The Brain - Chapter 15 Lecture Notes

Prerequisites

• Finish watching the rest of the nervous system lecture before starting this lecture.
• New definitions for CNS structures will be introduced.

Introduction

• Differences in definitions for CNS vs PNS:
  • CNS:
    • Bundle of axons called a "tract."
    • Bundle of soma called a "nucleus."
  • PNS:
    • Bundle of axons called a "nerve."
    • Bundle of soma called a "ganglion."

Brain Overview

• Weight: ~3 pounds
• Volume: Approx. 1 liter (like a liter of soda)
• Function: Receives sensory information (sensory division) and sends out motor responses (motor division).

Brain Structure

Cerebrum

• Largest region, associated with:
  • Frontal Lobe: Voluntary motor functions, speech
  • Temporal Lobe: Hearing, smell
  • Parietal Lobe: Touch (texture, shape)
  • Occipital Lobe: Vision
  • Insula: Taste
• Hemispheres: Left & right, separated by the longitudinal fissure.
• Cortex: Superficial gray matter, contains gyri (bumps) and sulci (grooves).
• Cerebral Nuclei: Deep gray matter structures.

Diencephalon

• Consists of:
  • Thalamus: Sensory sorting center
  • Hypothalamus: Connects to pituitary gland, key in endocrine function
  • Epithalamus & Pineal Gland: Regulates circadian rhythms

Brain Stem

• Mesencephalon: Contains visual and auditory reflex centers
• Pons: Controls depth and rate of breathing
• Medulla Oblongata: Essential for life, controls heart rate, blood pressure, and respiratory rate

Cerebellum

• Coordination, balance, and muscle memory.
• Arbor Vitae: Internal white matter.

Protection & Support

• Cranial Meninges: Protective layers:
  • Dura Mater: Outermost; contains periosteal and meningeal layers.
  • Arachnoid Mater: Contains CSF, arachnoid villi connect to dural sinuses.
  • Pia Mater: Closest to brain tissue.
• Cerebrospinal Fluid (CSF): Cushions the brain; circulates nutrients and waste.

Ventricles and CSF Flow

• Ventricles: Lateral, third, cerebral aqueduct, fourth.
• CSF Flow: Produced by choroid plexus, flows through ventricles, enters subarachnoid space, reabsorbed by arachnoid villi.

Functional Areas

• Primary Motor Cortex (Precentral Gyrus): Controls voluntary movement.
• Primary Somatosensory Cortex (Postcentral Gyrus): Processes touch.
• Broca’s Area: Speech production (located in the frontal lobe, only on the left side).
• Wernicke’s Area: Language comprehension, located at the parietal/temporal junction.
• Gnostic Area: Integrates sensory information.

Conclusion

• Understanding of the brain requires knowledge of its structural and functional aspects as well as its protective mechanisms. Further study is necessary to comprehend fully the intricate operations of the brain.