PSYC 1100 A10 SPRING 2025 03 Introduction to Neuroscience KPU Courses

Biological Psychology Overview

• Biological psychology explores the relationship between biological processes and psychological behaviors.

• Key idea: "Everything psychological is simultaneously biological."

• Psychological behaviors have underlying biological mechanisms, exemplified by motor functions and perceptions.

Natural Selection vs. Sexual Selection

• Natural Selection: Process where adaptive traits beneficial for survival are passed on.

  • Example: Large horns in male rams are advantageous in competition, leading to increased reproduction.

• Sexual Selection: Involves traits perceived as attractive by the opposite sex, regardless of survival advantages.

  • Example: Male peacocks with colorful feathers may attract more mates but are more visible to predators.

• Key distinction: Natural selection is always adaptive, while sexual selection may include maladaptive traits if they increase reproductive success.

Historical Context: Phrenology

• Phrenology, developed by Franz Gall, studied bumps on the skull to predict character traits.

• While scientifically disproven, it was the first step in exploring the localization of brain functions.

• Localization of function: Different parts of the brain are responsible for different psychological functions.

Neurons: The Building Blocks of the Nervous System

• Neurons are specialized cells that transmit information throughout the nervous system, present in the brain and other body parts.

  • Parts of a Neuron:

    • Dendrites: Receive and integrate information.

    • Soma (Cell Body): Contains the nucleus and maintains cell viability.

    • Axon Hillock: Junction where the axon begins, important for initiating action potentials.

    • Axon: Long extension carrying electrical impulses.

    • Myelin Sheath: Insulation that speeds up signal transmission along the axon.

    • Axon Terminal: End of the axon where neurotransmitters are released into the synapse.

Synapses and Neurotransmission

• Synapse: Gap between neurons where neurotransmission occurs.

  • Presynaptic Cell: Sends the message, releasing neurotransmitters.

  • Postsynaptic Cell: Receives the message through neurotransmitter binding to receptors.

• Neurotransmitter Fate:

  1. Remain in Synaptic Clef: Waiting for receptors (uncommon).

  2. Broken Down by Enzymes: Specialized enzymes break down neurotransmitters.

  3. Reuptake: Neurotransmitters can be recycled by reabsorbing into the presynaptic cell.

Membrane Potential and Action Potential

• Membrane Potential: Voltage difference across a cell membrane, crucial for neuronal communication.

• Resting Membrane Potential: Typically around -70 mV, dependent on ion concentrations (Na+, K+, Cl-).

• Steps of Action Potential:

  1. Summation: Integration of excitatory and inhibitory signals from dendrites.

  2. Hypopolarization: Membrane potential rises towards the threshold (-55 mV).

  3. Depolarization: Rapid influx of Na+ ions after reaching the threshold leads to rapid membrane potential increase.

  4. Overshoot: Membrane potential exceeds 0 mV due to excess Na+ inflow.

  5. Repolarization: K+ channels open, allowing K+ to exit, restoring negative membrane potential.

  6. Hyperpolarization: Overshooting the resting potential to about -80 mV before stabilizing.

  7. Refractory Period: Neuron temporarily unable to fire again until ions are rebalanced.

• Sodium-Potassium Pump: Restores resting potential by moving 3 Na+ out and 2 K+ into the neuron, essential for recovery from action potential.

Saltatory Conduction

• Myelination facilitates faster signal transmission by allowing action potentials to "jump" between Nodes of Ranvier.

• This results in quicker neuron communication compared to unmyelinated axons.