Unit One Summary - Biological Basis of Behavior
Unit One Summary - Biological Basis of Behavior
Introduction
Welcome to unit one summary of AP Psychology by Mr. Sin, focusing on the intricate biological underpinnings of human behavior.
Focus on biological basis impacting physical and mental actions, exploring how our physiology influences everything from thoughts to emotions and observable actions.
Importance of active learning: Engaging with the material through critical thinking, note-taking, and practice questions is essential for deeper understanding.
Nature vs. Nurture
Discussion of the age-old question: what impacts human behavior more? This debate explores the relative influence of genetic inheritance (nature) and environmental factors (nurture) on human development.
Modern understanding: it’s not just nature or nurture in isolation, but a complex, interactive combination of both, where genes and environment constantly influence each other.
Nature: Refers to heredity; the passing of physical and mental traits from one generation to another through genetic material (DNA).
Nurture: Encompasses environmental factors, including early childhood experiences, family life, social groups, cultural norms, education, and broader societal influences that shape an individual.
Psychological Perspectives on Heredity and Environment
Evolutionary Approach
Based on Charles Darwin’s theory of evolution by natural selection; this perspective leans heavily toward the influence of nature in explaining universal human behaviors and traits.
Natural selection: A process where beneficial traits that increase an organism's survival and reproductive success in a particular environment are more likely to be passed on to subsequent generations, leading to adaptive changes over time.
Controversies: The misuse of evolutionary principles has historically led to problematic practices such as eugenics, the belief in improving the human population through selective breeding, which has severe ethical implications.
Epigenetics
Explores how environmental factors can affect gene expression, turning genes on or off, without altering the underlying DNA sequence itself.
Genes can be turned on or off without changing the DNA sequence through mechanisms like DNA methylation and histone modification.
Example: The Minnesota Study of Twins Reared Apart, which provided valuable insights into the genetic versus environmental influences on a wide range of psychological traits by comparing identical and fraternal twins raised separately.
Plasticity
Refers to the brain’s remarkable ability to change and adapt structurally and functionally throughout life due to experiences, learning, and even injury.
Involves strengthening or weakening existing neural connections (synaptic plasticity) and, in some cases, the creation of new neurons (neurogenesis).
Nervous System Overview
Differentiate between Central Nervous System (CNS) and Peripheral Nervous System (PNS), the two main divisions that coordinate all bodily functions.
Central Nervous System (CNS)
Comprises the brain and spinal cord, serving as the command center that processes information and sends orders to the rest of the body.
Peripheral Nervous System (PNS)
Consists of nerves branching out from the brain and spinal cord, connecting the CNS to organs, muscles, and glands throughout the body, enabling communication between the CNS and the external environment.
Types of nerves in the system:
Afferent Neurons (Sensory Neurons): Transmit sensory signals to the CNS from sensory receptors in the body (e.g., touch, sight, sound).
Efferent Neurons (Motor Neurons): Transmit motor signals from the CNS to muscles and glands, initiating movement and glandular secretions.
Divisions of the Peripheral Nervous System
Somatic Nervous System: Controls voluntary movements of skeletal muscles and processes sensory information from the five senses (sight, hearing, touch, taste, smell).
Autonomic Nervous System: Regulates involuntary internal bodily activities such as heart rate, digestion, respiration, and gland secretion, operating largely without conscious control.
Sympathetic Division: Activates the body’s "fight or flight" response, preparing it for action by increasing heart rate, dilating pupils, inhibiting digestion, and releasing stress hormones.
Parasympathetic Division: Promotes "rest and digest" functions, returning the body to a calm state by slowing heart rate, constricting pupils, stimulating digestion, and conserving energy.
Neurons and Neural Communication
Two types of cells in the nervous system essential for its function:
Glial Cells: Support neurons by providing nutrients, insulating axons (myelin sheath), removing waste products, and maintaining the chemical environment; they do not transmit information directly.
Neurons: The fundamental functional units of the nervous system, specialized to transmit information rapidly using electrical impulses and chemical signals through their distinct structures: dendrites, soma (cell body), axon, and terminal buttons.
