01Core Approaches to Psychology
▼| Approach | Key Assumption | Method | Strength / Weakness |
|---|---|---|---|
| Biological | Behaviour caused by biology — genes, brain, hormones, nervous system | Brain scans, twin studies, drug studies | + Scientific, objective / − ignores environment & culture |
| Behaviourist | All behaviour is learned from environment through conditioning | Lab experiments, animal studies | + Measurable, practical / − ignores mental processes & free will |
| Cognitive | Mental processes (thinking, memory, perception) influence behaviour | Experiments, computer models | + Explains thought / − can be artificial (lacks ecological validity) |
| Psychodynamic | Unconscious mind & childhood experiences drive behaviour | Case studies, dream analysis | + Rich explanations / − unfalsifiable, unscientific |
| Humanistic | People have free will and natural drive toward self-actualisation | Interviews, self-report | + Positive, holistic / − too vague, not scientific |
| Social Learning | Behaviour learned by observing & imitating role models | Observation, experiments | + Bridges bio & behaviourist / − ignores biological factors |
💡For every approach question: state the assumption, give an example, evaluate with a strength AND weakness. That's the AO1 + AO2 + AO3 structure.
02Research Methods
▼| Method | Description | Strength | Weakness |
|---|---|---|---|
| Lab experiment | Controlled setting; IV manipulated; DV measured | High internal validity; replicable | Low ecological validity; demand characteristics |
| Field experiment | Real-world setting; IV still manipulated | High ecological validity | Less control; ethical issues |
| Natural experiment | IV occurs naturally, not manipulated by researcher | Real-world behaviour | Cannot establish cause & effect; rare events |
| Observation | Watching & recording behaviour (covert/overt, participant/non) | Ecological validity; real behaviour | Observer bias; ethical issues if covert |
| Self-report (questionnaire/interview) | Participants give own data via questions | Large samples; easy to gather | Social desirability bias; demand characteristics |
| Case study | In-depth study of one individual/group | Rich, detailed data | Cannot generalise; researcher bias |
| Correlation | Measures relationship between two variables | Ethical (no manipulation); finds links | No cause & effect; third variable problem |
ReliabilityConsistency — same result if repeated
ValidityAccuracy — measures what it claims to measure
Ecological ValidityHow well findings apply to real life
GeneralisationCan results apply to wider population?
SamplingRandom, opportunity, self-selected, stratified
⚠️Demand characteristics = participants guess aim and change behaviour. Investigator effect = researcher unintentionally influences results. Both reduce validity.
03Memory
▼Encoding
→
Storage
→
Retrieval
| Store | Duration | Capacity | Encoding |
|---|---|---|---|
| Sensory Register | Very brief (under 1s) | High | Modality-specific |
| Short-Term Memory (STM) | Up to 30 seconds | 7±2 chunks (Miller) | Acoustic (sound) |
| Long-Term Memory (LTM) | Potentially lifetime | Unlimited | Semantic (meaning) |
- Multi-Store Model (Atkinson & Shiffrin): info flows Sensory → STM → LTM via rehearsal. Criticism: oversimplified
- Working Memory Model (Baddeley & Hitch): STM has multiple components — central executive, phonological loop, visuo-spatial sketchpad, episodic buffer
- Forgetting — Interference theory: Proactive (old memories interfere with new) and Retroactive (new interferes with old)
- Forgetting — Cue-dependent: retrieval fails without the right context/state cue (state-dependent, context-dependent)
- Eyewitness testimony (Loftus & Palmer): leading questions alter memory. "Smashed" → faster speed estimates than "hit"
- Reconstructive memory (Bartlett): memory is not a recording — we reconstruct using schemas. "War of the Ghosts" study
04Learning Theory — Classical & Operant Conditioning
▼Classical Conditioning (Pavlov)
- UCS (food) → UCR (salivation)
- NS (bell) paired with UCS
- CS (bell) → CR (salivation)
- Extinction: CS without UCS → response fades
- Spontaneous recovery: CR returns after rest
- Generalisation: similar stimuli trigger response
- Discrimination: respond only to specific CS
Operant Conditioning (Skinner)
- Positive reinforcement: add pleasant stimulus → behaviour ↑
- Negative reinforcement: remove unpleasant → behaviour ↑
- Punishment: add unpleasant → behaviour ↓
- Skinner box: rat presses lever → food pellet
- Schedules: fixed ratio, variable ratio (most persistent)
- Token economy: applied to phobias/behaviour management
🧠Watson & Rayner — Little Albert: conditioned fear of white rat using loud noise. Generalised to other white furry objects. Ethical issues: no consent, no desensitisation.
05Social Learning Theory (Bandura)
▼- 4 processes of SLT: Attention (notice model) → Retention (remember behaviour) → Reproduction (able to copy) → Motivation (reason to imitate)
- Vicarious reinforcement: learning by seeing others rewarded or punished
- Bobo doll study (Bandura 1961): children who watched adult be aggressive to Bobo doll were more aggressive. Live > filmed > cartoon model
- Role models: more likely to imitate if model is: same sex, high status, similar to self, rewarded, powerful
- Self-efficacy: belief in own ability to succeed — affects motivation to attempt behaviour
- Applied to aggression: children learn violence from media/parents; TV violence debate
⚠️Criticism: Bobo doll designed to be hit — demand characteristics. Children may not reproduce in real life (lab ≠ natural). Ignores biological predispositions.
