Lecture 6 (2/5) Flashcards
Cell Theory
Theodor Schwann, 1839
German zoologist
Proposed all tissues are composed of microscopic units he called cells
Cells
The basic functional units of the nervous system
They do the work of the nervous system
2 Distinct Classes
Neurons
Glial Cells
Neurons
The information processing agents in the nervous system
Approx 100 Billion in the human nervous system
Has 3 main parts:
Cell body/soma
Dendrite
Axon
Cell Body/Soma
One of 3 main parts of a neuron
Contains cyoplasm, which contains organelles
Diffferent types of organelles: Nucleus Endoplasmic Reticulum Golgi Apparatus Mitochondria Nissl Body Neurofibril
Nucleus
Type of organelle in the cell body/soma
Relatively large
Contains the machinery for the cell to remain alive and repaired
Mitochondria
Type of organelle in the cell body/soma
Contains enzymes involved in the metabolism of the cell
Sometimes referred to as the cell’s “powerhouse”
The more the cell has the higher the metabolism of the cell
Neurofibril
Type of organelle found in the cell body/soma
Delicate fibers that serve as channels for intracellular communication between organelles
Dendrite
One of 3 main parts of a neuron
Has spines on it in a mature brain
Other cells may communicate through these spines
Axon (Overview)
One of 3 main parts of a neuron
Part of the cell that is specialized in the transfer of information to other cells/neurons
Extends up to about 1 meter in the human brain
Sends impulses AWAY from the soma only
Axon (Anatomy)
Main structures:
Myelin Sheaths
Nodes of Ranvier
Trigger Zone/Initial Segment
3 Main Parts:
Axon Hillock
Axon Proper
Axon Terminal
Myelin Sheaths
A fatty substance that surrounds large axons at very regular intervals
Essential for high speed information relay
Some diseases target them:
Multiple sclerosis - demyelinates the neurons
Nodes of Ranvier
Spaces between the myelin sheaths on an axon
Trigger Zone/Initial Segment
An area of the axon that is typically not myelinated and near the soma
Golgi Type 1 neurons
“Long distance carriers”
Long axons that carry information from one distant region to another
Golgi Type 2 neurons
Short axons that process information in a small, limited portion of the brain.
