Mary Jones. In This Chapter The neuron The nervous system and the endocrine system The brain.
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Transcript of Mary Jones. In This Chapter The neuron The nervous system and the endocrine system The brain.
Mar
y Jo
nes
In This Chapter
The neuron
The nervous system and the endocrine system
The brain
An Intriguing Puzzle
Neuroscience
• Scientific study of the brain and nervous system
Connectome
• Totality of connections between neurons in the nervous system
The NeuronThe structure of a neuron
How neurons communicate
Neurotransmitters, drugs, and poisons
Neurons and Glial Cells
• Neurons- Are responsible for information transmission
throughout the nervous system
• Glial cells- Support neurons by disposing of waste products
of neurons, keeping their chemical environment stable, and insulating them
The Structure of a Neuron
• Dendrites- Include fibers that project out of the cell body, receiving
information from other neurons
• Cell body- Contains the nucleus of the cell and other biological
machinery to keep the cell alive
• Axon- Transmits messages through the neuron
• Axon terminals - Are at the end of the axon and send messages to a
different neuron
The Structure of a Neuron
How Neurons Communicate
Communication within neuron is electrical
Communication between neurons
is chemical
The Electrical Impulse: Information from the Dendrites
Excitatory (telling neuron to generate an electrical impulse)
Inhibitory (telling neuron not to generate an electrical impulse)
The Electrical Impulse
• Myelin sheath- Insulating layer of fatty white substance that
encases the axon- Allows electrical message to be transmitted
faster within the neuron- Is responsible for distinction between brain white
and gray matter- Slows electrical impulses when damaged
Chemical Communication between Neurons
• Neurotransmitters– Are contained in axon terminals– Are naturally occurring chemicals in the nervous system– Specialize in transmitting information between neurons
• Synaptic gap– Is a small gap across which neurotransmitters are sent,
allowing neurons to communicate– Is found between axon terminals of one neuron and
dendrites of another neuron
Synaptic Communication Between Neurons
Brain Scans
Brain scans work because
neurons require oxygen and
other nutrients such as blood
sugar
Positron Emission Tomography (PET) scans use a dose of radioactive glucose, which moves to the
more-active areas of the brain
Functional Magnetic Resonance Imaging (fMRI) detects active areas of the brain by
highlighting those areas that require
more oxygen
Neurotransmitters, Drugs, and Poisons
Agonists• Drugs and poisons that
increase the activity of one or more neurotransmitters
Antagonists• Drugs and poisons that
decrease the activity of one or more neurotransmitters
Neurotransmitters
Acetylcholine (ACh)
Dopamine
Serotonin and norepinephrine
GABA
Glutamate
Endorphins
Acetylcholine (ACh)
Botulinum poison (botulin)
Curare
Black widow spider venom
Dopamine
Dopamine systems in brain
L-Dopa
Anti-psychotic drugs
Amphetamine
Cocaine
Serotonin and Norepinephrine
• Selective serotonin reuptake inhibitors (SSRIs)- Antidepressant drugs that work by blocking the
reuptake of serotonin- Prozac, Paxil, and Zoloft
• Selective serotonin and norepinephrine reuptake inhibitors (SSNRIs)- Antidepressant drugs that work by blocking the
reuptake of serotonin and norepinephrine- Cymbalta, Pristiq, and Effexor
GABA and Glutamate
• Anti-anxiety drugs- Are agonists for GABA
• Glutamate- Is involved in memory storage and pain
perception- Excessive glutamate can lead to neuron death;
deficient glutamate has been linked to schizophrenia
Endorphins
• Morphine and heroin- Are agonists that bind to receptor sites, thereby
increasing endorphin activity- Trigger brain's reward centers, causing release of
dopamine
Neurotransmitters and Some of Their Functions
The Nervous and Endocrine Systems
The central nervous system
The peripheral nervous system
The endocrine glandular system
Emotions and the autonomic nervous system
Nervous System and Its Major Subdivisions
Types of Neurons in the Nervous System
• Interneurons- Integrate information within the CNS through their
communication with each other and between sensory and motor neurons in the spinal cord
• Sensory neurons- Carry information to the central nervous system
from sensory receptors, muscles, and glands
• Motor neurons- Carry movement commands from the central
nervous system to the rest of the body
The Central Nervous System (CNS)
Central Nervous System
Spinal cord
Conduits for incoming sensory data and
outgoing movement commands
Provides for spinal reflexes
BrainControl center
for entire nervous system
The Peripheral Nervous System (PNS)
• PNS- Gathers information about the external
environment and the body's internal environment for the brain through sensory neurons
- Serves as the conduit for the brain's commands to the rest of the body through motor neurons
The Peripheral Nervous System
PNS consists of two parts
Somatic (or skeletal) nervous
system
Autonomic nervous system
Sympathetic nervous system
Parasympathetic nervous system
The Endocrine Glandular System
• Endocrine glandular system- Works with the autonomic nervous system in
response to stress- Secretes hormones- Plays a role in basic behaviors and bodily
functions such as sex, eating, metabolism, reproduction, and growth
The Endocrine Glandular System
• Endocrine glands- Are controlled by the hypothalamus which
controls the pituitary gland
• Pituitary gland- Releases hormones essential for human growth- Directs other glands to release their hormones
The Endocrine Glandular System
• Thyroid gland- Affects growth and maturation