06Development — Piaget's Cognitive Development
▼| Stage | Age | Key Feature |
|---|---|---|
| Sensorimotor | 0–2 yrs | Object permanence develops; learn through senses & movement |
| Pre-operational | 2–7 yrs | Egocentric; lack conservation; symbolic play begins; no logical thought |
| Concrete operational | 7–11 yrs | Conservation achieved; logical thinking about concrete objects; less egocentric |
| Formal operational | 11+ yrs | Abstract & hypothetical thinking; systematic reasoning |
- Schema: mental framework. Assimilation: new info fits existing schema. Accommodation: schema changes to fit new info
- Egocentrism: inability to see others' perspectives. Tested by Three Mountains Task
- Conservation: understanding quantity stays same despite appearance change. Tested by liquid, number, mass tasks
- Object permanence: knowing objects exist when out of sight (develops ~8 months)
- Criticism: underestimates children's abilities; ages may vary by culture; ignores social/emotional factors
07Attachment
▼- Attachment: strong emotional bond between infant and caregiver, providing security and safe base for exploration
- Bowlby's theory: attachment is innate and evolutionary; critical period (first 2 years); monotropy (one primary attachment figure)
- Internal working model: mental model of relationships formed from first attachment; template for all future relationships
- Ainsworth's Strange Situation: observed infant reactions to separation from and reunion with caregiver
| Attachment Type | Behaviour | Caregiver Style |
|---|---|---|
| Secure (Type B) | Explores, distressed when separated, easily comforted on return, ~65% | Sensitive & responsive |
| Insecure-Avoidant (A) | Little distress on separation, ignores caregiver on return, ~20% | Consistently unresponsive |
| Insecure-Resistant (C) | Very distressed, not comforted on return, clingy, ~15% | Inconsistent, unpredictable |
| Disorganised (D) | No consistent strategy; confused, fearful | Frightening/abusive |
🧠Harlow's rhesus monkeys: infant monkeys preferred cloth (comfort) mother over wire (food) mother — attachment is about comfort, not just food (against cupboard love theory).
08Obedience & Conformity
▼🧠Milgram (1963) — Obedience: 65% of participants gave apparent 450V shocks to a confederate when ordered by authority figure in a lab coat. Shows situational factors override personal morality.
- Factors increasing obedience: proximity of authority, prestigious location (Yale), uniform, participant responsibility removed
- Factors decreasing obedience: authority figure absent, victim visible/in same room, two rebels present (social support)
🧠Asch (1951) — Conformity: 75% conformed at least once when unanimous majority gave obviously wrong answer on line-length task. Normative social influence (fit in) and informational (assume majority right).
- Factors increasing conformity: larger group (up to 3), unanimous majority, ambiguous task, low self-esteem
- Factors decreasing conformity: one ally present, task is unambiguous, writing answers privately
- Types: Compliance (publicly conform, privately disagree), Internalisation (genuinely change belief), Identification (conform to group identity)
09Prejudice & Discrimination
▼- Prejudice: unjustified negative attitude toward a group. Three components: Cognitive (stereotype), Affective (hostility), Behavioural (discrimination)
- Stereotyping: oversimplified fixed image of a group. Reduces cognitive effort but causes bias
- Scapegoating (frustration-aggression hypothesis): blaming out-group for own problems. Dollard et al.
- Social identity theory (Tajfel & Turner): in-group/out-group distinction → in-group favouritism → discrimination. Minimal group paradigm experiments
- Robbers Cave (Sherif): competition created hostility between groups; superordinate goals reduced prejudice
- Authoritarian personality (Adorno): harsh upbringing → displacement of frustration onto weaker groups. Measured with F-scale
- Reducing prejudice: equal status contact, superordinate goals, intergroup cooperation, education, media representation
10Aggression
▼| Explanation | Key Idea | Evidence |
|---|---|---|
| Biological | Genetic predisposition; testosterone; amygdala activity | Twin studies; Raine — murderers' brains show differences in PET scans |
| Frustration-aggression | Frustration always leads to aggression (Dollard) | Later revised — frustration is just one cause |
| Social learning | Aggression learned by observation & imitation | Bandura's Bobo doll; media violence research |
| Deindividuation | In crowds, anonymity → loss of personal identity → aggression | Zimbardo — Halloween costumes study; Diener — trick-or-treat |
ℹ️Zimbardo Stanford Prison Experiment (1971): students quickly adopted roles of guard/prisoner. Guards became abusive. Shows situational power of social roles. Stopped after 6 days. Major ethical issues.
