabris (1999) showed that half of
the observers failed to see the gorilla-suited
assistant in a ball passing game.
Change Blindness
Change blindness is a form of inattentional
blindness in which two-thirds of individuals
giving directions failed to notice a change in the
individual asking for directions.
Change Blindness Another Example
© 1998 Psychonomic Society Inc. Image provided courtesy of Daniel J. Simmons.
Sleep & Dreams
Sleep – the irresistible tempter to whom we
inevitably succumb.
Mysteries about sleep and dreams have just started
unraveling in sleep laboratories around the world.
Biological Rhythms and Sleep
Illustration © Cynthia Turner 2003
Circadian Rhythms occur on a 24-hour cycle and include
sleep and wakefulness. Termed our “biological clock,” it
can be altered by artificial light.
Light triggers the nucleus to decrease
(morning) melatonin from the pineal gland
and increase (evening) it at nightfall.
Sleep Stages
Measuring sleep: About every 90 minutes, we
pass through a cycle of five distinct sleep stages.
Hank Morgan/ Rainbow
Awake but Relaxed
When an individual closes his eyes but remains
awake, his brain activity slows down to a large
amplitude and slow, regular alpha waves (9-14
cps). A meditating person exhibits an alpha brain
activity.
Sleep Stages 1-2
During early, light sleep (stages 1-2) the brain
enters a high-amplitude, slow, regular wave form
called theta waves. A person who is daydreaming
shows theta activity. (Hallucinations)
Theta Waves
Sleep Stages 3-4
During deepest sleep (stages 3-4), brain activity
slows down. There are large-amplitude, slow
delta waves.
Stage 5: REM Sleep
After reaching the deepest sleep stage (4), the
sleep cycle starts moving backward towards stage
1. Although still asleep, the brain engages in lowamplitude, fast and regular beta waves much like
awake-aroused state.
A person during this sleep exhibits
Rapid Eye Movements (REM)
and reports vivid dreams if you awaken shortly after the dream.
90-Minute Cycles During Sleep
With each 90-minute cycle, stage 4 sleep decreases
and the duration of REM sleep increases. (usually
about 4-6 periods of REM each night)
Why do we sleep?
We spend one-third of our
lives sleeping.
Jose Luis Pelaez, Inc./ Corbis
If an individual remains
awake for several days,
immune function and
concentration deteriorates
and the risk of accidents
increases.
Teenage Sleep
• Sleep less than 7 hours a night
• Why does this happen?
– Industrialized Countries?
Sleep Deprivation
1. Fatigue and subsequent death.
2. Impaired concentration and
performance.
3. Emotional irritability.
4. Depressed immune system.
• Inability to fight off disease
5. Greater vulnerability.
6. Alters metabolism and
hormonal functions
7. Jet Lag- consequence of travel
8. We sleep less today because
there are more distractions
Accidents
Frequency of accidents increase with loss of sleep
Sleep Theories
1. Sleep Protects: Sleeping in the darkness when
predators loomed about kept our ancestors out
of harm’s way.
2. Sleep Helps us Recover: Sleep helps restore
and repair brain tissue. Helps maintain mood
and emotion
3. Sleep Helps us Remember: Sleep restores and
rebuilds our fading memories.
4. Sleep may play a role in the growth process:
During sleep, the pituitary gland releases
growth hormone. Older people release less of
this hormone and sleep less.
Sleep Disorders
1. Insomnia: A persistent inability to fall
asleep, stay asleep, wakes early
2. Narcolepsy: Overpowering urge to fall
asleep that may occur while talking or
standing up.
3. Sleep apnea: Failure to breathe when
asleep.
–
–
Snoring- narrowing of the nasal passage
Sleep Apnea video
Sleep Disorders
Children are most prone to:
 Night terrors: The sudden arousal from sleep
with intense fear accompanied by
physiological reactions (e.g., rapid heart rate,
perspiration) which occur during Stage 4 sleep.
 Sleepwalking (somnambulism): A Stage 4
disorder which is usually harmless and
unrecalled the next day.



Sleeptalking (somniloquy): A condition that
runs in families, like sleepwalking.
Sleep Disorders Video
Night Terror Example
Dreams
The link between REM
sleep and dreaming
has opened up a new
era of dream research.
EEG
(electroencephalogram)
allows us to study
sleep
What We Dream
Manifest Content: A Freudian term meaning
the story line of dreams (what we most
remember).
1. Negative Emotional Content: 8 out of 10 dreams
have negative emotional content.
2. Failure Dreams: People commonly dream about
failure, being attacked, pursued, rejected, or
struck with misfortune.
3. Sexual Dreams: Contrary to our thinking, sexual
dreams are sparse. Sexual dreams in men are 1 in
10; and in women 1 in 30.
Why We Dream- video
1. Wish Fulfillment: Sigmund Freud suggested
that dreams provide a psychic safety valve to
discharge unacceptable feelings. The dream’s
manifest (apparent) content may also have
symbolic meanings (latent content) that signify
our unacceptable feelings.
2. Information Processing: Dreams may help sift,
sort, and fix a day’s experiences in our
memories.
Why We Dream
3. Physiological
Function: Dreams
provide the sleeping
brain with periodic
stimulation to
develop and preserve
neural pathways.
Neural networks of
newborns are quickly
developing; therefore,
they need more sleep.
Why We Dream
4. Activation-Synthesis Theory: Suggests that the
brain engages in a lot of random neural
activity. Dreams make sense of this activity.
5. Cognitive Development: Some researchers
argue that we dream as a part of brain
maturation and cognitive development.
All dream researchers believe we need REM sleep. When
deprived of REM sleep and then allowed to sleep,
we show increased REM sleep called REM Rebound.
Dream Theories
Summary
• Why do we dream? Nova 58 mins