Biological Bases of
Mental Life & Behavior
Psychology
• Involves the systematic examination of thoughts and behavior
• Examination of thoughts and behaviors requires that something happens– We think about something– We do something
• The neuron is the basic component of all thought and behavior
Neuron
• Fundamental unit of the nervous system
• Thinking and doing transpire through the connection of multiple neurons
• Estimates range from 10 billion to 100 billion neurons in the brain alone
• Lack of neuro activity is the definition of death
Neuron
• Sensory (afferent) Neurons– Transmit information from the sensory cells to the
brain
• Motor (efferent) Neurons– Transmit information from the brain to the organs and
muscles
• Interneurons– Pass information between the various sensory and
motor neurons
Neurons
• Dendrites– Numerous dendrites extend
out from the cell body and collect input
• Cell Body– Processes input from
dendrites
• Axon– Sends information forward
through the axon to the next neuron
Neuron
• Myelin Sheath– A coating of lipids (fat), derived from glial
cells, that surrounds most axons – Facilitates transmission of data – Multiple Scelerosis and Lou Gehrig’s disease
involve demyelization of axons
• Terminal Buttons– End of axon – Transmit signal to the next neuron
Triggering a Neuron
• Resting Potential– A neuron is polarized when no action underway
– Sodium and potassium ions in balance
• Action Potential– Depolarization
• Influx of + charged sodium ions
• Neuron more likely to fire
– Hyperpolarization• Outflow of + charged potassium ions
• Neuron less likely to fire
Triggering a Neuron
• Graded Potential– Brief voltages that travel down dendrites– Most frequent form of psychological processes– Create new information at the cellular level by allowing
the cell to integrate signals from multiple sources that are connecting through various dendrites
• Action Potentials (Nerve Impulse)– Triggers a cell body into action– All or none event– It triggers the neuron into action– Passes along already created information
Communication between Neurons
• Synapse– The bridge (connection)
between the axon of one neuron and the dendrite of the next neuron
• Presynaptic neuron- neuron sending signal
• Postsynaptic neuron- neuron receiving signal
• Synaptic Cleft– Actual connection point
between axon and dendrite
Neurotransmitters
• Synaptic Vesicles– Small sacs within terminal buttons that contain
the chemical neurotransmitters
• Neurotransmitters– Chemicals that carry the signal from one
neuron to another– When neuron fires the chemicals go into the
synaptic cleft
Neurotransmitters
• Once in the synaptic cleft, some of the neurotransmitters bind with neurotransmitters from the connected dendrite
• Excitatory Neurotransmitters increase action potential
• Inhibitory neurotransmitters decrease action potential
Types of Neurotransmitters• At least 75 different neurotransmitters
• Glutamate – Excites neurons
• GABA– Inhibits neurons in the brain
• Gylcene– Inhibits neurons in spinal cord
• Dopamine– Emotional arousal, pleasure, voluntary movement, attention
Types of Neurotransmitters
• Serotonin– Sleep and emotional arousal, aggression, pair
regulation, mood
• Acetylcholine– Learning and memory
• Endorphins and Enkephalins– Pain relief and elevation of mood
• Epinephrine and norepinephrine– Emotional arousal, anxiety, and fear
Endocrine System
• A collection of glands that secrete hormones (signals) directly into the blood stream
• A second system, similar to the nervous system, for intercellular communication
• Able to simultaneously stimulate numerous cells
Endocrine System
• Pituitary Gland– Master Gland– Hormones it releases stimulate and regulate
other glands
• Thyroid Gland– Releases hormones involved with growth and
metabolism– Impacts energy level and mood
Endocrine System
• Adrenal Glands– Release adrenalin during emergencies– Prepares one for fight or flight
• Gonads– Influence sexual development and behavior– Testosterone in males– Estrogens in females
Nervous System
• Central Nervous System (CNS)– Brain and Spinal Cord
• Peripheral Nervous System (PNS)– Neurons throughout the rest of the body that transmit
signals to and from the CNS
– Afferent Neurons send signals from the PNS to the CNS
– Efferent Neurons send signals from the CNS to the PNS
Somatic Nervous System
• Intentional actions– Regulates voluntary actions such as turning
your head or standing up
• Also regulates automatic behaviors such as balancing yourself on a set of skis
Autonomic Nervous System
Automatic body functions such as heart function:
• Sympathetic Nervous System– Responds to threats– Increases heart rate, stops digestion, etc.
