consciousness

1. Neuron and Synaptic Transmission

1.1 Overview of Synaptic Transmission

  • Action Potential (AP) reaches the Terminal Button (TB)

  • Neurotransmitters (NTs): Chemicals enabling neuron communication

  • Vesicles: Tiny sacs in TB containing NTs

  • Any neuron carries 1-3 types of NTs

  • Over 70 types of NTs identified

  • Synapse: Gap between neurons, they do not touch

    • Presynaptic Neuron: Before the synapse

    • Postsynaptic Neuron: After the synapse

      • Dendrites have receptor sites for NTs

1.2 Process of Synaptic Transmission

  • AP arriving at TB pushes vesicles to the end of TB

  • Vesicles fuse with TB membrane and release NTs into the synapse

  • NTs diffuse across the synapse to contact receptor sites on postsynaptic dendrites

1.3 Communication Mechanism

  • NTs must fit into their corresponding receptor sites (like a key in a lock)

  • Successful fitting generates a message to the postsynaptic neuron

  • Types of Messages:

    • Excitatory: Encourages neuron to fire

    • Inhibitory: Prevents neuron from firing

  • Neurons integrate thousands of messages; balance of excitatory vs inhibitory determines firing

1.4 After NT Activity

  • NTs are quickly disengaged from receptors and must be cleared from the synapse

  • Most common clearing method is Reuptake, where NTs are reabsorbed into the presynaptic neuron

  • Another method is Degradation, where a chemical breaks down NTs

2. Consciousness and Sleep

2.1 Understanding Sleep

  • Sleep: An altered state of consciousness, reduces responsiveness, and averages 8 hours/night

  • Sleep deprivation can lead to similar impairments as being intoxicated

  • Common sleep complaints: accidents, irritability, and paranoia

  • Recommended for college students: 7.5-8 hours

  • Historical decline in sleep duration linked to electric light and technology

2.2 Sleep Dynamics

  • Sleep Inertia: Slow reactions post-waking, lasting from 30 minutes to 3 hours

  • Sleep posture changes frequently (30-40 times through the night)

  • Visual and auditory processing can still occur during sleep

2.3 Measuring Sleep

  • Challenges in Measurement: Difficulty in reporting and recalling sleep experiences

  • Use of EEG (electroencephalogram) to monitor brain activity during sleep

    • Summarizes overall activity and correlates with behavior

2.4 Sleep Stages and Cycles

  • Stages of Sleep: 5 stages (4 Non-REM + 1 REM)

    • STAGE 1: Brief transition to sleep; lasts a few minutes

    • STAGE 2: Light sleep, accounts for 45-50% of sleep

    • STAGE 3 & 4: Deep, restorative sleep; sleepwalking can occur

    • REM Sleep: rapid eye movement; occurs 1.5-2 hours total in 8 hours, associated with vibrant dreaming

  • Each complete sleep cycle lasts approximately 90 minutes

    • Cycles vary across the night with stages changing over time

2.5 Functions and Theories of Sleep

  • Restoration Theory: Sleep restores physical and mental functions

  • Preservation: Protects during vulnerable times

  • Dream Theories:

    • Freudian View: Dreams fulfill unconscious wishes.

    • Memory Consolidation: Sleep contributes to long-term memory retention

    • Physiological Activation: Neurons need stimulation; REM provides regular activity

3. Implications of Sleep Deprivation

3.1 Effects of Complete and Partial Sleep Deprivation

  • Complete Sleep Deprivation: Leads to death in rats if REM sleep is denied, due to immune system damage

  • Partial Sleep Deprivation: Results in impaired judgment, poor motor skills, hallucinations

    • Notable examples (e.g., Peter Tripp's 200-hour wakefulness experiment)

  • Sleep Debt: Accumulating need for sleep that affects cognitive functions

    • Recovery methods: Longer sleep post-deprivation or bank sleep in advance of expected sleep loss.