What is Biopsychology?

Biopsychology (also called biological psychology, behavioural neuroscience, or psychophysiology) is the scientific study of how biological systems—especially the brain, nervous system, hormones, and genetics—produce and influence behaviour, thoughts, and emotions.

It connects:

• Psychology → behaviour, cognition, emotion
• Biology → neurons, brain structures, neurotransmitters, hormones

Biopsychology investigates:

• How brain structures support functions like memory, vision, emotion, and decision-making
• How neurons communicate using electrical and chemical signals
• How the nervous system coordinates movement, sensation, and homeostasis
• How drugs, neurotransmitters, and hormones influence behaviour
• How evolution shaped the brain and behaviour
• How damage or dysfunction in the nervous system affects psychological processes

Why It Matters

Biopsychology forms the foundation for understanding:

• Mental health disorders
• Effects of drugs and medications
• Learning and memory mechanisms
• Sensory and motor systems
• Emotional regulation and behavioural responses

Brain Evolution & Major Structures

Subcortical & Brainstem Structures

Structure	Main Function
Striatum	Motor control, action coordination
Thalamus	Sensory relay station; processes incoming sensory information before it reaches cortex
Superior Colliculus	Visual orienting; directs eyes/body toward visual stimuli
Inferior Colliculus	Processes auditory signals; sound localisation
Brainstem	Autonomic survival functions: breathing, heart rate, digestion; conduit linking spinal cord & brain
Pons	Regulates autonomic functions; assists breathing and basic motor control
Medulla	Vital reflexes: respiration, heart rate, blood pressure
Hypothalamus	Homeostasis: hunger, temperature, sleep; controls hormonal release via pituitary
Pituitary Gland	Anterior: synthesises & releases hormones → bloodstream → endocrine organs Posterior: stores & releases neurohormones (oxytocin, vasopressin)

Cerebral Cortex

Region	Function
Frontal Lobe	Decision-making, planning, emotional regulation, social behaviour
Motor Cortex	Executes voluntary movement
Parietal Lobe	Somatosensory processing: touch, spatial representation
Temporal Lobe	Hearing, memory, language comprehension
Occipital Lobe	Visual processing
Limbic System	Emotion, motivation, memory formation, decision-making

Species Differences

• Quadrupeds → elongated brains
• Upright animals (e.g., humans) → curved brains with expanded cortex

Anatomical Directions (Orientation Terms)

Body & CNS Orientation

• Neuroaxis: line from spinal cord through brain
• Anterior/Rostral: toward the front
• Posterior/Caudal: toward the tail/back
• Dorsal: back side
• Ventral: belly side
• Medial: toward midline
• Lateral: toward sides

The Nervous System Overview

Central Nervous System (CNS)

• Brain = control centre
• Spinal cord = communication pathway between brain & body

Peripheral Nervous System (PNS)

• All nerves outside CNS
• Two divisions:
  • Somatic NS → voluntary control of skeletal muscles
  • Autonomic NS → involuntary functions (heartbeat, digestion)

How the Nervous System Communicates

• Neurons transmit electrical impulses
• Supported by glial cells

Peripheral Nerves

Functions

Sensory Pathways

• Collect sensory input
• Send signals from body → spinal cord → brain

Motor Pathways

• send movement commands from CNS → muscles & glands
• Include autonomic signals (heart rate, digestion)

Integration

• Reflex arcs = fast, automatic responses without brain involvement

Nerve Categories

Region	Pairs
Cranial	12
Cervical	8
Thoracic	12
Lumbar	5
Sacral	5
Coccygeal	1

Somatic vs Autonomic Nervous System

Somatic NS

• Voluntary control
• Sensory in → dorsal roots
• Motor out → ventral roots
• “Skin in, muscle out”

Autonomic NS

Sympathetic (SNS) — Fight or Flight

• Increases heart rate
• Dilates pupils
• Inhibits digestion
• Mobilises energy
• “Fight, Flight, Fright, Fornicate”
• Spinal origin: thoracic & lumbar
• Short preganglionic, long postganglionic fibres

Parasympathetic (PNS) — Rest & Digest

• Slows heart rate
• Constricts pupils
• Stimulates digestion
• Conserves energy
• Origin: cranial & sacral
• Long preganglionic, short postganglionic fibres

