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Overview of Nature, Nurture, and the Nervous System

Interaction of Environment and Heredity

  • Nature (Genetics, Biology)

  • Nurture (Everything else)

  • Language Acquisition (Noam Chomsky)

    • Reinforcement, punishment, social environment, learning, rewards.

    • Universal Grammar: Genetic factor distinguishing humans from other animals.

    • J.B. Watson: Culture influences behavior regardless of innate talents or ancestry.

Epigenetics

  • Experiences and environment can alter genetics.

    • Rat licking studies shed light on the impact of nurture on nature.

    • Identical twins provide a genetic control by showing similarities in different environments.

Key Takeaways

  1. Nature and Nurture interact; they do not work independently.

  2. Epigenetics shows how environmental factors influence genetic expression.

Studies on Twins

  • Identical Twins: Monozygotic, same DNA, similar when raised apart due to genetics.

  • Fraternal Twins: Dizygotic, no more genetically similar than regular siblings.

  • High vs. Low Lickers: Babies adopt behaviors from their mothers even when switched.

  • Minnesota Twin Study: Extensive research showing that separated twins share many traits.

    • Enhanced LTP (Long-Term Potentiation) is influenced by enriched environments.

Heritability

  • Variation among individuals attributed to genetics.

    • 62% of differences in intelligence linked to genetic factors.

    • Twin studies help assess the relationship between nature and nurture.

Overview of the Nervous System

  • Somatic Nervous System: Communicates sensory information; includes sensory and motor neurons.

  • Autonomic Nervous System: Involuntary functions;

    • Sympathetic: Fight or flight response (increases heart rate, blood circulation).

    • Parasympathetic: Rest and digest (calms the body).

Takeaway

  • Human nervous system has several divisions, each with specialized functions.

The Neuron and Neural Firing

  • Neurons are the basic building blocks of the nervous system. They communicate through electrical impulses, or action potentials.

  • Types of Neurons:

    • Sensory neurons: Detect external stimuli.

    • Motor neurons: Control muscle movements.

  • Glia Cells: Support neurons but also communicate chemically, affecting neural signals.

Spinal Reflex Arc

  • Sensory neurons receive stimuli, interneurons process them, and motor neurons execute the response.

    • Reflects fast communication and interactions within the nervous system.

Important Functions of Neurons

  • Dendrites: Receive messages.

  • Axon: Carries messages away from the cell body.

  • Electrical impulses travel down the axon, causing neurotransmitter release into the synapse.

Neurotransmitters

  • Types:

    • Excitatory: Increase likelihood of neuron firing (e.g., Glutamate).

    • Inhibitory: Decrease likelihood of neuron firing (e.g., GABA).

  • Synaptic Transmission proceeds from:

    1. Presynaptic neuron.

    2. Release of neurotransmitters.

    3. Neurotransmitters bind to receptors on postsynaptic neurons.

Myelin Sheath

  • Fatty layer protecting axons, speeding up neural transmission. Damage can lead to conditions like Multiple Sclerosis.

Neurotransmitters and Their Effects

  • Dopamine: Pleasure, movement; low levels linked to Parkinson's.

  • Serotonin: Mood regulation; low levels associated with depression.

  • Acetylcholine (ACh): Involved in movement and memory; reduced in Alzheimer's.

  • Endorphins: Natural painkillers; can be triggered by intense exercise.

Drugs and Neurotransmitter Interaction

  • Agonists: Enhance neurotransmitter action (e.g., opioids mimic endorphins).

  • Antagonists: Block neurotransmitter action (e.g., Black Widow venom for ACh).

Brain Structures and Functions

Hindbrain

  • Medulla: Controls autonomic functions (heart rate, breathing).

  • Pons: Connects brainstem and cerebellum; involved in sleep coordination.

  • Cerebellum: Manages balance and coordination, implicit memory.

Limbic System

  • Thalamus: Processes sensory information.

  • Hypothalamus: Regulates bodily drives (hunger, thirst, sexual motivation).

  • Amygdala: Processes emotions like fear and aggression.

  • Hippocampus: Essential for memory consolidation.

Cerebral Cortex

  • Left and right hemispheres, each with distinct responsibilities.

    • Frontal Lobe: Decision-making, impulse control (includes Broca’s Area for speech).

    • Parietal Lobe: Sensory processing (sense of touch).

    • Temporal Lobe: Auditory processing.

    • Occipital Lobe: Visual processing.

Lateralization and Split Brain

  • Split-brain procedure involves severing the corpus callosum to reduce epilepsy.

  • Language functions are mainly lateralized to the left hemisphere, whereas face recognition is generally right.

Neuroplasticity

  • The brain can reshape itself based on experiences.

    • Neurogenesis: Creation of new cells.

    • Long-term potentiation (LTP): Reinforces synaptic connections through repeated activation.

Brain Research Methods

  • EEG: Measures electrical activity of the brain.

  • fMRI: Shows brain activity by tracking changes in blood oxygen levels.

Case Studies and Plasticity

  • Case study of Jody Miller illustrates high functional plasticity in young brains post-hemispherectomy.