Human Physiology and CNS Function

The Human Information Superhighway: CNS Overview

Instructor Introduction

  • Professor in PNB
  • Director of Biological Sciences
  • Director of PNB REU Program
  • Experience: 40 years in teaching Human Anatomy and Physiology (HAP)
  • Publications: Author of multiple textbooks on HAP and Human Physiology

Classroom Engagement

  • Interaction: Develop comfort in asking questions to enhance learning.
  • Class Attendance: Essential for effective learning and grade improvement.
  • Learning Objectives: Awareness of academic expectations and metacognition in understanding concepts.

Misconceptions about the Brain

  • Myth: We only use 10% of our brain.
  • Fact: We use 100%; the brain is a complex analog device, not merely a digital computer.
  • Neurological Variances: Male and female brains do not process data differently.
  • Memory Limitations: No discrete limit; capacity is estimated at 2.5 x 10^15 bytes.

Importance of Sensory Detection

  • Why Detection?: Critical for sensing internal and external environments.
  • Operational Traits Needed: Fast and flexible control mechanisms for cellular activities, ranging from milliseconds to longer durations.
  • Top-down Organization: CNS must maintain hierarchical and spatial neuron organization, allowing for effective control and processing.

Central Nervous System (CNS) Structure

  • CNS Composition: 10% neurons (50% volume), 90% neuroglia (50% volume).
  • Key Terms:
    • Afferent: Inward axonal projections
    • Efferent: Outward axonal projections
    • Gray Matter: Neuronal cell bodies
    • White Matter: Axonal projections
  • Ganglia: Collections of neuron cell bodies performing similar functions.

Functional Neuroanatomy

  • Neurons: Types include multipolar neurons (common), pyramidal neurons (largest, with multiple axons).
  • Neuroglial Cells: Supportive roles including myelin production and synaptic transmission.

Blood-Brain Barrier (BBB) and Protection Mechanisms

  • BBB Functions: Offers chemical isolation from the body's circulation to protect the CNS.
  • Meninges Structure:
    • Dura Mater: Tough outer layer with fibrous structure.
    • Arachnoid: Middle layer containing blood vessels and CSF.
    • Pia Mater: Innermost layer covering the brain surface.
  • CSF: Provides buoyancy, waste removal, and reduces brain weight.

Cerebral Spinal Fluid (CSF) Dynamics

  • Production: Up to 500 mL daily, with only 150 mL present at any time.
  • Choroid Plexus: Responsible for CSF formation, exits through apertures into subarachnoid space.
  • ISF & CSF Similarities: Similar ion concentrations, differences from plasma.

Neuroglial Roles in CNS

  • Astrocytes: Most abundant, maintain BBB, regulate CSF.
  • Oligodendrocytes: Produce myelin, crucial for neuronal insulation and conduction.
  • Microglia: Macrophages in CNS, remove debris and damaged cells.

Implications of CNS Sensitivity

  • Physiological Consequences: The sensitivity of brain interstitial fluid (ISF) to CO2 and pH changes impacts breathing and neuronal excitability.
  • Common CNS Disorders: Includes traumatic brain injury, multiple sclerosis, bacterial meningitis, epilepsy, etc.