Lecture Notes: Structure of the Nervous System

Overview of the Nervous System

• Function: Transmits electrical impulses quickly throughout the body.
• Main Divisions:
  • Central Nervous System (CNS): Composed of the brain and spinal cord.
    • Brain protected by the skull.
    • Spinal cord often confused with the backbone but is a soft organ protected by the backbone.
  • Peripheral Nervous System (PNS): Composed of cranial nerves and spinal nerves.
    • Cranial nerves connect to the brain.
    • Spinal nerves connect to the spinal cord.

Nerves and Neurons

• Nerves: Tissues made up of many cells grouped together, visible during surgeries.
• Neurons: Cells that make up nerve tissues.
  • Types:
    • Sensory Neuron: Transmits impulses from receptors to the CNS.
    • Relay Neuron: Connects sensory and motor neurons within the CNS.
    • Motor Neuron: Transmits impulses from CNS to effectors.

Neuron Functions and Signal Transmission

• Sensory Neuron: Detects stimuli (e.g., light) and transmits impulses to relay neurons.
  • Illustrated by a piece of cake example: Light reflects off the cake into the eyes, detected by photoreceptors.
• Relay Neuron: Bridges the gap between sensory and motor neurons.
  • Located only in the CNS (brain and spinal cord).
• Motor Neuron: Transmits impulses from relay neurons to effectors (e.g., stomach).
  • Causes physiological responses such as gastric juice production when seeing food.

Transmission Pathway

1. Stimulus Detection: Light detected by receptors (e.g., photoreceptors in the eyes).
2. Signal Transmission:
   • Sensory neuron sends impulse to relay neuron.
   • Relay neuron bridges to motor neuron.
   • Motor neuron carries impulse to the effector, resulting in a response (e.g., stomach growling).

Important Notes

• Relay Neurons: Only found in the CNS, not in other body parts.
• Understanding the structure and function of neurons is crucial for exams.

Next Steps

• Future video will cover the detailed structure of sensory and motor neurons.