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Chapter 4
The Brain
The Nervous System
Central Nervous System (CNS)
– receives, processes, interprets and stores info (taste, sound, smell, color etc.)
– Sends information to muscles, glands and internal organs
•Brain
•Spinal Cord – extension of brain, brain to center of back, protected by spinal column; bridge to lower body
– Spinal reflexes – movements without brains help (jerk from hot surface – before brain registers pain)
Peripheral Nervous System (PNS) All other nerves; sensory & motor nerves
Handles CNS input and output
All nervous system outside brain
Sensory nerves – put us in touch with outside world and inside activities
Motor nerves – enable use to move
2 parts of the Peripheral Nervous System
Somatic nervous system – (skeletal nervous system) sensory receptors
Autonomic nervous system – regulates internal organs and glands
Sympathetic nervous system – increase energy - mobilizes body in tine of emotion or stress (fight or flight)
Parasympathetic nervous system – conserves energy; slows down; operates in relaxed states
Communication: Nervous System
• Neuron –
basic unit of nervous system; nerve cell
building block of nervous system
microscopic; 100 billion; 200 types (size / shape)
• Glial Cells – supports; nurtures and insulates neurons
remove debris when neurons die; enhance
performance & maintenance of neural connection; modify
neuronal functioning;
– role in learning and memory
– Greek for glue
3 Structures of the Neuron
• Dendrite – branches that receive information from other neurons &
transmits information toward the cell body (tree like)
• Cell body - keeps neuron alive; determines if it will “fire”
“fire” – transmit message to other neurons
• Axon – extending fiber that conducts impulses away from cell body &
transmits them to other neurons
•
•
Myelin sheath – fatty insulation that may surround the axon
Nerve – bundle of nerve fibers (axons & sometimes dendrites) in peripheral nervous sys.
Stem cell research: Pro or Con
• Neurogenesis
– production of new neurons from immature stem
cells
• Stem Cells – immature cells that renew themselves
potential to develop into mature cells
in encouraged environment; grow into any cell type
– Need cells a few days old
• Abortion clinics
• Excess from fertility clinics
How Neurons Communicate
•
Synapse
– site where transmission of nerve impulse from one nerve
cell to another occurs;
–
–
–
axon terminal
synaptic cleft
receptor sites in membrane of receiving cells
How Neurons Communicate
• Action potential – brief change in electrical voltage
that occurs btw the inside /outside of axon
when a neuron is stimulated;
produces an electrical impulse
• Neurotransmitter – chemical substance that is released by
transmitting neuron at the synapse &
alters the activity of a receiving neuron
Neurotransmission / Synapse
1- Nerve impulses move down axon;
Positively charged ions flow faster
(mylenation = faster)
2- When impulse reach button tip;
must get across synaptic cleft;
synaptic vesicle release neurotransmitter
3- When reaches the other side;
briefly bond w/ receptor sites
(lock & key)
4- Receiving membrane will change;
excite – increase firing (+ voltage)
inhibit –decrease firing (- voltage)
-multiple +/- messages sent; take average;
how many fire; rate of fire; synchrony;
type of neuron & location
3 Types of Nervous System Chemicals
1) Neurotransmitters
• Serotonin – sleep; appetite; sensory perception; temperature
regulation; pain suppression; mood
• Dopamine – voluntary movement, learning; memory; emotion;
pleasure or reward; response to novelty
• Acetylcholine - muscle action; cognitive functioning; memory; emotion
• Norepinephrine - ^ heart rate; slow intestinal activity during stress;
learning, memory; dream; wake from sleep; emotion
• GABA - (gamma-aminobutyric acid) major inhibitory neurotransmitter in brain
• Glutamate – major excitatory neurotransmitter in brain; 90% of neurons
3 Types of Nervous System Chemicals
2) Endorphins – endogenous opioid peptide
natures opiate
reduce pain; increase pleasure
appetite; sex; mood; learning; memory
endorphin rush: “falling in love” / battle field
3 Types of Nervous System Chemicals
3) Hormones – produced by endocrine glands
effects the functioning of other organs
endocrine glands – organs produce hormone & release into blood stream
• Melatonin – secreted by pineal gland
regulate daily biorhythms; promote sleep
• Oxytocin – produced by pituitary gland
enhances uterine contractions during birth; ejection of milk – nursing
• Adrenal hormones - produced by adrenal glands
emotion and stress
respond to heat; cold; pain; exercise; caffeine; nicotine
Cortisol - ^blood sugar; boost energy; gain weight
Epinephrine – adrenaline; fight or flight; memory
• Sex hormones – development and maintenance of reproductive organs
stimulates male / female characteristics
androgen – testosterone – male characteristics at puberty
estrogen – female characteristics at puberty
progesterone – lining of uterus in prep for fertilized egg
Quick Quiz
a)
Which word in ( ) better fits each of the following definitions?
