Biological Bases of Behavior Notes

Biological Bases of Behavior

  • Understanding human behavior requires a science-driven approach that links psychology to biological processes.
  • The debate between nature (heredity) and nurture (environment) shapes human behavior.
  • Today, behavior is viewed as a result of "Nature VIA Nurture."
  • Nurture modifies the expressions of natural predispositions.
  • Natural Selection: Inherited traits that enable survival and reproduction are passed to future generations, conferring adaptive advantages.
  • Evolutionary Psychology: Views behavior in terms of shared, unconscious principles allowing for survival and reproduction, best observed in large populations over time.
  • Behavioral Genetics: Studies the interplay of genetics and environmental influences on behavior, highlighting how both contribute to individual differences.

Genetics and Environmental Interplay

  • Genomes: Complete instructions for creating an organism.
  • Chromosomes: Structures made of DNA that contain genes. Each human has 46 chromosomes (23 from each parent).
  • DNA: Coiled chains of molecules that contain genetic information.
  • Genes: The data that forms DNA, which can be expressed or inactive depending on environmental influences.
  • Epigenetics: Examines how environmental factors influence gene expression without altering DNA itself.

Twins and Behavioral Studies

  • Identical Twins (Monozygotic): Develop from a single fertilized egg and share 100% of their genes.
  • Fraternal Twins (Dizygotic): Develop from two separate fertilized eggs and share about 50% of their genes, similar to regular siblings.
  • Studies show that identical twins often exhibit similar behaviors, even if raised apart, indicating the role genetics play in personality.
  • Separation Studies: Identical twins adopted into different environments still share many behavioral traits when reunited, emphasizing the influence of both genetics and environment.

Influences on Human Development

  • Biological Influences: Shared genetic makeup and individual variations affect behavior.
  • Psychological Influences: Early experiences and interactions shape perceptions and behavior.
  • Social-Cultural Influences: Family dynamics, peer interactions, and societal norms contribute to behavior development.
  • The biopsychosocial approach combines these perspectives for a holistic view of behavior.

Nervous System and Communication

  • The Nervous System is the body's fast, electrochemical communication network, which includes:
    • Central Nervous System (CNS): Composed of the brain and spinal cord.
    • Peripheral Nervous System (PNS): Links the CNS to the rest of the body.
    • Somatic Nervous System: Controls voluntary movements.
    • Autonomic Nervous System: Manages involuntary functions (heartbeat, digestion).
    • Sympathetic Nervous System: Activates the body's fight or flight response.
    • Parasympathetic Nervous System: Calms the body after the stress response.

Neurons and Neural Communication

  • Neurons: The fundamental units of the nervous system that transmit information.
    • Sensory Neurons: Carry messages from sensory receptors to CNS.
    • Motor Neurons: Carry orders from CNS to muscles and glands.
    • Interneurons: Communicate between sensory and motor neurons.
  • Messages travel through neurons as electrical impulses (action potentials) and across synapses as chemical neurotransmitters.
  • Neural Networks: Neurons cluster into networks that work together to process information and respond to stimuli.

Neurotransmitters and Drugs

  • Neurotransmitters: Chemicals that transmit signals across synapses.
  • Agonists: Mimic neurotransmitters and stimulate responses (e.g., morphine mimicking endorphins).
  • Antagonists: Block receptor sites and inhibit responses (e.g., certain poisons).
  • Major neurotransmitters connected to human behavior include:
    • Dopamine & Cocaine: Both influence pleasure and reward.
    • Serotonin & Drugs: LSD and Ecstasy act as agonists.
    • Endorphins: Natural pain relievers, affected by opioids.

Endocrine System

  • The Endocrine System: A slower chemical communication system via hormones.
  • Key Glands:
    • Pituitary Gland: Master gland, influenced by hypothalamus, secreting growth hormone and oxytocin.
    • Adrenal Glands: Produce adrenaline and other hormones during stress.

Psychoactive Drugs

  • Psychoactive drugs alter perception and mood by influencing neurotransmitter activity.
  • Classified into three categories:
    • Depressants: Slow neural activity (e.g., alcohol, opioids).
    • Stimulants: Increased neural activity (e.g., nicotine, cocaine).
    • Hallucinogens: Distort perceptions (e.g., LSD, marijuana).

The Brain and Its Functionality

  • Phrenology: Early study linking skull structure and mental abilities, debunked but sparked interest in brain functionality.
  • Case Studies: Investigations of brain damage effects on behavior (e.g., Phineas Gage).
  • Biological Psychology: Examines the links between biological processes and psychology.

Brain Imaging Techniques

  • EEG: Monitors electrical activity in the brain.
  • MRI: Produces images of brain structure.
  • fMRI: Measures brain activity by blood flow to areas of high neural activity.

Neuroplasticity

  • The brain’s ability to change and reorganize itself in response to injury or experience, critical for recovery and learning.

Sensing and Perception

  • Sensation vs. Perception:
    • Sensation: Transmitting stimuli to the brain.
    • Perception: Interpreting sensory information.
  • Transduction: The conversion of sensory stimuli into neural impulses.
  • Thresholds:
    • Absolute Threshold: Minimum stimulation needed to detect a stimulus.
    • Difference Threshold: Minimum difference detectable between two stimuli.

Pain and Touch

  • Pain is vital for survival.
  • Gate Control Theory explains how pain signals are regulated.
  • Psychological factors influence the perception of pain, such as attention and expectations.

Taste and Smell

  • Taste (Gustation): Influenced by taste buds and chemical processes.
  • Smell (Olfaction): Managed through receptor cells in the nasal cavity, directly linked to memory.
  • Experience shapes taste and smell preferences, highlighting their emotional significance.