Biological Basis of Behaviour – Comprehensive Notes

Learning Objectives

• Meaning, scope and importance of biopsychology
• Historical roots and current trends in biopsychology
• Career opportunities in biopsychology
• Structure & functions of a neuron
• Process of neural communication
• Divisions & functions of the nervous system
• Parts & functions of the brain
• Major endocrine glands & their functions

Biopsychology: Definition & Scope

• Scientific study of the biology of behaviour
  • Examines how the nervous system controls behaviour & how behaviour influences the nervous system
• Alternate names
  • Behavioural neuroscience
  • Biological psychology / Physiological psychology
• Main investigative questions
  • Causes of psychological disorders
  • Why individuals behave differently
  • Brain regions responsible for functions (learning, memory, information storage/retrieval)
  • Brain activity following damage & expected behavioural outcomes

Emergence of Biopsychology as a Discipline

• 18th–19th Century foundations
  • William James (The Principles of Psychology) – argued for biology-grounded psychology
  • Donald Hebb (The Organization of Behaviour) – comprehensive brain–mind theory
  • Case studies & new methods (e.g.
  – Phineas Gage, brain lesions, early imaging) illustrated brain–behaviour links

Early Views of Brain & Behaviour

• Plato – reason in heart; desires/emotions in liver
• Aristotle & many ancient cultures – heart responsible for reasoning, brain cools blood
• Hippocrates – brain as locus of mind
• Greek anatomists
  • Herophilos – distinguished cerebellum/cerebrum; ventricles
  • Erasistratos – intelligence ∝ brain convolutions
  • Galen – brain site of sensation/thought; mapped spinal nerves to muscles

Middle Ages

• Avicenna – described schizophrenia-like Junun Mufrit; linked mental disorders to excess cranial “humidity”; first to tie mental deficits to frontal lobe/ventricles; catalogued insomnia, mania, epilepsy, etc.

Renaissance

• René Descartes – dualism: mind & body interact via pineal gland; animals as machines
• Luigi Galvani – electrical nature of nerve signals (contra Descartes’ “animal spirits”)

19th Century Milestones

• Bell & Magendie – sensory vs motor spinal nerves
• Gall & Spurzheim – phrenology; 27 cortical faculties; cranioscopy
• Phineas Gage (Harlow) – prefrontal cortex damage → personality/executive changes
• Paul Broca – left frontal lesion → speech production loss (Broca’s area)
• Carl Wernicke – left temporal lesion → comprehension deficit (Wernicke’s area)
• Camillo Golgi – silver nitrate stain → dendrite, soma, axon identified
• Santiago Ramón y Cajal – neurons are discrete; neuron doctrine

20th Century Discoveries

• Synapse & neurotransmitters identified
• Julius Bernstein – action potential
• Hans Berger – first human EEG (1924)
• Imaging devices: EEG, CT, MRI
• 1990s – functional MRI (fMRI) created at Bell Labs

Current Imaging Trends (Living Brain)

• CT (Computerized Tomography)
  • 3-D X-ray anatomy; pros—quick, painless; cons—radiation, stillness required
• MRI (Magnetic Resonance Imaging)
  • Strong magnets & radio waves; pros—clear soft-tissue images, no radiation; cons—cost, tracer allergy possibility, unsuitable for pregnancy (unknown risk)
• PET (Positron Emission Tomography)
  • 3-D functional images using radioactive tracer; pros—cancer, cardiac & blood-flow diagnostics; cons—radioactivity, possible allergic/false results
• fMRI
  • Tracks blood-oxygen-level-dependent (BOLD) signal for real-time activity; higher spatial & temporal resolution than PET

Careers in Biopsychology

• Research scientist (PhD) – universities, hospitals, institutes
• Neuropsychologist – brain-behaviour assessment; PhD + neuropsych training
• Psychopharmacologist – drug effects on mood/behaviour; psychology + med-mgmt training
• Cognitive neuroscientist – cognition processes; PhD + neurology tools
• Physiological psychologist – language, perception, motivation vs brain function
• Comparative psychologist – cross-species behavioural comparisons
• BSc/MSc holders – lab technicians, assistants, clinical support roles

