The Biology of Behavior

Introduction to Psychology Chapter 3: The Biology of Behavior

Topics

  • I. Genes and Behavior

  • II. The Nervous System

  • III. The Brain and Spinal Cord

  • IV. Challenging Assumptions about Neural Growth in the Adult Brain

  • V. Measuring the Brain

  • VI. The Endocrine System

I. Genes and Behavior

  • Heredity influences family traits (e.g., nose shape, height).

  • Genetics plays a crucial role in behavior and experiences.

Key Terms

  • Genetics: Study of heredity.

  • Heredity: Genetic transfer of characteristics.

  • Bases: Pairs of chemical units (A, T, C, G) forming genetic codes.

  • Genes: Sequences of bases that produce proteins.

  • DNA: Contains genes, organized into chromosomes.

  • Human Genome: Unique DNA with ~20,000 genes.

Genetic Concepts

  • Genotype: An organism’s complete genetic makeup.

  • Phenotype: Observed characteristics of an organism.

  • Polygenic: Traits generated by multiple genes (e.g., height).

  • Monogenic: Traits influenced by a single gene (e.g., lactose tolerance).

Alleles and Inheritance

  • Allele: Variations of a gene.

  • Homozygous: Same alleles present.

  • Heterozygous: Different alleles present.

  • Dominant Inheritance: Dominant allele expression.

  • Recessive Inheritance: Requires two recessive alleles.

Behavioral Genetics Principles

  • Examines heredity's role in behavior:

    • Connection between genes and behavior is complex.

    • Genes and environment effects can be differentiated.

    • Epigenetics: How environments affect gene expression.

    • Heritability: Genetic influence extent on traits.

II. The Nervous System

  • Nervous System: Controls body functions and automatic processes.

  • Divided into:

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

    • Peripheral Nervous System (PNS): Peripheral nerves.

PNS Divisions

  • Somatic Nervous System: Controls voluntary movements (skeletal muscles).

    • Contains Afferent (sensory) and Efferent (motor) nerves.

  • Autonomic Nervous System: Controls involuntary functions (internal organs).

    • Afferent and Efferent nerves present.

Efferent Nerves in Autonomic NS

  • Sympathetic: Activates fight-or-flight response (increased heart rate).

  • Parasympathetic: Calms body (slows heartbeat).

III. The Brain and Spinal Cord

  • Spinal Cord: Composed of gray and white matter; contains 31 spinal levels.

    • Gray matter: Unmyelinated; White matter: Myelinated.

    • CNS Structures: Nuclei (cell bodies), Tracts (axons); PNS Structures: Ganglia and Nerves.

Brain Anatomy

  • Divided into brain stem and multiple regions:

    • Myelencephalon: Regulates vital functions (medulla oblongata).

    • Metencephalon: Includes Pons (signal relay) and Cerebellum (coordination).

    • Mesencephalon: Involves Tectum (visual/auditory functions) and Tegmentum.

    • Diencephalon: Relay stations (Thalamus and Hypothalamus).

    • Telencephalon: Cerebrum (gray and white matter).

      • Contains four lobes: Frontal, Parietal, Occipital, Temporal.

    • Limbic System: Regulates emotions and motivations (e.g., fight, flight, feeding).

IV. Challenging Assumptions About Neural Growth in the Adult Brain

  • Neurons do not grow repeatedly like other cells.

  • Evidence of neurogenesis (neural growth) in adults from studies (1960s):

    • Joseph Altman: Growth of new neurons in rats.

    • Observations of neural growth in avian species.

    • Demonstrated changes in synaptic connections in enriched environments.

Key Figures

  • Fred Gage: Demonstrated neurogenesis in humans using BrdU.

  • Elizabeth Gould: Showed brain growth in primates in natural settings.

V. Measuring the Brain

Common Techniques

  1. Electroencephalography (EEG): Measures electrical activity through electrodes.

  2. Magnetic Resonance Imaging (MRI): Provides images using magnetic fields.

  3. Functional Magnetic Resonance Imaging (fMRI): Detects blood flow to indicate activity.

  4. Positron Emission Tomography (PET): Uses radioactive tracers for imaging.

  5. Diffusion Tensor Imaging (DTI): Visualizes water movement for structural imaging.

  6. Near-Infrared Spectroscopy (NIRS): Monitors blood oxygenation changes.

VI. The Endocrine System

  • Endocrine System: Glands secreting hormones regulating biological processes.

  • Hormones: Chemical messengers impacting metabolism, growth, etc.

Major Endocrine Glands

  • Hypothalamus: Controls pituitary gland.

  • Pituitary Gland: Master gland for hormone regulation.

  • Thyroid: Regulates metabolism.

  • Pancreas: Manages blood sugar via insulin/glucagon.

  • Sex Glands: Influence sexual development and characteristics.

  • Adrenal Glands: Manage stress responses.

  • Pineal Gland: Regulates circadian rhythms.

  • Thymus Gland: Aids immune function.