Overview
This lecture covers the major regions and functions of the human brain, focusing on the brain stem, cerebellum, their sub-regions, and their roles in motor control and reflexes.
Brain Stem: Structure and Functions
- The brain stem is the lowest part of the brain, connecting to the spinal cord and supporting vital autonomic and reflex functions.
- It is divided into three sub-regions: medulla oblongata, pons, and midbrain.
- The medulla oblongata controls autonomic functions like breathing, heart rate, blood pressure, and reflexes such as coughing and swallowing.
- The medulla contains nuclei for cranial nerves VIII, IX, X, XI, and XII and serves as a communication link between the brain and spinal cord.
- The pons bridges the cerebellar hemispheres and relays information between the brain, brain stem, and cerebellum.
- The pons regulates breathing rate and depth, REM sleep, and contains nuclei for cranial nerves V, VI, VII, and VIII.
- The midbrain connects the brain stem to the diencephalon, coordinates motor signals, and houses visual/auditory reflex centers.
- The midbrain contains nuclei for cranial nerves III and IV; major structures include the superior and inferior colliculi for visual and auditory reflexes.
Cerebellum: Role in Movement
- The cerebellum is the second largest brain region, responsible for smooth, coordinated, and precise body movements.
- It adjusts motor plans based on body position and ongoing feedback, sending adjustments to the cerebrum as needed.
- The cerebellum’s surface gray matter is called folia; inner white matter is called arbor vitae due to its tree-like appearance.
- Cerebellar damage leads to ataxia, seen as jerky, uncoordinated movements.
Key Terms & Definitions
- Brain stem — Inferior brain region connecting to the spinal cord; vital for basic life functions.
- Medulla oblongata — Lowest brain stem section; controls autonomic life functions.
- Pons — Middle brain stem segment; bridges cerebellar hemispheres and regulates REM sleep and breathing.
- Midbrain — Uppermost brain stem part; integrates sensory inputs and coordinates reflexes.
- Cerebellum — "Little brain" coordinating movement and balance.
- Folia — Surface folds of the cerebellum (gray matter).
- Arbor vitae — Tree-like white matter inside the cerebellum.
- Ataxia — Uncoordinated movement resulting from cerebellar damage.
Action Items / Next Steps
- Review the structure and functions of the brain stem, cerebellum, and associated cranial nerves.
- Prepare to study the cerebrum, limbic system, and cerebral white matter in upcoming lectures.