Biological Bases of Behavior

Unit 1: Biological Bases of Behavior

Module 1.1: Interaction of Heredity and Environment

  • Psychology

    • Definition: The science of behavior and mental processes.

    • Behavior: Anything an organism does.

    • Mental Process: Internal subjective experiences.

    • Biological Underpinning: Everything psychological is biological; every thought, mood, and action stems from an internal biological event.

Nature vs. Nurture

  • Nature-Nurture Issue: This is considered the most significant and enduring issue in psychology, focusing on the relative contributions of genes (nature) and experience (nurture) in developing psychological traits and behaviors.

    • Modern psychologists view traits and behaviors as a product of the interaction between hereditary and environmental factors.

    • Natural Selection (Charles Darwin):

    • Principle that inherited traits that aid an organism's survival and reproduction in a given environment are likely to be passed down to future generations.

    • The theory has been misapplied in the 20th century to support eugenics and discriminatory practices.

  • Evolutionary Psychology:

    • Focuses on the evolution of behavior and mind through the lens of natural selection, studying the similarities among humans.

  • Behavior Genetics:

    • Examines the relative impact of genetic and environmental influences on behavior, highlighting human differences.

  • Interplay of Nature and Nurture:

    • Concept that nurture works on what nature provides, where biological predispositions can be further influenced by environmental factors (e.g., predisposition to depression combined with environmental stressors such as poverty).

Evolutionary Psychology

  • Evolutionary Psychology Principles:

    • Offspring compete for survival based on various biological and behavioral traits.

    • Variations that enhance reproductive and survival prospects are more likely to be passed on to future generations, leading to gradual changes in population characteristics.

Evolution and Natural Selection Experiment

  • Dmitry Belyaev's Experiment:

    • Mating of 100 female foxes and 30 male foxes; the tamest 20% of offspring were selected for breeding over 40 years, resulting in a new breed of tamer foxes.

Evolution

  • Mutation: A random error in gene replication that results in a genetic change.

    • Positive mutations are more likely to be passed on to the next generation.

  • Genes: Provide adaptation capabilities to new environments; interconnectedness of genes and experiences enhances fitness (the ability to survive and reproduce).

  • Genetic Variation:

    • 95% of genetic variation occurs within populations, rather than between them.

    • Difference between individuals within a population can be greater than between populations.

Behavior Genetics

  • Behavioral Genetics:

    • Studies the genetic and environmental roots of human differences.

    • Environment: Any non-genetic influence, including prenatal nutrition and personal experiences.

    • Heredity: Genetic transmission of traits from parents to offspring, primarily represented by genes.

    • Genome: Complete set of instructions for making an organism, with 96% genetic similarity to chimpanzees.

    • Key Point: Differing traits are influenced by many genes, each with a small effect.

Gene-Environment Interaction

  • Interaction: The effect of one factor (e.g., environment) depends on another factor (e.g., heredity).

  • Epigenetics:

    • Study of how environmental factors can influence genetic expression without altering DNA (e.g., trauma effects in Holocaust survivors).

Module 1.2: The Nervous System

  • Nervous System Function: The body's rapid electrochemical communication network, encompassing the entire peripheral and central nervous systems.

    • Central Nervous System (CNS): Comprises the brain and spinal cord.

    • Peripheral Nervous System (PNS): Includes sensory and motor neurons connecting CNS to the rest of the body.

Types of Neurons

  • Information transmits through three types of neurons:

    • Sensory (Afferent) Neurons: Carry incoming information to the brain and spinal cord from sensory receptors.

    • Motor (Efferent) Neurons: Carry outgoing information from the brain and spinal cord to muscles and glands, facilitating movement.

    • Interneurons: Neurons that act within the CNS, processing information internally.

Peripheral Nervous System Components

  • Somatic Nervous System: Controls voluntary skeletal muscles.

  • Autonomic Nervous System (ANS): Controls involuntary activities; composed of:

    • Sympathetic Nervous System: Activates the body’s fight-or-flight response.

    • Parasympathetic Nervous System: Calms the body and conserves energy.

Central Nervous System

  • Spinal Cord Functions:

    • Serves as the information highway connecting PNS and the brain.

    • Ascending fibers relay sensory information; descending fibers relay motor control.

    • Reflex: An automatic response requiring no brain involvement (e.g., knee-jerk response due to sensory neurons triggering motor neurons directly).

