Week 5 - Psychobiology & Neuroscience

The Nervous System 

the pathway along which the brain sends and receives information about the body and environment. 

The Nervous System - Central Nervous System (CNS) 

• Brain 

• Spinal cord 

Responsible for processing and integrating information. 

The Nervous System - Peripheral Nervous System (PNS) 

Acts as a relay between CNS and: 

• Organs 

• Limbs 

• Skin 

Divisions of the PNS - Somatic Nervous System

Controls voluntary movement. 

• Sensory (afferent) neurons → carry information TO CNS 

• Motor (efferent) neurons → carry information FROM CNS 

Divisions of the PNS - Autonomic Nervous System

Controls involuntary functions. 

• Sympathetic system → prepares body for fight or flight 

• Parasympathetic system → calms body after danger 

Neurons 

• there are ~85 billion neurons in the brain 

• Receive, integrate, and transmit information 

• Many types but similar structure 

Structure of a Neuron - Dendrites 

Receive information from other neurons 

Structure of a Neuron - Cell Body (Soma) 

Contains nucleus and genetic code 

Structure of a Neuron - Axon 

Carries electrical signal away from soma 

Structure of a Neuron - Myelin Sheath 

• Fatty covering axon

• Increases speed of transmission 

Structure of a Neuron - Axon Terminal 

Where neurotransmitters are released 

The Neuronal Impulse/Action Potential 

An electrical signal sent down the axon to the axon terminal

• All-or-nothing event 

• Either fires fully or not at all 

The Neuronal Impulse/Action Potential - Stages

1. Resting Potential: The neuron is "charged" and ready, but quiet (at -70mV).

2. Depolarisation: The "fire" button is pressed. Sodium rushes in, and the charge spikes up to +40mV.

3. Repolarisation: The reset begins. Potassium rushes out, and the charge drops back down.

4. Hyperpolarisation: The reset "overshoots," making the neuron briefly more negative than usual so it can't fire again too quickly.

5. Return to Rest: The cell uses its internal "pumps" to get back to the original -70mV level.

The Synapse & Synaptic Transmission 

1. Vesicles & Transport: Synaptic vesicles (tiny sacs) carry chemical messengers called neurotransmitters to the very end of the neuron (the axon terminal).

2. The Release: The electrical impulse pushes these vesicles to the edge, where they release the neurotransmitters into the synapse (the tiny gap between neurons).

3. The Binding (Lock & Key): The neurotransmitters float across the gap and bind to receptors on the next neuron. Like a lock and key, each chemical only fits its specific receptor to pass the signal along.

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Drugs and Neurotransmission - Amphetamines 

• Stimulate dopamine release (entire supply of dopamine is released into synaptic gap)

• Block reuptake 

Hence ‘high’ is even more intense than with cocaine → leads to stronger mood crash

Drugs and Neurotransmission - Cocaine 

Blocks reuptake of dopamine & noradrenaline 

Drugs and Neurotransmission - SSRIs 

• Block serotonin reuptake 

• Increase serotonin in synaptic cleft 

The Brain - Major divisions - Forebrain 

• Thought 

• Emotion 

• Behaviour 

The Brain - Major divisions - Midbrain 

Sensory and motor clusters 

The Brain - Major divisions - Hindbrain 

• Cerebellum 

• Medulla 

• Pons 

Hindbrain Structures - Medulla & Pons 

• Essential functions 

Cardiac function (pump for the circulatory system)

Breathing 

Sleep-wake cycle 

Hindbrain Structures - Cerebellum 

• Movement 

• Balance 

• Posture 

• Learned motor skills (e.g., riding a bike) 

Cerebral Cortex 

• Spread out = ~2500 cm² 

• Convoluted surface 

Gyrus = ridge 

Sulcus = groove/valley 

Cerebral Cortex - Grey vs White Matter 

• Grey matter → cell bodies, dendrites, synapses 

• White matter → axons connecting grey matter 

Lobes of the Cerebrum - Frontal Lobe 

• Largest lobe 

Executive functions: 

