Nature vs. Nurture: Heredity, Environment, and Behavior

Nature vs. Nurture

• Human behavior and mental processes are impacted by nature and nurture, not either/or.
• Heredity is the passing of physical and mental traits from one generation to another.
• Environmental factors include family life, social groups, education, and societal influences.

Psychological Perspectives

• Different psychological perspectives view the nature vs. nurture debate differently.

Evolutionary Approach

• Darwin's theory of evolution leans toward the nature side.
• Charles Darwin focused on how heredity and environment impact individuals.
• Evolution occurs through natural selection.
• Beneficial individual traits survive and are passed on, while undesirable traits die off.
• Eugenics is the belief in improving the genetic quality of the human population.
• Accomplished through selectively breeding desirable traits and discouraging reproduction among those with undesirable traits.

Epigenetics

• Studies how heredity and the environment shape behaviors and mental processes.
• Focuses on the impact of the environment and behavior on genes.
• Sustained environmental pressures can turn genes on or off without changing the DNA sequence.
• Identical twins with nearly 100% identical genes can have vastly different characteristics.
• The Minnesota Study of Twins Reared Apart examined similarities and differences in separated twins.
• The Colorado Adoption Project (1975) studies genetics and environment influences on cognitive abilities, personalities, and mental processes.

Plasticity

• The brain's ability to change and adapt as a result of experiences.
• Involves strengthening or weakening neural connections.
• Allows the brain to be flexible and adapt to changing experiences.

The Nervous System

• The CNS (Central Nervous System) includes the brain and spinal cord, sending orders to the body.
• The PNS (Peripheral Nervous System) consists of nerves branching from the brain/spine, connecting the CNS to organs and muscles.
• Afferent neurons (sensory neurons) send signals from sensory receptors to the central nervous system; remember: Afferent approaches the brain.
• Efferent neurons (motor neurons) send signals from the central nervous system to the peripheral nervous system; remember: Efferent exits the brain.
• The Somatic Nervous System controls the five senses and skeletal muscle movements consciously.
• The Autonomic Nervous System controls involuntary activities like heart beating, stomach digesting, and breathing involuntarily.
• Sympathetic mobilizes the body for action (fight or flight) with effects like faster heartbeat, dilated eyes, and increased breathing.
• Parasympathetic relaxes the body (rest and digest), slowing heart rate, increasing digestion, and focusing on saving energy.
• Both systems work together in emergencies for fight or flight response.
• Parasympathetic can be remembered as a parachute; it slows you down.

Neurons and Neural Firing

• Glial cells provide structure, insulation, communication, and waste transportation.
• They form the basis of the nervous system and are the building blocks of behavior and mental processes.
• Glial cells are the most abundant cells in the nervous system.
• They support neurons through protection and provide them with nutrients.
• Glial cells do not process information or send messages/signals.
• Neurons are the basic functional unit of the nervous system.
• Neurons communicate using electrical impulses and chemical signals throughout the nervous system.
• Reflex arc is a nerve pathway that allows the body to respond to a stimulus without thinking.
• It involves sensory neurons, motor neurons, and interneurons.
• Skin receptors detect heat and send a signal through a sensory neuron to the spinal cord.
• The signal goes to interneurons, which are neurons within the brain and spinal cord.
• These interneurons communicate internally and connect the sensory neurons to motor neurons within the CNS.
• Sensory neurons are also known as afferent neurons.
• Motor neurons are also known as efferent neurons.
• When a signal goes to the motor neurons, it returns to muscles in the hand and arm, resulting in the hand being pulled away.
• This happens through the body's autonomic response, without conscious thought.
• Reflex arc allows the body to respond to a threat before processing it.