Module 1.3: The Neuron and Neural Firing

  • Neurons: Basic building blocks of nervous tissue that facilitate information transmission.

    • Consist of a cell body, dendrites, and an axon, with the axon often covered by a myelin sheath that enhances transmission speed.

Synapse and Neurotransmitters

  • Synapse: The junction between sending (axon tip) and receiving neurons (dendrite or cell body).

  • Axon Terminal: End of an axon where neurotransmitters are released.

  • Glial Cells: Support, nourish, and protect neurons and aid in memory and learning.

Neural Impulse

  • Action Potential: A neural impulse; a brief electrical charge that travels down the axon and triggers neurotransmitter release.

    • Neurons communicate internally through electrical signals and chemically via neurotransmitters.

Resting Potential

  • When inactive, a neuron has a negatively charged interior compared to a positively charged exterior. Upon stimulation, depolarization occurs if excitatory signals exceed inhibitory ones, potentially reaching a threshold to trigger an action potential.

Refractory Period

  • A temporary period following an action potential where further firing cannot occur until the neuron returns to resting potential.

    • All-or-None Response: Neurons fire either at full strength or not at all, with stimulus strength influencing how many neurons fire, not the intensity of each firing.

Communication Across Neurons

  • The synapse is the gap where neurotransmitters are released and bind to receptor sites on the receiving neuron.

  • Excess neurotransmitters can dissipate or be reabsorbed (reuptake).

Major Neurotransmitters

  • Acetylcholine (ACh): Involved in muscle action and memory; deficits linked to Alzheimer's.

  • Dopamine: Regulates movement and emotion; imbalances linked to schizophrenia and Parkinson's.

  • Serotonin: Influences mood and appetite; low levels associated with depression.

  • Norepinephrine: Functions in alertness; imbalances can lead to mood disorders.

  • GABA: Major inhibitory transmitter; implicated in anxiety.

  • Glutamate: Major excitatory neurotransmitter; involved in cognitive functions.

  • Endorphins: Natural painkillers; excessive opiate use may lead to decreased endorphin production.

  • Substance P: Key role in transmitting pain signals.

Drugs and Their Effects on Neurotransmitters

  • Agonist: Enhances neurotransmitter function (e.g., cocaine for dopamine).

  • Antagonist: Blocks neurotransmitter function (e.g., Botox for acetylcholine).

The Endocrine System

  • Endocrine System: The body's slower chemical communication system, comprising various glands that secrete hormones into the bloodstream.

    • Hormones: Slow-acting yet enduring chemical messengers.

    • Pituitary Gland: Known as the master gland, secreting most hormonal signals.

Sleep-Related Bellringer

  1. Describe how neural communication facilitates quick responses.

  2. Explain endocrine system's role in sustaining alertness.

  3. Contrast neural versus endocrine signaling.

Module 1.4: The Brain

  • Franz Gall: Proposed phrenology, linking skull features with personality traits.

    • Though non-scientific, it promoted the idea of functional localization in the brain.

  • Neuroplasticity: The brain's adaptive capabilities to reorganize and develop new pathways based on experience, especially during early life or after injury.

Brain Imaging Techniques

  • CT/CAT Scan: Provides structural brain images using X-rays.

  • MRI: Produces detailed images of brain anatomy using magnetic fields.

  • EEG: Records electrical activity on the brain's surface.

  • MEG: Measures magnetic fields from brain activity.

  • PET Scan: Tracks brain activity by observing glucose flow.

  • fMRI: Monitors brain blood flow and activity during various tasks.

Brain Structures

  • Hindbrain: Includes structures for survival functions and coordination.

  • Midbrain: Connects hindbrain and forebrain; manages motor functions.

  • Forebrain: Involves the cerebral cortex and surrounding areas for complex functions.

  • Brainstem: Controls automatic survival functions (heartbeat, breathing).

Cerebellum

  • Maintains coordination, balance, and nonverbal learning.

Limbic System Components

  • Amygdala: Emotion processing (fear, aggression).

  • Hypothalamus: Regulates homeostatic functions & governs the endocrine system.

  • Hippocampus: Facilitates formation of explicit memories.

Cerebral Cortex

  • Composed of the cerebral hemispheres, facilitating sensory processing and high-level cognitive tasks.

    • Lobes: Frontal (decision making), Parietal (sensor integration), Occipital (vision), Temporal (hearing and memory).

Neuroplasticity and Recovery

  • Unused brain areas can be repurposed for other functions post-injury.

