Lecture Notes: The Cerebral Hemispheres

Introduction

• Presenter: Dr. Mike
• Topic: Examination of the cerebral hemispheres
• Context: Part of the brain, specifically the cerebrum, cerebellum, and brain stem

Overview of the Cerebrum

• Size and Development: Largest and most developed part of the brain
• Structure: Segmented into two hemispheres - left and right

Functions of the Cerebrum

1. Motor and Sensory Cortices

• Cortex: Outer 1-5 mm of the cerebrum, contains grey matter
• Grey Matter: Site of integration, contains neuron cell bodies and synapsing areas
• White Matter: Consists of axons (highways for signals)
• Primary Motor Cortex: Initiates voluntary motor movements (located in the frontal lobe)
• Primary Sensory Cortex: Processes sensory information for conscious awareness (located in the parietal lobe)

2. Association Areas

• Function: Help primary cortices by associating past and current information
• Motor Association Areas: Plan and sequence complex movements
• Sensory Association Areas: Analyze sensory information (smooth, rough, etc.)

3. Conscious Experience

• Site: Cerebral cortex (1-5 mm layer)
• Awareness: Consciousness arises here; deeper brain areas may process information without conscious awareness

4. Limbic System

• Components: Memory and emotional aspects of behavior
• Functions: Emotional aspects of feeding, relationships, reproduction, and responses (fight or flight)

5. Cognitive Function

• Location: Mainly in the frontal lobe (prefrontal cortex)
• Functions: Planning, judgment, emotion, and appropriate behavior

Structure and Anatomy

Layers

• Surface: Cortex (grey matter)
• Deeper: White matter (axonal projections)

Fiber Types

• Commissural Fibers: Connect the two hemispheres (via corpus callosum)
• Projection Fibers: Connect superficial and deeper brain areas
• Association Fibers: Connect different cortical areas within the same hemisphere

Lobes

• Frontal Lobe
• Parietal Lobe
• Occipital Lobe
• Temporal Lobe
• Insular Lobe

Gyri and Sulci

• Purpose: Increase brain surface area for neuron accommodation
• Key Features:
  • Central Sulcus: Divides frontal and parietal lobes
  • Precentral Gyrus: Primary motor cortex
  • Postcentral Gyrus: Somatosensory cortex
  • Parieto-occipital Sulcus: Divides parietal and occipital lobes
  • Lateral Sulcus/Fissure: Divides temporal lobe from frontal and parietal lobes

Summary

• Cerebral Hemispheres: Most complex, largest part of the brain
• Functions: Conscious awareness, cognitive functions, emotional and behavioral understanding
• Future Focus: Detailed examination of each lobe