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