WEEK 3 BIOLOGICAL PSYCHOLOGY

Why Biology Matters for Psychology

• Neuroscience studies the nervous system and how:

  • Injury, disease, medication, and genetics affect behaviour

• All psychological processes come from neural activity:

  • Attention, memory, emotion, perception, speech

• Psychologists need:

  • Knowledge of the brain (neuroanatomy)

  • Ability to interpret biological + behavioural data

Why Psychologists Need Biology

• Brain dysfunction → cognitive, emotional, behavioural issues

• Behaviour comes from networks, not single brain areas

• Key influences on behaviour:

  • Biological: brain, hormones

  • Developmental: changes across lifespan

  • Genetic: traits, personality, mental illness risk

  • Environmental: learning, stress, culture

👉 Psychologists must combine biology + behaviour when diagnosing and treating

Diagnosis & Neuroscience

DSM-5-TR:

• DSM-5-TR:

  • Classifies disorders based on symptoms, not brain causes

• Neuroscience helps explain:

  • Underlying biological mechanisms

• Good practice = integrate:

  • Behavioural observation + biological knowledge

Neurons (Basic Units of Nervous System)

Structure

Structure

• Dendrites → receive signals

• Cell body → processes information

• Axon → sends signals

• Axon terminals → release neurotransmitters

Function

• Communication via:

  • Electrical signals (action potentials)

  • Chemical signals (neurotransmitters)

Types of Neurons

• Sensory neurons → carry info to CNS

• Motor neurons → send commands from CNS

• Interneurons → connect neurons within CNS

. Central Nervous System (CNS)

Main Divisions of the Brain

🟢 Hindbrain (Basic Survival)

• Controls vital functions

• Medulla: breathing, heart rate (damage = fatal)

• Pons: sleep, movement, breathing

• Cerebellum: balance, coordination

• Reticular formation: alertness & consciousness

Midbrain (Movement & Attention)

• Tegmentum: movement, reward, motivation

• Tectum: visual + auditory reflexes

 Forebrain (Complex Thinking)

• Hypothalamus:

  • Homeostasis (temperature, hunger, hormones)

  • Links nervous + endocrine systems

• Thalamus:

  • Sensory relay station

• Limbic system:

  • Amygdala: emotion

  • Hippocampus: memory

• Basal ganglia:

  • Movement + habits

Brain Structures

• Corpus callosum: connects brain hemispheres

• Ventricles: produce cerebrospinal fluid (protection + cleaning)

 Lobes of the Brain

• Frontal lobe: decision-making, motor control

• Parietal lobe: sensory integration

• Temporal lobe: memory, language

• Occipital lobe: vision

Real-World Example: Concussion

• Brain moves inside skull → cell + network damage

• Effects:

  • Memory issues

  • Slow thinking

  • Irritability

  • Fatigue

• Shows how behaviour depends on brain systems

PNS- Somatic nervous system

Somatic Nervous System

• Voluntary control

• Sends:

  • Sensory info → CNS

  • Motor commands → muscles

Autonomic Nervous System

Controls involuntary functions

Sympathetic (Fight or Flight)

• Increases heart rate

• Dilates pupils

• Stops digestion

• Prepares for action

Parasympathetic (Rest & Digest)

• Slows heart rate

• Stimulates digestion

• Calms the body

Endocrine system

• Uses hormones (slower than nervous system)

• Key system:

  • HPA Axis (Hypothalamus–Pituitary–Adrenal) → stress response

• Works with brain to regulate:

  • Stress

  • Growth

  • Mood

 Genetics, Environment & Behaviour

Key Terms

• Genotype: genetic makeup

• Phenotype: observable traits (genes + environment)

 

Genetic Influence

• Personality: 15–50% heritable

• Intelligence: ~50%+ heritable

• Genes influence:

  • Behaviour

  • Mental illness

  • Interests

⚠ Heritability ≠ fixed traits

• It explains differences between people, not individuals

Environment & Epigenetics

• Environment affects:

  • Learning

  • Stress

  • Behaviour

• Epigenetics: environment turns genes on/off

👉 Behaviour = genes × environment interaction