1.
2.
3.
4.
5.
6.
Basic building blocks f the nervous system (nerves, neurons)
Cell parts that receive nerve impulses (axons, dendrites)
Site of communication between neurons (synapse, myelin sheath)
Opiate-like substance in the brain (dopamine, endorphin)
Chemicals that make it possible for neurons to communicate (neurotransmitters,
hormones)
Hormone closely associated with emotional excitement (epinephrine, estrogen)
The Brain
Location of function – brain areas for particular functions
• Brain stem – top of spinal cord ; pons & medulla
• Pons – sleeping; waking and dreaming
• Medulla – some automatic functions; breathing and heart rate
functions that are not consciously willed
Hanging – cut medulla
stop respiration
Reticular activating system:
–Dense network of neurons at core of brain stem
–Arouses cortex and screens incoming information
The Brain
• Thalamus – relays sensory message (except smell) to the cerebral cortex
Traffic officer of the brain – directs to higher area
olfactory bulb (smell)
• The cerebellum – Lesser brain
memory of simple skills
movement and balance
gross motor - walking
fine motor – hold pencil; thread needle
• Hypothalamus and pituitary gland
– Hypothalamus – Emotions; survival (hunger; fear; thirst; sex;
reproduction)
Regulates the autonomic system
– Pituitary gland – master gland
• Small endocrine gland at base of spine
• Release hormones
• Regulate other endocrine glands
The Brain
The limbic system – memory; emotional reactions and motivated behavior
• Amygdala – arousal and regulation of emotions
initial emotional response to sensory information
danger or threat
• Hippocampus – “sea horse” in Latin
storage of new information in memory
gateway to memory
compare new info with what is expected
• (also hypothalamus)
The Brain
• The Cerebrum – higher forms of thinking
largest grain structure
upper part of brain; 2 hemispheres
most sensory; motor and cognitive processes
Cerebral hemispheres – 2 halves of cerebrum
Corpus callosum – bundle of nerves fibers connecting 2 cerebral hemispheres
Lateralization – specialization of 2 hemispheres for particular operations
Cerebral cortex – collection of several thin layers of cells covering cerebrum
higher mental functions
1/8” thick – ¾ of all cells in human brain
deep crevices and wrinkles (more neurons) rat-smooth
Grey matter – grey tissue of brain
(White matter – long myelin coved axons)
Lobes of the Cortex
• Occipital – visual cortex
receive visual information
blindness / recognition
• Parietal – somatosensory cortex
receive info; pressure; pain; touch
• Temporal – auditory cortex
memory; perception; emotion
• Frontal – motor cortex
600 muscles
make plans; think creatively;
emotions; initiative; short term memory
Left lobe - Broca’s area – speech
Prefrontal Cortex - personality
• Rats and mice only 3.5%
• Humans – 29%
• Phineas Cage – railroad worker
inch thick – 31/2 foot rod through head
miracle lived; think; speak; remember
Dr. Jekyll / Mr. Hyde change
“not Phineas”
mild mannered to mean & angry
responsible to not work; hold jobs
Right and Left Brain
Right Brain
• Spatial visual ability
• Facial recognition
• Read facial expressions
• Music
• Intuitive
• Some language
• Some math
Left Brain
• Logic
• Symbolic
• Sequential tasks
• Understanding technical
materials
• Rational / analytic
• Math
Split Brain
Split Brain:
is left dominant?
•
Shown composite of photo (a) asked to pick
out the face seen from series of photos (b);
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Stated; seen face on right side of composite;
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Yet, pointed with their left hands to the face
that had been on the left
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2 hemisphere not communicate
•
Verbal left side – only saw right half
•
Mute right side – aware of left half
Quick Quiz
1) Keeping in mind what both sides of the brain are involved in most
activities, which of the following is / are more closely associated with the
left hemisphere?
a)
b)
c)
d)
e)
Enjoying a musical recording
Wiggling the left big toe
Giving a speech in class
Balancing a checkbook
Recognizing a long lost friend
His and Her Brains?
His and Her Brains
• Gender differences (intuition, abilities) are stereotypes
– More alike than different.
• Sex differences; result rather than cause of behavioral differences
– Nature or nurture
• Brain difference not explain behavior or performance
– Difference in brain activity but not ability to complete
– Listen to John Grisham; women left and right temporal; men only left.