Topic: Comparison of sensory neuron and motor neuron structures.
Previous Knowledge: Understanding of neuron functions and the central nervous system (CNS) components (brain and spinal cord).
Neuron Locations in CNS
Sensory Neuron: Partially located within the CNS.
Motor Neuron: Partially located within the CNS.
Relay Neuron: Fully located in the CNS but not the focus of this lecture.
Key Structures of Neurons
Cell Body:
Contains the nucleus.
Sensory Neuron: Cell body is outside the CNS.
Motor Neuron: Cell body is within the CNS.
Axons:
Long structures for impulse transmission.
Can extend up to a meter long.
Dendrites:
Increase surface area to receive signals.
Branching like roots to facilitate signal reception.
Terminal Branches and Synaptic Knobs:
End points of neurons.
Contain neurotransmitter vesicles.
Differences Between Sensory and Motor Neurons
Cell Body Location:
Sensory Neuron: Cell body located mid-neuron.
Motor Neuron: Cell body located at the beginning of the neuron.
CNS Location:
Motor Neuron: Cell body within the CNS.
Sensory Neuron: Cell body not within the CNS.
Myelin Sheath
Structure:
Appears as orange "sponges" along the axon.
Not continuous; gaps known as Nodes of Ranvier.
Presence:
Not all neurons have myelin; some are unmyelinated.
Formation:
Myelin sheath is formed by Schwann cells.
It wraps around the axon like a "cinnamon roll."
Function:
Speeds up the transmission of impulses (to be discussed in detail later).
Nodes of Ranvier
Gaps between myelin sheath segments on the axon.
Important for neuron function (detailed discussion in future).
Conclusion
Focus: Understanding neuron structures and differences for exams.
Upcoming Discussions: Detailed study of electrical impulses and myelin sheath functions.
Note: This lecture was an introduction to neuron structures and their components. More detailed discussions on functions will follow in subsequent lectures.