Neural Transmission

• Neurons need enough stimulation to cause an action potential in order to send a message.
• Action potential is when a neuron fires and sends an impulse down the axon.
• This requires positively and negatively charged ions, separated by the cell membrane, creating a neuron's potential.
• Permeability refers to how easily some ions can cross the membrane.
• When not signaling, a neuron has more negative ions inside, known as resting potential.
• To trigger an action potential, a neuron must depolarize and a stimulus must meet the threshold.
• An "All or Nothing" response means a neuron only fires if the threshold is met.
• After an action potential, the neuron repolarizes, rebalancing charges by letting positive ions outside the cell membrane.
• During repolarization, the neuron cannot respond to any other stimulus.
• This period is the refractory period; the cell needs to wait to repolarize and return to resting potential.
• Once a signal reaches the axon terminal, it's converted and sent to another neuron through the synapse.
• Synapse is a small pocket of space between the axon terminal of one neuron and the dendrite of another.
• Chemical synapses use neurotransmitters (chemical messengers), and electrical synapses for quick messages.
• When neurotransmitters are sent, they diffuse through the synaptic gap to deliver messages.
• The synaptic gap is the narrow space between the presynaptic terminal of one neuron and the postsynaptic terminal of another.
• The presynaptic terminal converts the electrical signal to a chemical one, sending neurotransmitters into the synaptic gap.
• The postsynaptic terminal is where the neurotransmitters are accepted in the dendrite of the receiving neuron.
• After neurotransmitters deliver the message, they unbind with the receptors and undergo reuptake.
• Reuptake is when the sending neuron reabsorbs the extra neurotransmitters.
• Depending on the receptors neurotransmitters bind to, the neuron will either get excited or become inhibited.
• Excitatory neurotransmitters increase the likelihood that a neuron will fire an action potential through depolarization.
• Inhibitory neurotransmitters decrease the likelihood that a neuron will fire an action potential, leading to hyperpolarization.
• Hyperpolarization occurs when the inside of the neuron becomes more negative, needing more to reach an action potential.

Chain of Events for Neural Transmission

1. An action potential sends a signal down the axon to the presynaptic terminal.
2. Channels in the axon terminal open, and neurotransmitters are released into the synaptic gap.
3. Neurotransmitters diffuse through the synaptic gap and bind to receptor sites in the postsynaptic terminal.
4. Neurotransmitters unbind with the receptors; some are destroyed, and others go through reuptake.

Neurological Disorders

• Disruption of neural transmission can lead to neurological disorders.
• Multiple Sclerosis (MS) damages the myelin sheath, disrupting electrical signal transmission, causing muscle weakness, coordination problems, and fatigue.
• Myasthenia Gravis is an autoimmune disorder where antibodies block or destroy acetylcholine receptors, preventing muscle contraction and causing muscle weakness & fatigue.

Neurotransmitters

• Acetylcholine enables muscle action, learning, and memory.
• Substance P transmits pain signals from the sensory nerves to the CNS.
• Dopamine helps with movement, learning, attention, and emotions.
• Serotonin impacts hunger, sleep, arousal, and mood.
• Endorphins help with pain control and impact pain tolerance.
• Epinephrine helps with the body's response to high emotional situations and helps form memories.
• Norepinephrine increases blood pressure, heart rate, and alertness, being part of the fight or flight response.
• Glutamate is involved with long-term memory and learning.
• GABA helps with sleep, movement, and slows down the nervous system.

Hormones

• Hormones perform different functions similar to neurotransmitters.
• Adrenaline helps with the body's response to high emotional situations, expands air passages, and redistributes blood.
• Leptin regulates energy balance by inhibiting hunger.
• Ghrelin signals to the brain that we are hungry and helps promote the release of growth hormones.
• Melatonin regulates sleep-wake cycles, more prevalent in the evening.
• Oxytocin promotes feelings of affection and emotional bonding.
• Hormones are part of the endocrine system, and the nervous system uses neurons to quickly send messages to localized areas.

Psychoactive Drugs

• Agonist drugs increase the effectiveness of a neurotransmitter.
• They bind to receptors in the synapse to increase effectiveness, mimicking or blocking reuptake.
• Examples of agonist drugs include anti-anxiety medications (Xanax) that increase GABA, and Prozac.
• Antagonist drugs decrease the effectiveness of a neurotransmitter.
• They block neurotransmitters from being released, or connecting to postsynaptic receptors.
• Agonists can delay reuptake and make neurotransmitters more available; example: medication for depression delays serotonin reuptake.
• Antagonists can block receptors or release of neurotransmitters; example: medication for schizophrenia blocks dopamine receptors and alcohol blocks glutamate release.
• Psychoactive drugs alter perceptions, consciousness, or mood.