  • Neurogenesis: Creation of new neurons from stem cells.

The Divided Brain

  • Lateralization: Each hemisphere specializes in particular functions; the left hemisphere controls the right body side and vice versa.

  • Corpus Callosum: Facilitates communication between hemispheres; severed in split-brain patients.

The Split Brain Effect

  • Post-surgery, patients show inability to recognize stimuli processed in one visual field and can perform tasks independently with each hand.

Learning and Memory Review

  • Frontal: Planning; Parietal: Sensory; Temporal: Auditory; Occipital: Visual; Cerebellum: Movement; Brainstem: Life functions.

Module 1.5: Sleep

  • Consciousness: Awareness of oneself and surroundings, crucial for setting and achieving goals.

  • Cognitive Neuroscience: Studies brain activity related to cognitive function.

Sleep Dynamics

  • Sleep: Natural periodic loss of consciousness; involves different sleep stages.

  • Circadian Rhythm: 24-hour biological clock; variations occur with age.

Sleep Stages

  • NREM Sleep: Non-rapid eye movement sleep, includes distinct stages:

    • STAGE 1: Light sleep with hallucinations.

    • STAGE 2: Deeper sleep with sleep spindles.

    • STAGE 3: Deep sleep with delta waves.

  • REM Sleep: Characterized by vivid dreams and muscle relaxation.

Effects on Sleep Patterns

  • Genetic and environmental interactions influence sleep cycles.

  • SCN: Hypothalamus component regulating circadian rhythms through light exposure.

Sleep Functions

  • Protection, body and brain restoration, memory consolidation, creativity enhancement, and growth hormone secretion during deep sleep.

Sleep Deprivation Consequences

  • Mood changes, academic decline, weight gain, immune suppression, slowed reaction times.

Dreams

  • Sequences of perceptions, thoughts, and emotions during sleep.

    • Theories: Information Processing, Activation Synthesis, Physiological Function, Cognitive Development.

Module 1.6: Sensation

  • Sensation: Reception of stimuli through sensory receptors and representation in the nervous system.

  • Perception: Brain's organization and interpretation of sensory input, facilitating object recognition.

Processing Sensation and Perception

  • Bottom-Up Processing: Begins with sensory receptors, integrating sensory info.

    • Example: Detecting lines and colors to form an image.

  • Top-Down Processing: Guided by higher mental processes, relying on experience and expectations.

Transduction and Thresholds

  • Transduction: Process of converting physical energy into neural impulses.

  • Absolute Threshold: The minimum stimulus energy to detect a stimulus 50% of the time.

    • Difference Threshold: Minimum difference between stimuli required to detect a difference.

Adaptation

  • Sensory Adaptation: The reduced sensitivity due to constant stimulation, allowing focus on significant stimuli.

Vision

  • Light Energy: The stimulus for vision; wavelength influences hue and intensity, which affects brightness perception.

  • Eye Anatomy: Includes the cornea, pupil, iris, lens, and retina, where photoreceptors (rods and cones) convert light into neural signals.

Color Processing

  • Young-Helmholtz Trichromatic Theory: Color perception involves three receptor types sensitive to red, green, and blue wavelengths.

  • Opponent-Process Theory: Suggests color perception is mediated by opposing retinal processes, explains afterimages.

Hearing

  • Audition: The sense of hearing, which involves sound wave vibration causing eardrum movement, transmitted through the middle ear to the inner ear (cochlea).

  • Hearing Loss: Results from damage to hair cells or auditory nerve; cochlear implants can assist recovery in cases of sensorineural hearing loss.

Touch and Pain

  • Touch: Tactile sensations including pressure, warmth, cold, and pain.

  • Pain: Signals bodily harm; involves both biological (e.g., gate-control theory) and psychological factors (e.g., focus and memory of past pain).

Taste

  • Gustation: Involves six basic tastes with evolutionary implications, reflecting nutritional value.

  • Taste Perception: Influenced by presentation, aroma, and personal expectation.

Smell

  • Olfaction: The sense of smell; has direct neural pathways bypassing the thalamus, highlighting its primal importance.

Sensory Interaction and Synesthesia

  • Sensory Interaction: One sense can alter perceptions of another (e.g., taste influenced by smell).

  • Embodied Cognition: Body sensations and gestures can influence cognitive judgments.

  • Synesthesia: One sense triggering experiences in another (e.g., seeing colors while hearing music).