neuroscience and consciousness chapter 2. neural communication the body’s information system is...
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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 PotentialA 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
CentralNervousSystem(CNS)
PeripheralNervousSystem(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 NeuronsSensory 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 [muh-DUL-uh] is the base
of the brainstem that controls heartbeat
and breathing.
Brainstem
The Thalamus [THAL-uh-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
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).
Cerebellum
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.
The Limbic System
Amygdala
The Amygdala [ah-MIG-dah-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 CortexThe 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. M
a. M
aisog, S. Courtney, L
.G.
Ungerleider, and J.V
. Haxby,
National Institute of M
ental Health
Auditory Function
The functional MRI scan shows the
auditory cortex is active in patients who
hallucinate.
LanguageAphasia 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 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.
The Brain’s Plasticity
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
Consciousness, modern psychologists believe, is an awareness of ourselves and our environment.
Forms of ConsciousnessB
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Dig
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Vis
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Get
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Chr
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Stu
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Mag
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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
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.
Dan
iel S
imon
s, U
nive
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Ill
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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 startedunraveling in sleep laboratories around the world.
Biological Rhythms and SleepCircadian 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.
Illu
stra
tion
© C
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Measuring sleep: About every 90 minutes, we pass through a cycle of five distinct sleep stages.
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.
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)
Sleep Stages 1-2
Theta Waves
During deepest sleep (stages 3-4), brain activity slows down. There are large-
amplitude, slow delta waves.
Sleep Stages 3-4
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 low- amplitude, fast and
regular beta waves much like awake-aroused state.
A person during this sleep exhibitsRapid 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.
If an individual remains awake for
several days, immune function and concentration
deteriorates and the risk of accidents
increases.
Jose Luis Pelaez, Inc./ C
orbis
Teenage Sleep
• Sleep less than 7 hours a night
• Why does this happen?– Industrialized Countries?
Sleep Deprivation1. 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 functions7. Jet Lag- consequence of
travel8. We sleep less today
because there are more distractions
Accidents
Frequency of accidents increase with loss of sleep
Sleep Theories1. 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.
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
Sleep Disorders
DreamsThe 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
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.
Manifest Content: A Freudian term meaning the story line of dreams (what we most remember).
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. Whendeprived of REM sleep and then allowed to sleep,
we show increased REM sleep called REM Rebound.
Dream TheoriesSummary