11Stress
▼- Stress: response when demands exceed ability to cope. Stressor = cause of stress
- General Adaptation Syndrome (Selye): Alarm → Resistance → Exhaustion. Body's physiological response to chronic stress
- Fight or flight: acute stress → adrenaline released → increased HR, breathing, blood to muscles
- Life events (Holmes & Rahe — SRRS): major life changes cause stress. Death of spouse = 100 LCUs. Score >300 = high illness risk
- Daily hassles (Kanner): minor daily irritants more damaging than major events. Accumulate over time
- Workplace stress: lack of control, high demand (Karasek model), role ambiguity, poor relationships
- Coping strategies: Problem-focused (tackle cause) vs Emotion-focused (manage emotional response). Lazarus & Folkman
- Social support: reduces stress. Types: emotional, informational, instrumental, appraisal
12Psychopathology — Abnormality & Mental Disorders
▼Statistical InfrequencyBehaviour statistically rare (below/above average)
Deviation from Social NormsViolates unwritten social rules
Failure to Function AdequatelyUnable to maintain daily life
Deviation from Ideal Mental HealthFalls short of Jahoda's criteria
| Disorder | Key Features | Treatment |
|---|---|---|
| Phobia | Irrational fear, disproportionate anxiety, avoidance; learned by classical conditioning | Systematic desensitisation, flooding (exposure therapy) |
| Depression | Persistent low mood, anhedonia, fatigue, negative thinking; cognitive distortions | CBT (Beck — challenge negative automatic thoughts), antidepressants (SSRIs) |
| OCD | Obsessions (intrusive thoughts) + compulsions (repetitive behaviours to reduce anxiety) | CBT + ERP (exposure and response prevention), SSRIs |
💡Systematic desensitisation: gradual exposure + relaxation. Three stages: anxiety hierarchy constructed → relaxation learned → paired with each step from least to most feared.
13Sleep & Dreaming
▼| Sleep Stage | EEG Waves | Features |
|---|---|---|
| Stage 1 (NREM) | Alpha → Theta | Light sleep; easily woken; hypnic jerks |
| Stage 2 (NREM) | Theta + sleep spindles + K-complexes | Temperature drops; heart rate slows |
| Stage 3 & 4 (NREM) | Delta (slow waves) | Deep sleep; hardest to wake; growth hormone released |
| REM | Beta-like (paradoxical) | Rapid eye movement; vivid dreaming; muscle atonia; memory consolidation |
- One full cycle = ~90 minutes. 4–5 cycles per night. REM increases across the night
- Hobson & McCarley — Activation-Synthesis: dreams are brain's attempt to make sense of random neural signals during REM
- Freud — Wish Fulfilment: dreams represent unconscious wishes in disguised form. Manifest content (what we dream) vs latent content (hidden meaning)
- Sleep deprivation effects: cognitive impairment, mood changes, hallucinations, microsleeps; REM rebound when allowed to sleep
- Circadian rhythm: ~24-hour biological clock regulated by light via SCN (suprachiasmatic nucleus) → melatonin from pineal gland
14Perception
▼- Sensation vs Perception: sensation = raw data from senses; perception = interpretation of that data
- Depth cues — monocular: relative size, overlap/interposition, linear perspective, texture gradient, height in visual field, motion parallax, aerial perspective
- Depth cues — binocular: retinal disparity (slightly different image in each eye) and convergence (eyes turn inward)
- Perceptual set: readiness to perceive in a certain way due to expectations, emotions, culture, motivation
- Visual illusions: Müller-Lyer (misapplied size constancy), Ponzo (depth cue misapplication), Rubin's vase (figure-ground)
- Nature vs nurture in perception: Nativists (Gibson — direct perception, innate); Constructivists (Gregory — perception is hypothesis based on experience)
15Gender Development
▼Biological Explanation
- Sex determined by XX/XY chromosomes
- Testosterone → male development
- Oestrogen → female development
- Brain differences (e.g. corpus callosum)
- Congenital adrenal hyperplasia (CAH)
Social/Cognitive Explanations
- Gender schema theory (Martin & Halverson)
- Social learning — imitation of same-sex models
- Parents/media reinforce gender roles
- Kohlberg — gender identity → stability → constancy
