Transcript Ch 2 Biology and Behavior

Parts of the Nervous System
• Neurons – communication specialists, transmit signals to,
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from, and within CNS.
~ apprx. 100 billion in human brain
~ building blocks of CNS
~ Neurons can regenerate and reproduce themselves
3 parts to Neuron:
Dendrites – message receivers
Cell Body – contains biochemical machinery to keep neuron
alive
Axon – sends messages away from cell body
– Myelin Sheath – fatty material which covers axons; keeps signals from
other neurons from interfering with each other.
• Loss of myelin causes loss of sensation, paralysis, weakness
• Action Potential – electrical pulse
• Refractory Period – short recovery period between firing.
Central Nervous System
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Functions – receives, processes, interprets and stores
incoming information; sends out information to muscles,
glands, internal organs.
Parts – brain and spinal cord
Peripheral Nervous System
Functions
Sensory nerves – bring input from skin, muscles and organs.
Motor nerves – carry output to muscles, glands and organs
Somatic nervous system
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Nerves connected to sensory receptors
Nerves connected to skeletal muscles – voluntary actions
Autonomic nervous system
Functions – regulates blood vessels, glands, organs
Biofeedback – helps people control autonomic responses
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Sympathetic – mobilizes the body for action
Parasympathetic – enables body to conserve and store energy.
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Peripheral Nervous System
Nuclei – CNS clusters of neuron cell bodies
Fiber Tracts (Pathways) – bundles of axons
Nerves – made of bundles of neuron fibers
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43 pairs of peripheral nerves
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1 nerve of each pair to left side & to right side of body.
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Most come out of the spinal cord
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12 are in the brain called cranial nerves.
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Reflexes – incoming signal is “reflected” back out
Neurotransmitters
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Chemical created in synapses to carry signals from neuron to neuron.
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If neurotransmitters don’t get to correct neuron, message doesn’t get carried
out.
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Three Classes of Neurotransmitters: Small Molecules, Peptides, Gases
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Small Molecules
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Serotonin – affect sleep, appetite, sensory perception, mood, temperature
regulation.
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Dopamine – affects voluntary movement, learning, memory, emotion.
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Acetylcholine – affects muscle action, cognitive function, memory, emotion
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Norepinephrine – affects learning, waking from sleep, memory, dreaming,
heart rate due to stress.
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GABA – the major inhibitory neurotransmitter in the brain.
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Glutamate – strengthens synaptic connections – easier to send messages.
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High and low levels of these neurotransmitters can have harmful affects.
• Peptides
– Endorphins
• Any neurotransmitter that can bind to same receptors stimulated by
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opiates.
Natural opiates; reduce pain, promote pleasure & bring on sleep in
high doses.
Limit or prolong effects of the neurotransmitters
Effect appetite, blood pressure, mood, learning, memory, sexual
activity
Levels increase when animal or person is afraid or stressed; needed
for survival.
Endorphins levels increase when given affection by someone else.
Therefore, people tend to seek out affection or love.
• Gases
– Nitric Oxide and Carbon Dioxide
• Released by neurons & affects chemical reactions
• Key to diverse functions; sexual performance to formation of
memories
Endocrine System
– Regulates growth, energy consumption, sexual behavior, & readies body for
action.
• Hormones
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Originates in endocrine glands
Released directly into blood stream.
Aids digestion, regulates metabolism, promotes bodily growth.
Some hormones are more interesting to psychologists then others:
• Melatonin
– Promotes sleep
– Coordinates body rhythms, ex. Sleep cycle
• Adrenal Hormones
– Involved in emotion and stress
– Levels affected by pain, temperatures, physical exercise, injury, caffeine &
nicotine.
– Get body ready for action.
– Adrenal hormones enhance memory as long as levels are normal.
• Sex Hormones
– Androgens and Testosterone – male hormones
– Estrogens – female hormones
– Progesterone – prepares and maintains uterine lining for fertilized egg.
The Brain
The Hindbrain
• Continuation of spinal cord; reflex & feedback
system are important
• Vital autonomic functions are controlled here,
in the Medulla
• Reticular Formation in Hindbrain to Midbrain
– Involved in arousal & attention
• Cerebellum
– Involved in both physical & cognitive agility
– Well-rehearsed movements, language, abstract
thinking, finely coordinated movements.
The Brain
The Midbrain
• Midbrain & hindbrain makeup brainstem.
• Smooth movements
The Forebrain
• Complex aspects of behavior & mental life.
• Cerebral Cortex is its outer surface.
• Thalamus – processes & makes sense of pain & sensory information
• Hypothalamus
– regulates hunger, thirst & sex drives
– Connected to autonomic system & other parts of brain.
• Amygdala
– Links different sensory info in memory.
– Role in fear & connecting emotion to sensation.
• Hippocampus
– Emotions & formation of new memories
– Shrinks as you get older, 40% smaller in Alzheimer suffers
The Brain
Cerebral Cortex
• Analyzes info from senses
• Controls voluntary movement
• Abstract thinking & other complex behaviors
Corpus Callosum
• Connects the two hemispheres of brain
Sensory Cortex
• Receives info from different senses
• Makes up for lost senses with other senses.
Motor Cortex
• Controls voluntary movement for specific parts of the
body.
Plasticity
• Ability to strengthen & create new connections
Right side
• Controls left side of the body
• Some language ability
• Solves problems requiring spatial-visual
abilities.
• Excels reading maps or follow dress patterns
• Excels in facial recognition & reading facial
expressions.
• Recognizes non-verbal sounds
• Learning style is more intuitive & holistic
• Active in creation & appreciation of art &
music
Left side
• Process language in the left hemisphere
• Used with logical, symbolic, & sequential tasks
• Good at learning things.
• Tries to explain actions & emotions, especially
non-verbal.
• Speech ability is stronger
• 2 hemispheres cooperate naturally and neither
is dominant over the other.
• They both have their talents and they are used
when needed.
• What happens when they are unable to
communicate with each other?
– Ronald Myers & Roger Sperry split the 2
hemispheres of several cats’ brains and severed the
eye nerves that lead to the brain.
• Result:
– Trained cats to perform tasks with one eye covered
– Cats were only able to perform task learned while
right eye was uncovered when the right eye was
uncovered and vice-a-versa.
• Explanation: since two sides of brain cannot
communicate with each other then they can’t
share learned information.