Lecture on the Nervous System

Introduction

• Morning activities illustrate the functions of the nervous system.
• Nervous system processes and executes actions via electrical and chemical signals.
• Importance: Controls all organs, reactions, and even the endocrine system.
• Focus: Anatomy, organization, communication, and damage.

Functions of the Nervous System

1. Sensory Input: Detects stimuli (e.g., spider on skin).
2. Integration: Processes input and decides response.
3. Motor Output: Activates response (e.g., removing spider).

Organization of the Nervous System

• Central Nervous System (CNS): Brain and spinal cord, main control center.
• Peripheral Nervous System (PNS): Nerves branching off from the brain and spine.
  • Sensory (Afferent) Division: Picks up stimuli and sends to the brain.
  • Motor (Efferent) Division: Sends directions from brain to muscles/glands.
    • Somatic System: Controls voluntary movements.
    • Autonomic System: Controls involuntary actions.
      • Sympathetic Division: Mobilizes body into action.
      • Parasympathetic Division: Relaxes body.

Nervous Tissue and Cells

• Mainly made up of densely packed cells.
• Neurons: Respond to stimuli, transmit signals, long-lived, irreplaceable, high metabolic rate.
• Neuroglia (Glial Cells): Support neurons, half of brain's mass, outnumber neurons 10 to 1.

Types of Glial Cells

• CNS Glial Cells:
  • Astrocytes: Anchor neurons, exchange materials.
  • Microglial Cells: Immune defense.
  • Ependymal Cells: Line cavities, circulate cerebrospinal fluid.
  • Oligodendrocytes: Form myelin sheath.
• PNS Glial Cells:
  • Satellite Cells: Similar to astrocytes, support neurons.
  • Schwann Cells: Form myelin sheath.

Neuron Structure

• Soma (Cell Body): Life support with nucleus, mitochondria, etc.
• Dendrites: Receive messages.
• Axons: Transmit impulses.

Neuron Types

• Multipolar: Many processes, common in CNS.
• Bipolar: Two processes, rare, sensory roles.
• Unipolar: Single process, mainly sensory.

Functional Classification of Neurons

• Sensory (Afferent) Neurons: Transmit impulses towards CNS.
• Motor (Efferent) Neurons: Transmit impulses away from CNS.
• Interneurons: Transmit impulses within CNS, most abundant.

Spider Example

• Sensory neurons detect the spider.
• Signal travels to spinal cord and brain via different neurons.
• Interneurons help process the response (e.g., move leg, recognize spider).

Conclusion

• Understanding the communication between nerve cells involves chemistry and electricity.
• Next episodes will explore these communication methods further.
• Credits to the team and supporters.