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Biological Foundations
of Behavior
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Nervous System: Biological
Control Center
• Brain – thinks, calculates, feels, and
controls motivation
• Spinal cord
– Bundle of long nerves running through spine
– Connects brain to every part of body
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Neurons: The Units of the
Nervous System
• Neuron – individual nerve cell
• Parts of neurons
– Cell body: central part of nerve cell; contains
nucleus or cell’s control center
– Dendrites: small branches extending from cell;
receive messages from other neurons
– Axons: small branches at other end of neuron;
send messages to other neurons
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Neurons: The Units of the Nervous System
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Neural Transmission
• Neurons
– Function like wires and batteries
– Have sacs filled with fluid chemicals containing
surrounded by a second type of chemical
– Ions: positive or negative changed particles
– Cell membrane
• semipermeable in normal resting state
– Polarized when negative ions inside cell
membrane and positive ions outside
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Neural Transmission
• Neurons
–
–
–
–
Depolarization – positive ions enter membrane
All-or-none principle
Action potential
Myelin sheath
• Average thickness in females is greater
• May indicate females process certain
information better than males
• Multiple sclerosis destroys myelin sheath
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Neural Transmission
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Neurotransmitters and Synaptic
Transmission
• Neurons work together through
– Synapse
– Synaptic gap
– Neurotransmitters: excitatory, inhibitory
– Synaptic vesicles
– Synaptic terminals
– Receptor sites
• Brain can be altered by use of drugs
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Neurotransmitters and Synaptic
Transmission
Chemicals in brain
Glial cells
– Acetylcholine
– Outnumber neurons
– Dopamine
– Produce myelin sheath
– Serotonin
– Uses chemical ATP
– Norepinephrine
(adenosine triphosphate)
– Glutamate
– Neuropeptides
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Divisions of the Nervous System
• Central Nervous System
– Brain and spinal cord
– Interneuron
• Peripheral Nervous System
– Branches to all parts of body from CNS
– Afferent and efferent neurons
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Pain receptors in skin
Hot object
Axion of
afferent neuron
Cell body of interneuron
Cell body of
afferent neuron
Axion of
efferent neuron
Dendrite of
afferent
neuron
Cell body of
efferent neuron
Direction of impulse
Muscle contracts and
withdraws part being
stimulated
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Divisions of Peripheral Nervous
System
• Somatic nervous system
– Voluntary movements and skeletal muscles
– Receives and send messages
• Autonomic nervous system
– Carries messages to organs, has 2 functions
• Essential body functions
• Emotion
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Divisions of Autonomic Nervous
System
• Sympathetic nervous system
– Responds to psychological or physical stress
– Activates and inhibits organs
• Parasympathetic nervous system
– Helps maintain balanced regulation of internal
organs and large body muscles
– Stimulates maintenance activities and energy
conservation
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Structures and Functions of
the Brain
• Hindbrain
– Routine functions that keep body working
– Three main parts
• Medulla – breathing and reflexes
• Pons – balance, hearing
• Cerebellum – coordinates complex muscle
movements
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Hindbrain and Midbrain
Midbrain
Pons
Cerebellum
Medulla
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Biological foundations of Behavior
Structures and Functions of
the Brain
• Reticular formation
– Spans medulla and pons
– Influence wakefulness, arousal, attention,
– Muscle control and cardiac responsiveness
• Midbrain
– Center for postural reflexes linked to senses
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Forebrain: Cognition, Motivation,
Emotion, and Action
• Forebrain – two distinct areas
– Thalamus, hypothalamus, most limbric system
• Thalamus – message switching station
• Hypothalamus – motives and emotions
• Amygdala system – aggression, emotions
• Hippocampus – memories
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Forebrain
Cerebral Cortex
Thalamus
Hypothalamus
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Forebrain: Cognition, Motivation,
Emotion, and Action
• Forebrain – two distinct areas
– Primarily cerebral cortex
• Sensory, cognitive, and motor functions
• Conscious experiences
• Voluntary actions
• Language and intelligence
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Lobes of the Cerebral Cortex
• Lobes – four sections of brain
– Frontal lobes – thinking, memory, decisions
• Broca’s area – ability to speak
• Phineas Gage
– Association areas – general roles in cerebral