• Adrenal glands- Are involved in metabolism and help trigger the “fight
or flight” response with commands from the autonomic nervous system
• Pancreas- Is involved in digestion and maintaining blood-sugar
levels
The Endocrine Glandular System
Emotions and the Autonomic Nervous System
• Emotion involves- Complex psychological state- Physiological arousal- Outward behavioral expression of the emotion- Cognitive appraisal of the situation to determine
the specific emotion and its intensity
The Three Components of Emotion
• Physical component- Includes the “fight or flight” response of the autonomic nervous
system- Involves increase in heart rate and breathing, blood pressure
surges, sweating, pupil dilation, slowing of digestion
• Behavioral component- Is the product of motor neurons- Involves facial-feedback hypothesis which assumes that the facial
muscles send messages to the brain, allowing the brain to determine which emotion is being experienced
• Cognitive component- Includes an appraisal of the situation to determine what emotion we
are experiencing
Theories of Emotion
Theories
Commonsense theory
James-Lange theory
Cannon-Bard theory
Schachter-Singer Two-Factor theory
Theories of Emotion: Commonsense Explanation
Proposes that the subjective experience of the emotion triggers the
physiological arousal and behavioral response
Contends that cognitive recognition of
dangerous situation prompts emotional feeling that arouses autonomic nervous
system
James-Lange Theory
Autonomic nervous system physiological
arousal is a response to a
stimulus
Such a physiological response is
subsequently interpreted as the
emotion
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Cannon-Bard Theory
Brain produces the emotional feeling
Autonomic nervous system produces the physiological response
Motor neurons produce the behavioral response
Emotion-provoking stimulus sends
messages to both the peripheral nervous
system and the brain
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Schachter-Singer Two-Factor Theory
Physiological arousal tells us how
intense the emotion is
Cognitive appraisal of the entire situation allows us to identify
the emotion, leading to the emotional feeling
Two important determinants of emotion
Integrating the Theories
• LeDoux (1996, 2000)- Different brain systems exists for different
emotions
• Examples- Fear does not require higher-level cognitive
processing and is generated almost instantaneously by the amygdala
- Love or guilt do not require instantaneous responding for survival and may require higher-level processing
The Brain
Going up the Brain Stem
Processing in the Cerebral Cortex
Specializations of the Left and Right Hemispheres
Consciousness and the Sleeping Brain
Going Up the Brain Stem: The Central Core
Brain stemMedulla
Reticular formation
Cerebellum
ThalamusBasal ganglia
Basal ganglia
Central Core Structures and Functions
The Limbic System
• Limbic system- Plays a role in survival, memory, and emotions
• Parts- Hypothalamus - Hippocampus - Amygdala
The Limbic System
Limbic System Structures and Functions
Processing in the Cerebral Cortex
• Cerebral cortex- Most important brain
structure- Information
processing center for nervous system
- Center for all higher-level cognitive processing
- Site of hemispheric communication
Brain Lobes
• Frontal lobe- Area in the front of each hemisphere and in front of
central fissure and above lateral fissure
• Parietal lobe- Area located behind central fissure and above
lateral fissure
• Temporal lobe- Located beneath the lateral fissure
• Occipital lobe- Located in the lower back of each hemisphere
The Four Lobes and the Sensory-Motor Processing Areas
The Motor Cortex
• Frontal lobe strip of cortex- Directly in front of central fissure in each
hemisphere- Allows movement in different parts of the body- Each hemisphere controls voluntary movement
of the opposite side of the body- Amount of motor cortex devoted to a specific
body part is related to the complexity and precision of movement of which that part is capable
The Somatosensory Cortex
• Parietal lobe strip of cortex- Directly behind central fissure in each
hemisphere- Where body sensations of pressure,
temperature, limb position, and pain are processed
- Contralateral relationship- Amount of sensorimotor cortex devoted
to a body part is directly proportionate to the sensitivity of that body part
Homunculi for the Motor Cortex and the Somatosensory Cortex
The Visual Cortex and the Auditory Cortex
• Visual cortex- Located in occipital lobes at back of hemispheres
• Auditory cortex - Located in temporal lobes- Contains primary areas- Passes the results of their analyses on to
areas in the other lobes to complete the brain's interpretation of the incoming visual or auditory information
A Matter of Teamwork!
• McGurk effect- Demonstrates that the brain integrates visual and
auditory information when processing spoken language
- Arises out of conflicting auditory and visual information
Association Cortex
• Association cortex- Involves secondary cortical processing
areas but includes about 70 percent of cortex- Includes higher-level processing such as
decision making, reasoning, perception, speech, and language occurs
The Four Cerebral Lobes
The Case of Phineas Gage
• Phineas Gage - Railroad worker who
survived when a metal tamping iron flew through his left cheek and head, exiting through his frontal lobes
• Results- He became irresponsible,
impulsive, disorderly, indecisive, and began cursing
- Lead neuroscientists to think the frontal lobes are important in such behaviors
Phineas Gage's doctor had this picture of the tamping iron and Phineas's skull taken in 1868 to document the case.
