2.1 Interaction of Heredity and Environment

Key Concepts

• Heredity: Passing on of physical and mental traits from one generation to the next.

• Environment: External factors influencing an individual's traits and behaviors.

Important Figures and Contributions

• Charles Darwin:

  • Theory of Evolution: Evolution happens through natural selection.

  • Natural Selection: Beneficial traits are passed on, while undesirable traits die off.

Heritability

• Definition: Mathematical measure estimating how much variation in a population is due to genetics.

  • Scale: 0 to 1 (e.g., 0.6 means 60% genetic influence and 40% environmental).

Nature vs. Nurture Debate

• Nature (Genetics, Biology, Heredity):

  • Genetics determine individual traits.

  • Supported by Charles Darwin and Evolutionary Psychology.

• Nurture (Environment):

  • Environment shapes an individual's development.

  • Factors include upbringing, education, wealth, and social influences.

Epigenetics

• Definition: Study of how environment and behavior affect gene expression.

  • Mechanism: Environment can turn genes on or off without changing DNA sequence.

  • Example: Sustained environmental pressure influencing genetic expression.

Reciprocal Determinism

• Definition: Environment, individual behavior, and personal beliefs/feelings all influence each other.

2.2 The Endocrine System

Overview

• Endocrine System: Glands producing hormones to regulate biological processes.

• Nervous System vs. Endocrine System:

  • Nervous System: Neurons deliver localized, fast, and short-lived messages.

  • Endocrine System: Glands produce hormones targeting broad areas of the body; slower and long-lasting.

Concept: Homeostasis

• Definition: Body's ability to maintain internal stability (e.g., body temperature).

Glands and Hormones

• Hypothalamus:

  • Function: Controls the pituitary gland and directs autonomic functions.

  • Hormones: CRH, TRH

• Pituitary Gland (Master Gland):

  • Function: Communicates with other glands to regulate hormones.

  • Hormones: Growth hormones, Oxytocin, Vasopressin

• Pineal Gland:

  • Function: Regulates sleep cycles.

  • Hormone: Melatonin

• Thyroid and Parathyroid Glands:

  • Function: Regulate metabolism, growth, and calcium levels.

  • Hormones: Thyroid hormones, Parathyroid hormones, Calcitonin

• Adrenal Glands:

  • Function: Regulate salt levels, blood pressure, and oxygen intake.

  • Hormones: Norepinephrine, Epinephrine, Aldosterone

• Pancreas:

  • Function: Regulates blood sugar levels.

  • Hormones: Insulin, Glucagon

• Gonads (Ovaries/Testes):

  • Function: Enable reproduction.

  • Hormones: Testosterone, Estrogen, Progesterone

2.3 Overview of the Nervous System and the Neuron

Nervous System Structure

• Central Nervous System (CNS): Brain and spinal cord.

  • Sends out orders to the body.

• Peripheral Nervous System (PNS): Nerves branching off brain and spine.

  • Communicates between CNS and body.

  • Divisions:

    • Sensory (Afferent): Conducts impulses from stimuli to CNS.

    • Motor (Efferent): Sends signals from CNS to muscles/glands.

Motor Division

• Somatic Nervous System: Voluntary movements (e.g., skeletal muscle movement).

• Autonomic Nervous System: Involuntary activities (e.g., heartbeat, digestion).

  • Sympathetic Division: Mobilizes body for action (fight or flight).

  • Parasympathetic Division: Relaxes the body (rest and digest).

Neurons and Glial Cells

• Neurons: Basic functional unit of the nervous system, responsible for sending signals.

  • Parts:

    • Dendrites, Cell Body (Soma), Axon, Myelin Sheath, Axon Terminal

• Glial Cells: Support neurons with nutrients and structural support.

Neuron Types

• Afferent Neurons (Sensory): Send signals to the brain and spinal cord.

• Efferent Neurons (Motor): Send signals from the brain and spinal cord to the body.

2.4 Neural Firing

Key Concepts

• Action Potential: Electrical impulse that travels down the axon.

• Resting Potential: More negative ions inside the neuron than outside.

• Depolarization: Triggered when stimulus meets threshold, causing neuron to fire.

• Repolarization: Process of returning neuron to resting potential after firing.

• Refractory Period: Period during repolarization when the neuron cannot fire again.

Synaptic Transmission

• Synapse: Space between the axon terminal of one neuron and the dendrite of another.

• Chemical Synapses:

  • Neurotransmitters: Chemical messengers.

  • Reuptake: Presynaptic neuron reabsorbs extra neurotransmitters.

Types of Neurotransmitters

• Acetylcholine (ACh): Enables muscle action, learning, and memory.

• Dopamine: Movement, learning, attention, and emotion.

• Serotonin: Hunger, sleep, arousal, and mood.

• Endorphins: Pain control and tolerance.

• Epinephrine: Emotional response and memory.

• Norepinephrine: Increases blood pressure, heart rate, and alertness.

• Glutamate: Long-term memory and learning.

• GABA: Sleep, movement, and slows nervous system.

Excitatory vs. Inhibitory Neurotransmitters

• Excitatory: Increase likelihood of action potential.

• Inhibitory: Decrease likelihood of action potential.

2.5 Influence of Drugs on Neural Firing

Agonist vs. Antagonist Drugs

• Agonist Drugs:

  • Increase effectiveness of neurotransmitters.

  • Bind to receptors, mimic neurotransmitters, or block reuptake.

  • Examples: Xanax (GABA), Prozac (Serotonin), Opioids (Endorphins).

• Antagonist Drugs:

  • Decrease effectiveness of neurotransmitters.

  • Block neurotransmitter release or receptor binding.

  • Examples: Antipsychotics (Dopamine), Alcohol (Glutamate).

