Comprehensive Study Notes on Neuron Function and Psychology Definitions

Action Potential in Neurons

1. Overview of Neuron Firing

1.1. Resting State

  • Resting potential: -70 mV

  • Ion distribution:

    • Sodium ions (Na+) are more concentrated outside the neuron.

    • Potassium ions (K+) and chloride ions (Cl-) are in lower concentrations inside the neuron.

    • This results in a negative charge within the neuron compared to outside.

  • Neuron stimulation occurs via neurotransmitters released by other neurons.

1.2. Threshold for Action Potential

  • As the neuron is stimulated:

    • Na+ ions slowly start to enter the neuron.

    • The voltage rises from -70 mV towards -55 mV, reaching this threshold is crucial for action potential (AP) to occur.

2. Phases of Action Potential

2.1. Depolarization

  • Occurs when the threshold of -55 mV is reached:

    • Sodium (Na+) channels open, allowing Na+ to rush into the neuron.

    • This influx causes the inside of the neuron to become more positive, reaching approximately +40 mV.

  • The action potential is characterized as all-or-none, meaning that the neuron fires completely or not at all.

2.2. Repolarization and Hyperpolarization

  • Repolarization:

    • Following the peak of action potential, K+ ions flood out of the neuron.

    • This causes the internal charge to become more negative again, potentially below -70 mV (hyperpolarization).

3. Neuron Structure and Function

3.1. Major Neuron Components

  • Dendrites: Receive impulses from the presynaptic neuron (analogous to a hand receiving signals).

  • Axon: Sends impulses away from the cell body to subsequent neurons.

  • Myelin Sheath: Fatty tissue that insulates the axon, facilitating faster signal transmission.

  • Nodes of Ranvier: Gaps in the myelin sheath allowing ion exchange, essential for action potential propagation.

  • Axon terminals: Connect to the next neuron at a synapse, where neurotransmitters are released.

  • Synapse: The gap between neurons where signaling molecules cross.

3.2. Impact of Multiple Sclerosis

  • Condition: An autoimmune disease resulting in the immune system attacking the myelin sheath.

  • Consequences: Leads to demyelination, impairing action potential conduction and causing difficulties in mobility and sensory perception.

4. Psychology Definitions

4.1. Definitions of Psychology

  • Definition #1: The Science of Mind and Behavior

  • Definition #2: The Science of Experimental Epistemology

    • Examines the origins of knowledge (nature vs. nurture).

    • Nativism: Knowledge is innate (nature).

    • Empiricism: Knowledge comes from experience (nurture, 'tabula rasa').

  • Definition #3: The Science of Knowing and Experiencing

    • Differentiation between data storage and experiential understanding of knowledge.

    • Experiencing: Involves direct sensory interaction, not merely memorization.

4.2. Memory and Behavior Concepts

  • Behaviorism: Focuses on observable behaviors, as outlined by John Watson.

    • Stresses elimination of the subjective mind in favor of measurable behavior.

  • Cognitivism: Emphasizes mental processes such as attention and memory, akin to computational input and output.

5. Mind-Body Problem

5.1. Philosophical Perspectives

  • Dualism (Descartes): Proposes a separation between the physical and non-physical (mind and body).

  • Materialism: Argues that everything, including thoughts, has a physical basis (thoughts as electrical signals).

6. Reflex Actions

6.1. Reflex Definition

  • Reflex: An automatic movement in response to a stimulus, bypassing conscious thought.

6.2. Knee Tap Reflex Steps

  1. Knee tap stimulates sensory neuron.

  2. Neuron signals travel through the spinal cord.

  3. Signal relays to the muscle for motor action (kicking foot).

7. Brain Structure and Function

7.1. Brain Parts

  • Hindbrain: Involved in basic autonomic functions (e.g., medulla regulates heart rate).

  • Midbrain: Organizes motor movements and regulates visual/auditory reflexes.

  • Forebrain: Associated with higher-order functions (e.g., cognitive and emotional processing).

    • Hypothalamus: Governs basic motivational needs.

7.2. Neurotransmitter Function

  • Neurotransmitters act as 'keys' that bind to receptor sites (the 'locks') on dendrites of the postsynaptic neuron, triggering action potentials.

7.3. Types of Potentials

  • EPSP (Excitatory Postsynaptic Potential): Makes the postsynaptic neuron more likely to fire.

  • IPSP (Inhibitory Postsynaptic Potential): Decreases the likelihood of firing.

8. Neuroplasticity

  • The ability of different brain parts to compensate and adapt by reorganizing pathways, as seen in recovery from brain injuries.