• Parasympathetic Nervous System– Regulates routine duties such as secreting
salvia
Central Nervous System
• Spinal Cord– Collects sensory information from the PNS and
transmits it to the brain– Transmits instructions from the brain to the
PNS (motor signals)
• Brain– CPU of the body
Spinal Cord
• Segmented– Each segment interfaces with a different part of
the body
• Spinal Nerves– 31 pairs of sensory and motor neuron bundles
to transmit and receive data to/from CNS
Spinal Cord
Paralysis– Injury to the spinal cord
– Prevents data from flowing to/from the brain
– Results in inability to move the parts of the body that are below the spinal injury
Brain
• Hindbrain– Directly above and linked to the spinal cord
– Most primitive, yet essential, part of our nervous system
– Includes:• Medulla Oblongata
• Cerebellum
• Parts of the reticular formation
• Pons
Brain
Medulla Oblongata– Extension of spinal cord that links it to the brain
– Nerve bundles cross from one side of the body to the opposite side of the brain
– Weakness in left side of the body suggests a problem on the right side of the brain
– Regulates heartbeat, circulation, respiration
Brain
• Reticular Activating System (RAS)
– Network of neurons that extends from medulla to the upper end of the midbrain
– Sends signals to many parts of the CNS
– Maintain consciousness, regulates arousal levels and modulates activity of neurons throughout the CNS
Brain
• Cerebellum
– Involved with motor learning and movement, balance and posture
– When impacted our movements are not well coordinated
Midbrain
• Tectum – Vision and hearing
• Tegmentum– Orienting body and eyes towards a sensory
stimuli
Brain
• Subcortical Forebrain
– Complex sensory, emotional, cognitive and behavioral processes
– Consists of the • Hypothalamus• Thalamus• Limbic System• Basal Ganglia
Brain
• Hypothalamus– Eating, sleeping, sexual activity, emotional experience
– Key link between the nervous system and the endocrine system
– Activates the pituitary during stressful events
• Thalamus– Process sensory data and transmit it to higher brain
centers
– Also regulates signals (more/less important)
Brain
• Amygdala– Learning and remembering emotionally significant
events– Involved in recognizing emotions in other people (fear
in others)
• Hippocampus– Involved in storing information in our memory
• Basal Ganglia– Movement and judgments requiring minimal conscious
thought
Brain
• Cerebral Cortex– 80% of brain mass
– Allows flexible construction of voluntary movements
– Subtle discrimination among complex sensory patters
– Enables symbolic thinking (foundation of human thought)
Brain• Cerebral hemispheres
– Two halves of the cortex that are divided by a longitudinal fissure
– The corpus callosum connects the two hemispheres
– Left fontal and temporal lobes play a more important role in speech and language than the right side counterpart
• Occipital Lobes– Vision
• Parietal Lobes– Touch
Brain
• Frontal Lobes– Movement, planning, abstract thinking, memory, some
aspects of personality
– Motor cortex initiates voluntary movements
– May be site of neural dysfunction that underlies schizophrenia
• Temporal Lobes– Hearing, language, and recognizing objects by sight
Left Brain—Right Brain
• Cerebral Lateralization– Some division of labor does exist between both sides of
the brain
• Left Brain– Language, logic, complex behavior and consciousness
(analytical)
• Right Brain– Nonlinguistic functions such as visual images, music,
feeling
Genetics
• Genes– DNA (deoxyribonucleic acid)– Two alleles in each gene (one from each parent)
• Dominant
• Recessive
• Genotype– Our genetic blueprint
Genetics
• Degree of relatedness– The probability of sharing genes with relatives
• Twins– Monozygotic = Same sperm and (one) egg
– Dizygotic= Two sperm and two eggs
• Heritability Coefficient– Degree of variation in a trait across individuals
Evolution
• Traits common to a particular species that contribute to the survival and reproductive fitness of members of that species
• Charles Darwin
Genetic Engineering
• Deliberate effort to influence genetic code of a given member of a species
• Cloning