Gross Neuroanatomy

Major Divisions of the Brain

  1. Three Main Parts:

    • Brain Stem

    • Forebrain

    • Hindbrain

  2. Five Developmental Divisions:

    • Myelencephalon

    • Metencephalon

    • Mesencephalon (midbrain)

    • Diencephalon

    • Telencephalon

Brainstem (Hindbrain)

  • Myelencephalon (Medulla Oblongata):

    • Connects the brain to the spinal cord.

    • Major functions include:

    • Regulation of cardiovascular functions.

    • Respiratory regulation (breathing).

    • Along with other life-sustaining functions.

    • Involvement in contralateral control (right side of the brain controlling the left side of the body).

    • Described as an axial twist where neurons cross over like train tracks.

  • Metencephalon:

    • Cerebellum: Important for:

      • Balance

      • Coordination

      • Posture

      • Reflexes (coughing, sneezing, eye-blinking, etc.)

    • Pons: Functions to regulate:

      • Sleep

      • Arousal

      • Pain perception

Medulla functions:

  • A highway consisting of myelinated axons for communication between brain and spinal cord.

  • High reflexive values for automatic bodily functions.

Cerebellum

  • Intricate neuronal structures:

    • Houses approximately 80% of neurons in the brain.

    • Functions for movement control and coordination.

    • Role in motor learning and muscle memory.

    • Implications of alcohol consumption leading to cerebellar ataxia (lack of coordination).

Midbrain (Mesencephalon)

  • Central role in mood regulation and addiction through:

    • Dopamine-related pathways

    • Key structures:

    • Substantia Nigra: Responsible for voluntary movements.

    • Ventral Tegmental Area (VTA): Involved in reward and pleasure.

    • Raphe Nucleus: Associated with serotonin regulation (mood, sleep).

    • Superior and Inferior Colliculi: Integral for reflexive responses to visual and auditory stimuli.

Forebrain (Diencephalon and Telencephalon)

  • Diencephalon:

    • Thalamus:

    • Functions as the major sensory relay station (except olfactory sense).

    • Acts as a gatekeeper for attention in sensory information processing.

    • Hypothalamus:

    • Internal regulatory center for homeostasis.

    • Involves communication of hormones, hunger, thirst, motivation, etc.

    • Important for the HPA Axis (Hypothalamic-Pituitary-Adrenal Axis).

  • Telencephalon:

    • Composed of the cerebral cortex and limbic system.

    • Cerebral Cortex:

    • Increased surface area due to gyri (folds) for neural capacity.

    • Areas include:

      1. Prefrontal Cortex: Coordinates higher-order functions (decision-making).

      2. Primary Motor Cortex: Initiates voluntary muscle movements.

      3. Primary Somatosensory Cortex: Processes sensory information from the body.

  • Topographic Organization:

    • Neurons in primary motor and somatosensory cortices correspond to specific body parts, establishing a 'map.'

  • Muscle Memory:

    • Refers to learned movements stored in basal ganglia rather than in muscles themselves.

  • Memories:

    • Distinction between types of memories handled by different brain areas:

      • Episodic Memory: Stored in hippocampus for personal experience.

      • Semantic Memory: Conceptual knowledge located in the cortex.