Fundamentals of the Nervous System

Overview

• Importance of the nervous system in daily activities and overall functioning of the body.
• Examples from daily life (e.g., waking up, feeling cold, making decisions).
• All functions processed by electrical and chemical signals in nerve cells.

Main Functions of the Nervous System

• Sensory Input: Detecting information from the environment (e.g., sensory receptors).
• Integration: Processing and deciding upon the action (e.g., being zen or freaking out about a spider).
• Motor Output: Responding to processed information (e.g., removing a spider and screaming).

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 sensory stimuli and sends to the brain.
  • Motor (efferent) division: Sends directions from the brain to muscles and glands.
    • Somatic (voluntary) nervous system: Controls skeletal muscle movement.
    • Autonomic (involuntary) nervous system: Controls heart, lungs, stomach, etc.
      • Sympathetic division: Mobilizes body into action.
      • Parasympathetic division: Relaxes the body.

Nervous Tissue

• Composed mainly of cells rather than extracellular space.
• Neurons (nerve cells): Respond to stimuli and transmit signals.
  • Long-lived, irreplaceable, and high metabolic rate.
  • Structure: soma (cell body), dendrites (listeners), axon (talker).
• Glial Cells (neuroglia): Support and protect neurons.
  • Astrocytes: Anchor neurons to blood supply and exchange materials.
  • Microglial cells: Immune defense in CNS.
  • Ependymal cells: Create, secrete, and circulate cerebrospinal fluid.
  • Oligodendrocytes: Produce myelin sheath in CNS.
  • Satellite cells: Surround and support neuron cell bodies in PNS.
  • Schwann cells: Produce myelin sheath in PNS.

Neuron Classification

• Structural classification:
  • Multipolar neurons: Most common, multiple processes (one axon, many dendrites).
  • Bipolar neurons: Rare, two processes (one axon, one dendrite).
  • Unipolar neurons: One process, mostly in sensory receptors.
• Functional classification:
  • Sensory (afferent) neurons: Transmit impulses from sensory receptors to CNS.
  • Motor (efferent) neurons: Transmit impulses from CNS to muscles and glands.
  • Interneurons: Transmit impulses within CNS between sensory and motor neurons.

Example: Spider on the Knee

• Sensory neurons detect the spider.
• Signal travels to spinal cord via axon.
• Interneurons in spinal cord process the signal.
• Motor neurons trigger muscle response (e.g., kick leg or scream).
• Further processing in the brain determines detailed response.

Conclusion

• The nervous system's role in sensory input, integration, and motor output.
• Organization and functions of CNS and PNS.
• Role of neurons and glial cells.
• Overview of neuron types and their functions.
• Next topic: How nerve cells use chemistry and electricity to communicate.

Acknowledgements

• Episode credits: Writers, editors, consultants, directors, and graphics team.

Additional Notes

• Importance of supporting educational content (e.g., Subbable subscribers).