Biological Psychology: Structure and Function of the Nervous System

Biological Psychology

Introduction to Biological Psychology

Biological psychology explores the relationship between the nervous system and behaviour, focusing on how brain structure and function influence psychological processes. Researchers in this field are known as biological psychologists or neuroscientists.

• Key Point: Biological psychology bridges neuroscience and psychology, examining how neural mechanisms underpin behaviour.

• Example: Studying how neurotransmitter imbalances contribute to mental disorders.

Brain Mapping Methods

Historical and Modern Techniques

Brain mapping methods are used to study the structure and function of the brain. Early methods like phrenology, which linked skull shape to cognitive abilities, have been discredited. Modern techniques include neuropsychological tests, brain lesion studies, and advanced imaging technologies.

• Phrenology: Early, now discredited, method that attempted to link skull shape to mental faculties.

• Neuropsychology: Uses tests to assess cognitive function in individuals with brain damage, considering language and cultural influences.

• Animal Studies: Controlled brain lesions in animals to study behaviour.

Electroencephalograph (EEG)

EEG measures electrical activity in the brain using electrodes placed on the scalp. It is excellent for studying changes in brain activity over milliseconds but less effective for pinpointing small regions.

Neuroimaging Techniques

Neuroimaging allows visualization of brain structure and function.

• Computed Tomography (CT): Uses X-rays to create 3D images of the brain.

• Magnetic Resonance Imaging (MRI): Uses magnetic fields to visualize brain structure.

• Functional MRI (fMRI): Visualizes brain activity by detecting changes in blood flow.

• Positron Emission Tomography (PET): Measures glucose consumption to map neural activity.

• Magnetoencephalography (MEG): Measures tiny magnetic fields generated by the brain.

Brain Stimulation Techniques

• Deep Brain Stimulation (DBS): Uses implanted electrodes to modify brain function, potentially treating disorders like Parkinson’s disease and depression.

• Transcranial Magnetic Stimulation (TMS): Applies magnetic fields to the skull to enhance or interrupt brain function.

Neurons: The Brain’s Communicators

Structure and Function of Neurons

Neurons are specialized cells for communication, with approximately 86 billion neurons and 160 trillion synaptic connections in the human brain.

• Cell Body (Soma): Builds new cell components.

• Dendrites: Receive information from other neurons.

• Axons: Transmit information to other neurons.

• Axon Terminal: Contains synaptic vesicles filled with neurotransmitters.

• Synapse: The gap between neurons where neurotransmitters are released.

Synaptic Transmission

Synaptic transmission is the process by which neurotransmitters are released from one neuron and bind to receptors on another, enabling communication.

Electrical Responses of Neurons

Action Potential

The action potential is an abrupt wave of electrical discharge that travels down the axon, triggering neurotransmitter release. It is an all-or-none response, originating near the cell body and moving to the axon terminal.

• Resting Potential: The membrane potential when the neuron is not stimulated, typically around -60 mV.

• Threshold of Excitation: The level of stimulation required to trigger an action potential.

• Refractory Period: Brief period after firing when the neuron cannot fire again.

Glial Cells

Types and Functions

Glial cells support neurons and are equally numerous in the brain.

• Astrocytes: Star-shaped, most abundant, increase reliability of neuronal transmission, found in the blood-brain barrier.

• Oligodendrocytes: Promote new connections and produce the myelin sheath around axons.

Neurotransmission

Neurotransmitters and Communication

Communication within neurons is electrical, while communication between neurons is chemical. Neurotransmitters bind to receptor sites on the next neuron, following a lock-and-key mechanism.

• Reuptake: Process where neurotransmitters are reabsorbed into the axon terminal.

• Excitatory vs. Inhibitory: Some neurotransmitters excite, others inhibit neural activity.

Types of Neurotransmitters

• Glutamate: Excitatory, involved in learning and memory; toxic in high doses.

• GABA: Inhibitory, dampens neural activity.

• Acetylcholine: Influences arousal, attention, sleep, memory, and muscle movement.

• Monoamines: Includes norepinephrine (arousal, mood), dopamine (motor function, reward), serotonin (mood, sleep).

• Anandamides: Influence eating, motivation, memory, sleep; bind to same receptors as THC.

• Neuropeptides: Short amino acid chains; endorphins relieve pain, others regulate hunger and memory.

Psychoactive Drugs

Effects on Neurotransmitter Systems

Psychoactive drugs interact with neurotransmitter systems, affecting mood, arousal, and behaviour.

• Agonists: Increase activity of neurotransmitter systems (e.g., opiates mimic endorphins).

• Antagonists: Decrease activity (e.g., dopamine blockers for schizophrenia).

Neural Plasticity

Development and Learning

Plasticity refers to the nervous system’s ability to change. Neurons change through growth, synaptogenesis, pruning, and myelination. Learning can potentiate synapses.

• Adult Plasticity: Decreases with age; recovery from injury is limited.

• Stem Cells: Can become any cell, including neurons; potential for neurogenesis.

Brain-Behaviour Network

Central and Peripheral Nervous Systems

Sensory information enters and decisions exit the central nervous system (CNS). The peripheral nervous system (PNS) consists of nerves outside the CNS.

