Lecture 17

Brain Structure Overview

• The brain is divided into two large hemispheres: the left hemisphere and the right hemisphere.
• The brain stem controls basic functions and connects the brain to the spinal cord.
• The fissure is a distinct separation deep within the brain's structure.

Gray and White Matter

• Gray matter: Refers to areas containing cell bodies of neurons (outermost portion, cerebral cortex).
• White matter: Contains myelinated axons, acting as communication highways between different brain areas.
• Significance of myelin: Insulates and speeds up action potentials.

Lobes of the Brain

• Frontal Lobe: Most anterior, responsible for functions related to planning and movement (Motor Cortex).
• Temporal Lobe: Located behind the frontal lobe, involved in hearing and smell processing.
• Parietal Lobe: Integration of sensory information.
• Occipital Lobe: Primarily responsible for vision.

Sensory and Motor Cortices

• Anterior to the central sulcus: Motor Cortex controlling voluntary movements.
• Posterior to the central sulcus: Sensory Cortex where sensory information is processed (smell, taste, etc.).
• Each hemisphere controls the opposite side of the body (contralateral).

Left vs. Right Brain Functionality

• Left hemisphere: Generally associated with logical tasks (math, language, logic).
• Right hemisphere: Associated with creative tasks (art, music, emotional processing).
• Brain communication: Both hemispheres communicate through interconnecting structures.

Basal Nuclei

• Collections of gray matter within the brain responsible for processing and sorting sensory information.
• Parkinson’s disease affects this region, causing difficulties in sensory processing and movement.

Thalamus and Hypothalamus

• Thalamus: Acts as relay station for sensory signals and emotions.
• Hypothalamus: Regulates autonomic functions and emotional responses.
  • Plays key role in body temperature, hunger, and hormones with its connection to the pituitary gland.

Cerebellum

• Located at the back of the brain, controlling smooth and coordinated movements and also contributes to motor learning and memory.
• Contains its own choroid plexus for CSF production.

Meninges

• Three layers protecting the brain:
  • Dura Mater: Outer layer, thick and protective.
  • Arachnoid Mater: Middle layer, covering major blood vessels.
  • Pia Mater: Innermost layer that closely wraps the brain.
• Subdural space and subarachnoid space: Fluid-filled areas critical for CSF circulation.

Cerebrospinal Fluid (CSF) Circulation

• Formed in the choroid plexus, primarily in the diencephalon region.
• Flows through left and right lateral ventricles, then to the third and fourth ventricles.
• Enters subarachnoid space, circulates around the spinal cord and brain before being reabsorbed into blood.
• Ciliated cells assist in the flow of CSF.

Brainstem

• Made up of three regions: midbrain, pons, and medulla oblongata.
• Controls basic autonomic functions such as breathing and heart rate.

Clinical Applications

• Meningitis: Inflammation of the meninges, can be caused by bacterial or viral infections.
• Hydrocephalus: Blockage in CSF flow leading to increased intracranial pressure.
• Concussions: Brain jostled within the skull, risking damage to neurons.
• Stroke: Can lead to brain damage by affecting blood flow.
• Alzheimer's disease: Involves tau protein tangling, affecting neuronal function and health.