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 the environment interact to shape physical traits and behavioral characteristics. In psychology, genetics helps explain individual differences in cognition, emotion, and behavior.

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

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

• Genotype: The unique set of genes an individual possesses.

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

• Inheritance: Traits are passed from parents to offspring through genetic material.

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

Gene Editing and Epigenetics

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

• Gene Editing: Technologies like CRISPR allow for targeted changes in DNA, raising ethical questions about enhancement and modification of 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 and Twin Studies

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

• Twin Studies: Compare identical (monozygotic) twins, who share all their genes, with fraternal (dizygotic) twins, who share about half.

• Heritability: The proportion of variation in a trait attributable to genetic differences within a population.

• Longitudinal Studies: Follow the same individuals over time to assess changes and influences.

Example: Heritability of depression and anxiety: monozygotic twins (h² = 0.76), dizygotic twins (h² = 0.48).

Type of Twin	Genetic Similarity	Heritability of Depression/Anxiety
Monozygotic (Identical)	100%	0.76
Dizygotic (Fraternal)	~50%	0.48

Natural Selection

Natural selection is a process by which traits that enhance survival and reproduction become more common in a population over generations.

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

• Adaptation: Favorable traits increase in frequency due to environmental pressures.

• Evolution: Change in gene frequencies over time leads to species diversity.

Example: Darwin's observations in the Galapagos Islands led to the theory of evolution by natural selection.

Cells of the Nervous System

Types of 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.

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

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

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

Equation:

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

Example: The influx of Na+ during an action potential depolarizes the neuron, allowing signal transmission.

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; dopamine deficiency is associated with Parkinson's disease.

Neurotransmitter	Main Function	Associated Disorders
Glutamate	Excitatory, learning & memory	Epilepsy (excess)
GABA	Inhibitory, anxiety regulation	Anxiety disorders (deficiency)
Acetylcholine	Muscle action, memory	Alzheimer's disease (deficiency)
Dopamine	Movement, reward	Parkinson's (deficiency), schizophrenia (excess)
Serotonin	Mood, sleep	Depression (deficiency)

Summary

Understanding genetics, the cells of the nervous system, and neurotransmitters is crucial for explaining how biological processes underlie psychological phenomena. These topics form the basis for further study in biological psychology and neuroscience.