Central Nervous System

Protection and Structure

The CNS is protected by meninges and cerebrospinal fluid-filled ventricles.

Organization of the CNS

The brain is divided into systems based on location and function.

Cerebral Cortex

Lobes and Functions

The cerebral cortex is the largest part of the forebrain, divided into four lobes: frontal, parietal, temporal, and occipital, each with distinct functions.

Hemispheres and Corpus Callosum

The forebrain consists of two hemispheres connected by the corpus callosum, enabling communication.

Lateralization

Some cognitive functions are more dominant in one hemisphere.

Right Hemisphere	Left Hemisphere
Coarse language skills, tone of voice, visuospatial skills, perceptual grouping, face perception	Fine-tuned language skills, speech comprehension and production, reading, writing, making facial expressions, motion detection

Localization of Function

Brain Regions and Complex Tasks

Many brain areas are associated with specific functions, but complex tasks require coordination across multiple regions.

Split Brain Surgery

Severing the corpus callosum can reduce epileptic seizures, illustrating the importance of interhemispheric communication.

Frontal Lobes

Functions and Mapping

The frontal lobes assist in motor function, language, memory, and executive functioning. Broca’s area is involved in speech production; the motor cortex maps the body.

Phineas Gage Case

Phineas Gage’s injury to his prefrontal cortex led to dramatic behavioural changes, illustrating the role of this region in personality and executive function.

Parietal Lobe

Somatosensory Cortex

The parietal lobe contains the somatosensory cortex, sensitive to pressure, pain, and temperature, and communicates with the motor cortex.

Temporal Lobe

Auditory and Language Processing

The temporal lobe plays a role in hearing, language comprehension (Wernicke’s area), and memory. Lesions can cause neglect and other deficits.

Occipital Lobe

Vision

The occipital lobe is specialized for vision and located at the back of the brain.

Cortical Hierarchies

Sensory Processing

Sensory information first enters the primary sensory cortex, then moves to association cortex for more complex processing.

Basal Ganglia

Movement and Reward

The basal ganglia are forebrain structures that help control movement and reinforcement. Damage can contribute to Parkinson’s disease.

Limbic System

Emotion, Motivation, and Memory

The limbic system is the emotional centre of the brain, involved in smell, motivation, and memory.

• Hypothalamus: Regulates internal bodily states and controls the pituitary gland.

• Thalamus: Relays sensory information to the cortex.

• Amygdala: Key role in fear, excitement, and arousal.

• Hippocampus: Spatial memory; damage causes inability to form new memories.

Brain Stem

Basic Functions and Structure

The brain stem connects the cerebral cortex and spinal cord, performing basic bodily functions and serving as a relay station.

• Cerebellum: Balance and movement coordination.

• Pons: Connects cortex to cerebellum, triggers dreams.

• Medulla: Regulates breathing and heartbeat.

Spinal Cord

Signal Transmission and Reflexes

The spinal cord conveys signals between the brain and body, with sensory nerves carrying information to the brain and motor nerves carrying information to the body. Interneurons allow reflexes.

Peripheral Nervous System

Somatic and Autonomic Branches

The PNS is divided into the somatic nervous system (controls voluntary movement) and the autonomic nervous system (controls involuntary actions).

• Sympathetic Division: Engaged during crisis (fight or flight).

• Parasympathetic Division: Controls rest and digestion.

Endocrine System

Hormones and Behaviour

The endocrine system consists of glands and hormones that regulate bodily functions and emotions.

• Pituitary Gland: Controlled by the hypothalamus, releases hormones influencing growth and other functions, including oxytocin.

• Adrenal Glands: Release adrenaline and cortisol during emotional arousal.

• Sexual Reproductive Glands: Testes and ovaries produce testosterone and estrogen.

Genetics and Behaviour

Nature vs. Nurture

Genes are carried on chromosomes; humans have 46 chromosomes.

• Genotype: Set of genes an individual has.

• Phenotype: Observable traits.

• Dominant/Recessive Genes: Dominant genes mask others; recessive genes are masked.

• Epigenetics: Gene expression can be modified by life experiences.

Behavioural Adaptation and Evolution

Adaptation and Fitness

Organisms develop adaptations to better survive and reproduce.

• Fitness: Ability to survive and reproduce at higher rates.

• Natural Selection: Adaptations become more common in the population.

Behavioural Genetics

Heritability and Research Designs

Behavioural genetics studies the impact of genes and environment on psychological traits, estimating heritability.

• Family Studies: Examine trait similarities among relatives.

• Twin Studies: Compare identical and fraternal twins.

• Adoption Studies: Compare adopted children to biological and adoptive parents.

Summary Table: Organization of the Central Nervous System

System	Main Function
Cortex	Frontal: executive functions; Parietal: touch, vision; Temporal: auditory, language, memory; Occipital: visual information
Basal Ganglia	Movement and motor planning
Limbic System	Thalamus: sensory relay; Hypothalamus: endocrine/autonomic control; Amygdala: arousal/fear; Hippocampus: spatial memory
Cerebellum	Balance and movement coordination
Brain Stem	Midbrain: movement/reflexes; Pons: cortex-cerebellum relay; Medulla: breathing/heartbeat
Spinal Cord	Signal transmission between brain and body