• Planning 

• Inhibition 

• Working memory 

• Attention shifting 

• Goal-directed behaviour 

Lobes of the Cerebrum - Temporal Lobe 

• Auditory processing 

• Primary auditory cortex 

• Speech comprehension (left hemisphere) 

Lobes of the Cerebrum - Parietal Lobe 

• Integrates sensory information 

• Spatial processing 

• Navigation 

• Number processing (intraparietal sulcus) 

Lobes of the Cerebrum - Occipital Lobe 

• Visual cortex 

Vision: 

• Form 

• Motion 

• Colour 

Limbic System - Amygdala 

• Emotion processing 

• “Danger detector” 

• Triggers fight or flight 

• Fear conditioning 

• Social cue processing 

• Emotionally arousing memories 

Limbic System - Hippocampus 

• Memory processing 

• Learning 

• Spatial recognition 

• Imagining the future 

Damage → anterograde amnesia 

Case Study: H.M. 

• Hippocampus removed for epilepsy 

• Personality unchanged 

• Could not form new memories 

Brain Organisation - Localisation 

Specific cognitive abilities located in specific brain areas. 

Brain Organisation - Lateralisation 

Some functions dominant in one hemisphere. 

Brain Organisation - Lateralisation - Left Hemisphere 

• Controls right side of body 

• Language dominant 

Brain Organisation - Lateralisation - Right Hemisphere 

• Controls left side of body 

• Spatial orientation 

• Face recognition 

• Creativity 

Split Brain Research (Sperry) 

Corpus callosum (bundle of nerve fibers that allow your brain's left and right hemispheres to communicate) cut to treat epilepsy. Joe stares at center dot and objects are flashed either to the right side of the dot really or left

If object in: 

• Right visual field → Left hemisphere → Can name it 

• Left visual field → Right hemisphere → Cannot name it 

Demonstrates hemispheric specialisation. 

Neural Plasticity 

Brain’s ability to change structure and function in response to experience or damage. 

Higher in childhood but continues in adulthood. 

e.g. London taxi drivers (Maguire et al. 2001): Taxi drivers who had completed "The Knowledge" (memorising thousands of London routes) had significantly larger posterior hippocampi than non-taxi drivers. Size correlated with years of experience. Demonstrates that sustained cognitive activity produces structural brain changes.

e.g. Musicians (Bengtsson et al., 2005) 

• Larger temporal cortex 

Evidence for Plasticity 

London Taxi Drivers (Maguire et al., 2001) 

• Larger posterior hippocampus 

Musicians (Bengtsson et al., 2005) 

• Larger auditory cortex 

Brain Damage Recovery (Thiel et al., 2006) 

• Right hemisphere compensates for left hemisphere language damage 

Research Methods in Neuroscience - Lesion Studies 

Study individuals with brain damage. 

Advantages: 

• Stronger causal inference 

• Identify structure-function relationships 

Disadvantages: 

• Often post-event 

• Lack experimental control 

• Ethical limitations 

Research Methods in Neuroscience - EEG (Electroencephalogram) 

Measures electrical activity via scalp electrodes. 

Excited state: 

• Low amplitude 

• High frequency 

Relaxed state: 

• High amplitude 

• Low frequency 

Advantages: 

• Excellent temporal resolution 

• Inexpensive 

• Child-friendly 

Disadvantages: 

• Poor spatial resolution 

Research Methods in Neuroscience - fMRI 

measures brain activity by detecting changes associated with blood flow

Active brain areas use more oxygen → detectable via magnetic changes. 

 

fMRI Advantages: 

• Good spatial resolution 

• Examines brain networks 

Disadvantages: 

• Poor temporal resolution 

• Expensive 

• Motion artefacts 

• Hard with children 

• Can cause anxiety