- Sex = biological (chromosomes, hormones). Gender = psychological/social (masculine/feminine identity)
- Androgyny: having both masculine and feminine traits (Bem). Associated with greater psychological wellbeing
- Case study — David Reimer: raised as girl after botched circumcision; rejected female identity. Evidence for biological influence
16Criminological Psychology
▼- Biological theories: Lombroso — criminal atavism (skull features); XYY chromosome; genetic predisposition
- Social learning: criminal behaviour modelled from family, peers, media
- Eysenck's personality theory: high E (extraversion) + high N (neuroticism) + high P (psychoticism) = criminal personality. Extraverts under-aroused → seek stimulation
- Offender profiling: FBI top-down approach (organised/disorganised crime scene types); British approach (Canter — bottom-up, statistical analysis)
- Custodial sentencing: aims = deterrence, rehabilitation, incapacitation, punishment. Recidivism high → rehabilitation arguably most effective
- Alternatives: restorative justice — victim meets offender; community service; fines; electronic tagging
17Sport Psychology
▼- Arousal & performance — Inverted-U hypothesis (Yerkes-Dodson): moderate arousal = optimal performance. Too low (bored) or too high (anxious) → poor performance
- Motivation: Intrinsic (internal enjoyment) vs Extrinsic (external reward). Over-justification effect: extrinsic rewards reduce intrinsic motivation
- Self-efficacy (Bandura): belief in ability to succeed. Sources: mastery experience, vicarious experience, verbal persuasion, physiological arousal
- Audience effects: Social facilitation — audience improves performance on well-learned tasks. Social inhibition — impairs performance on novel/complex tasks. Zajonc
- Aggression in sport: frustration (losing), arousal cues, observational learning from other players/fans
- Imagery & mental practice: visualising performance improves outcome — supported by EMG studies
18Health Psychology
▼- Health belief model (Becker): health behaviour depends on perceived susceptibility, severity, benefits of action, barriers, and cues to action
- Locus of control (Rotter): internal (believe they control health) vs external (fate/luck controls health). Internals more likely to adopt healthy behaviours
- Changing health behaviour: health campaigns (fear appeals — Janis & Feshbach), social norms approach, motivational interviewing
- Drug addiction: tolerance, withdrawal, craving. Biological (dopamine reward pathway) + psychological (coping, SLT) factors
- Obesity: biological (genetics, leptin, set-point theory), psychological (emotional eating, SLT), social (food environment, poverty)
19Ethics in Psychology
▼| Ethical Principle | Meaning |
|---|---|
| Informed consent | Participants must agree knowing what is involved |
| Deception | Must be justified; participants must be debriefed |
| Right to withdraw | Can leave at any time without penalty |
| Confidentiality | Data kept private and anonymous |
| Protection from harm | No physical or psychological harm beyond everyday life |
| Debriefing | Full explanation after study; emotional support offered |
| Privacy | Right to own data; no invasion of private life |
⚠️Studies like Milgram, Zimbardo, Little Albert violated ethics severely. Know the specific breach for each: Milgram = no right to withdraw, harm. Zimbardo = harm, deception. Watson = no debriefing/protection from harm.
20Key Studies Summary (Must Know)
▼| Psychologist | Study | Finding |
|---|---|---|
| Milgram | Obedience (1963) | 65% gave max shock; situational factors dominate |
| Asch | Line conformity (1951) | 75% conformed at least once; normative influence |
| Bandura | Bobo doll (1961) | Children imitate aggressive models; SLT |
| Loftus & Palmer | Eyewitness testimony (1974) | Leading questions alter memory; "smashed" vs "hit" |
| Bartlett | War of the Ghosts (1932) | Memory is reconstructive; schemas distort recall |
| Zimbardo | Stanford Prison (1971) | Social roles lead to extreme behaviour; deindividuation |
| Ainsworth | Strange Situation (1970) | Three attachment types; secure most common |
