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Psychology Study Notes: Nervous System and Brain Structures

Nervous System Overview

  • The nervous system is a complex network responsible for relaying information throughout the body.

  • Questions about its structure and functions, particularly focusing on the Central Nervous System (CNS) and the brain, are crucial for understanding.

Central Nervous System: The Brain

Brain Evolution

  • The brain's development began with basic structures essential for sustaining life.

  • The most ancient parts of the brain are dedicated to fundamental survival functions.

Brainstem Structures (Survival Functions)

  • Medulla:

    • Primary regulator of vital functions like breathing and heart rate.

    • Damage to the medulla is typically fatal, highlighting its critical role in survival.

  • Pons:

    • Plays a significant role during sleep and dreaming states.

    • Functions as a 'bridge,' facilitating communication and connection between the lower and upper brain regions.

Cerebellum

  • Functions:

    • Crucial for the coordination of voluntary muscle movements and maintaining balance.

    • Impact of Alcohol: Alcohol consumption impairs cerebellar function, leading to a noticeable loss of coordination, which is often assessed in field sobriety tests.

    • Memory: Responsible for the storage and retrieval of procedural memories, such as the learned skill of riding a bike or playing an instrument.

Limbic System (Emotional Center)

  • Often referred to as the emotional center of the brain due to its primary role in emotional experiences.

  • Key Structures:

    • Hypothalamus:

      • Regulates essential bodily functions including stress response, hunger, thirst, sex drive, and sleep cycles.

      • Plays a vital role in maintaining homeostasis, the body's internal balance.

    • Thalamus:

      • Serves as the brain's main sensory relay station.

      • Directs almost all incoming sensory information (with the notable exception of smell) to the appropriate areas of the cerebral cortex for processing.

    • Amygdala:

      • Central to the processing and experience of fear.

      • Involved in other emotional responses and memory consolidation of emotional events.

    • Hippocampus:

      • Absolutely essential for the formation of new long-term memories.

      • Its function is significantly affected by substances like alcohol, leading to memory impairment, commonly known as blackouts.

Cerebral Cortex & Its Lobes

Cerebral Cortex Overview

  • The Cerebral Cortex is the outermost layer of the brain.

  • It is highly convoluted and wrinkled, a design feature that significantly increases its surface area, thereby enhancing its capacity for complex information processing.

  • The cortex is divided into two distinct hemispheres: the left and right, with each hemisphere further subdivided into four principal lobes.

The Four Lobes

  • Occipital Lobe:

    • Location: Situated at the very back of the head.

    • Function: Primarily responsible for processing visual information received from the eyes.

  • Temporal Lobe:

    • Location: Located on the sides of the head, near the ears.

    • Functions:

      • Processes auditory information (hearing).

      • Contains Wernicke's area, which is critical for the comprehension and understanding of language.

      • The hippocampus, though part of the limbic system, is sometimes considered functionally integrated with this lobe due to its role in memory formation.

  • Parietal Lobe:

    • Functions: Processes sensory information related to taste, temperature perception, and touch.

    • Somatosensory Cortex: Interprets sensations received from the body.

      • Areas of the body with a higher density of sensory receptors (e.g., lips) correspond to larger representation areas within the somatosensory cortex compared to less sensitive areas (e.g., elbow).

  • Frontal Lobe:

    • Functions:

      • Manages executive functions such as planning, impulse control, decision-making, and other complex cognitive behaviors, especially attributed to the prefrontal cortex.

      • Contains the motor cortex, which is responsible for initiating and controlling voluntary movements.

      • Houses Broca's area, which is vital for speech production.

    • Development: This is the last part of the human brain to fully mature, with development continuing through adolescence and into early adulthood.

Hemispheric Specialization & Split Brain Research

Corpus Callosum

  • A robust bundle of neural fibers that serves as the primary communication link between the left and right cerebral hemispheres.

  • Its function is to allow continuous communication and information exchange between the two halves of the brain.

Contralateral Control

  • A fundamental principle of brain organization where the left hemisphere of the brain controls the movements and sensations of the right side of the body, and the right hemisphere controls the left side of the body.

Split Brain Patients

  • In certain cases, usually to alleviate severe, intractable epilepsy, the corpus callosum is surgically severed.

  • This surgical intervention results in a condition where the two hemispheres operate with distinct and limited communication, revealing their specialized functions.

  • Left Hemisphere Specialization:

    • Dominant for language functions, including both spoken and written communication.

    • Responsible for logical reasoning, mathematical calculations, and processing details.

  • Right Hemisphere Specialization:

    • Specializes in nonverbal processing.

    • Manages visual-spatial perception, musical aptitude, emotional processing, and the recognition of patterns and faces.

  • Experimental Insights: Studies with split-brain patients vividly demonstrate that each hemisphere possesses unique specialized abilities and operates with significantly reduced communication post-surgery.

Neurons & Neurotransmitters

Neuron Basics

  • Neurons: The fundamental building blocks of the nervous system, responsible for transmitting information throughout the entire network.

  • Dendrites: Branch-like extensions of a neuron that receive information from other neurons.

  • Axons: Long, slender projections that transmit information away from the neuron's cell body to other neurons.

  • Synapse: The microscopic gap between two neurons where chemical signals, called neurotransmitters, are released and transmitted.

  • Myelin Sheath: A fatty, insulating layer that covers many axons, significantly increasing the speed and efficiency of electrical impulse transmission along the axon.

Neurotransmitter Types

  • Excitatory Neurotransmitters: Increase the likelihood that the target neuron will fire an action potential.

    • Norepinephrine: Associated with alertness, physiological arousal, and mood regulation.

    • Glutamate: A primary excitatory neurotransmitter, crucial for learning and memory; high levels are implicated in migraines.

    • Dopamine: Involved in pleasure, reward, voluntary movement, motivation, and emotion; abnormalities are implicated in conditions such as schizophrenia and addiction.

  • Inhibitory Neurotransmitters: Decrease the likelihood that the target neuron will fire an action potential.

    • Endorphins: Natural pain relievers produced by the body; responsible for feelings of euphoria (e.g.,