Biological Psychology I: Genetics, Nervous System Cells, and Neurotransmitters

Biological Psychology I

Introduction

This study guide covers foundational topics in biological psychology, focusing on genetics, the cells of the nervous system, and neurotransmitters. These concepts are essential for understanding how biological factors influence behavior and mental processes.

Genetics

Overview of Genetics in Psychology

Genetics is the study of how genes and environmental factors influence physical traits and behavioral characteristics. In psychology, genetics helps explain individual differences in behavior, cognition, and susceptibility to mental health disorders.

• Chromosomes: Structures within cells that contain DNA; humans typically have 23 pairs.

• Genes: Segments of DNA that contain instructions for making proteins, which influence traits and behaviors.

• Genotype: The unique set of genes that comprises an individual's genetic makeup.

• Phenotype: The observable physical traits and behavioral characteristics produced by the interaction of genotype and environment.

Example: Eye color, height, and risk for certain psychological disorders are influenced by both genetic and environmental factors.

Gene Editing and Epigenetics

Gene editing refers to the deliberate modification of an organism's genetic material. Epigenetics studies how environmental factors can change gene expression without altering the DNA sequence.

• Gene Editing: Technologies like CRISPR allow for targeted changes to DNA, raising ethical questions about modifying body and mind.

• Epigenetics: Environmental influences (e.g., stress, diet) can activate or silence genes, affecting behavior and health.

Example: Exposure to chronic stress can lead to epigenetic changes that increase vulnerability to depression.

Behavioral Genetics

Twin and Adoption Studies

Behavioral genetics examines the relative contributions of genes and environment to individual differences in behavior.

• Monozygotic (Identical) Twins: Share 100% of their genes; arise from a single fertilized egg.

• Dizygotic (Fraternal) Twins: Share about 50% of their genes; arise from two separate eggs fertilized by two sperm.

• Adoption Studies: Compare similarities between adopted children and their biological vs. adoptive parents to assess genetic and environmental influences.

Heritability: The degree to which genetic differences account for individual differences in a trait within a population.

• Heritability of Depression: $h^2 = 0.76$ in children

• Heritability of Anxiety: $h^2 = 0.48$ in children

Example: Twin studies show higher concordance rates for psychological disorders among identical twins compared to fraternal twins.

Longitudinal Studies

Longitudinal studies follow the same individuals over time to observe changes and stability in traits and behaviors.

• Useful for understanding developmental trajectories and the influence of genetics and environment across the lifespan.

Natural Selection and Evolution

Principles of Natural Selection

Natural selection is a process by which favorable traits become more common in a population over generations, influencing both physical and behavioral adaptations.

• Variation: Individuals within a species show differences in traits.

• Adaptation: Traits that enhance survival and reproduction become more prevalent.

• Evolution: Change in the frequency of genes in a population over time.

Example: Darwin's observations of finches in the Galapagos Islands demonstrated how beak shapes adapted to different food sources.

Cells of the Nervous System

Types of Nervous System Cells

The nervous system is composed of specialized cells that transmit and process information.

• Neurons: The primary signaling cells; transmit electrical and chemical signals.

• Glial Cells: Support neurons; include astrocytes, microglia, and oligodendrocytes (which produce myelin).

• Myelin: Fatty substance that insulates axons, speeding up signal transmission.

Example: Multiple sclerosis is a disease where myelin is damaged, impairing neural communication.

Neural Communication

Neurons communicate through electrical impulses and chemical signals.

• Action Potential: A rapid change in membrane potential that travels along the axon.

• Resting Membrane Potential: The electrical charge difference across the neuron's membrane at rest, typically around $-70$ mV.

• Ion Movement: Sodium (Na+) and potassium (K+) ions move across the membrane, generating electrical signals.

Equation:

$V_m = V_{inside} - V_{outside}$

where $V_m$ is the membrane potential.

Neurotransmitters

Major Neurotransmitters and Their Functions

Neurotransmitters are chemicals that transmit signals across synapses between neurons, influencing mood, cognition, and behavior.

• Glutamate (GLU): The main excitatory neurotransmitter; involved in learning and memory.

• GABA (Gamma-Aminobutyric Acid): The main inhibitory neurotransmitter; reduces neuronal excitability.

• Acetylcholine (ACh): Involved in muscle contraction, attention, and memory.

• Dopamine (DA): Regulates movement, motivation, and reward; implicated in Parkinson's disease and schizophrenia.

• Norepinephrine (NA): Influences arousal and alertness.

• Epinephrine (A): Also known as adrenaline; involved in fight-or-flight response.

• Serotonin (5-HT): Regulates mood, appetite, and sleep; associated with depression and anxiety.

Example: Low levels of serotonin are linked to depression, while dopamine dysregulation is associated with Parkinson's disease.

Table: Major Neurotransmitters and Their Functions

Neurotransmitter	Main Function	Associated Disorders
Glutamate (GLU)	Excitatory; learning and memory	Epilepsy, neurotoxicity
GABA	Inhibitory; anxiety regulation	Anxiety disorders
Acetylcholine (ACh)	Muscle contraction, attention	Alzheimer's disease
Dopamine (DA)	Movement, reward	Parkinson's, schizophrenia
Norepinephrine (NA)	Arousal, alertness	Depression
Epinephrine (A)	Fight-or-flight response	Stress disorders
Serotonin (5-HT)	Mood, sleep, appetite	Depression, anxiety

Additional info: Some content was expanded for clarity and completeness, including definitions, examples, and a summary table of neurotransmitters.