Lecture Notes: Brain Anatomy and Development — Flashcards

Neuroanatomy notes: cortex, development, and limbic system

• Opening ideas

  • Signal described as leaving the stomach side of the spinal cord; brief mention of the brain stem (stem = brain stem).

  • Cerebrum gives rise to the term cerebral hemispheres; the cortex has sulci (folds) and gyri (bumps).

  • Some sulci and gyri are labeled with specific functions, e.g., somatosensory cortex and motor cortex, which correspond to sensing and moving.

  • The bumps and grooves (sulci and gyri) are a crude map used to navigate the brain’s regions.

  • Across species, there are different amounts of folds; more folds generally mean more cells (more cell bodies) and thus a larger surface area for neurons.

  • Some animals have smooth brains; brain folding has evolutionary trade-offs. A more convoluted brain isn’t always better for all species (body size and flight considerations matter).

  • Evolutionary trade-off examples:

  • Giraffes can have convoluted brains.

  • Birds often have lighter, less convoluted brains (to stay buoyant/fly).

  • More sulci/gyri correlates with more cells in the cortex, but not uniformly with intelligence.

  • Development of sulci/gyri happens after birth; in the fetus, brains start smooth and later develop folds and connections through development and myelination.

• Brain development timeline and concepts

  • Frontal lobe maturation: Not fully online until around 26 years old (frontal lobe development supports planning and inhibition of impulses).

  • Reflection on adolescence: Five years after high school, you might view earlier actions as foolish as the frontal regions mature.

  • Developmental views involve rostral (toward the beak) and caudal (toward the tail) orientation when thinking about early neural tube development.

  • Early neural development:

  • The brain starts as a plate of cells (a flat sheet) that will fold and fold again.

  • The middle portion becomes the midbrain (mesencephalon).

  • The hindbrain comes from the rhombencephalon and will later form structures like the pons, cerebellum, and medulla.

  • Key embryonic divisions mentioned:

  • Rhombencephalon → metencephalon (pons and cerebellum) and myelencephalon (medulla).

  • Mesencephalon (midbrain) remains as the midbrain.

  • Diencephalon is discussed as giving rise to thalamus and hypothalamus (part of forebrain, but mentioned in the context of these developmental divisions).

  • Mnemonic/notation used in the lecture:

  • “T is for top.” Everything else is presented in an alphabetical order going down: diencephalon, mesencephalon, metencephalon, hyalencephalon (note: this is the spoken mnemonic in the lecture; the standard anatomy terms are diencephalon, mesencephalon, metencephalon, myelencephalon).

  • There are chemoreceptors in this region that detect blood chemistry to help survival.

  • The reticular formation extends upward through the pons toward the brain and contributes to wakefulness.

• Major brain regions and landmarks (from dorsal view and sagittal context)

  • Central sulcus

  • The first sulcus that starts at the top of the brain and runs down the side; serves as a major landmark.

  • Precentral gyrus / motor cortex

  • Located in front of the central sulcus (precentral = before central sulcus).

  • Involves planning and executing voluntary movements.

  • Somatosensory cortex

  • Involved in processing touch and body sensation (labeled as a key cortical area in the cortex).

  • Dorsal (top) view vs sagittal view

  • Dorsal view: top-down view of the brain.

  • Sagittal view: side view of the brain.

• Neural tube development and major divisions (expanded)

  • Rostral vs caudal terminology in development

  • Rostral: toward the nose/beak end.

  • Caudal: toward the tail end.

  • Forebrain and beyond

  • Front of the brain (prosencephalon) develops into structures including the diencephalon (thalamus and hypothalamus).

  • Midbrain (mesencephalon) stays as the midbrain.

  • Hindbrain (rhombencephalon) divides into metencephalon (pons and cerebellum) and myelencephalon (medulla).

  • Pons as a bridge

  • The pons is a bridge that holds the cerebellum and relays sensory information from the spinal cord upward.

  • The reticular formation continues upward through the pons and contributes to wakefulness.

  • Cerebellum

  • Part of the metencephalon; important for coordination and motor control.

  • Midbrain details (mesencephalon)

  • Substantia nigra (dopamine-producing area). "Substantia nigra" literally means black substance; dopamine contributes to its dark appearance.

  • In Parkinson's disease, dopaminergic neurons in the substantia nigra degenerate, leading to motor control problems.

  • The midbrain includes the floor and the tectum; a structure called periaqueductal gray (PAG) surrounds the cerebral aqueduct (the aqueduct of Sylvius).

  • Visual reflexes are associated with the colliculi (superior colliculus for visual, inferior colliculus for auditory). The inferior colliculus is specifically mentioned as involved in auditory reflexes.

  • The peri-aqueductal region is around the aqueduct and participates in reflexive behaviors and pain modulation.

