Comprehensive Study Notes: Psychology 2e (OpenStax)

Biopsychology and Genetics

  • Biopsychology explores the biological mechanisms that underlie behavior.

    • Key areas include:

    • Genetics: how inherited genes can affect physiological and psychological traits.

    • The structure and function of the nervous system.

    • How the nervous system interacts with the endocrine system.

  • Brain imaging techniques provide insight into different aspects of brain function (illustration order left to right): PET scan, CT scan, and fMRI.

    • CT scan: computed tomography using X-rays to image brain structure.

    • PET scan: positron emission tomography shows activity by tracking radioactive tracers.

    • fMRI: functional MRI shows changes in metabolic activity over time.

    • Credits note that images may be credited to various sources.

  • Overall focus: how biology underlies behavior in biopsychology.

Human Genetics

  • Studying human genetics helps researchers understand the biological basis of differences in behavior, thoughts, and reactions.

    • Questions addressed include:

    • Why do two people with the same disease experience different outcomes?

    • Are there genetic components to psychological disorders (e.g., depression)?

    • How are genetic diseases inherited within families?

Theory of Evolution

  • Charles Darwin proposed evolution by natural selection: inheritance of traits over generations.

    • Core idea: organisms better suited to their environment survive and reproduce; poorly suited die off.

    • Survival-related characteristics/behaviors include:

    • Traits that protect against predators.

    • Traits that increase access to food.

    • Traits that help offspring survive.

  • Quote: “It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is most adaptable to change.” – Charles Darwin

Evolutionary Example: Sickle Cell Anemia

  • Normal blood cells travel through vessels; sickle-shaped cells form blockages, hindering blood flow.

  • Sickle cell anemia: crescent-shaped red blood cells; can cause early death but is common among people of African descent.

  • Carriers with one copy of the sickle cell gene are more resistant to malaria, a deadly disease common in Africa.

  • In this example, carrying the gene can be advantageous in a malaria-rich environment, illustrating environment-dependent fitness.

  • Question: Why do harmful genetic diseases persist despite causing mortality?

Genetic Variation and Basic Genetics

  • Genetic variation: differences in genes between individuals; contributes to a species’ adaptation.

  • Chromosomes: humans have 23 chromosomes in eggs and 23 in sperm.

  • DNA: deoxyribonucleic acid; a helix-shaped molecule made of nucleotide base pairs.

  • Genes: sequences of DNA that control or influence physical traits; genes may have multiple alleles.

  • Alleles: different versions of a gene (e.g., hair color alleles).

Genotype vs. Phenotype

  • Genotype: an individual’s genetic makeup (DNA inherited from parents).

  • Phenotype: observable characteristics (hair color, skin color, height, build).

  • Examples:

    • Genotype vs. Phenotype distinctions credited to researchers; practical implications for trait expression.

Dominant vs. Recessive Alleles and Polygenic Traits

  • Many traits are polygenic (influenced by multiple genes); some traits are controlled by a single gene.

  • Alleles can be dominant or recessive.

  • Example: A (dominant) for purple flowers; a (recessive) for white flowers.

    • Phenotype with at least one dominant allele (A_) shows the dominant trait.

    • Phenotype for recessive trait appears only if homozygous recessive (aa).

  • Genetic shorthand:

    • Heterozygous: Aa

    • Homozygous: AA or aa

  • Note: The display uses standard Punnett-square logic to predict offspring traits.

Punnett Squares: Basic Use and Examples

  • Punnett square: a tool to predict how genes will combine in offspring.

  • Example: Dominant allele B for cleft chin; recessive b for no cleft chin.

    • Any genotype containing B (e.g., BB or Bb) yields cleft chin phenotype.

    • Only bb yields a smooth chin phenotype.

  • PKU example: N represents normal allele; p represents recessive allele associated with PKU.

    • If both parents are heterozygous (Np), offspring have a 25% chance of PKU phenotype: P( ext{PKU}) = rac{1}{4} = 0.25.

  • PKU cross allele notation: when two heterozygotes (Np) mate, genotypic ratio is 1 NN : 2 Np : 1 pp and phenotypic PKU only for pp.

  • Where do harmful genes come from? Mutations: sudden, permanent changes in a gene. Many mutations are harmful, some beneficial.

Gene-Environment Interactions

  • Nature and nurture interact to shape individuals.

  • Key frameworks:

    • Range of reaction: genes set the boundaries within which the environment operates; environment determines where within that range an individual falls.

    • Genetic–environment correlation: genes influence our environment, and the environment influences gene expression.

    • Epigenetics: study of how same genotype can lead to different phenotypes depending on environmental factors.

Neurons: Structure and Function

  • Neuron structure supports signaling:

    • Semi-permeable membrane: allows small or uncharged molecules to pass; blocks larger or charged molecules.

    • Dendrites receive signals from other neurons; axon transmits signals.

  • Myelination: axons are often insulated by a myelin sheath (fatty substance) to speed signal transmission.

  • Terminal buttons: at the end of axons; contain synaptic vesicles storing neurotransmitters.

The Synapse

  • Synapse: the gap between a neuron's terminal button and another neuron's dendrite.

