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Chapter 3: The Biological
Bases of Behavior
Communication in the Nervous System
• Two basic forms of communication
– Chemical
– Electrical
Communication in the Nervous System
• Glia – structural support and insulation
• Neurons – communication
– Soma
– Dendrites
– Axon
– Myelin sheath
– Terminal Branches / Button
Figure 3.1 Structure of the neuron
Figure 3.1 Structure of the neuron
Neural Impulse
• The “information” traveling through the
• Hodgkin & Huxley (1952) - Studied a giant
squid to understand mechanics of neural
Resting Potential
• Resting potential
– Cell is inactive, Stable negative charge
• Membrane is Polarized
The Action Potential
Brief change in the electrical charge
Stimulation causes cell membrane to open
Membrane is Depolarized
Electrical charge travels along neuron
All – or – none law
The Synapse
• Presynaptic Neuron
– Terminal Button
• Synaptic Cleft
• Postsynaptic Neuron
– Cell Membrane
– Dendrite or Soma
The Synapse
• Presynaptic Neuron
– Synaptic Vesicles
– Neurotransmitters
• Synaptic Cleft
• Postsynaptic Neuron
– Receptor Sites
– Lock and Key
When a Neurotransmitter Binds:
The Postsynaptic Potential
• Voltage change at receptor site –
Postsynaptic Potential (PSP)
– Changes the probability of the postsynaptic
neuron firing
• Positive voltage shift – Excitatory PSP
• Negative voltage shift – Inhibitory PSP
Figure 3.4 Overview of synaptic transmission
Neurotransmitters and Behavior
• Specific neurotransmitters work at specific
• More than 40 neurotransmitters known at
present – 9 are commonly researched.
• Agonist – mimics neurotransmitter action
• Antagonist – opposes action of a
Acetylcholine (Ach)
• Only neurotransmitter found between motor
neurons and voluntary muscles.
• Contributes to the regulation of attention,
arousal and memory--Alzheimer's patients
have decreased levels of ACh.
– Nicotine is an Agonist
– Alzheimer’s medication is an Agonist
– Curare is an Antagonist
– Botox is an Antagonist
• Three neurotransmitters that regulate
everyday behaviors.
– Dopamine (DA)
– Serotonin
– Norepinephrine (NE)
• Inattention and distractibility appear to be related to
low levels of Norepinephrine. ADHD Children/Adults
can't judge which things in their environment are
important and which should be ignored. Low levels of
Norepinephrine also make it very difficult for ADHD
Children/Adults to sustain their focus on a task, plan
ahead, and understand such concepts as sequence
and time.
• The impulse and behavior problems found in
Attention-Deficit Hyperactivity Disorder (ADHD)
appear related to low levels of Dopamine in the brain.
Low levels of dopamine in the brain makes control of
impulsive behavior almost impossible in the ADHD
• Gamma-aminobutric acid
• Inhibitory
• Anxiety
• Internally produced chemicals that resemble
opiates in structure and effects.
Table 3.1 Common Neurotransmitters and Some of their Functions
Organization of the Nervous System
• Central nervous system (CNS)
– Brain
– Spinal Cord
– CerebroSpinal Fluid
• Peripheral nervous system
– Somatic nervous system
– Autonomic nervous system (ANS)
• Sympathetic
• Parasympathetic
Figure 3.5 Organization of the human nervous system
Figure 3.6 The central and peripheral nervous systems
Figure 3.7 The autonomic nervous system (ANS)
Studying the Brain: Research Methods
Spinal Tap
Electrical stimulation (ESB)
Damage studies/lesioning
Brain imaging –
– Computerized Tomography (CAT/CT)
– Magnetic Resonance Imaging (MRI)
– Positron Emission Tomography (PET)
• Transcranial magnetic stimulation (TMS)
CT Scan
Magnetic Resonance
Imaging (MRI)
Positron Emission
Tomography (PET)
Transcranial Magnetic
Stimulation (TMS)
Filed Depth
Brain Region
Magnetic Field
Figure 3.12 Structures and areas in the human brain
Brain Regions and Functions
• Hindbrain
• Vital Functions
– Medulla
– Pons
– Cerebellum
Figure 3.12 Structures and areas in the human brain
Brain Regions and Functions
• Midbrain
• Sensory functions
• Reticular Activating System
Figure 3.12 Structures and areas in the human brain
Brain Regions and Functions
• Forebrain
• Emotion, complex thought
– Thalamus
– Hypothalamus
– Limbic System
– Cerebrum
• Cerebral Cortex
Right Brain/Left Brain:
Cerebral Specialization
• Cerebral Hemispheres – two specialized
halves connected by the corpus collosum
– Left hemisphere – verbal processing:
language, speech, reading, writing
– Right hemisphere – nonverbal
processing: spatial, musical, visual
Figure 3.14 The cerebral hemispheres and the corpus callosum
Mac OS X
Animation 3.7 Right Brain/Left Brain
The Cerebrum:
The Seat of Complex Thought
• Four Lobes:
– Occipital – vision
– Parietal - somatosensory
– Temporal - auditory
– Frontal – movement, executive control
Figure 3.15 The cerebral cortex in humans
Figure 3.16 Language processing in the brain
The Endocrine System:
Another Way to Communicate
• Hormones – chemical messengers in the
• Endocrine glands
– Pituitary – “master gland,” growth hormone
– Thyroid – metabolic rate
– Adrenal – salt and carbohydrate metabolism
– Pancreas – sugar metabolism
– Gonads – sex hormones
Basic Principles of Genetics
• Chromosomes – strands of DNA carrying
genetic information
– Human cells contain 46 chromosomes in
pairs (sex-cells – 23 single)
– Each chromosome – thousands of genes,
also in pairs
• Polygenic traits
• Dominant Recessive Traits
Research Methods in Behavioral Genetics
• Family studies – does it run in the family?
• Twin studies – compare resemblance of
identical (monozygotic) and fraternal
(dizygotic) twins on a trait
• Adoption studies – examine resemblance
between adopted children and their biological
and adoptive parents
Figure 3.19 Genetic relatedness
Figure 3.20 Twin studies of intelligence and personality
The Evolutionary Bases of Behavior
• 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