CNS Chapter 11 Flashcards
Neuroglia
– non-excitable, renewable (mitotic)
– Provide a supportive / protective scaffolding for neurons, protective
– Segregate and insulate neurons
Structural classification of neurons
1) Unipolar: one short single process. Dendrites and axons are continuous. (afferent neurons, ganglion). Most abundant in PNS.
2) bipolar: one dendrite one axon continues, (special sensory organs: olfactory, retina)
3) multipolar: many dendrites, one axon. Most common class of neurons (interneurons, cerebellum, cerebral cortex, purkinje cells in heart). Most abundant in CNS
Sensory Neurons
- Afferent neurons.
- Action Potential from PNS to CNS
Motor neurons
- Efferent neurons
- Action Potential from CNS to PNS
Interneurons
- Association neurons
- Most of the neurons in the CNS (90%)
Neuroglia in CNS
1) Oligodendrocytes
2) Astrocytes
3) Ependymal cells
4) Microglia
Neuroglia in PNS
1) Schwann cells
2) Satelite cells
Satellite cells
- Surround neuron cell bodies in ganglia.
- Regulates O2, CO2, nutrient, and neurotransmitter levels around neurons in ganglia.
Schwann cells
- Surround axons in PNS, spinal cord
- Are responsible for myelination of peripheral axons.
- Participate in repair process after injury
Oligodendrocytes
- Myelinate CNS axons
- Provide structural framework
Astrocytes
- Maintain blood-brain barrier
- Provide structural support
- Regulate ion, nutrient, and dissolved gas concentrations.
- Absorb and recycle neurotransmitters
- Form scar tissue after injury.
Microglia
- Remove cell debris, wastes, and pathogens by pahgocytosis
Ependymal cells
- Line ventricles (brain) and central canal (spinal cord)
- Assist in producing, circulating, and monitoring of cerebrospinal fluid.
Nodes of Ranvier
Periodic gap in the insulating sheath (myelin) on the axon of neurons that serves to facilitate the rapid conduction of nerve impulses.
Myelination
- Fatty sheath along the length of axon
- Electrically insulates axon
- Increases the speed of nerve impulse transmission
- Helps neural regeneration in PNS
Multiple Sclerosis
destruction of myelin sheath (demyelination)
Repair in PNS
1) The axon becomes fragmented at the injury site. Wallerina degeneration occurs distal to injury
2) Macrophages clean out the dead axon distal to the injury
3) Axon sprouts, or filaments, grow through a regeneration tube formed by Schwann cells.
4) The axon regenerates and a new myelin sheath forms
Wallerian degeneration
degeneration of nerve fibers that occurs following injury or disease and that progresses from the place of injury along the axon away from the cell body while the part between the place of injury and the cell body remains intact
Nerve signals direction
1) Dendrite 2) Cell body 3) Axon 4) Axon bulbs - Terminal 5) next neuron / effector
Development of the the neural tube from embryonic ectoderm
1) The neural plate forms from surface ectoderm.
2) the Neural plate invaginates, forming the neural groove flanked by neural folds.
3) Neural fold cells migrate, form the nural crest, will form much of the PNS and other surfaces.
4) the Neural groove becomes the neural tube, which will form CNS structures.
