Lecture on Body Cell Diversity and the Nervous System

Introduction to Cell Diversity

• Cells are not just simple circles; they show significant diversity.
• Parietal cells: Part of the digestive system, capable of making stomach acid.
• Mast cells: Part of the immune system, contain histamine for inflammatory response.
• Skeletal muscle cells: Known as muscle fibers, facilitate muscle contraction with their unique cylindrical shape and multi-nuclei structure.
• Neurons: Specialized cells in the nervous system, focus of this lecture.

Overview of the Nervous System

• Divided into two main regions:
  • Central Nervous System (CNS): Brain and spinal cord.
  • Peripheral Nervous System (PNS): All other neural components, transmits sensory info to CNS and executes motor responses.

Central Nervous System (CNS)

• Brain Regions:
  1. Hindbrain:
     • Medulla: Regulates breathing, blood pressure, heart rate.
     • Pons: Coordinates signals, involved in regulation functions.
     • Cerebellum: Manages balance and motor coordination.
  2. Midbrain:
     • Involved in alertness, sleep/wake cycle, and motor activity.
     • Includes structures like the medulla and pons as part of "brainstem."
  3. Forebrain:
     • Cerebrum: Divided into right and left hemispheres, involved in speech, reasoning, emotion, and more.
     • Thalamus: Handles sensory and motor information.
     • Hypothalamus: Major control of the endocrine system.

Peripheral Nervous System (PNS)

• Functional Divisions:
  • Somatic Nervous System (SNS):
    • Controls motor functions of skeletal muscles, including voluntary actions and somatic reflexes.
  • Autonomic Nervous System (ANS):
    • Manages internal environment involving gastrointestinal, excretory, and muscle systems.
    • Divided into:
      • Sympathetic System: "Fight or flight" response, increases heart rate and respiration.
      • Parasympathetic System: "Rest and digest," decreases heart rate, and promotes digestion.

Cells in the Nervous System

• Neurons:
  • Structure:
    • Cell Body: Contains nucleus and organelles.
    • Dendrites: Receive signals.
    • Axon: Carries signals away to other cells ("away axon").
    • Synapse: Junction where neuron communicates with another cell.
• Glial Cells (Glia):
  • Support neurons, help maintain blood-brain barrier, produce myelin, manage chemical balance, produce cerebrospinal fluid, and support immune function.

Action Potential

• Resting Potential:
  • Neuron at rest is more negative inside than its surroundings (~ -70 mv).
  • Maintained by the sodium-potassium pump (Na+ outside, K+ inside).
• Action Potential Process:
  • Signal received at dendrite, causing depolarization as Na+ floods in.
  • Propagation along the axon, restoring of previous regions after signal passes.
  • Myelinated neurons enable faster signal via "node jumping."
  • Considered "all or none" - either a signal is fully transmitted or not at all.
• Neurotransmitter Release:
  • Action potential reaching axon terminals triggers release of neurotransmitters into synapse.
  • Neurotransmitters bind to receptors on the next neuron to propagate signal.

Conclusion

• Comprehensive overview of nervous system and its cells.
• Emphasis on neuron communication and action potential.
• Encouragement to explore careers in neurology and related research.

Note: Further reading available on myths about brain usage and detailed action potential processes.