NEURON
Overview of Topics
Lesson Objectives
Structure of Neuron
Neuron as Structural Unit
Identity of Neurons
Degeneration
Lesson Objectives --- Neuron
- Describe the basic funcgion of the neuron giving evidence for this.
- Explain how other functions can be obtained by anatomical modifications of the neuron.
- List the 3 basic types of neurons and their location in the CNS.
- Explain the Neuron Doctrine and the evidence for it.
- Describe the components of the neuron and their function.
- How does regeneration differ between the CNS & PNS and explain why they are different.
Neuron as Structural Unit
Neuron Doctrine
- 1890, Waldeyer
- First proposed view that nervous system composed of individual cells (neuron).
Identity of Neurons
Neuron a Tropic Unit
- Degeneration (Retrograde & Wallerian)
- Chromatolysis
Neuron a Genetic Unit
- No cell division after birth
- No nerve cell tumor
Structure of the Neuron
Soma - Cell Body
- Large nucleus w/membrane
- Very large nucleolus
- Paranuclear body (Barr bodies)
- Rough endoplasmic reticulum (Nissl Substance) [begins synthesis]
- Smooth endoplasmic reticulum [stores products of synthesis]
- Golgi apparatus [completes assembly of protein & encloses in membrane]
- Cytoplasm movement
- Secretory function
- Neurofibrils
- Mitochondria [contain enzymes to produce ATP]
- Chromatolysis
- Axon hillock
Dendrites - Greek for "tree" [obtain information & transport to cell body & axon]
Axon - Unipolar - Bipolar - Multipolar
Anatomical vs physiological distinction
Synapse (one-way valve). Occurs when impulse leaves Terminal Boutons to effect post-synaptic membrane.
Coverings on neurons -
neuralemma, myelin sheath
Detailed Structure of Nerve Cell
Membrane - defines boundary
- Major structural component - phospholipids
- Lipid-protein-lipid layers.
- The protein is floating in the middle and has special functions.
- Detect hormones outside cell and communicate with inside.
- Control access of ions into the cell.
Nucleus; center - surrounded by nuclear membrane
- Contains nucleolus and ribosomes.
- DNA - present; genetic code; messenger RNA.
- Protein - serves as enzymes which serve as catalysts.
- Cytoplasm - semi-liquid fluid within cell.
Mitochondria; bead-shaped with inner cristae (layers)
- Produce ATP (adenosine triphosphate) source of energy
Endoplasmic reticulum
- Rough - contains ribosomes; produces substance out of the cell.
- Smooth - concerned with transport of substance around the cell.
Golgi Apparatus
- Packaging apparatus - secretory cells; product wrapped in membrane.
- Produces lysosomes containing enzymes that break down substances.
Microfilaments - long protein fibers found just under the membrane; probably control the movement of protein molecules.
Microtubules - larger and consist of bundles of filaments arranged around a hollow core; play a role in mobility of cells.
Degeneration
CNS - no regeneration? Role of Schwann cell
PNS:
- Distal - Wallerian degeneration
- Proximal - retrograde; chromatolysis
- Myelin sheath forms chains
- Eventual axon degeneration
- Debris removed by phagocytes
Regeneration - earliest indication of separate cells
composing CNS.
- Scar tissue
- Neurilemma
- Chemotropism
Terms to Know
| neuron |
neurilemma |
neuron doctrine |
| nucleolus |
mitochondria |
unipolar neurons |
| nucleus |
dendrite |
bipolar neurons |
| Barr bodies |
synapse |
multipolar neurons |
| neurofibrils |
teleodendria |
Schwann Sheath cell |
| Nissl substance |
node of Ranvier |
Wallerian degeneration |
| axon |
synaptic vessicles |
retrograde degeneration |
| axon hillock |
chromatolysis |
|
Links to Associated Areas