Categories of Psychoactive Drugs

• Stimulants excite neural activity, give energy, reduce appetite, cause irritability; examples: caffeine, nicotine, cocaine.
• Depressants reduce neural activity, cause drowsiness, muscle relaxation, and lowered breathing; examples: alcohol, sleeping pills.
• Hallucinogens cause hallucinations, reduce motivation, can lead to panic; examples: marijuana, peyote, LSD.
• Opioids relieve pain, function as depressants, but are highly addictive; examples: morphine, heroin, oxycodone.
• Tolerance to psychoactive drugs can develop, requiring more to achieve the same effect, potentially leading to addiction and withdrawal symptoms.

Brain Structures and Regions

• Three main regions when looking at the brain include Hindbrain (bottom), Midbrain (center), Forebrain (top).
• The Spinal Cord connects the brain to the rest of the body, serving as an information highway.
• The Brainstem, located at the base, includes the medulla, pons, and midbrain, controlling autonomic functions; severe damage is often fatal.
• Medulla Oblongata is above the spinal cord and below the pons, regulating cardiovascular and respiratory systems, as well as other autonomic functions.
• The Pons is a bridge between different areas of the nervous system, connecting the medulla with the cerebellum, coordinating movement, and helping with sleep and dreams.
• The Reticular Activating System regulates arousal, alertness, and sleep-wake cycles; Stimulates other brain structures important for attention.
• The Cerebellum is located in the back of the brain, coordinates voluntary movements, maintains posture and balance and refines motor skills.

Midbrain

• Helps with visual and auditory information processing, motor control, and integrating sensory and motor pathways.

Forebrain

• Cerebrum is the largest part, dealing with complex thoughts, divided into left and right hemispheres, each subdivided into four lobes.
• The cerebrum is made up of gray matter called the cerebral cortex and white matter.
• Cerebral Cortex is a thin outer layer of billions of nerve cells covering the brain.
• Corpus Callosum is a thick band of nerve fibers connecting the two cerebral hemispheres.

Lobes of the Brain

Contralateral Hemispheric Organization

• The brain's hemispheres control opposite sides of the body and processes sensory information.
• The left motor cortex controls movement on the right side, and the right motor cortex movement on the left side.
• The Motor Homunculus is a visual representation of brain area dedicated to body parts in the motor cortex.
• The Sensory Homunculus provides a visual representation of brain area dedicated to body parts in the sensory cortex.
• Broca's Area is found only in the left hemisphere in front of the motor cortex, crucial for language production, particularly in speech; damage results in Broca's Aphasia, the loss in ability to produce language.
• Wernicke's Area is typically located in the left temporal lobe, responsible for creating meaningful speech; damage results in Wernicke's Aphasia, the loss of ability to create meaningful speech.
• The occipital lobe may detect an object's color and shape.
• The temporal lobe helps with identifying objects.
• The parietal lobe helps with understanding spatial orientation.
• The Thalamus is located deep within the brain, just above the brainstem functioning as a relay station.
• It receives sensory information from sensory organs except smell.
• It relays information to appropriate areas of the cerebral cortex for processing.
• The Limbic System is located on both sides of the thalamus.
• It is made up of different brain structures.
• The Limbic System's main function is emotions, learning, memory, and some basic drives.
• It includes structures such as the amygdala, hippocampus, and the thalamus.
• The Hypothalamus helps keep your body balanced and allows you to have homeostasis.
• It controls drives such as thirst, hunger, temperature, and sex.
• It works with the pituitary gland to regulate and control hormones.
• The Pituitary Gland is often referenced as the master gland.
• It produces and releases hormones that regulate bodily functions.
• It controls other endocrine glands throughout the body.
• Brain lateralization refers to the differing functions of the left and right hemispheres, dividing labor.
• Each hemisphere has areas in which it is more efficient.
• We all use both hemispheres to accomplish different tasks; no one is simply just right-brained or left-brained.
• Hemispheric Specialization includes the Left Hemisphere recognizing words/letters/interpreting language.
• The Right Hemisphere does Spatial concepts, facial recognition, and discerns direction.

