AQA Psychology A-level - Biopsychology Study Notes

Nervous System and Endocrine System

1. Structure of the Nervous System

   • Central Nervous System (CNS): Consists of the Brain (center of conscious awareness) and the Spinal Cord (responsible for reflex actions and transferring messages to the PNS).

   • Peripheral Nervous System (PNS): Transmits messages via millions of neurons to and from the CNS.

     • Somatic Nervous System (SNS): Controls muscle movement and receives information from sensory receptors.

     • Autonomic Nervous System (ANS): Governs vital functions such as heart rate, digestion, and stress response.

     • Sympathetic State: Prepares body for 'fight or flight' (increased heart rate, inhibited digestion, dilated pupils).

     • Parasympathetic State: Returns the body to 'rest and digest' (decreased heart rate, stimulated digestion, constricted pupils).

2. The Endocrine System

   • Works alongside the nervous system to control vital functions using hormones secreted into the bloodstream.

   • The Pituitary Gland: Located in the brain; often called the 'master gland' as it releases hormones that stimulate other endocrine glands (e.g., ACTH during stress response).

   • Glandular Examples: Adrenal glands release adrenaline; Thyroid releases thyroxine which affects metabolism.

Neurons and Synaptic Transmission

1. Types of Neurons

   • Sensory: Carry messages from PNS to CNS (long dendrites, short axons).

   • Relay: Connect sensory to motor or other relay neurons (short dendrites, short axons).

   • Motor: Connect CNS to effectors like muscles/glands (short dendrites, long axons).

2. Synaptic Transmission

   • The Process: Signals move electrically along the neuron but must move chemically across the synapse. When the impulse reaches the presynaptic terminal, it triggers the release of neurotransmitters from synaptic vesicles.

   • Summation: Decides whether a post-synaptic neuron fires. Excitatory potentials (e.g., Noradrenaline) increase positive charge, making firing more likely. Inhibitory potentials (e.g., Serotonin) increase negative charge, making firing less likely. The net effect involves calculating the sum of these signals.

Brain Function Localization

1. Key Functional Areas

   • Motor Area: Located in the frontal lobe; controls voluntary movement on the opposite side of the body.

   • Somatosensory Area: Located in the parietal lobe; processes sensory information from the skin (touch, heat, pressure).

   • Visual Area: Occipital lobe; each eye sends information from the right visual field to the left visual cortex and vice versa.

   • Auditory Area: Temporal lobe; analyzes speech-based information.

2. Language Centres

   • Broca’s Area: In the left frontal lobe; responsible for speech production. Damage leads to Broca’s Aphasia (slow, laborious, and non-fluent speech).

   • Wernicke’s Area: In the left temporal lobe; responsible for language comprehension. Damage leads to Wernicke’s Aphasia (fluent but meaningless speech; use of neologisms).

3. Evidence: Case studies like Phineas Gage, who suffered personality changes after a tamping iron passed through his frontal lobe, supporting the link between specific brain regions and executive function/personality.

Brain Plasticity and Recovery

1. Plasticity: The brain’s ability to change throughout life. During infancy, the brain experiences rapid growth in synaptic connections ($\approx 15,000$ per neuron at age 2-3).

   • Synaptic Pruning: Deleting rarely used connections and strengthening frequently used ones.

2. Functional Recovery after Trauma: Healthy brain areas take over functions of damaged areas.

   • Axonal Sprouting: Growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.

   • Recruitment of Homologous Areas: Using similar areas on the opposite side of the brain to perform specific tasks (e.g., if the left Broca’s area is damaged, the right-side equivalent may take over).

Split-Brain Research

1. Hemispheric Lateralisation: The two hemispheres are not identical. The left is typically the 'analyser' (language/logic), while the right is the 'synthesiser' (spatial/creative).

2. Sperry’s Research (1968): Studied individuals who had undergone a commissurotomy (corpus callosum severed to treat epilepsy).

   • Visual Task: If an image was shown to the right visual field (processed by left hemisphere), the patient could describe what they saw. If shown to the left visual field (right hemisphere), they could not describe it (lack of language centers) but could select a matching object with their left hand.

Investigating Brain Function

1. fMRI (Functional Magnetic Resonance Imaging): Detects changes in blood oxygenation and flow. High spatial resolution ($1-2$ mm) but poor temporal resolution ($5$ second lag).

2. EEG (Electroencephalogram): Measures electrical activity via electrodes on the scalp. High temporal resolution (millisecond range) but poor spatial resolution (cannot pinpoint exact source).

3. ERP (Event-Related Potentials): Uses EEG data filtered to show specific brain responses to sensory, cognitive, or motor events.

4. Post-Mortem Examinations: Analysis of a person's brain after death, often used to study rare disorders (e.g., Broca’s study of 'Tan').

Biological Rhythms

1. Circadian Rhythms: Cycles of $\approx 24$ hours.

   • Siffre’s Cave Study: Spent long periods underground with no natural light; his 'free-running' biological clock settled into a rhythm of $\approx 25$ hours.

   • Endogenous Pacemakers: The Suprachiasmatic Nucleus (SCN) in the hypothalamus acts as the primary master clock.

   • Exogenous Zeitgebers: External cues like light that reset the SCN.

2. Infradian Rhythms: Longer than 24 hours (e.g., Menstrual cycle; Seasonal Affective Disorder).

3. Ultradian Rhythms: Shorter than 24 hours (e.g., Sleep cycles consisting of $5$ stages lasting $\approx 90$ minutes each, alternating between REM and Non-REM).