Copy of Anatomy H Chapter 12 Part 1

Chapter 12: The Central Nervous System

Overview

• Human Anatomy and Physiology Eleventh Edition

• By Karen Dunbar Kareiva, Ivy Tech Community College

Adult Brain Regions

• Regions: Four major regions in adult brain:

  • Cerebral Hemispheres

  • Diencephalon

  • Brain Stem:

    • Midbrain

    • Pons

    • Medulla

  • Cerebellum

Gray and White Matter

• Gray Matter: Contains short, nonmyelinated neurons and cell bodies.

• White Matter: Composed of myelinated and unmyelinated axons.

• CNS Pattern: Central cavity surrounded by gray matter with white matter external to gray matter.

Brain Stem and Cortical Structure

• Gray Matter Nuclei: Additional nuclei dispersed within white matter in brain stem.

• Cerebral Hemispheres:

  • Outer layer of gray matter called the cortex.

  • Contains scattered areas of gray matter nuclei within white matter.

The Cerebral Hemispheres

• General Structure: Form superior part of the brain, accounting for 83% of total brain mass.

• Surface Markings:

  • Gyri: Ridges

  • Sulci: Shallow grooves

  • Fissures: Deep grooves

    • Longitudinal Fissure: Separates two hemispheres

    • Transverse Cerebral Fissure: Separates cerebrum from cerebellum.

Sulci and Lobes

• Lobes of the Cerebral Hemispheres: Each hemisphere divided into four lobes by several sulci:

  • Frontal Lobe

  • Parietal Lobe

  • Temporal Lobe

  • Occipital Lobe

• Major Sulci:

  • Central Sulcus: Separates frontal and parietal lobes.

  • Parieto-occipital Sulcus: Separates occipital from parietal lobe.

  • Lateral Sulcus: Outlines the temporal lobes.

Cerebral Cortex

• Definition: The "executive suite" of the brain, involved in:

  • Awareness

  • Sensory perception

  • Initiation of voluntary movements

  • Communication

  • Memory storage and understanding.

• Structure: Thin (2–4 mm) superficial layer of gray matter, includes neuron cell bodies, dendrites, glial cells, and vascular components (no axons).

Functional Imaging of the Cortex

• Functional neuroimaging (PET and MRI): Reveals specific motor and sensory functions in discrete cortical areas.

• Cortex Considerations:

  • Three functional area types:

    • Motor Areas: Control voluntary movement.

    • Sensory Areas: Awareness of sensation.

    • Association Areas: Integrates diverse information.

  • Each hemisphere affects the opposite side of the body.

Motor Areas of the Cortex

• Primary Motor Cortex: Located in precentral gyrus, essential for voluntary movement control.

• Other Areas:

  • Premotor Cortex: Planning movements.

  • Broca's Area: Speech production.

  • Frontal Eye Field: Controls voluntary eye movements.

Clinical Aspects: Homeostatic Imbalances

• Primary Motor Cortex Damage: Results in paralysis on the body's opposite side.

• Functional Capacity After Damage:

  • Strong individual movement preserved; voluntary control may be lost, retraining possible.

Sensory Areas of the Cortex

• Areas dedicated to conscious awareness of sensations in parietal, insular, temporal, and occipital lobes:

  • Primary Somatosensory Cortex: Spatial discrimination of sensations activated through skin and proprioception.

  • Visual Areas: Interpretation of visual stimuli.

  • Auditory Areas: Interpretation of sounds.

  • Vestibular Cortex: Balancing awareness.

  • Olfactory Cortex: Conscious awareness of scents.

  • Gustatory Cortex: Taste perception.

Multimodal Association Areas

• Function: Integrate inputs from multiple sensory areas, facilitate meaning and memory association.

• Divisions:

  • Anterior Association Area (Prefrontal Cortex): Intellect and cognition-related tasks.

  • Posterior Association Area: Recognizes patterns and integrates language.

  • Limbic Association Area: Emotional processing and memory establishment.

Lateralization of Cortical Functioning

• Definition: Uneven division of labor between hemispheres.

• Cerebral Dominance: Typically, the left hemisphere is dominant for language in 90% of people.

• Functional Roles:

  • Left Hemisphere: Language, math, logic.

  • Right Hemisphere: Visual-spatial skills, intuition, artistic abilities.

Conclusion

• The cerebral cortex is essential for various cognitive functions, with specific areas dedicated to motor control, sensory perception, and complex associations of information contributing to our identity.