| Harlow | Rhesus monkeys | Comfort more important than food in attachment |
| Piaget | Conservation tasks | Cognitive stages; egocentrism in pre-op stage |
| Pavlov | Dogs & bells | Classical conditioning; conditioned reflexes |
🧠 Psychology Quick Fire
1. In Milgram's study, what percentage of participants delivered the maximum 450V shock?
2. Which memory store has unlimited capacity and potentially lifetime duration?
3. According to Piaget, which stage sees children develop conservation and become less egocentric?
4. A researcher watches people in a shopping centre without their knowledge. This is called:
5. What type of attachment involves a child showing little distress when separated and ignoring the caregiver on return?
6. Which approach assumes that all behaviour is learned from the environment?
7. Loftus & Palmer found that using the word "smashed" rather than "hit" in a question led to:
8. Which sleep stage is associated with vivid dreaming and memory consolidation?
01Cells & Organisation
▼| Organelle | Function |
|---|---|
| Cell membrane | Controls what enters/exits; partially permeable |
| Nucleus | Contains DNA; controls cell activities |
| Mitochondria | Site of aerobic respiration; ATP production |
| Ribosomes | Protein synthesis |
| Endoplasmic reticulum | Rough (+ ribosomes, protein transport); Smooth (lipid synthesis) |
| Golgi apparatus | Packages and secretes proteins; modifies proteins |
| Lysosomes | Digest waste using enzymes |
Cell
→
Tissue
→
Organ
→
Organ System
→
Organism
- Specialised cells: red blood cells (no nucleus, biconcave, haemoglobin), neurones (long axon, myelin sheath), sperm (tail, mitochondria), egg (large cytoplasm)
- Stem cells: undifferentiated; can become any cell type. Embryonic (unlimited) vs adult (limited). Medical applications + ethical debate
02Movement in & out of Cells
▼| Process | Definition | Requires Energy? |
|---|---|---|
| Diffusion | Movement of molecules from high to low concentration (down gradient) | No (passive) |
| Osmosis | Diffusion of WATER across a partially permeable membrane from high to low water potential | No (passive) |
| Active transport | Movement against concentration gradient; uses carrier proteins | YES (ATP) |
| Phagocytosis | Cell engulfs large particles by membrane folding (endocytosis) | YES |
- Factors affecting diffusion rate: concentration gradient, surface area, distance, temperature, molecule size
- Osmosis in RBCs: Hypertonic solution → water leaves cell → crenation. Hypotonic solution → water enters → lysis
- Surface area:volume ratio: larger cells have smaller ratio → diffusion less efficient → need transport systems
03Nutrition & Digestion
▼| Nutrient | Function | Source |
|---|---|---|
| Carbohydrates | Energy source; glucose for respiration | Rice, bread, pasta, sugar |
| Proteins | Growth & repair; enzymes; antibodies | Meat, eggs, beans, fish |
| Fats/Lipids | Energy store; insulation; cell membranes; fat-soluble vitamins | Butter, oils, nuts |
| Vitamins | C (immune system/collagen); D (calcium absorption); A (vision); B12 (RBC) | Fruits, dairy, sunlight |
| Minerals | Ca²⁺ (bones/teeth); Fe²⁺ (haemoglobin); Na⁺ (nerve impulses) | Dairy, meat, salt |
| Water | Solvent; medium for reactions; transport; temperature regulation | Drinks, food |
| Fibre | Prevents constipation; healthy gut; reduces bowel cancer risk | Vegetables, wholegrain |
Mouth
→
Oesophagus
→
Stomach
→
Small intestine
→
Large intestine
→
Rectum/Anus
| Enzyme | Site | Substrate → Product |
|---|---|---|
| Salivary amylase | Mouth | Starch → maltose |
| Pepsin | Stomach (pH 2) | Proteins → polypeptides |
| Pancreatic amylase | Small intestine | Starch → maltose |
| Lipase | Small intestine | Fats → fatty acids + glycerol |
| Protease (trypsin) | Small intestine | Proteins → amino acids |
| Maltase | Small intestine (villi) | Maltose → glucose |
🫀Villi adaptations: large surface area, single cell thick epithelium (short diffusion distance), good blood supply (lacteal + capillaries), finger-like projections + microvilli (brush border)
04Enzymes
▼- Enzymes: biological catalysts made of protein; speed up reactions without being used up
- Active site: specific 3D shape; only fits complementary-shaped substrate (lock and key / induced fit)
- Temperature: up to optimum (~37°C in humans) → more kinetic energy → more collisions → faster rate. Above optimum → enzyme denatures (bonds break, shape changes permanently)
- pH: changes ionic bonds in enzyme → alters active site shape. Pepsin works best at pH 2; amylase at pH 7
- Substrate concentration: ↑ substrate → ↑ rate until all active sites occupied (Vmax)
- Inhibitors: Competitive (blocks active site); Non-competitive (binds elsewhere, changes active site shape)
DenaturationPermanent change in enzyme shape — NOT the same as inactivation
05Respiration
▼Aerobic RespirationC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP (lots)
Anaerobic (humans)C₆H₁₂O₆ → 2C₃H₆O₃ + ATP (little) — lactic acid
Anaerobic (yeast)Glucose → CO₂ + ethanol
| Aerobic | Anaerobic (human) | |
|---|---|---|
| Oxygen required | Yes | No |
| ATP yield | High (~38 ATP) | Low (2 ATP) |
| Products | CO₂ + H₂O | Lactic acid |
| Duration | Long sustained exercise | Short intense bursts |
| Location | Mitochondria | Cytoplasm |
- Oxygen debt: extra O₂ needed after exercise to break down lactic acid → CO₂ + H₂O
- Muscle fatigue: lactic acid accumulates → pH drops → enzymes less effective → muscle cramps
- ATP = universal energy currency. Used in muscle contraction, active transport, protein synthesis, cell division
06Breathing & Gas Exchange
▼Inhalation
- Diaphragm contracts (flattens)
- External intercostals contract