Examining the Brain

• Phineas Gage was a railroad worker who had a tamping rod shot through his head.
• He survived but experienced a severe personality change.
• The rod severed his limbic system, impacting judgment and emotional regulation, which allowed researchers to better understand different brain structures.
• Split-brain patients undergo a procedure that cuts the corpus callosum.
• This disconnects the left and right hemispheres.
• This is done to help treat people with severe epilepsy.
• When the corpus callosum is cut, the right and left hemispheres can no longer communicate.
• Patients do not see any impact or change with their personality or intelligence.
• Researchers test for cortex specialization by showing patients words in their right visual field, so they could say the word.
• Also, when words were shown to the left visual field, the patient would say they did not see anything, yet they could draw the word with their left hand.
• The left hemisphere contains language, Broca's area, and Wernicke's area.
• Lesion Studies involves doctors and researchers destroying brain parts to gain insight into functions.
• Today, this is done to try and treat specific disorders.
• Autopsies are examinations of an individual's body after death to discover the cause of death.
• Allows individuals to better understand the extent of a disease and helps determine the exact cause of death.
• Neuroplasticity is the brain's ability to change, modify itself, and even repair itself.
• It constantly learns new skills, information, and grows, meaning that new neural pathways form with learning.
• Brain damage can result from infections, neurotoxins, genetic factors, head injuries, tumors, or a stroke.
• The more you practice a skill or study information, the more developed the neural pathways become.
• Neuroimaging techniques include the EEG (Electroencephalogram).
• EEG uses electrodes placed on the individual's scalp to record electrical signals from neurons firing and helps with sleep and seizure research.
• Another imaging technique is (fMRI) Functional Magnetic Resonance Imaging, which is similar to an MRI but shows metabolic functions and helps with better understanding brain activity.
• Compared to other scans like a PET scan, it shows a much more detailed picture.

Consciousness and Sleep

• Consciousness is awareness of ourselves and our environment.
• Two types: Wakefulness (awake, aware, can think, feel, and react) and Sleep (lower awareness, not fully aware, but brain still active).
• Cognitive neuroscience studies how brain activity is linked with cognition.
• The circadian rhythm is your biological clock, a 24-hour cycle involving changes in blood pressure, temperature, hormones, and sleep-wake regulation.
• It impacts when we feel alert/awake and sleepy/ready for bed and adjusts with age/life experiences.
• Can become disrupted by working the night shift or traveling across time zones.
• Jet Lag is when your internal clock becomes out of sync with the local time.
• EEGs can visualize different brain waves to understand the different stages of sleep.
• Frequency is the number of waves per second.
• Amplitude is the size of the wave.
• Alpha Waves are slower waves that have a high amplitude.
• Beta Waves are low in amplitude and are the fastest brain waves, generally occurring when we're engaged in mental activities.
• Theta Waves have a greater amplitude compared to Beta and Alpha waves, and even a slower frequency; they are strong during times of relaxation.
• Delta Waves have the greatest amplitude.

Stages of Sleep

• Stages of sleep marked by specific brain waves and physiological events.
• Non-REM Stage 1 has a very light sleep that lasts approximately five to ten minutes.
• The body starts to relax, and the mind begins to slow down.
• Alpha waves are the most common brain waves during this stage.
• Non-REM Stage 2 is a transitional stage typically lasting 10 to 20 minutes.
• It is characterized by K complexes and sleep spindles (bursts of neural activity).
• Theta waves are the most common brain waves during this stage.
• Non-REM Stage 3 is one of the deepest states of sleep, lasting around 30 minutes.
• The Growth hormones are produced during this stage in which sleepwalking or sleep-talking may occur.
• Delta waves are the most common brain waves during this stage.
• REM (Rapid Eye Movement) is the last stage of sleep, characterized by rapid eye movement.
• During REM, external muscles are paralyzed, and internal muscles/structures become active.
• Beta waves are emitted by the brain during this stage, which typically lasts about 10 minutes.
• With Dreams or nightmares potentially occurring, body is at its most relaxed.
• This is considered paradoxical sleep because the brain waves are similar to wakefulness.
• As the sleep cycle progresses, periods of REM sleep become longer and more frequent.
• REM Rebound occurs when an individual is deprived of REM sleep, so they enter REM sleep more quickly & spend more time in REM sleep the next time they sleep.
• Activation Synthesis Theory is the idea that dreams are the brain's way of making sense of random neural activity during sleep.
• During REM sleep, there is brain activity, so the brain tries to create a story or dream to interpret this activity.
• Consolidation Theory is that dreams help process and strengthen memories and experiences during sleep, especially during REM sleep.
• It states that brain organizes and strengthens connections between neurons related to recent experiences and information; focuses on memory consolidation & learning.
• Dreams are a reflection of the brain's effort to process and integrate new information.
• Restoration Theory is that we sleep to restore our energy and resources depleted from daily activities.