  • Thalamus and hypothalamus (diencephalon)

  • Thalamus: two-lobed structure near the midline that acts as a sensory relay center.

    • All touch, vision, and hearing pass through the thalamus on the way to the cortex; olfaction largely bypasses this relay (not all sensory modalities go through the thalamus).

    • The thalamus is also involved in general arousal and wakefulness.

    • Electrical stimulation of the thalamus can cause sleep or arousal effects; the exact outcomes depend on stimulation sites.

  • Hypothalamus: connected with limbic system and involved in various homeostatic and motivational processes (not fully elaborated in the transcript but mentioned as a partner with the thalamus).

  • Limbic system and related structures (emotion, memory, motivation)

  • Amygdala: involved in fear and immediate reactions to threats; part of the limbic system to drive survival instincts.

  • Hippocampus: memory formation and contextual memory; interacts with other limbic structures for memory processing.

  • Anterior cingulate cortex: involved in emotion and memory integration; mentioned as part of memory/emotion processing.

  • Septum: a small structure; damage to the septum can produce dramatic behavioral changes (septal rage) in animal studies.

  • Nucleus accumbens: a core part of the limbic/reward/motivation circuitry; critical in motivation and reward processing.

  • Olfactory system and olfactory bulb: not shown in this particular image but connected to the limbic system; the olfactory bulb is part of the olfactory system and is highlighted for its memory associations; the lecturer notes that the alembic (olfactory) system is sometimes included or omitted in texts.

  • Basal ganglia and striatum (motor control and action initiation)

  • Striatum includes caudate nucleus and putamen; sometimes referred to as the caudate-putamen or striatum.

  • It is the entry point for cortical input from the motor areas to help facilitate action execution.

  • Dysfunction in this pathway is implicated in movement disorders:

    • Parkinson's disease: difficulty initiating movement due to reduced dopamine signaling from the substantia nigra to the striatum.

    • Huntington's disease: involvement in movement disorders and degeneration within the basal ganglia circuitry.

  • Nucleus accumbens: involved in motivation and reward processing; a key component of the mesolimbic pathway.

  • Cerebral anatomy naming and cross-species notes

  • There are different naming conventions across species (e.g., birds).

  • The lecture notes that birds often have different naming conventions (e.g., pallidum vs striatum) and that this can complicate cross-species comparison.

  • The speaker emphasizes the importance of understanding mammalian brain structures when comparing to birds and the challenge posed by inconsistent naming.

  • Olfactory system and memory emphasis

  • The olfactory system is particularly emphasized for memory associations; this system is strongly linked to memory and emotion.

• Practical and conceptual implications

  • The cortex’s folds (sulci/gyri) increase surface area, allowing more neurons and more complex processing; evolution trades off body size, weight, and flight capabilities.

  • Frontal lobe maturation timeline has implications for behavior and decision-making during adolescence and early adulthood.

  • Dopamine and basal ganglia circuits are central to initiating actions, motivation, and reward; disruptions lead to specific disorders (Parkinson's, Huntington's).

  • The thalamus as a sensory relay and its role in wakefulness highlight how sensory information is processed before cortical perception; certain sensory modalities (smell) may bypass the thalamus.

  • The limbic system integrates emotion, memory, and motivation; the amygdala triggers fear responses; the hippocampus stores and retrieves memories; anterior cingulate and septum contribute to emotional regulation and behavior.

  • The midbrain’s dopaminergic system (substantia nigra) is critical for movement and is a focal point in neurodegenerative disease research.

• Quick references to terms and labels mentioned

  • Central sulcus: a primary landmark marking the boundary between motor and somatosensory cortices.

  • Precentral gyrus: motor cortex, located anterior to the central sulcus.

  • Somatosensory cortex: posterior to the central sulcus; processes tactile information.

  • Inferior colliculus: auditory reflex center within the midbrain.

  • Periaqueductal gray (PAG): region around the cerebral aqueduct involved in reflexive responses and pain modulation.

  • Tectum: dorsal part of the midbrain; related to colliculi (superior and inferior).

  • Cerebellum and pons: structures in the metencephalon; pons serves as a bridge and gateway for information; cerebellum coordinates movement.

  • Thalamus: dual-lobed sensory relay hub near the midbrain; routes sensory information to the cortex; involved in arousal.

  • Hypothalamus: homeostasis, autonomic regulation, and limbic interactions.

  • Hippocampus, amygdala, anterior cingulate: core limbic system components for memory and emotion.

  • Septum: linked to emotional regulation; damage linked to “septal rage.”

  • Nucleus accumbens: motivation and reward center.

  • Striatum (caudate nucleus and putamen): basal ganglia input region critical for action initiation and movement.

  • Substantia nigra: dopamine-producing midbrain structure; degeneration linked to Parkinson's disease.

  • Olfactory bulb: part of the olfactory system; memory and emotion connections emphasized; depicted/not depicted depending on image.