- Ribcage moves up and out
- Volume increases
- Pressure decreases
- Air flows IN
Exhalation
- Diaphragm relaxes (domes)
- Internal intercostals contract
- Ribcage moves down and in
- Volume decreases
- Pressure increases
- Air flows OUT
🫀Alveolar adaptations: millions of alveoli (huge SA), one-cell thick walls, moist surface (dissolves gases), surrounded by dense capillary network, good ventilation (concentration gradient maintained)
- Gas exchange by diffusion — O₂ moves from alveolus (high) → blood (low); CO₂ moves from blood (high) → alveolus (low)
- Smoking effects: tar → carcinogens → lung cancer; nicotine → addiction + CVD; CO → reduces O₂ carrying capacity; mucus → infection risk (COPD)
- Tidal volume: volume of one breath. Vital capacity: max air exhaled. Residual volume: air that can't be exhaled
07Blood & Circulatory System
▼| Component | Function |
|---|---|
| Red blood cells (erythrocytes) | Carry O₂ as oxyhaemoglobin; no nucleus; biconcave (large SA); flexible |
| White blood cells (leucocytes) | Phagocytes (engulf pathogens); lymphocytes (antibody production) |
| Platelets (thrombocytes) | Cell fragments; blood clotting; form fibrin mesh |
| Plasma | Liquid; transports: glucose, amino acids, CO₂, urea, hormones, heat, antibodies |
Arteries
- Carry blood AWAY from heart
- High pressure, thick walls
- Thick muscle + elastic layer
- Small lumen
- Pulse present
Veins
- Carry blood TO heart
- Low pressure, thin walls
- Large lumen
- Valves prevent backflow
- No pulse
- Capillaries: one cell thick; site of exchange with tissues; large total surface area; slow flow
- Double circulation: pulmonary circuit (heart → lungs → heart) + systemic circuit (heart → body → heart)
- Heart structure: left side = oxygenated blood; right side = deoxygenated. Ventricles pump; atria receive. Left ventricle thicker wall (systemic pressure)
- Coronary heart disease: atherosclerosis → plaque → narrowed artery → angina / heart attack. Risk factors: smoking, high fat diet, lack of exercise, stress, genetics
08Immunity & Disease
▼- Pathogens: bacteria (reproduce in body, produce toxins), viruses (hijack cells, replicate), fungi, parasites
- Non-specific defence: skin (barrier + sebum), mucus + cilia (traps + sweeps pathogens), stomach acid (kills), inflammation, fever, phagocytes
- Specific immunity: lymphocytes recognise antigens → B-cells produce specific antibodies → antibodies bind antigen → pathogen destroyed
- Memory cells: remain after infection → faster, stronger response on second exposure (immunological memory)
- Active immunity: body produces own antibodies (infection or vaccine). Long-lasting
- Passive immunity: antibodies given from outside (breast milk, injection). Immediate but short-lived
- Vaccination: introduces dead/weakened/antigen from pathogen → immune response → memory cells formed without disease
- Antibiotics: kill bacteria; useless against viruses. Antibiotic resistance = serious global health threat
09Nervous System
▼Stimulus
→
Receptor
→
Sensory neurone
→
CNS
→
Motor neurone
→
Effector
→
Response
- Reflex arc: Stimulus → receptor → sensory neurone → relay neurone (spinal cord) → motor neurone → effector. Bypasses brain for speed
- Neurone structure: cell body, axon (carries impulse), dendrites (receive signals), myelin sheath (insulates, speeds transmission), nodes of Ranvier
- Synapse: gap between neurones. Nerve impulse → neurotransmitter released from vesicles → diffuses across gap → binds receptor on next neurone
- CNS: brain + spinal cord. PNS: all other nerves. Somatic (voluntary); Autonomic (involuntary — sympathetic & parasympathetic)
- Eye: cornea (refraction), iris (controls pupil), lens (accommodation), retina (rods for dim light, cones for colour), fovea (highest acuity), optic nerve
- Accommodation: close object → ciliary muscles contract → suspensory ligaments slacken → lens bulges (fat) → more refraction
10Hormones & Endocrine System
▼| Gland | Hormone(s) | Effect |
|---|---|---|
| Pituitary (master) | FSH, LH, ADH, growth hormone | Controls other glands; water balance; growth |
| Thyroid | Thyroxine | Controls metabolic rate; growth & development |
| Adrenal glands | Adrenaline (epinephrine) | Fight or flight: ↑ HR, ↑ blood glucose, ↑ breathing rate |
| Pancreas (islets of Langerhans) | Insulin (β cells), Glucagon (α cells) | Blood glucose regulation |
| Ovaries | Oestrogen, Progesterone | Female sex characteristics; menstrual cycle; pregnancy |
| Testes | Testosterone | Male sex characteristics; sperm production |
🫀Nervous vs Hormonal system: Nervous = fast, electrical, short-lived, specific target. Hormonal = slow, chemical (blood), long-lasting, widespread effect.
11Homeostasis — Blood Glucose & Temperature
▼Blood Glucose Regulation
- ↑ glucose → β cells secrete insulin
- Insulin: liver/muscle cells take up glucose → glycogen stored
- ↓ glucose → α cells secrete glucagon
- Glucagon: glycogen → glucose (glycogenolysis)
- Negative feedback: returns glucose to normal range
- Type 1 diabetes: no insulin produced (autoimmune)
- Type 2 diabetes: cells resistant to insulin
Temperature Regulation (37°C)
- Too hot: vasodilation (more blood to skin), sweating (evaporation cools), hair lies flat
- Too cold: vasoconstriction (less blood to skin), shivering (muscle contraction generates heat), hair stands up (traps air), goosebumps
- Hypothalamus = thermostat (thermoreceptors)
- Negative feedback back to normal range
💡Vasodilation = blood vessels near skin WIDEN → more heat lost. Vasoconstriction = blood vessels NARROW → less blood near surface → less heat lost. Blood is NOT moving to a different location — the vessel diameter changes.