Reflex Arc
A direct connection among sensory neurons, interneurons (in the spinal cord), and motor neurons that allows for a rapid, involuntary response to stimuli without requiring processing by the brain.
Example: Pulling a hand back instinctively from a hot surface involves a reflex arc where sensory neurons detect heat, signals are relayed to motor neurons via interneurons in the spinal cord, causing muscle contraction before the brain consciously perceives the pain.
Neural Transmission Process
Action Potential: An electrochemical impulse that travels down the axon of a neuron when the level of excitatory stimulation exceeds a specific threshold, causing the neuron to "fire."
Resting potential: The neuron's dormant state, where the inside of the axon is more negatively charged compared to the outside (approximately millivolts), maintained by the sodium-potassium pump that expels three ions for every two ions brought in.
Depolarization: Occurs when a stimulus reaches the threshold, causing voltage-gated channels to open, allowing a rapid influx of positively charged ions into the cell, making the inside less negative and eventually positive.
Repolarization: Following depolarization, voltage-gated channels close, and voltage-gated channels open, allowing positively charged ions to flow out of the cell, restoring the negative charge inside the neuron.
Refractory Period: A brief period immediately after an action potential during which the neuron cannot fire another action potential, ensuring that the impulse travels in one direction and preventing overstimulation; the pump actively restores the ion balance.
Chemical Communication
Synapse: The microscopic gap between the axon terminal of one neuron (presynaptic neuron) and the dendrite or cell body of another neuron (postsynaptic neuron), where chemical communication occurs.
Chemical Synapses: Utilize neurotransmitters, chemical messengers, to send signals across the synaptic gap. When an action potential reaches the axon terminal, it triggers the release of neurotransmitters into the synapse, which then bind to receptors on the postsynaptic neuron.
Neurotransmitters: Chemical messengers with specific functions, released from the presynaptic neuron into the synaptic cleft, and then binding to receptors on the postsynaptic neuron to excite or inhibit it:
Acetylcholine (ACh): Involved in muscle action (at neuromuscular junctions), learning, and memory. Deficiencies are linked to Alzheimer's disease.
Dopamine (DA): Influences movement, attention, motivation, and emotion. Imbalances are associated with Parkinson's disease (low levels) and schizophrenia (high levels).
Serotonin (5-HT): Affects mood, hunger, sleep, and arousal. Low levels are implicated in depression and anxiety disorders.
Endorphins: Natural opioid-like neurotransmitters that reduce pain and produce feelings of pleasure and well-being.
Epinephrine/Norepinephrine: Both act as hormones and neurotransmitters. Epinephrine (adrenaline) is primarily involved in energy and stress response. Norepinephrine (noradrenaline) influences alertness, arousal, and vigilance, often associated with the "fight or flight" response.
GABA (Gamma-aminobutyric acid): The primary inhibitory neurotransmitter in the brain, reducing neural excitability and promoting relaxation, important for sleep and movement regulation. Imbalances can lead to anxiety disorders.
Glutamate: The primary excitatory neurotransmitter in the brain, crucial for learning and memory formation. Excess levels can be associated with neurodegenerative diseases.
- **Psychoactive Drugs**
- **Agonist**: A substance (drug or chemical) that binds to a receptor and mimics or enhances the effects of a natural neurotransmitter, increasing its effectiveness.
- Examples: Xanax (enhances GABA's inhibitory effects to reduce anxiety), Prozac (an SSRI that increases serotonin availability by blocking reuptake), opioids (mimic endorphins to reduce pain).
- **Antagonist**: A substance that binds to a receptor but blocks or inhibits the effects of a neurotransmitter, decreasing its effectiveness.
- Examples: Many antipsychotic medications for schizophrenia (block dopamine receptors to reduce symptoms associated with excess dopamine), alcohol (acts as a GABA agonist but also an NMDA glutamate receptor antagonist, contributing to impaired judgment and memory).
Brain Structure and Function
Regions of the Brain
Hindbrain: The oldest part of the brain, located at the base of the skull, responsible for basic life-sustaining functions. Includes the medulla (controls heartbeat, breathing, blood pressure), pons (connects hindbrain and midbrain, involved in sleep and arousal), and cerebellum (coordinates voluntary movement, balance, and motor learning).