activities
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Motor
area
Somatosensory
Voluntary
movement and
thinking
Body sensations
Broca’s
area
Wernicke’s
area
Vision
Hearing
The Brain’s Four Lobes
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Images of the Brain at Work
• Techniques create images
– Electroencephalogram (EEG)
– Positron emission tomography (PET)
– Magnetic resonance imaging (MRI)
• Functional MRI measures
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Functions of the Hemispheres of the
Cerebral Cortex
Corpus Callosum
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Biological foundations of Behavior
Functions of the Left and Right
Cerebral Hemispheres
• Left cerebral hemisphere
– Language control in 90% of population
– Analyzes logical verbal information
• Right cerebral hemisphere
– Processes shapes and location of things
– Visual and spatial information
• Corpus callosum
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Split Brains
• Severed corpus
callosum
• Psychological
experiments reveal
processing limitations
of hemispheres
– Optic chiasm not
severed
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Hemispheres of the Cerebral Cortex
and Emotion
• Left hemisphere
– Processes positive emotions
– Stroke in left hemisphere – depression
• Right hemisphere
– Processes negative emotions
– Stroke in right hemisphere – no depression
• Plasticity of cortex
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Human Diversity: Sex Differences
in the Cerebral Cortex
• Female brain – average size smaller than
that of male brain
– More folds and complex
– Greater surface area
– More accurate in verbal task performance
– More activation in left cerebral hemisphere
• Male brain
– More activation in right cerebral hemisphere
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
The Brain is a Developing System
• Brain structure changes over lifetime
• Total brain weight same after age 5
– Gray matter decreases as white matter
increases in cerebral cortex
– White matter: continued myelin growth but
decreases after fifth decade of life
– Gray matter decrease: neural pruning
– Neurogenesis: controversial issue
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
The Brain is an Interacting System
• Cerebral cortex – evaluates threats
• Limbic system – process emotional
arousal
• Motor areas of cortex work with
hindbrain and midbrain to coordinate
muscular movements
• Parallel rather than serial processing
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
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Endocrine System: Chemical
Messengers of the Body
• Endocrine system – regulation of bodily
processes
– Glands – secrete neuropeptides and hormones
– Hormones
• Directly regulated by brain
• Chemically identical to some neurotransmitters
• Activate body organs during physical stress or
emotional arousal
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Glands
• Pituitary Gland
– Largely controlled by hypothalamus
– Regulates body’s reaction to stress and resistance
to disease
• Adrenal glands
– Pair of glands atop kidney
– Secrete variety of hormones in emotional arousal
• Epinephrine and norepinephrine
• Cortisol
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Islets of Langerhans
• Embedded in pancreas – regulate
sugar in blood
• Glucagon – causes liver to put
sugar in blood stream
• Insulin – reduces sugar level in
blood
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Glands
• Gonads – produce sex cells
– Ovaries and estrogen
– Testes and testosterone
• Thyroid gland
– Regulation of metabolism
– Secretes thyroxin
– Serious deficiency: cretinism, rare
type of mental retardation
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Glands
• Parathyroid glands
– Four small glands in thyroid
– Secrete parathormone
– Regulates ion levels in neurons
• Too much – lethargy
• Too little – excessive nervous activity
• Pineal gland
– Attached to top of thalamus
– Secretes melatonin – regulates moods
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
Biological foundations of Behavior
Genetic Influences on Behavior
• What is inherited?
– Physical traits
– Specific behavioral patterns
• Biological mechanisms of inheritance
– Genetic codes
• Mendel – science of genetics
• Genes, chromosomes, and DNA
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Genetic Influences on Behavior
• Biological mechanisms of inheritance
– Sex cells
• Gametes
• Fertilization and zygote
– Dominant and recessive genes and traits
– Chromosome abnormalities
• Down syndrome
– Genes influence on mental processes
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological foundations of Behavior
Research on Inheritance in Humans
• Studies of twins
– Monzygotic: identical twins
– Dizygotic: fraternal twins
• Studies of adopted children
– Heredity and environmental influences
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved
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Biological Foundations of Behavior
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The End
© 2007 The McGraw-Hill Companies, Inc. All Rights Reserved