Biology Lecture Notes: Reception, Response, and Coordination in Animals

Overview

• Topic: Structure and function of nerve cells (neurons)
• Previous Lesson Recap:
  • Irritability in animals
  • Nervous system
  • Endocrine system

Nerve Cells (Neurons)

• Definition: Basic unit of the nervous system, specialized for transmission of nerve impulses (electrical in nature).
• Function: Transmit electrical messages (impulses) within the nervous system.

Structure of a Neuron

• Cell Body:

  • Contains the nucleus, which holds genetic material.
  • Equivalent to a typical cell structure.

• Dendrites:

  • Extensions from the cell body that receive and transmit nerve impulses to adjacent nerve cells.

• Axon:

  • Main projection from the cell body, essential for conducting impulses.
  • Contains axoplasm, equivalent to cytoplasm in cells.

• Myelin Sheath:

  • Fatty layer surrounding the axon.
  • Insulates the axon and aids in the propagation of nerve impulses.

• Schwann Cell:

  • Secretes the myelin sheath.
  • Contains a membrane called the neurilemma.

• Terminal Dendrites:

  • Located at the end of the neuron, involved in transmitting signals.

Special Features

• Node of Ranvier:
  • Gaps in the myelin sheath that speed up nerve impulse transmission.

Assignment Questions

1. Name the basic unit of a nervous system.
2. Draw a well-labeled diagram of a neuron.
3. Explain the roles of the following:
   • Myelin Sheath
   • Nodes of Ranvier

Conclusion

• The nerve cell is essential for transmitting electrical impulses, similar to how current flows through a wire.
• Understanding the structure and function of neurons is fundamental for studying the nervous system.