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
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
Neurons: The Units of the Nervous System
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
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
Neural Transmission
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
Biological foundations of Behavior
Neurotransmitters and
Synaptic Transmission
Chemicals in brain
– Acetylcholine
– Dopamine
– Serotonin
– Norepinephrine
– Glutamate
– Neuropeptides
Glial cells
 Outnumber neurons
 Produce myelin sheath
 Uses chemical ATP
(adenosine triphosphate)
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
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
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
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
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
Hindbrain and Midbrain
Midbrain
Pons
Cerebellum
Medulla
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
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
Forebrain
Cerebral Cortex
Thalamus
Hypothalamus
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
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
Motor
area
Somatosensory
Voluntary
movement and
thinking
Body sensations
Broca’s
area
Wernicke’s
area
Vision
Hearing
The Brain’s Four Lobes
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
Biological foundations of Behavior
Functions of the Hemispheres
of the Cerebral Cortex
Corpus Callosum
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
Biological foundations of Behavior
Split Brains
 Severed corpus
callosum
 Psychological
experiments reveal
processing
limitations of
hemispheres
 Optic chiasm not
severed
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
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
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
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
Biological foundations of Behavior
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
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
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
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
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
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
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
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
Biological Foundations of Behavior