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The Case of Eduardo Leite
• Construction worker in Brazil who was impaled by falling metal bar
• Bar entered in front of the motor cortex in the right hemisphere and exited the right frontal lobe just above the right eye through a “non-eloquent” area of brain
Association Cortex: Language
• Broca's area- Located in left frontal lobe- Is responsible for fluent speech production- When damaged, fluent speech generation is
damaged, but comprehension is left intact- Houses singing and musical abilities
• Wernicke's area - Located in the temporal lobe- Is responsible for the comprehension of speech and
reading
Broca's Area and Wernicke's Area
Einstein's Brain
• Harvey kept Einstein's brain for many years.
• Later research- Unexceptional size but
unusual morphology- Expanded prefrontal
cortex, unusual parietal lobes, and other differences in complexity and patterns of convolusions
Dr. Thomas Harvey with a jar containing pieces of Albert Einstein's brain.
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Specializations of the Left and Right Hemispheres
Studying the two hemispheres • Light waves from the left visual field go to the right half
of each eye and connect with the right hemisphere.
• Light waves from the right visual field go to the left half of each eye and connect with the left hemisphere.
Pathways for Processing Information in the Left and Right Visual Fields
• Half of the fibers from each eye cross over at the optic chiasm to go to the opposite hemisphere
• The right half in the left eye go to the right hemisphere and the left half in the right eye go to the left hemisphere.
Studying the Two Hemispheres
• Sperry- Led most of the
early split-brain research and in 1981 won the Nobel Prize in Physiology or Medicine for his discoveries concerning the functional specializations of the cerebral hemispheres
• Gazzaniga- Sperry's
student - Conducted the first
studies with human split-brain participants in the early 1960s
• Bogen- Continued this line of
inquiry for the past five decades
Studying the Two Hemispheres
• Split-brained people- Information cannot transfer between
hemispheres because the corpus callosum has been severed
- Can only identify information orally when it is presented briefly in the right visual field and thus processing in the left hemisphere
What we know…
• Left hemisphere- Language- Math and logic skills- More analytical, analyzing wholes into pieces
• Right hemisphere- Spatial perception- Solving spatial problems- Drawing- Face recognition
Sample Hierarchical Stimulus and Recall Results for Such Stimuli by Brain-Damaged Patients
a) The sample hierarchical stimulus is a capital H made up of little As.
b) Patients with right hemisphere damage (dependent on the left hemisphere) could remember the details of the hierarchical stimulus (the As) but not the overall pattern (H).
c) Patients with left hemisphere damage (dependent upon the right hemisphere) could remember the overall pattern (H) but not its details (the As).
True or False?
It is not very accurate to say someone is “left-brained” or “right-brained”?
Consciousness and the Sleeping Brain
• Consciousness- Person's subjective awareness of both their inner
thinking and feeling and their external environment
• Five stages of sleep can be determined by use of an electroencephalogram (EEG)- As we slip into sleep and pass through the first
four stages, our brain waves change, in general becoming progressively slower, larger, and more irregular, especially in Stages 3 and 4
Five Stages of Sleep
Stage 1: Lasts about 5 minutes
Stage 2: Lasts about 20 minutes; sleep spindles
Stage 3: Transitional sleep; delta waves
Stage 4: Lasts about 30 minutes; active parasympathetic nervous system
Stage 5: REM steep: paradoxical sleep
Five Stages of Sleep
Five Stages of Sleep
REM sleep rebound effect involves a significant increase in the proportion of REM sleep following deprivation of REM sleep
Stages 3 and 4 get shorter with each cycle, and REM and Stage 2 get longer with each cycle
These 5 stages (sleep cycle) repeat themselves about every 90 minutes
The Pattern of Sleep-Stage CyclesDuring a Night's Sleep
• After passing through the first four stages of sleep, we return through Stages 3 and 2 to enter REM sleep
• This completes the first sleep-stage cycle
• As this cycle is repeated throughout a typical night's sleep, the deep sleep stages (3 and 4) get briefer and disappear, and the Stage 2 and REM sleep periods get longer
Why do we sleep and dream?
• Results of sleep deprivation - Impaired concentration and a general bodily
feeling of weakness and discomfort- Suppression of the immune system, lessening
one's ability to fight off infection and disease- Increased vulnerability to accidents- Increased difficulty in concentrating, studying,
and taking exams
Why do we sleep and dream?
• Explanations for dreaming- Sigmund Freud
• Proposed that dreams were disguised outlets for inner conflicts of our unconscious mind, a view not accepted by modern sleep researchers
- Activation-synthesis hypothesis• Contends that dreams are merely the sleeping brain's
attempt to make sense of random neural activity without the rational interpretation of the frontal lobe
Why do we sleep and dream?
• Explanations for dreaming- Neurocognitive theory
• Argues that explaining dreams as our subjective interpretations of random neural firing is too simple
• Contends dreams are meaningful products of our cognitive abilities, with continuity between waking and dreaming cognition
• Suggests developmental differences in dreaming parallel graduate cognitive advances