Biological Psychology: Genetic and Neurological Foundations of Behaviour

Biological Psychology

Introduction to Biological Psychology

Biological psychology is the application of biological principles to the study of mental processes and behaviour. It seeks to understand the physiological processes underlying psychological phenomena by examining the relationship between biological variables and behaviour.

• Definition: Biological psychology (also known as biopsychology or psychobiology) studies how the brain, neurotransmitters, genetics, and other biological processes influence behaviours, thoughts, and feelings.

• Research Focus: Biological psychologists often measure biological variables (e.g., hormone levels, brain activity) and relate them to psychological or behavioural variables (e.g., mood, cognition).

• Example: Schizophrenia may be explained by atypical neurological functioning, such as excess dopamine activity.

Genetic Basis of Behaviour

Genes, Chromosomes, and Heredity

Genetics plays a crucial role in shaping human behaviour and characteristics. Psychologists study the extent to which traits are inherited versus influenced by the environment.

• Chromosomes: Structures within cells that store genetic information. Each chromosome contains many genes and is composed of DNA, which is shaped like a double helix.

• Gene: A segment of DNA that codes for a specific trait. Genes are the basic units of heredity and are made up of four types of nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T).

• Alleles: Different forms of a gene. Each individual inherits one allele from each parent for every gene.

• Dominant and Recessive Inheritance: Some alleles are dominant (expressed if present), while others are recessive (expressed only if both alleles are recessive).

Examples of Dominant and Recessive Traits

Dominant	Recessive
Dark hair	Light or red hair
Type A blood	Type O blood
Facial dimples	No dimples
Farsightedness	Normal vision
Normal blood clotting	Hemophilia

Gene Expression and Epigenetics

Gene expression refers to how and when genes are activated to produce their effects. Epigenetics studies how environmental factors can alter gene expression without changing the DNA sequence.

• Methylation: A biochemical process where a methyl group is added to DNA, often silencing gene expression. Environmental factors can trigger methylation, affecting gene activity and potentially influencing behaviour across generations.

• Intergenerational Trauma: Experiences such as trauma can affect gene expression and may be passed down to subsequent generations through epigenetic mechanisms.

• CRISPR: A gene-editing technology that allows for precise modification of genetic material, with potential applications in treating genetic disorders and understanding gene function.

Genotype and Phenotype

The distinction between genotype and phenotype is fundamental in understanding heredity and behaviour.

• Genotype: The genetic makeup of an individual; the set of genes inherited from both parents.

• Phenotype: The observable characteristics or traits of an individual, resulting from the interaction of genotype and environment.

• Relationship: Genotype + Environment = Phenotype

• Example: Height is influenced by genotype (potential maximum height) and environmental factors (nutrition).

Behavioural Genetics

Methods in Behavioural Genetics

Behavioural genetics investigates how genes and environment influence behaviour by comparing individuals with varying degrees of genetic relatedness.

• Twin Studies: Compare monozygotic (identical) and dizygotic (fraternal) twins to assess the relative contributions of genetics and environment to traits.

• Adoption Studies: Compare adopted children to their biological and adoptive parents to disentangle genetic and environmental influences.

• Example: If identical twins raised apart show similar intelligence, genetics is likely influential; if they differ, environment plays a larger role.

Neurological Basis of Behaviour

The Nervous System

The nervous system is responsible for receiving sensory input, processing information, and producing responses. It is divided into central and peripheral components.

• Central Nervous System (CNS): Composed of the brain and spinal cord; processes information and coordinates activity.

• Peripheral Nervous System (PNS): Consists of nerves outside the CNS; includes the somatic (voluntary control) and autonomic (involuntary control) systems.

• Autonomic Nervous System: Regulates organs and glands; divided into sympathetic (fight or flight) and parasympathetic (rest and digest) branches.

Structure and Function of the Neuron

Neurons are the basic units of the nervous system, specialized for communication.

• Key Structures: Soma (cell body), dendrites (receive signals), axon (sends signals), myelin sheath (insulates axon), axon terminals, and synapse (gap between neurons).

• Neurotransmitters: Chemical messengers that transmit signals across synapses. Each neurotransmitter has a specific shape and function (e.g., dopamine, serotonin, noradrenaline).

• Action Potential: When a neuron is stimulated, an electrical impulse (action potential) travels down the axon, leading to neurotransmitter release.

Action Potential and Neural Communication

• Resting Potential: The neuron at rest has a negative charge inside relative to outside.

• Action Potential: Upon stimulation, positive ions enter the neuron, reversing the charge and generating an electrical impulse.

• Refractory Period: After firing, the neuron returns to resting potential and cannot fire again immediately.

The Endocrine System

Hormones and Behaviour

The endocrine system consists of glands that secrete hormones into the bloodstream, influencing various bodily functions and behaviour.

• Major Glands: Hypothalamus, pituitary gland, pineal gland, thyroid gland, adrenal glands, pancreas, ovaries, and testes.

• Functions: Hormones regulate metabolism, growth, stress responses, and reproductive processes. They contribute to homeostasis and influence mood and behaviour.

Brain Development and Neuroplasticity

Brain Across the Lifespan

The brain undergoes significant changes throughout life, affecting cognitive and physical abilities.

• Early Development: The brain reaches near-adult size in early childhood; development occurs in spurts and is correlated with intellectual and physical skills.

• Aging: Brain weight and volume decline with age, with notable shrinkage after age 40. Some regions are more affected than others, potentially impacting complex mental activities.

Neuroplasticity

Neuroplasticity is the brain's ability to reorganize and adapt by forming new neural connections throughout life.

• Definition: The capacity of the brain to change and rewire itself in response to experience, learning, or injury.

• Examples: The hippocampus can generate new neurons; damaged neurons can sprout new dendrites and re-establish connections; brain regions can assume functions of lost areas.

• Applications: Research into neuroplasticity informs treatments for spinal cord injury, Parkinson's disease, stroke, and dementia.

Additional info: The notes reference the importance of social, emotional, cultural, and environmental factors in behaviour, which are covered in other sections of the course.