12Excretion — Kidneys & Urea
▼- Excretion: removal of metabolic waste (CO₂ from lungs; urea from kidneys; bile from liver)
- Urea production: excess amino acids → deamination in liver → ammonia → converted to urea (less toxic)
- Kidney function: Ultrafiltration (blood filtered under high pressure → glucose, urea, water, ions enter Bowman's capsule) → Selective reabsorption (all glucose, most water, some ions back into blood) → Urine formed (urea, excess water, excess ions)
- ADH (antidiuretic hormone): released when blood is too concentrated → makes collecting duct more permeable → more water reabsorbed → concentrated urine
- Dialysis: acts as artificial kidney; blood passed over dialysis membrane; urea diffuses out; glucose & ions maintained
13Reproduction
▼| Male | Female | |
|---|---|---|
| Gamete | Sperm (small, motile, many) | Egg/Ovum (large, stationary, few) |
| Gonads | Testes | Ovaries |
| Hormones | Testosterone (FSH/LH from pituitary) | Oestrogen, Progesterone (FSH, LH from pituitary) |
- Menstrual cycle (28 days): Day 1–5 menstruation; Day 6–13 follicle develops (FSH), oestrogen rises, uterus lining thickens; Day 14 ovulation (LH surge); Day 15–28 corpus luteum secretes progesterone, maintains lining
- Fertilisation: sperm meets egg in fallopian tube → zygote → travels to uterus → implants in endometrium (day ~6)
- Placenta: exchange organ. O₂ + glucose + antibodies pass from mother → fetus. CO₂ + urea pass fetus → mother. Blood does NOT mix
- Contraception: hormonal (pill — prevents ovulation), barrier (condom), IUD, surgical (vasectomy/tubal ligation), rhythm method
- STIs: chlamydia (bacterial, often asymptomatic), gonorrhoea (bacterial), HIV (virus, attacks T-helper cells → AIDS), syphilis (bacterial, 3 stages)
14Genetics & Inheritance
▼GeneSection of DNA coding for a protein/trait
AlleleAlternative version of a gene
GenotypeGenetic makeup (e.g. Aa, BB)
PhenotypeObservable characteristics (e.g. brown eyes)
DominantAllele expressed when one copy present (A)
RecessiveOnly expressed when two copies present (aa)
HomozygousBoth alleles same (AA or aa)
HeterozygousTwo different alleles (Aa)
- Monohybrid cross: use Punnett square. Parents Aa × Aa → 1AA : 2Aa : 1aa = 3:1 dominant:recessive ratio
- Codominance: both alleles expressed equally — blood group AB (Iᴬ Iᴮ). ABO blood groups: Iᴬ and Iᴮ codominant, i is recessive
- Sex determination: XX = female, XY = male. Y chromosome carries SRY gene → testes development
- Sex-linked conditions: haemophilia, colour blindness — genes on X chromosome. Males more affected (only one X)
- Cystic fibrosis: autosomal recessive. CFTR gene mutation → thick mucus → lung/digestive problems
- Sickle cell: codominant. HbˢHbˢ = sickle cell disease; HbᴬHbˢ = carrier (sickle cell trait) — some protection against malaria
15DNA, Genes & Protein Synthesis
▼- DNA structure: double helix; two antiparallel strands; nucleotides (deoxyribose sugar + phosphate + base). Base pairs: A-T, G-C
- DNA replication (semi-conservative): double helix unwinds → each strand is template → complementary bases added → two identical double helices
DNA (nucleus)
→
Transcription → mRNA
→
mRNA leaves nucleus
→
Translation at ribosome
→
Protein made
- Codon: 3 bases on mRNA coding for one amino acid. 64 codons for 20 amino acids (degenerate code)
- Mutation: change in DNA base sequence. Point mutation (one base) or frameshift (insertion/deletion). Causes: radiation (UV, X-rays), mutagenic chemicals
- Genetic engineering: restriction enzymes cut DNA; ligase joins; plasmid vector used to insert gene into organism (e.g. insulin production in bacteria)
16Cell Division — Mitosis & Meiosis
▼Mitosis
- Produces 2 genetically identical daughter cells
- Diploid → Diploid (2n → 2n)
- For growth, repair, asexual reproduction
- Stages: PMAT — Prophase, Metaphase, Anaphase, Telophase
- Used in: cloning, tissue repair
Meiosis
- Produces 4 genetically different cells
- Diploid → Haploid (2n → n)
- For gamete production (sex cells)
- Two divisions (Meiosis I & II)
- Crossing over → genetic variation
- Human cells: 46 chromosomes (23 pairs). Gametes: 23 chromosomes (haploid)
- Cancer: uncontrolled mitosis; cells don't respond to normal control signals; mutations in proto-oncogenes/tumour suppressor genes
- Interphase: cell grows, DNA replicates before division begins
17Evolution & Natural Selection
▼- Darwin's natural selection: variation exists → competition for limited resources → organisms with advantageous traits survive → pass traits to offspring → gradual change over generations
- Variation sources: mutations, sexual reproduction (meiosis + random fertilisation), crossing over
- Evidence for evolution: fossil record, comparative anatomy (homologous structures), DNA sequence similarities, selective breeding, antibiotic resistance
- Antibiotic resistance example: random mutations → some bacteria survive antibiotic → reproduce → resistant population. Misuse of antibiotics accelerates this
- Speciation: populations geographically isolated → different selection pressures → accumulate different mutations → can no longer interbreed → new species