  • Synaptic vesicles contain neurotransmitters; approx. 10,000 molecules per vesicle (illustration note).

Resting Potential and Ion Gradients

  • At rest, Na+ is higher outside the cell; K+ is higher inside the cell.

  • Other ions (Cl−) and negatively charged proteins contribute to the resting membrane potential.

  • Resting potential is typically around -70\text{ mV}.

  • Extracellular fluid is relatively positively charged; intracellular fluid more negative.

Action Potential: Neural Signaling

  • Step 1: Neurotransmitters bind to receptors on the dendrites; membrane potential changes.

    • Depolarization: membrane potential becomes less negative; neuron more likely to fire (excitation).

    • Hyperpolarization: membrane potential becomes more negative; neuron less likely to fire (inhibition).

  • Step 2: If threshold of excitation is reached, an action potential occurs.

    • Ion channels open; Na+ rushes in; inside becomes briefly more positive.

    • All-or-none principle: signal is either sufficient to reach threshold or not.

  • Key terms:

    • Threshold of excitation: membrane potential level that triggers the action potential.

    • Action Potential: electrical signal along the neuron.

Action Potential: Graphical Overview

  • Membrane potential changes from resting around -70\text{ mV} to a peak (approximately +30 mV) and back toward resting through repolarization and hyperpolarization.

  • Time course illustrates the rapid, transient spike in membrane potential during firing.

Reuptake and Neurotransmitter Clearance

  • After a neurotransmitter is released, excess neurotransmitters may: drift away, be broken down, or be reabsorbed.

  • Reuptake: neurotransmitter is moved from the synapse back into the axon terminal for reuse.

Neurotransmitters: Major Players

  • Neurotransmitter: chemical messenger of the nervous system.

  • Neurotransmitter systems imbalance is linked to disorders (biological perspective).

  • Key neurotransmitters and roles:

    • Acetylcholine: muscle action and memory.

    • Beta-endorphin: pain and pleasure.

    • Dopamine: mood, sleep, learning.

    • Norepinephrine: heart, intestines, and alertness.

    • Serotonin: mood and sleep.

Psychotropic Drugs: Agonists and Antagonists

  • Psychotropic medication treats psychiatric symptoms by restoring neurotransmitter balance.

  • Agonist: mimics or enhances a neurotransmitter’s effects.

  • Antagonist: blocks or reduces a neurotransmitter’s activity.

  • Clinical examples:

    • Parkinson’s disease: low dopamine; dopamine agonists prescribed.

    • Schizophrenia: often associated with excess dopamine; many antipsychotics are dopamine antagonists.

The Nervous System: CNS and PNS

  • The nervous system is divided into two major parts:

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

    • Peripheral Nervous System (PNS): nerves to and from the CNS.

The Peripheral Nervous System: Subsystems

  • Somatic nervous system: relays sensory and motor information to and from the CNS.

  • Autonomic nervous system: controls internal organs and glands; divided into:

    • Sympathetic nervous system: involved in stress-related activities; fight or flight response.

    • Parasympathetic nervous system: rest and digest; routine body operations.

  • Homeostasis: balance maintained by sympathetic and parasympathetic systems working together.

Subdivisions of the Nervous System

  • CNS (Brain and Spinal Cord) vs PNS (Nerves to and from CNS).

  • Within PNS: Somatic, Autonomic (Sympathetic, Parasympathetic).

The Brain and Spinal Cord: Overview

  • Brain:

    • Composed of billions of interconnected neurons and glia.

    • Bilateral (two-sided); interacts across lobes.

  • Spinal cord:

    • Delivers messages to and from the brain.

    • Contains reflexes to allow rapid motor responses without brain input.

    • Divided into 30 segments, each connected to a body region via the PNS.

The Surface of the Brain: Gyri, Sulci, and Fissures

  • Gyri: ridges on the brain surface.

  • Sulci: grooves between gyri.

  • Fissure: deep sulcus; e.g., longitudinal fissure divides left and right hemispheres.

  • Lateralization: each hemisphere specializes in certain functions; left controls right side of body; right controls left side.

The Corpus Callosum

  • Corpus callosum connects the left and right hemispheres, enabling interhemispheric communication.

Major Brain Regions: Forebrain, Midbrain, Hindbrain

  • Forebrain: largest part; includes cerebral cortex, thalamus, hypothalamus, pituitary gland, limbic system.

  • Midbrain: contains reticular formation, substantia nigra, ventral tegmental area (VTA).

  • Hindbrain: contains medulla, pons, cerebellum; brain stem collectively.

Forebrain Structures and Functions

  • Cerebral cortex: higher-level processes (consciousness, thought, emotion, language, memory).

  • Thalamus: sensory relay to cortex (except smell).

  • Hypothalamus: maintains homeostasis (temp, hunger, thirst, etc.).

  • Pituitary gland: master gland; controls secretions of other glands.

  • Limbic system: emotion and memory circuitry.

Lobes of the Cerebral Cortex

  • Frontal Lobe: executive functions (planning, organization, judgment, attention, reasoning), motor control, emotion, language.