Communication Systems: Nervous vs Hormonal

Nervous System

• Fast
• Electrical
• Targeted
• Conscious & unconscious actions

Endocrine System

• Hormones released via hypothalamus + pituitary
• Slower spread
• Longer-lasting effects
• Drugs often mimic hormones (e.g., melatonin agonists)

Brain Protection & Support

Blood Vessels

• Capillaries form the blood-brain barrier (BBB)
  • Only tiny or lipophilic molecules pass (O₂, CO₂, hormones)

Cerebrospinal Fluid (CSF)

• Produced in lateral & third ventricles
• Cushions brain
• Provides nutrients

Meninges

Three protective layers:

1. Dura Mater — tough outer layer
2. Arachnoid Mater — web-like structure
3. Pia Mater — delicate inner layer

Subarachnoid space: CSF flows here

Cortical Maps: Homunculi

• Motor homunculus → amount of cortical space devoted to movement
• Sensory homunculus → cortical space for sensation
• Body parts with fine control (hands, lips) are disproportionately large

Grey vs White Matter

Grey Matter	White Matter
Cell bodies & dendrites	Myelinated axons
Processing	Communication highways
Darker	Lighter

Subcortical Areas of the Forebrain

Structure	Function
Thalamus	Sensory relay, alertness, sleep regulation
Lateral Ventricles	Produce CSF
Cingulate Gyrus	Emotion + cognition
Corpus Callosum	Communication between hemispheres
Nucleus Accumbens	Reward, reinforcement, addiction
Hypothalamus	Homeostasis, hormone regulation
Basal Ganglia	Caudate + putamen + globus pallidus; motor control, decision-making; implicated in Parkinson’s + schizophrenia
Limbic System Components	Cingulate gyrus, thalamus, hypothalamus, mammillary bodies, hippocampus, amygdala, olfactory bulbs

Hindbrain & Midbrain

Midbrain

• Orientation reflexes (visual + auditory)
• Movement modulation
• Pain processing

Hindbrain

• Pons + medulla + cerebellum
• Autonomic functions & balance

Cerebellum

• Balance, posture
• Coordination of voluntary movement
• Motor learning

Measuring the Brain

(From images; paraphrased)

Common methods include:

• Structural imaging (MRI, CT)
• Functional imaging (fMRI, PET)
• Electrophysiological methods (EEG, MEG)
• Lesion studies to infer function from damage

The Neuron

Basic Structure

• Dendrites → receive signals
• Soma → integrates signals
• Axon hillock → action potential initiation
• Axon → carries electrical signal
• Myelin sheath → speeds conduction
• Axon terminals → release neurotransmitters

Neuron Classification

By Neurites

• Unipolar → 1 projection
• Bipolar → 2 projections
• Multipolar → many projections

By Dendrite Type

• Stellate (star-shaped)
• Pyramidal (triangle-shaped)
• Spinous (with spines)
• Aspinous (without spines)

Dendritic spines = crucial for learning & memory

By Axon Length

• Golgi Type I → long axons connecting distant regions
• Golgi Type II → short interneurons within a local circuit

By Neurotransmitter Type

• e.g., glutamatergic, GABAergic, dopaminergic

By Connection

• Sensory neurons
• Motor neurons

Afferent vs Efferent

• Afferent → arriving; toward CNS
• Efferent → exiting; away from CNS

How Neurons Work

Resting Membrane Potential

• Inside of neuron is negatively charged relative to outside
• Maintained by:
  • Selective ion channels
  • Sodium–potassium pump
  • Phospholipid bilayer

Action Potential Steps

1. Stimulus Arrival

• Neurotransmitters bind to receptors → ion flow into soma
• Signals integrate at axon hillock

2. Depolarisation

• Threshold (~ –50 mV) reached
• Voltage-gated Na⁺ channels open
• Massive sodium influx → membrane potential becomes more positive

3. Rising Phase

• Action potential initiated
• Na⁺ rushes in
• K⁺ channels are closed

4. Repolarisation → Absolute Refractory Period

• At +30 mV, Na⁺ channels close
• K⁺ channels open → K⁺ flows out
• Another AP cannot be triggered

5. Hyperpolarisation → Relative Refractory Period

• Membrane dips to around –80 mV
• K⁺ channels close
• Na⁺/K⁺ pump restores resting potential
• Neuron can fire again, but requires stronger stimulus