Overview
This lecture covers basic brain anatomy, major cortical regions, the flow of sensory and motor information, and the importance of cross-connections in brain function.
Brain Regions and Their Locations
- The brain can be modeled as a fist: thumb = temporal lobe, knuckles = frontal lobe, back of hand = parietal lobe, wrist = occipital lobe.
- The limbic cortex (limbus) lies at the boundary where the cortex meets the corpus callosum.
- Major lobes: frontal (tan), parietal (green), occipital (salmon pink), temporal (blue).
Gross Organization and Sulci
- Sulci such as the central sulcus and sylvian fissure are consistent anatomical landmarks across humans and many primates.
- The central sulcus divides the frontal and parietal lobes; the sylvian fissure separates the temporal lobe.
Flow of Sensory and Motor Information
- Information from senses (vision, hearing, touch) passes through the thalamus before reaching primary cortical areas.
- Primary sensory areas: visual (occipital lobe), auditory (deep to sylvian fissure), somatosensory (postcentral gyrus).
- Primary motor cortex is anterior to the central sulcus; primary somatosensory cortex is posterior.
Sensory and Motor Pathways
- Sensory input from the periphery (touch, pain, temperature) travels to the thalamus, then to the primary somatosensory cortex.
- Motor output originates in the primary motor cortex and descends via corticospinal and corticobulbar tracts.
- These tracts cross (decussate) at the pyramids in the brainstem, resulting in contralateral control (left brain controls right body, and vice versa).
Overview of Cortical Systems
- The lecture will detail seven primary cortical systems: motor, somatosensory, vestibular, vision, hearing, taste, and smell.
Key Terms & Definitions
- Limbic cortex — cortex bordering the corpus callosum, involved in emotion and memory.
- Central sulcus — groove separating frontal and parietal lobes.
- Sylvian fissure — deep groove separating the temporal lobe.
- Thalamus — relay center for sensory and motor signals to the cortex.
- Pyramidal decussation — crossing point of motor fibers in the brainstem.
Action Items / Next Steps
- Review the primary cortical systems (motor, somatosensory, vestibular, vision, hearing, taste, smell).
- Prepare questions about sensory and motor pathways for the next session.