    • Motor cortex: planning and coordinating movement.

    • Prefrontal cortex: higher-level cognitive functioning.

    • Broca’s area: language production (left hemisphere).

    • Phineas Gage: famous case showing frontal lobe damage altering personality and impulse control.

  • Parietal Lobe: processing sensory and perceptual information; primary somatosensory cortex; topographically organized.

  • Temporal Lobe: hearing, memory, emotion, language; contains auditory cortex; Wernicke’s area for language comprehension.

  • Occipital Lobe: visual processing; primary visual cortex; retinotopically organized.

Phineas Gage: Case Study

  • Gage suffered a traumatic injury with frontal lobe damage.

  • Before: well-mannered and soft-spoken; after: changes in personality and impulse control observed.

  • Significance: demonstrated link between frontal lobe function and personality/executive control.

Temporal and Language Areas

  • Broca’s area: language production (left hemisphere).

  • Wernicke’s area: language comprehension; damage leads to language comprehension deficits.

  • Lesion impacts differ by area, producing distinct language deficits.

Additional Brain Regions: Imaging and Functionality

  • Thalamus: sensory relay center for most senses (except smell).

  • Limbic system components and their roles:

    • Amygdala: emotion processing, especially fear.

    • Hippocampus: learning and memory (spatial memory).

    • Hypothalamus: maintains homeostasis (temperature, appetite, blood pressure).

Midbrain Structures and Roles

  • Reticular formation: regulates sleep-wake cycle, arousal, alertness, and motor activity.

  • Substantia nigra: dopamine production; involved in movement control; degeneration linked to Parkinson’s disease.

  • Ventral tegmental area (VTA): dopamine production; linked to mood, reward, and addiction.

Hindbrain Structures

  • Medulla: autonomic processes (breathing, blood pressure, heart rate).

  • Pons: connects brain and spinal cord; regulates brain activity during sleep.

  • Cerebellum: balance, coordination, movement; also involved in certain memory processes.

  • Together, these form the brain stem.

Brain Imaging Techniques: Overview

  • Imaging modalities include:

    • CT Scan (computed tomography): uses X-rays to image brain structure.

    • PET Scan (positron emission tomography): shows metabolic activity via radioactive tracer uptake.

    • MRI (magnetic resonance imaging): uses magnetic fields to image tissue structure.

    • fMRI (functional MRI): measures changes in metabolic activity over time.

    • EEG (electroencephalography): records electrical activity of the brain via scalp electrodes; good temporal resolution for timing of brain activity.

CT Scan Details

  • CT uses X-rays to produce cross-sectional images and can show brain tumors.

  • Example images illustrate healthy brain vs. brain tumor in the left frontal lobe.

PET Scan Details

  • PET involves injecting a mildly radioactive substance and monitoring blood flow in brain regions.

  • Useful for showing activity in different parts of the brain.

MRI and fMRI Details

  • MRI provides detailed images of brain tissue.

  • fMRI shows changes in metabolic activity over time, providing functional information.

EEG Details

  • EEG uses caps with electrodes to record brain activity.

  • Provides precise timing information about brain activity by tracking amplitude and frequency of brainwaves.

The Endocrine System: Glands and Hormones

  • Pituitary gland: master gland; controls secretions of other glands.

  • Thyroid gland: secretes thyroxine (regulates growth, metabolism, appetite).

  • Adrenal glands: secrete hormones involved in stress response.

  • Gonads: ovaries and testes; secrete sex hormones important for reproduction and regulate sexual motivation and behavior.

  • Pancreas: secretes hormones regulating blood sugar.

  • The Hypothalamus links the nervous system and endocrine system by controlling the pituitary gland.

  • Other glands shown include thymus, pineal gland, parathyroid glands (posterior to thyroid), and other organs in schematic figures.

Major Neurotransmitters and Behavioral Effects (Summary Table)

  • Acetylcholine: muscle action, memory; associated with increased arousal and enhanced cognition when involved in cognition-related pathways.

  • Beta-endorphin: pain and pleasure; linked to decreased anxiety and tension in some contexts.

  • Dopamine: mood, sleep, learning; associated with increased pleasure and suppressed appetite in reward circuits.

  • Gamma-aminobutyric acid (GABA): main inhibitory neurotransmitter; associated with decreased anxiety and tension.

  • Glutamate: memory and learning; associated with increased learning and memory formation.

  • Norepinephrine: heart, intestines, and alertness; associated with increased arousal and suppressed appetite.

  • Serotonin: mood and sleep; modulates mood and appetite suppression.

Additional Notes on Neurobiology and Ethics

  • Neurobiological explanations for behavior underscore both the power and limits of biological accounts of mental processes.

  • Practical implications include understanding and treating neurological and psychiatric conditions through pharmacology and behavioral interventions.

Note: All LaTeX-style equations and symbols used in this study guide are enclosed in double dollar signs as requested, for example: 23, -70\text{ mV}, P(\text{PKU}) = \frac{1}{4} = 0.25, V{th}, A\text{B} where appropriate. The content mirrors the topics and details found in the provided transcript for exam preparation.