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Chapter 3: The
Biological Bases of
Behavior
1
Communication in the Nervous
System
• Hardware:
1) Glia: structural support and insulation (Glue)
2) Neurons: communication (receives, integrate & transmits)
Dendrites – receive message
Soma – cell body
Axon – transmit message
Myelin sheath- speeds up transmission
Terminal Button- end of axon, release
message
Synapse- gap between Button & Dendrite
2
Figure 3.1 Structure of the
neuron
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The Neural Impulse
1) Resting Potential- Neuron is Ready
› -70 millivolts
2) Action Potential- Neuron Fires (down axon)
› Sodium + ions flow in, Potassium - ions flow out
3) Refractory Period- Neuron is Recharging
› The minimum time after firing, cannot fire until charged
All or None Principle- Neuron fires at the
same speed whether it was strong or
weak. Either fires or doesn't.
4
Figure 3.2 The neural impulse
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The Synapse: Chemicals as
Signal Couriers
• Neurotransmitters: is the chemical message
that transmit info from one neuron to another.
– Presynaptic neuron (Terminal Button)
• Synaptic vesicles: Contain Neurotransmitters
– Postsynaptic neuron (Dendrites)
• Receptor sites: Located on dendrites, each receptor
site receive specific neurotransmitters
6
7
When a Neurotransmitter Binds:
The Postsynaptic Potential
Postsynaptic Potential (PSP)
Changes the probability of the postsynaptic neuron firing
– Excitatory PSP: Positive voltage shift, increase firing
– Inhibitory PSP: Negative voltage shift, decrease firing
• Reuptake: All the excess neurotransmitters that
don’t bind to a receptor site get sucked up into the
terminal button
• Synaptic connections
– Elimination and creation
– Synaptic pruning
8
Figure 3.4 Overview of synaptic
transmission
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Figure 3.5 Synaptic pruning
10
Types of Neurons
• Sensory Neurons
– Nerves that carry information to the central
nervous system Connect the sense organs to
the brain and spinal cord
• Motor Neurons
– Nerves that carry information from the central nervous
system Carries messages from the brain and spinal
cord to other parts of your body
• Inter Neurons
– Nerve cells in the brain and spinal cord responsible
for processing information related to sensory input
and motor output
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The Neural Chain
12
Neurotransmitters
Specific neurotransmitters work at specific
synapses
– Lock and key mechanism
– (15 – 20) neurotransmitters known at present
• Agonist – mimics neurotransmitter action
• Antagonist – opposes action of a
neurotransmitter
13
Table 3.1 Common Neurotransmitters
and Some of their Functions
14
Neurotransmitter Helpful Hints
• ACh• DA-
•
•
•
•
AAM
Sell Dope at the Park (Parkinson)
Movement and Pleasure
NENorma PMS (Mood & Arousal)
Serotonin- Sleep/Wakefulness,
Eating/Aggression (Ninja
Turtles, SEWA)
GABA- Inhibitor
Endorphins- Natural pain reliever
15
Organization of the Nervous System
• Central nervous system (CNS)
 Brain & Spine (It is the center)
– Hindbrain. Back bottom
– Midbrain. Core
– Forebrain. Outer
• Peripheral nervous system (PNS)
 Bones. Organs. Muscles. (Is everything else)
– Somatic nervous system (SNS) voluntary
• Afferent = (In) toward the CNS
• Efferent = (Out) away from the CNS
– Autonomic nervous system (ANS) automatic
• Sympathetic (Fight or Flight)
• Parasympathetic (Calming)
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Figure 3.6 Organization of the
human nervous system
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Figure 3.7 The central and
peripheral nervous systems
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Figure 3.8 The autonomic nervous
system (ANS)
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Studying the Brain: Research Methods
•
•
•
•
Electroencephalography (EEG). Brain Waves
Damage studies/lesioning
Electrical stimulation (ESB). Mapping out the Brain
Brain Imaging –
– CT Scan (computerized tomography). X-Ray of brain structure
– PET Scan (positron emission tomography). Brain function,
shows activity in the brain with chemicals
– MRI Scan (magnetic resonance imaging). 3D pictures
– fMRI Scan (functional magnetic resonance imaging).
