- Describe the structure of the cell body and its components and explain its functions.
- Describe the basic function 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 discuss their location and function.
- Explain the Neuron Doctrine and the evidence for it.
- Describe the components of the neuron and discuss their function.
- How does regeneration differ between the CNS & PNS and explain why they are different.
Neuron as Structural Unit
- 1890, Waldeyer
- First proposed view that nervous system composed of individual cells (neuron).
- Golgi, discovered siver stain technique that revealed complete neurons.
- Electron microscope finally resolved any lasting doubt of the structural role of neurons.
Identity of Neurons
Neuron a Tropic Unit
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
- Mitochondria [contain enzymes to produce ATP]
- axon hillock
Dendrites - Greek for TREE [obtain information & transport to cell body & axon]
axon - Unipolar - Bipolar - Multipolar
Anatomical vs physiological distinction
(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
Mitochondria; bead-shaped with inner cristae (layers)
- Contains nucleolus and ribosomes.
- DNA - present; genetic code; messenger RNA.
- Protein - serves as enzymes which serve as catalysts.
- Cytoplasm - semi-liquid fluid within cell.
- Produce ATP (adenosine triphosphate) source of energy
- Rough - contains ribosomes; produces substance out of the cell.
- Smooth - concerned with transport of substance around the cell.
- 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.
CNS - no regeneration? Role of Schwann cell
- 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
Terms to Know
Links to Associated Areas