18Ecology & Environment
▼PopulationAll individuals of one species in an area
CommunityAll populations in an area
EcosystemCommunity + abiotic environment
HabitatPlace where an organism lives
NicheRole/position of organism in ecosystem
- Food chains: Producer → Primary → Secondary → Tertiary consumer. Energy lost at each level (~90%) as heat, movement, waste
- Pyramids: of numbers, biomass, energy. Energy pyramid is always true pyramid shape. Numbers can be irregular (one large tree)
- Carbon cycle: photosynthesis (CO₂ → organic), respiration (organic → CO₂), decomposition, combustion, fossilisation
- Nitrogen cycle: nitrogen fixation (Rhizobium in roots) → nitrification (ammonia → nitrites → nitrates) → denitrification (nitrates → N₂)
- Human impacts: deforestation, overfishing, pollution (eutrophication), pesticides, habitat destruction, climate change
- Eutrophication: fertiliser run-off → algal bloom → algae die → bacteria decompose → O₂ depleted → aquatic organisms die
19Skeleton, Muscles & Movement
▼- Skeleton functions: support, protection (skull/ribcage), movement (levers with muscles), blood cell production (red marrow), mineral storage (Ca/P)
- Joints: Fixed (skull), Cartilaginous (vertebrae), Synovial (ball & socket — hip; hinge — knee/elbow; pivot — neck)
- Synovial joint: synovial fluid (lubrication), cartilage (cushions), ligaments (hold bone to bone), tendons (muscle to bone)
- Antagonistic muscles: work in opposite pairs. Bicep contracts (arm flexes) → tricep relaxes. Tricep contracts → bicep relaxes
- Muscle contraction: sliding filament theory. Actin + myosin filaments. ATP required. Ca²⁺ releases binding sites
20Drugs & Alcohol
▼| Drug Type | Effect | Examples |
|---|---|---|
| Stimulants | Increase CNS activity, heart rate, alertness | Caffeine, cocaine, ecstasy, nicotine, amphetamines |
| Depressants | Decrease CNS activity, slow reactions, reduce anxiety | Alcohol, heroin, tranquilisers, anaesthetics |
| Painkillers (analgesics) | Block pain signals | Aspirin, morphine, paracetamol |
| Hallucinogens | Distort perception | LSD, cannabis, psilocybin |
- Alcohol effects: depressant; slows reaction time; impairs judgement; liver disease (cirrhosis); brain damage; addiction
- Alcohol metabolism: liver breaks down ethanol → acetaldehyde → acetate. Rate ~1 unit/hour
- Tolerance: need more drug for same effect (receptor down-regulation)
- Dependence: physical (withdrawal symptoms) or psychological (cravings)
- Heroin: opioid; binds endorphin receptors; highly addictive; overdose = respiratory depression
21Diet, Health & Disease
▼| Condition | Cause | Effect |
|---|---|---|
| Kwashiorkor | Protein deficiency | Swollen abdomen, muscle wasting, poor immunity |
| Marasmus | General calorie deficiency | Extreme wasting, stunted growth |
| Scurvy | Vitamin C deficiency | Bleeding gums, poor wound healing, joint pain |
| Rickets | Vitamin D / Ca deficiency | Soft, deformed bones in children |
| Anaemia | Iron deficiency (Fe²⁺) | Low Hb → fatigue, breathlessness |
| Obesity | Energy intake > expenditure | Type 2 diabetes, CVD, joint problems |
| Type 2 diabetes | Insulin resistance (often obesity-related) | High blood glucose → organ damage |
- BMI = mass (kg) ÷ height² (m). Under 18.5 = underweight; 18.5–24.9 = healthy; 25–29.9 = overweight; 30+ = obese
- Healthy diet: balanced macronutrients, adequate micronutrients, sufficient fibre, limited saturated fat + added sugar + salt
22Skin, Senses & Homeostasis Summary
▼- Skin functions: protection (barrier, keratin), temperature regulation (sweat, vasodilation), sensory reception, vitamin D synthesis, excretion (sweat = water + urea + salts)
- Skin layers: epidermis (outer, keratin-rich, dead cells shed), dermis (hair follicles, sweat glands, capillaries, nerve endings, sebaceous glands), subcutaneous fat
- Homeostasis: maintenance of a constant internal environment. Key variables: blood glucose, temperature, water content (osmoregulation), CO₂ levels
- Negative feedback: a change detected → corrective mechanism activated → return to set point. Example: core temperature rises → sweating begins → cools body → temperature returns to 37°C
- Receptor organs: Eye (light), Ear (sound/balance), Nose (smell), Tongue (taste), Skin (pressure, pain, temperature, touch)
🫀 Human Biology Quick Fire
1. What is the main difference between aerobic and anaerobic respiration in humans?
2. Which blood vessel carries oxygenated blood from the lungs to the heart?
3. High blood glucose triggers the pancreas to release insulin. Insulin causes cells to take up glucose. Blood glucose returns to normal. This is an example of:
4. Which enzyme breaks down starch in the mouth?
5. A person has the genotype Aa for a dominant trait. What type of individual are they?
6. During inhalation, what happens to the diaphragm?
7. Active immunity differs from passive immunity because:
8. Which process in the kidney results in glucose being returned to the blood even though it was filtered out?