Additional oxygen & blood flow. Structure & function
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Brain Regions and Functions
• Hindbrain:
– Medulla. vital functions
– Pons. sleep & arousal
– Cerebellum. movement & balance
• Midbrain: (Plug into hard drive)
– Reticular Formation. sensory functions
• Forebrain:
– Thalamus. All senses except smell
– Hypothalamus. 4 “F’s”
– Limbic system
• Hippocampus. Learning & Memory (Hip to the campus)
• Amygdala. Emotion (Amy is emotional)
– Cerebrum. Outer layer of brain (largest)
– Cerebral cortex. Wrinkles in the outer layer 1.5 sqf
21
The Cerebrum:
Two Hemispheres, Four Lobes
• Cerebral Hemispheres – two specialized
halves connected by the corpus collosum
– Corpus Collosum- connects the hemispheres
– Left hemisphere – verbal processing: language,
speech, reading, writing
– Right hemisphere – nonverbal processing:
spatial, musical, visual recognition
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The Cerebrum:
Two Hemispheres, Four Lobes
• Four Lobes:
– Occipital – vision
– Parietal – somatosensory/motor cortex
– Temporal - auditory
– Frontal – movement, executive control
systems
23
Figure 3.16 Structures and areas in the
human brain
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Figure 3.18 The cerebral hemispheres and the
corpus callosum
25
Figure 3.19 The cerebral cortex in
humans
26
Figure 3.20 The primary motor cortex
27
Figure 3.21 Language processing in the brain
28
The Endocrine System:
Hormones
 Hormones – Chemical messengers
produced by the endocrine glands and
circulated in the blood
 Similar to neurotransmitters in that they
are also messengers
 Slower communication system, but with
longer lasting effects
29
The Endocrine System:
Glands
• Endocrine glands
– Pituitary – “master gland,” growth hormone
– Thyroid – helps regulate the energy level in
the body metabolic rate
– Adrenal – help to arouse the body in times of
stress, Located above the kidneys, Release
epinephrine (adrenaline) and norepinephrine
– Pancreas – regulates the level of sugar in the
blood
– Gonads – sex hormones, Ovaries (females)
and testes (males) influence emotion and
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physical development.
Genes and Behavior:
The Field of Behavioral Genetics
• Behavioral genetics = the study of the
influence of genetic factors on behavioral traits
• Chromosomes – strands of DNA carrying
genetic information
– Human cells contain 46 chromosomes in pairs
(sex-cells – 23 single)
– Each chromosome – thousands of genes, in pairs
• Dominant, recessive/Homozygous,
heterozygous
• Genotype- Genetic makeup
• Phenotype- manifested in characteristics
• Polygenic Inheritance- characteristics
influenced by more than one gene
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Figure 3.25 Genetic material
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Research Methods in Behavioral
Genetics
• Family studies – does it run in the family?
• Twin studies – compare resemblance of
identical and fraternal twins on a trait
• Adoption studies – examine resemblance
between adopted children and their
biological and adoptive parents
33
Figure 3.27 Genetic relatedness
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Figure 3.28 Family studies of risk
for schizophrenic disorders
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Figure 3.30 Twin studies of intelligence
and personality
36
Modern Approaches to the
Nature vs. Nurture Debate
• Molecular Genetics = the study of the
biochemical bases of genetic inheritance
– Genetic mapping – locating specific genes The Human Genome Project
• Behavioral Genetics
– The interactionist model
– Richard Rose (1995) – “We inherit
dispositions, not destinies.”
37
Evolutionary Psychology:
Behavior in Terms of Adaptive Significance
• Based on Darwin’s ideas of natural
selection
– Reproductive success key
• Adaptations – behavioral as well as
physical
– Fight-or-flight response
– Taste preferences
– Parental investment and mating
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