Importance of Sleep

• Physical and Mental Restoration; sleep is necessary for physical and mental restoration.
• Protection; a way for individuals to protect themselves; Different animals sleep for varying lengths of time depending on their activity and potential threats.
• Memory Consolidation; strengthens neural pathways, allowing better recall in the future.
• Growth and Energy Conservation: Sleep supports growth and conserves energy; the pituitary gland releases growth hormones, aiding muscle development.
• Creativity; sleep and dreams can enhance creativity.
• Sleep disorders are problems falling or staying asleep.

Sleep Disorders

• Insomnia is a sleep disorder where an individual has trouble falling asleep or staying asleep.
• Caused by stress, pain, medication, or an irregular sleep schedule.
• Sleep Apnea occurs when an individual has difficulty falling asleep or staying asleep due to breathing problems.

Sensation

• Sensation is the process of detecting information from the environment.

Sensory Receptors

• Whenever an outside stimulus is taken through one of the senses, it activates sensory neurons, creating a sensation(Known as sensory transduction).
• In order to experience a sensation, an individual needs to hit the absolute threshold.
• Sensory Adaptation happens when an individual has a stimulus that is continuous and doesn't change.
• Habituation is when an individual is repeatedly exposed to a stimulus and starts to have a reduced response.
• The difference threshold is the minimum change between two stimuli to cause an individual to detect the change.
• Weber's Law states that there must be a constant percentage between stimuli not a set number.

Sensory Interaction

• Happens when an individual is experiencing something, senses take in a variety of information.
• Sensory interaction is when sight, hearing, taste, touch, and smell work together.
• Synesthesia is a neurological condition where one sense is experienced through another.

Visual System

• Light enters through the cornea and passes through the pupil.
• Then, the lens focuses the light onto the retina.
• The retina is made up of photoreceptors.
• This converts the light from the retina captures light and visual information, transduction occurs.
• Information that then travels through the optic nerve from the eye, through the thalamus and then travels to the visual cortex.
• Rods and Cones are two types of photoreceptors that help converts the light.
• Rods are mainly for peripheral vision to see in dim light but do not provide any color vision.
• Cones are located in the fovea that allow to see the fine details, provide clear vision, and help you see color.
• Trichromatic Theory states different wavelengths of light stimulate different color receptor photoreceptors work in teams of three: red, green, and blue.
• The opponent process theory states information received from the cones is sent to ganglion cells causing neurons to be excited and others to be inhibited.
• Colors based on three pairings: red and green, blue and yellow, and black and white.
• Wavelength and amplitude are also influential to colors. Shorter wavelength means higher frequency and cooler colors, while long wavelength means low frequency and warmer colors.
• Accommodation is the eye's ability to change shape to focus light onto the retina.

Visual Disorders

• Myopia Nearsightedness: Light focuses in front of the retina, distant objects appear blurry.
• Hyperopia Farsightedness: Light focuses behind the retina, close objects appear blurry.
• Prosopagnosia is the inability to recognize faces.

Auditory Sensory System

• Sound is a wave in the movement of air molecules.
• Localization is the brain's process of determining where the sounds are coming from.
• The frequency theory dictates frequency of auditory corresponds directly to the frequency of the sound wave.
• A decline in loudness and range of sound occurs to damage to the cochlea.
• An intervention could be a cochlear, which converts sound.

The Chemical Sensory System

• Smell is also converted to electrical signals.
• The nose is then sent to various brain regions which is involved in processing emotions.

Gustation (Taste)

• Six basic tastes: sweet, sour, bitter, salty, umami, oleogustus.
• Chemicals also stimulate sensory neutrons and are sent to the lympthic system.

Touch

• Touch and pain are a sensation that detects harmful stimuli such as temperatures and damage. The gate control then tries to explain how the bodies process.