A Level Psych Biopsychology

Nervous System Overview

Central Nervous System (CNS):
Consists of the brain and spinal cord. Responsible for processing, interpreting, and responding to information.

Peripheral Nervous System (PNS):
Transmits messages to/from CNS. Split into:

• Somatic Nervous System (SNS): Controls voluntary movements (e.g., moving limbs).

• Autonomic Nervous System (ANS): Controls involuntary functions (e.g., breathing, heart rate).

  • Sympathetic Branch: “Fight or flight” – increases heart rate, dilates pupils.

  • Parasympathetic Branch: “Rest and digest” – calms body, slows heart rate.

Structure and Function of Neurons

Types of Neurons:

• Sensory Neurons: Carry messages from the senses to the CNS.

• Relay Neurons: Connect sensory and motor neurons. Found in the CNS.

• Motor Neurons: Carry messages from CNS to muscles/glands.

Neuron Structure:

• Dendrites: Receive signals.

• Axon: Transmits electrical impulse.

• Myelin Sheath: Insulates axon, speeds up transmission.

• Nodes of Ranvier: Gaps allowing faster impulse travel.

• Axon Terminal: Passes message to next neuron.

Synaptic Transmission

Process:

• electrical impulses (action potentials) reach the presynaptic terminal

• electrical impulses (action potentials) trigger release of neurotransmitters (or named example)

• neurotransmitters cross the synapse from vesicles

• neurotransmitters combine with receptors on the postsynaptic membrane

• stimulation of postsynaptic receptors by neurotransmitters result in either excitation (depolarisation) or inhibition (hyperpolarisation) of the postsynaptic membrane

Excitation vs. Inhibition:

• Excitatory neurotransmitters (e.g., adrenaline): increase likelihood of firing.

• Inhibitory neurotransmitters (e.g., serotonin): decrease likelihood of firing.

After transmission, the neurotransmitter is either:

• Reabsorbed into the presynaptic neuron (reuptake), or

• Broken down by enzymes in the synaptic cleft.

Endocrine System and Glands

Endocrine System:
A network of glands that secrete hormones directly into the bloodstream to regulate bodily functions.

Major Glands:

• Pituitary Gland: “Master gland” – controls other glands.

• Adrenal Gland: Releases adrenaline during stress (fight/flight).

• Ovaries/Testes: Produce sex hormones (oestrogen/testosterone).

Fight or Flight Response

Triggered by: Perception of a threat.

Process:

1. Hypothalamus activates the sympathetic nervous system.

2. Adrenal medulla releases adrenaline into the bloodstream.

3. Body prepares for action – heart rate ↑, pupils dilate, digestion stops.

4. Once threat passes, parasympathetic system returns body to normal.

Localisation of Function in the Brain

Key Areas & Functions:

• Motor Cortex (Frontal Lobe): Controls voluntary movements.

• Somatosensory Cortex (Parietal Lobe): Processes touch sensations.

• Visual Cortex (Occipital Lobe): Processes visual info.

• Auditory Cortex (Temporal Lobe): Processes sound.

• Broca’s Area (Left Frontal Lobe): Language production.

• Wernicke’s Area (Left Temporal Lobe): Language comprehension.

Support:

• Broca (Tan): Could understand speech but couldn’t speak → damage to Broca’s Area.

• Wernicke (1874): Patients could speak fluently but made no sense → Wernicke’s area damage.

Hemispheric Lateralisation & Split Brain Research

Hemispheric Lateralisation:
Some mental processes are specialised to one hemisphere (e.g., language on the left).

Split-Brain Research – Sperry (1968):
Studied patients who had corpus callosum severed.
Findings:

• If a word was shown to left visual field (right hemisphere) → couldn’t verbalise it.

• If shown to right visual field (left hemisphere) → could name it.
  Conclusion: Language is lateralised to the left hemisphere.

Plasticity & Functional Recovery

Brain Plasticity:
The brain’s ability to change and adapt (e.g., by forming new neural connections).

Functional Recovery:
After brain injury, the brain can “re-wire” itself using secondary neural pathways.

Examples of Functional Recovery:

• Axonal Sprouting – new nerve endings form connections.

• Reformation of Blood Vessels.

• Recruitment of Similar Brain Areas (opposite hemisphere may take over).

Support:

• Maguire et al. (2000): London taxi drivers had larger hippocampi → supports brain’s ability to adapt with experience.

Ways of Studying the Brain

Method	Description	Strength	Limitation

fMRI

Measures blood flow to brain areas (activity)

Non-invasive, high spatial resolution

Expensive, poor temporal resolution

EEG

Measures electrical activity via scalp electrodes

Real-time data, good temporal resolution

Can't localise activity

ERP

Event-related potentials linked to specific stimuli

High temporal resolution

Requires many trials

Post-Mortem

Analysis of brain after death

Detailed examination of abnormalities

No cause-effect, invasive

Circadian Rhythms (e.g., Sleep/Wake Cycle)

Definition:
Biological rhythms lasting about 24 hours.

Key Study – Siffre (1975):
Lived in a cave for 6 months with no natural light → his sleep/wake cycle settled to ~25 hours.
Conclusion: Body has an internal clock but is influenced by external cues (e.g., light).

Other Research:
Aschoff & Wever – similar findings in WWII bunker → supports existence of endogenous pacemaker.

Infradian & Ultradian Rhythms

Infradian Rhythms: Last longer than 24 hours (e.g., menstrual cycle).

• Study: Stern & McClintock → found menstrual cycles synced via pheromones.

Ultradian Rhythms: Occur more than once in 24 hours (e.g., sleep cycle).

• Sleep has 5 stages including REM and deep sleep (90-minute cycles).

• Dement & Kleitman: Monitored sleep using EEG – found REM associated with dreaming

Endogenous Pacemakers & Exogenous Zeitgebers

Endogenous Pacemakers:
Internal body clocks (e.g., the suprachiasmatic nucleus (SCN) in the hypothalamus controls circadian rhythms).

Exogenous Zeitgebers:
External cues like light or social routines that reset biological clocks.

• Light → SCN → Pineal Gland → Melatonin (sleep hormone).

Research:

• DeCoursey et al. (2000): Destroyed SCN in chipmunks → disrupted sleep/wake cycles.

• Campbell & Murphy: Light exposure to back of knees shifted circadian rhythms – supports light as a zeitgeber.