Neuron Anatomy & Function

• Fundamental nervous-system cell; conveys & receives info
• Essential parts
  • Soma (cell body) – nucleus with DNA; metabolic centre
  • Dendrites – branch-like; receive neurotransmitter signals; one neuron may get \ge 1000 inputs
  • Axon – single, long; conducts action potential to terminals; ends in axon terminals/terminal buttons
  – Axon hillock – trigger zone where AP starts
  – Myelin sheath – fatty insulation; gaps = Nodes of Ranvier (speed conduction)
• Synapse – microscopic gap between terminal & next neuron/muscle/gland cell

Neural Communication

• Action Potential (AP)
  • All-or-none law – neuron fires completely or not at all; threshold reached → full AP
  • Resting potential – inside negative relative to outside (about -70\,mV)
  • Ion movement: Na⁺ influx depolarises → AP travels; afterwards, Na⁺ pumped out to restore resting potential
• Synaptic Transmission
  • AP reaches terminal → vesicles release neurotransmitter (NT) into synaptic cleft
  • NT diffuses, binds matching receptor (key–lock specificity) on postsynaptic membrane
  • Receptor binding → excitatory or inhibitory postsynaptic potential; enough excitation → next neuron fires
  • NTs then re-uptaken, degraded, or diffuse away

Illustrated Example (Hot Stove)

1. Heat stimulus activates skin sensory receptors
2. AP travels along sensory neuron to spinal cord
3. Interneurons pass signal to motor neurons → hand muscles contract (reflex arc)
4. NTs cross synapses all along pathway
5. Hand withdraws; neurons reset to resting potential

Key Neurotransmitters & Effects

• Acetylcholine – muscle action, learning, memory, REM sleep; throughout CNS & at neuromuscular junctions
• Norepinephrine – alertness, wakefulness; autonomic neurons
• Dopamine – movement, attention, learning; substantia nigra origin; ↓ → Parkinson’s, ↑ → schizophrenia
• Serotonin – mood, eating, sleep, arousal, pain; brain & spinal cord
• GABA – major inhibitory NT; abnormal in sleep/eating disorders
• Endorphins – pain relief, euphoria; brain

SSRI Example

• Depression linked to low serotonin
• SSRIs block re-uptake, keeping serotonin longer in cleft to bind receptors → mood improvement

Nervous System Overview

• Two main divisions
  • Central Nervous System (CNS): brain & spinal cord – control centre
  • Peripheral Nervous System (PNS): all nerves outside CNS – messenger network

Spinal Cord

• Conduit between brain & PNS; controls reflexes without brain input

PNS Subdivisions

1. Somatic Nervous System – voluntary skeletal-muscle control; afferent (sensory) & efferent (motor) pathways
2. Autonomic Nervous System – involuntary organ/gland control
   • Sympathetic – “fight or flight”; mobilises energy (↑HR, dilated pupils)
   • Parasympathetic – “rest & digest”; restores baseline (↓HR, digestion)

Neuron Types in Reflexes

• Sensory (afferent) – body → CNS
• Interneurons – within CNS; relay
• Motor (efferent) – CNS → muscles/glands

Brain Structure & Function

• Three major regions
  • Hindbrain (medulla, pons, cerebellum)
  • Midbrain (primitive vision/hearing centres)
  • Forebrain (thalamus, hypothalamus, limbic system, cerebral cortex)

Hindbrain Details

• Medulla – vital reflexes: breathing, BP, coughing, posture
• Pons – balance, hearing, sleep & dreaming; some parasympathetic control
• Cerebellum – coordinates complex motor movements & balance

Midbrain

• Top of hindbrain; reflex centres for vision, hearing, posture

Forebrain – Subcortical Structures

• Thalamus – relay station for sensory info to cortex
• Hypothalamus – regulates emotion, eating, drinking, body temperature, endocrine control, ANS link
• Limbic System components
  • Amygdala – emotion (fear/anger)
  • Hippocampus – memory consolidation
• Corpus callosum – fibre bridge between hemispheres

