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Modules 4 & 6
The Biology of Mind
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Neuron
- 100 Billion
- Communication System
Glial cells
Cell body (nucleus)
Dendrites
Axon
Axon Terminals (terminal buttons)
Synaptic cleft
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Communication Within a Neuron
Receptors on Dendrites
- Sensory (chemical reactions)
- Chemicals from other neurons
- Chemicals from endocrine glands
- Chemicals from outside sources (e.g., Drugs)
Chemical Messages can be Excitatory or Inhibitory.
Effect on dendrite is a summed effect.
- threshold
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Action Potential
- all or none law
- digital message (yes/no)
- one strength
- one speed
- one way (dendrite to Axon)
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Inside and outside of neuron are fluid environments.
Fluid chemicals have ionic charges.
- sodium and potassium
Resting Potential
- inside negative relative to outside.
- sodium-potassium pump
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If threshold is reached at dendrite, then an action potential
begins.
Gates in membrane open allowing sodium to flow in.
Inside becomes more positive.
Momentary change in charge.
Passed along the membrane, carrying message to Axon
Terminal.
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Myelin Sheath
- Nodes of Ranvier
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Effects of Myelin
Allows action potential to skip along the membrane.
- speeds conduction.
Brain neurons have no myelin (appear gray)
Sensory and Motor neurons have myelin (appear white)
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Myelin and Multiple Sclerosis
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Terminal Branches
Terminal Button
Neurotransmitters (chemicals) are released into
Synaptic space.
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Communication
- within neuron (electric potential).
- between Neurons (neurochemical).
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Neurotransmitters are cleared from the
synaptic space by
1) re-uptake into the terminal button
2) destroyed by enzymes
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Neurotransmitters effects on behavior
depends on which receptor
Acetylcholine (ACh)
Motor control (paralysis)
Attention and Memory (Alzheimer’s)
Dopamine
Emotions, learning, memory & Motor control
Too Much  Schizophrenia
Too Little  Parkinson’s
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Serotonin – too little
associated with Depression
Endorphins – nature’s pain killer
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Hormones
- Chemical Messengers released by endocrine
glands into the blood system
- many are identical to
neurotransmitters
- have wider reaching,
longer lasting effects
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Permanent Effects
e.g., puberty
Temporary effects
e.g., metabolism (Insulin and Thyroxin)
Hormones also effect mood
e.g., premenstrual syndrome
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Hormone Disorders
• Diabetes
• Thyroid disorders
• Depression
Hormones as drugs
Problem: They effect a wide range of
functions = large number of side effects.
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Fen/Phen (Redux)
- effect hunger drive/increases metabolism
- also effects maintenance of heart valve
(lethal side effect)
Steroids
- effect development of muscles
- also effects mood and thought
processes in the brain.
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Nervous System
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Nervous System
Central Nervous System (CNS)
- Brain and Spinal Cord
Spinal Cord
1. carries messages to & from Brain
Sensory Neurons
 Sensory info to CNS
Motor Neurons
 from CNS to muscles and glands
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2. Reflexes - fast, automatic actions
Sensory message
Interneuron
Motor Message
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Autonomic Nervous System
1) Sympathetic
- readies the body for fight or flight
 Heart rate  Blood Pressure
 breathing  Digestion
2) Parasympathetic
- relaxation response
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Module 5
Older Brain Structures
Thalamus
Reticular formation
Pons & Medulla
Cerebellum
Limbic system
Hypothalamus
* Know the major functions
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Module 6
Cerebral Cortex
Sensory- motor functions
• use about 20% of cortex.
Association Areas. (thinking,
memory . . .)
• uses about 80% of cortex
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Localization of Function
Specific areas of the brain have specific functions.
Damage to specific areas produces specific function
deficits.
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Ways of studying the brain
1) Lesion studies (done on animals)
2) Case studies of brain damaged individuals.
- relate behavior to brain areas.
3) Imaging techniques
CAT scans
PET scans
FMRI
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Cortex has 2 halves (hemispheres)
Each controls opposite side of the body.
Each hemisphere has 4 lobes
1) Frontal Lobe
- Primary motor cortex
(controls movement)
- prefrontal cortex
(planning of movements and working memory)
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Frontal Lobotomies
Nerve connections to the prefrontal lobe are
severed.
- done to control violence and aggression
Results: loss of ability to plan and carry out
even simple tasks.
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2) Parietal Lobe
- primary somatosensory cortex
Sensations and location of body parts
Unilateral Neglect
- can sense the neglected side but fail to
to attend to it.
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3) Occipital lobe
- primary visual cortex
4) Temporal Lobe
- primary auditory
(hearing) area.
- complex aspects or vision
- face blindness
- motionblindness
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Corpus Callosum
Band of Neurons connecting the two hemispheres.
Video
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Split Brain Studies
Left Hemisphere - Language
- critical thought (making sense)
Right hemisphere - spatial ability
- face recognition
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Within the left hemisphere there are
2 areas for language
Brocas’s area - frontal lobe
- production of speech
Wernike’s area - temporal lobe
- comprehension of speech
Damage causes aphasia (speech disorder)
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Can a person recover from brain damage?
- neurons are not replaced.
- plasticity of the brain
- other parts take over function of damaged
parts.
- requires retraining
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