SE

Introduction to Psychology - Chapter 3: Biological Foundations of Behavior

Neuroscience

  • Definition: Neuroscience is the study of the body's electrochemical communication circuitry.
    • Emphasizes the brain and nervous system as the primary centers where electrical and chemical signaling enable behavior, thought, and emotion.

Nervous System

  • Characteristics:
    • Complex
    • Integrated
    • Adaptable (plasticity)
    • Electrochemical transmission governs communication

Nervous System: Pathways

  • Afferent pathways: information travels from the body to the brain (Body → Brain)
  • Efferent pathways: information travels from the brain to the body (Brain → Body)
  • Nerves carry important information throughout the body via these pathways

Nervous System: Divisions

  • Central Nervous System (CNS): brain and spinal cord
  • Peripheral Nervous System (PNS):
    • Somatic Nervous System (SNS): sensory nerves and motor nerves controlling voluntary muscle activity
    • Autonomic Nervous System (ANS): involuntary body functions
    • Sympathetic Nervous System: arousal and energy expenditure
    • Parasympathetic Nervous System: relaxation and energy conservation

Nervous System: Cells

  • Glial Cells: provide support and nutrition to neurons
  • Neurons (roughly 85 to 100 billion in the brain): information processing and transmission
    • Key roles in computing, communication, and specialized functions such as mirror neurons
    • Mirror neurons: specialized neurons implicated in imitation and social perception

Neurons: Structure

  • Cell Body (soma)
  • Dendrites: input structures that receive signals
  • Axon: conduction fiber that transmits impulses
  • Impulse: electrical signal that travels along the neuron
  • Myelin Sheath: fatty insulation that speeds conduction

Neural Impulse

  • Charge dynamics:
    • Polarization: imbalance of charges across the membrane
    • Resting Potential: approximately V_{rest} \,\approx -70\ \text{mV}
    • Axon membrane becomes excited producing an impulse
    • Typical schematic shows different regions of the axon with varying voltages (e.g., 0 mV at peak changes)
  • Key concepts:
    • Semipermeable membrane allows selective ion flow via ion channels
    • Depolarization leads to an action potential
    • All-or-None Principle: once threshold is reached, the action potential fires with a consistent amplitude; if not reached, no action potential occurs
  • Formal representation (conceptual): \text{AP}(t) = \begin{cases} A, & Vm(t) \ge V{th} \ 0, & Vm(t) < V{th} \end{cases}
    • Here, A is the fixed amplitude of the action potential and V_{th} is the threshold potential

Synapses and Neurotransmitters

  • Synapse components: Synapse Vesicle, Neurotransmitters, Synaptic Gap, Receptor Site
  • Synaptic transmission process:
    • Electrical impulse is converted into a chemical signal at the synapse
    • Axon vesicle releases neurotransmitter into the synaptic gap (send)
    • Dendrite receptor sites detect the neurotransmitter (receive)

Neurotransmitters

  • Acetylcholine (ACh):
    • Roles: muscle actions, learning, memory
    • Interactions: Black widow venom ↑ Ach levels; Botulinum (Botox) ↓ Ach levels; Alzheimer's disease features ↓ Ach levels
  • GABA (Gamma-aminobutyric acid):
    • Role: inhibitory, regulatory; reduces neural excitability
    • Association: Anxiety linked to lower GABA levels
  • Glutamate:
    • Role: excitatory; important for learning and memory
    • Involvement: implicated in many psychological disorders
  • Norepinephrine (Noradrenaline):
    • Roles: stress response and arousal; modulates sleep alongside Ach
    • Effects: ↑ levels in mania/stress; ↓ levels in depression
  • Dopamine:
    • Roles: voluntary movement, reward anticipation
    • Drug interactions: stimulant drugs activate dopamine receptors
    • Clinical associations: Parkinson’s disease (↓ dopamine), Schizophrenia (↑ dopamine)
  • Serotonin:
    • Roles: regulation of sleep, mood, attention, learning
    • Depression: ↓ serotonin levels; antidepressants like Prozac ↑ serotonin levels
  • Endorphins:
    • Nature: natural opiates; modulate feelings of pleasure and pain
  • Oxytocin:
    • Dual role: hormone and neurotransmitter
    • Functions: related to lactation onset, attachment, and emotional bonds
  • Note on drug interactions: Drugs can mimic, enhance, or block neurotransmitter effects, altering neural signaling

Neural Networks

  • Interconnected pathways of nerve cells
  • Function: integrate sensory input and motor output
  • Development: evolves over years
  • Storage principle: information is distributed across multiple connections and neurons, not stored in a single neuron

Studying the Brain

  • Brain lesioning: naturally occurring or experimentally induced to study function
  • Electrical recording techniques:
    • Electroencephalograph (EEG)
    • Single-unit recording

Brain Imaging

  • X-ray: 2D imaging
  • CT Scan: 3D imaging
  • PET: tracks glucose metabolism to infer function
  • MRI: uses radio waves to image soft tissues
  • fMRI: measures live brain function by detecting blood flow changes

Hindbrain (Brainstem)

  • Medulla: controls breathing and reflex regulation
  • Pons: involved in sleep and arousal
  • Cerebellum: coordinates motor movement

Midbrain

  • Relays information between brain and the eyes/ears
  • Substantia Nigra: associated with Parkinson’s disease
  • Reticular Formation: patterns for stereotyped behaviors (e.g., walking, sleeping, alertness)

Forebrain

  • Limbic System: memory and emotion
    • Amygdala: discriminates objects needed for survival; emotional awareness and expression
    • Hippocampus: formation and recall of memories
    • Thalamus: relay station for much sensory information
  • Basal Ganglia: coordinates voluntary movements
  • Hypothalamus: regulates internal states (eating, drinking, sexual behavior) and links emotion, stress, and reward

Cerebral Cortex

  • Neocortex: outermost layer
  • Four Lobes:
    • Occipital: vision
    • Temporal: hearing, language processing, memory
    • Frontal: intelligence, personality, voluntary muscles
    • Parietal: spatial location, attention, motor control
    • Schematic arrangement: Occipital, Temporal, Frontal, Parietal

Somatosensory, Motor, and Association Cortex

  • Somatosensory Cortex (parietal lobe): body sensations and touch
  • Motor Cortex (frontal lobe): voluntary movements; point-to-point mapping
  • Association Cortex: ~75% of cortex; involved in higher-level processing, linking information across modalities

Split-Brain Research

  • Corpus Callosum: large bundle of axons that connects the two brain hemispheres
  • Split-brain studies reveal how the two hemispheres specialize and communicate

Hemispheres of the Cortex

  • Left Hemisphere: verbal processing, speech, grammar
    • Broca’s Area (speech production)
    • Wernicke’s Area (language comprehension)
  • Right Hemisphere: spatial perception, visual recognition, emotion

Endocrine System

  • Set of glands regulating the body by secreting hormones into the bloodstream
  • Glands include: Pituitary, Thyroid, Parathyroid, Pancreas, Adrenal, Ovaries, Testes
  • Characteristics:
    • Chemical messages that are interconnected with the nervous system
    • Relatively slow communication system compared to nervous system signaling

Genes and the Environment

  • Genotype + Experience interactions shape phenotype
  • Genetic heritage contributes to observable characteristics, but environment modifies how genetic traits develop (both physical and psychological)

Topics for Future Classes

  • Note: Post due on Saturday!
  • Sensation and Perception
  • Start studying for Exam 1
  • References: King, L. A. (2017). The science of psychology: An appreciative view (4th ed.). McGraw-Hill Education