2.6 The Brain

Brain Structure

• Broca's Area: Speech production (damage leads to Broca's Aphasia).

• Wernicke's Area: Comprehension of meaningful speech (damage leads to Wernicke's Aphasia).

• Medulla Oblongata: Regulates cardiovascular and respiratory systems.

• Pons: Connects brainstem regions; coordinates movement and sleep/dream.

• Cerebellum: Maintains balance and coordination.

• Brainstem: Includes medulla, pons, and midbrain; controls autonomic functions.

• Spinal Cord: Connects brain to body; information highway.

Cerebral Cortex and Hemispheres

• Cerebrum: All brain parts excluding brainstem and cerebellum.

• Cerebral Cortex: Thin layer covering the brain; divided into lobes.

• Corpus Callosum: Connects the two hemispheres of the brain.

Lobes of the Brain

• Frontal Lobe:

  • Prefrontal Cortex: Judgment, foresight, speech.

  • Motor Cortex: Voluntary movement (represented by Motor Homunculus).

• Parietal Lobe:

  • Receives sensory information (touch, pain, temperature).

  • Somatosensory Cortex: Register touch/movement (represented by Sensory Homunculus).

• Occipital Lobe:

  • Visual processing via Visual Cortex.

• Temporal Lobe:

  • Recognizes faces, smell, hearing, and balance.

  • Wernicke's Area: Language comprehension.

  • Angular Gyrus: Transforms visual words into auditory form.

  • Auditory Cortex: Processes sounds.

Limbic System

• Thalamus: Sends sensory information to forebrain for interpretation.

• Hippocampus: Creates new memories.

• Amygdala: Emotional reactions (fear, anxiety, aggression).

• Hypothalamus: Homeostasis (thirst, hunger, temperature).

• Nucleus Accumbens: Pleasure, reward, motivation.

• Basal Ganglia: Intentional body movement (linked to motor cortex).

Hemispheric Specialization

• Left Hemisphere: Language, words, logical thinking.

• Right Hemisphere: Spatial concepts, facial recognition.

Brain Regions

• Hindbrain: Bottom of the brain.

• Midbrain: Surrounded by the forebrain.

• Forebrain: Most visible part of the brain.

2.7 Tools for Examining Brain Structure and Function

Historical Studies

• Phineas Gage: Damaged prefrontal cortex and limbic system, leading to personality change.

• Split-Brain Research (Roger Sperry, Michael Gazzaniga):

  • Corpus Callosum Severed: Left and right hemispheres can't communicate.

  • Findings: Left hemisphere - language; Right hemisphere - spatial.

Neuroimaging Techniques

• EEG (Electroencephalogram):

  • Electrodes on scalp record electrical signals from neurons.

  • Used for sleep and seizure research.

• CT Scan (Computed Tomography):

  • Advanced X-rays of the brain.

  • Detects brain damage or tumors.

• PET Scan (Positron Emission Tomography):

  • Radioactive glucose injection tracks brain activity.

  • Real-time brain function.

• MRI (Magnetic Resonance Imaging):

  • Magnetic field creates detailed images of brain structures.

• fMRI (Functional Magnetic Resonance Imaging):

  • Similar to MRI but shows metabolic functions.

  • Detailed brain activity.

2.8 The Adaptable Brain

Neuroplasticity

• Definition: Brain's ability to change, modify, and repair itself.

• Mechanism: Creating and strengthening neural pathways through practice and learning.

Brain Damage

• Causes: Infections, neurotoxins, genetics, head injuries, tumors, stroke.

• Impact: Life-altering changes based on severity.

Consciousness

• Definition: Being awake and aware of external stimuli and mental activity.

• William James: Stream of consciousness, interconnected.

• Freud: Conscious, subconscious, and unconscious mind.

Psychoactive Drugs

• Depressants: Reduce neural activity (alcohol, sleeping pills).

• Opioids: Depressants with high addiction potential (morphine, heroin).

• Stimulants: Excite neural activity (caffeine, cocaine).

• Hallucinogens: Alter perception (LSD, marijuana).

2.9 Sleep and Dreaming

Circadian Rhythm

• Definition: Biological clock regulating sleep-wake cycles, blood pressure, hormones.

Theories of Sleep

• Restoration Theory: Sleep restores energy and resources.

• Adaptive Theory: Evolutionary aspect; conserves energy for survival.

• Information Processing Theory: Sleep helps form and consolidate memories.

Brain Waves and Sleep Stages

• Alpha Waves: Slow, high amplitude (relaxed).

• Beta Waves: Fast, low amplitude (mental activity).

• Theta Waves: Medium amplitude, slower (relaxation).

• Delta Waves: High amplitude, slowest (deepest sleep).

Sleep Stages

• Non-REM Stage 1: Light sleep, alpha waves.

• Non-REM Stage 2: Transitional stage, sleep spindles and K-complexes, theta waves.

• Non-REM Stage 3: Deepest sleep, growth hormone, delta waves.

• REM Stage: Rapid Eye Movement, beta waves, dreams, paralysis of muscles.

Hypnagogic Sensations

• Definition: Sensations perceived as real during light sleep.

Dream Theories

• Activation-Synthesis Model: Brain tries to make sense of random neural activity.

• Cognitive Development Theory: Dreams reflect cognitive development.

• Activation Theory: Different brain areas activated determine dream content.

• Physiological Function Approach: Dreams stimulate and preserve neural pathways.

Sleep Disorders

• Insomnia: Trouble falling or staying asleep.

• Sleep Apnea: Difficulty breathing during sleep; can't enter REM sleep.

• Sleep Terrors/Night Terrors: Intense fear during sleep, leading to sleep deprivation.

• Narcolepsy: Uncontrollably falling asleep during the day.