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.