Midbrain: Situated above the hindbrain, involved in auditory and visual processing, as well as voluntary movement control. Contains structures like the tectum (visual and auditory reflexes) and tegmentum (involved in movement and arousal).
Forebrain: The largest and most complex part of the brain, responsible for sophisticated thought processes, emotions, and voluntary actions. Comprises the cerebrum, thalamus, and the limbic system.
Structure Features: The cerebrum is divided into four lobes, each with specialized functions.
Frontal Lobe: Located at the front of the brain, responsible for higher reasoning, planning, decision-making (prefrontal cortex), personality, voluntary motor control (motor cortex), and language production (Broca's area).
Parietal Lobe: Situated behind the frontal lobe, processes sensory information from the body, including touch, temperature, pain, and pressure (somatosensory cortex), and is involved in spatial awareness.
Temporal Lobe: Located below the parietal lobe, crucial for auditory processing (auditory cortex), memory formation (housing the hippocampus), and language comprehension (Wernicke's area).
Occipital Lobe: Positioned at the back of the brain, primarily responsible for visual processing (visual cortex), interpreting color, form, and motion.
Corpus Callosum: A thick band of neural fibers connecting the left and right cerebral hemispheres, facilitating rapid communication and information exchange between them.
Limbic System: A set of brain structures located beneath the cortex, crucial for emotion, motivation, and memory. Key components include:
Hippocampus: Essential for the formation of new long-term memories.
Amygdala: Involved in processing emotions, particularly fear and aggression.
Hypothalamus: Regulates basic drives like hunger, thirst, sex, and controls the pituitary gland, acting as a link between the nervous and endocrine systems.
Neuroimaging and Studies
Phineas Gage: A famous case study from the 19th century where severe brain injury (a metal rod through his frontal lobe, specifically the prefrontal cortex) led to drastic changes in personality and behavior, highlighting the brain's role in executive functions and emotional regulation.
Split-Brain Research: Studies pioneered by Roger Sperry and Michael Gazzaniga involving patients whose corpus callosum had been severed (often to treat severe epilepsy). This research revealed the specialization of the left hemisphere (typically language, logic) and the right hemisphere (spatial reasoning, facial recognition) and how they process information independently.
Language processing is typically localized in the left hemisphere for most right-handed individuals, meaning split-brain patients could verbally identify objects only if seen in their right visual field (processed by the left hemisphere).
Lesion Studies: Involve intentionally damaging (ablating) specific brain regions in animals to observe the resulting behavioral or cognitive deficits, thereby inferring the function of that region. Autopsies are used to examine brain damage in humans posthumously, often to understand the neurological basis of diseases and disorders.
Neuroplasticity
The remarkable ability of the brain to continuously change its structure and function throughout life in response to learning, experience, environmental influences, and even injury.
Influencing factors: Learning new skills leads to stronger neural connections; recovery from brain injury often involves re-routing pathways; and environmental enrichment can promote neurogenesis (growth of new neurons) in certain areas.
Sleep and Consciousness
Types of consciousness: Encompasses various states of awareness, ranging from full wakefulness to different stages of sleep.
Circadian Rhythm: The body's natural, internal biological clock that regulates various physiological processes, including the sleep/wake cycle, over approximately a -hour period. It is primarily regulated by the suprachiasmatic nucleus (SCN) in the hypothalamus, which responds to light cues and influences melatonin production.
Sleep stages: Classified into Non-REM (NREM) stages and REM sleep, characterized by distinct brain wave patterns and physiological activities.
Non-REM stages (1-3) and REM sleep:
NREM Stage 1 (N1): Light sleep, characterized by theta waves; includes hypnagogic sensations (brief, dream-like hallucinations or jerks).
NREM Stage 2 (N2): Deeper sleep, characterized by sleep spindles (bursts of brain activity) and K-complexes (high-amplitude brain waves); muscles relax, heart rate slows.
NREM Stage 3 (N3): Deepest sleep (slow-wave sleep), characterized by delta waves; essential for physical restoration and growth.
