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Somatic Motor Neurons homework 3 lab
Nov 5, 2024
Lecture Notes: Somatic Motor Neuron Model
Classification
Multipolar Neurons
Have many projections off the soma (cell body).
Classified as motor neurons or interneurons.
Interneurons are in central nervous system (CNS) gray matter.
Myelination
Myelin presence indicates white matter.
Since myelin is present, this neuron is a motor neuron, not an interneuron.
Parts of the Motor Neuron
Soma (Cell Body)
Contains the nucleus.
Nissl Bodies
: Analogous to rough ER, produce proteins.
Dendrites
Thickened projections off of the soma.
Receive information from other neurons.
Contain ligand gates (mechanical gates are for sensory neurons).
Synaptic End Bulbs
Belong to a presynaptic neuron.
Do not touch the soma or dendrites due to a synaptic cleft.
Axon Hillock
Cone-shaped area off of the soma.
Contains the
trigger zone
with sodium voltage gates.
Action potential begins here if threshold (-55 mV) is reached.
Axon
Covered by myelin sheath.
Myelin formed by Schwann cells in the peripheral nervous system (PNS).
Schwann Cells
: Multiple cells wrap around the axon, forming the myelin sheath.
Neurolemma
: Outer layer of Schwann cell's myelin sheath.
Node of Ranvier
: Indentations on axon lacking myelin, allowing action potential to "jump" (saltatory conduction).
Structural Support
Neurofibrils
: Provide structure and support for the neuron shape.
Conduction
Myelin blocks voltage gates; action potential jumps between nodes, speeding conduction (saltatory conduction).
Endoneurium
: Connective tissue layer protecting delicate Schwann cells and myelin.
Summary
Motor neuron, somatic type, targets skeletal muscle.
Function
: Sends information to glands and muscles to prompt action.
Structure
: Multipolar, distinguished by soma, Nissl bodies, dendrites, axon hillock, myelinated axon, and nodes of Ranvier.
Key Terms
Soma
: Another term for cell body.
Nissl Bodies
: Blue rough areas for protein production.
Dendrites
: With ligand gates for receiving signals.
Axon Hillock
: Trigger zone for action potential.
Schwann Cells
: Form myelin sheath in PNS.
Neurolemma
: Outer membrane of Schwann cells.
Node of Ranvier
: Indentations for saltatory conduction.
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