Cerebral Cortex

• Outermost cerebrum layer; two hemispheres; three functional areas
  • Sensory input (vision, hearing, touch)
  • Motor output (voluntary movement)
  • Association (memory, thought, language)

Four Cortical Lobes

1. Frontal Lobe
   • Thinking, planning, speaking, motor control, behaviour prediction
   • Motor cortex (rear of lobe) – voluntary movement mapping
   • Broca’s area (left) – speech production; lesion → Broca’s aphasia (telegraphic speech)
2. Parietal Lobe
   • Somatosensory cortex – touch, pressure, temperature, pain
   • Spatial orientation, direction sense, tactile object recognition; lesion → astereognosis
3. Temporal Lobe
   • Primary auditory cortex – hearing from both ears
   • Wernicke’s area (left) – language comprehension & coherent speech; lesion → fluent but nonsensical speech (Wernicke’s aphasia) or auditory aphasia
4. Occipital Lobe
   • Primary visual cortex – registers vision; association areas interpret & store visual memories

Endocrine System: Hormone-Behaviour Interaction

• Chemical communication via bloodstream; effects can last days–months
• Endocrine vs exocrine glands (exocrine secrete via ducts, e.g.
  sweat)
• Identified 1902 (Bayliss & Starling)

Key Endocrine Glands & Hormones

• Hypothalamus (neuroendocrine controller) – releasing/inhibiting hormones; regulates temperature, hunger, thirst, circadian rhythm
• Pituitary ("master gland", pea-sized, under hypothalamus)
  • Secretes growth hormone, TSH, ACTH, FSH, LH, prolactin, oxytocin
  • Hyper/hypo-secretion → gigantism/dwarfism
• Thyroid (neck)
  • Produces thyroxine (T4) & triiodothyronine (T3) – metabolism, growth, energy
  • Parathyroids (4) behind thyroid – PTH regulates Ca²⁺ & phosphate
• Adrenal glands (atop kidneys)
  • Cortex – salt & water balance, metabolism
  • Medulla – epinephrine & norepinephrine; stress response → sympathetic activation
• Pancreas (both exocrine & endocrine)
  • Insulin lowers, glucagon raises blood glucose
• Pineal gland (deep brain)
  • Produces melatonin – sleep-wake (circadian) regulation
• Gonads
  • Testes – testosterone (puberty, sperm, voice, muscle)
  • Ovaries – estrogen (secondary female traits), progesterone (menstrual cycle, pregnancy)

Neurotransmitters vs Hormones

Ethical, Philosophical & Practical Implications

• Mind–body debate (dualism vs monism) influences research & clinical practice
• Brain imaging reduces need for invasive surgery; ethical oversight for radiation & magnetic exposure
• Pharmacological manipulation of NTs (e.g.
  SSRIs) raises questions about personality, autonomy & long-term effects
• Genetic & comparative studies inform evolutionary perspectives on behaviour

Real-World Relevance

• Diagnostic tools (EEG, CT, MRI, PET, fMRI) guide treatment for epilepsy, tumours, stroke, mental illness
• Understanding NT–receptor specificity underpins psychopharmacology & targeted drug design
• Knowledge of ANS informs stress-management, emergency medicine (e.g.
  epinephrine injection)
• Endocrine insights support treatment of metabolic disorders (diabetes, thyroid diseases) & hormonal therapies

Formula & Numerical References (LaTeX)

• Resting membrane potential ≈ -70\,\text{mV}
• All-or-none firing: \text{AP} = \begin{cases}\text{full}\;\text{spike}, & V \ge V{\text{threshold}}\0, & V < V{\text{threshold}}\end{cases}
• Historical years: 1902 (hormones named), 1924 (first EEG), 1990s (fMRI invention)
• Number of cortical abilities per phrenology: 27