REM sleep (Rapid Eye Movement): Characterized by rapid eye movements, muscle paralysis (paradoxical sleep), vivid dreaming, and brain activity resembling wakefulness. Importance of REM for memory consolidation, learning, and emotional processing.
Sleep Disorders
Insomnia: Persistent difficulty falling asleep, staying asleep, or experiencing non-restorative sleep, leading to fatigue and impaired functioning.
Sleep Apnea: A serious condition where a person repeatedly stops breathing during sleep, often leading to snoring, gasping, and fragmented sleep.
REM Sleep Behavior Disorder: A neurological disorder where the normal muscle paralysis during REM sleep is absent or incomplete, causing individuals to physically act out their vivid dreams.
Somnambulism (Sleepwalking): A parasomnia where a person walks or performs other complex behaviors while still asleep, more prevalent in children and typically occurs during NREM stage 3 sleep.
Night Terrors: Episodes of intense fear, screaming, and thrashing during NREM stage 3 sleep, often accompanied by physiological symptoms like sweating and rapid heart rate, but with no recollection of a dream upon waking.
Narcolepsy: A chronic neurological condition characterized by uncontrollable episodes of sudden, overwhelming sleepiness during the day, often accompanied by cataplexy (sudden loss of muscle tone triggered by strong emotions).
Sensation Overview
Sensation vs. Perception
Sensation: The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment, involving the initial detection of physical stimuli.
Perception: The process of organizing and interpreting sensory inputs, enabling us to recognize meaningful objects and events.
Absolute Threshold: The minimum stimulation needed for an individual to detect a particular stimulus of the time. It marks the boundary between detectable and undetectable sensation.
Difference Threshold (Just Noticeable Difference - JND): The minimum change in a stimulus required for an individual to detect a difference between two stimuli of the time.
Weber’s Law: States that for an average person to perceive a difference, two stimuli must differ by a constant minimum percentage or constant ratio, rather than a constant amount. Mathematically expressed as , where is the difference threshold, is the original stimulus intensity, and is a constant.
Sensory Systems
Visual System: The process of light perception through the eye, where light energy is transduced into neural signals.
Role of rods and cones in vision: Rods detect light and dark, crucial for peripheral vision and dim light. Cones detect color and fine detail, concentrated in the fovea for sharp central vision. Color vision theories include the Trichromatic Theory (explaining color perception based on three types of cones sensitive to red, green, and blue light) and the Opponent-Process Theory (explaining afterimages and color pairs like red-green, blue-yellow, black-white).
Auditory System: The process of perceiving sound waves.
Sound wave properties: Frequency (pitch, measured in Hertz, ) and amplitude (loudness, measured in decibels, ). Theories of pitch perception include the Place Theory (high pitches detected by specific locations on the cochlea's basilar membrane), Frequency Theory (pitch related to the frequency of neural impulses), and Volley Theory (neural cells alternate firing to sense pitches above Hz).
Chemical Senses (smell and taste)
Olfactory processing: Odor molecules bind to receptors in the olfactory epithelium, sending signals directly to the olfactory bulb and then to the brain. Pheromones are chemical signals that can influence behavior in other individuals of the same species.
Gustation and taste bud functionality: Taste (gustation) involves taste buds located on the tongue that detect five basic tastes: sweet, sour, salty, bitter, and umami. Each taste bud contains receptors for these chemical stimuli.
Touch & Pain System
Skin receptors (mechanoreceptors, thermoreceptors, nociceptors) respond to various stimuli like pressure, temperature, and pain. The Gate Control Theory of Pain proposes that a 'gate' in the spinal cord can open or close to either transmit pain signals to the brain or block them, influenced by psychological factors and other sensory input.
Balance and Movement
Role of vestibular sense (inner ear structures like semicircular canals and otolith organs) in maintaining balance and spatial orientation. Kinesthesis (proprioception) is the sense of body position and movement of body parts, provided by receptors in muscles, joints, and tendons.
Conclusion
Review unit 1 materials using the ultimate review packet for practice quizzes and additional resources to reinforce understanding of the biological basis of behavior.