Neuro - Anat & Phys (Cells, Sensory corpuscles, & Peripheral nerve) Flashcards
Pg. 447-448 in First Aid 2014 Pg. 411-412 in First Aid 2013 Sections included: -Neurons -Astrocytes -Microglia -Myelin -Oligodendroglia -Schwann cells -Sensory corpuscles -Peripheral nerve
What are neurons? What is important to know about their nature?
Signal-transmitting cells of the nervous system; Permanent cells - do not divide in adulthood (and, as a general rule, have no progenitor stem cell population).
What are the parts of the neuron and their major functions? What can be used to distinguish these parts, and how does it work?
Signal-relaying cells with dendrites (receive input), cell bodies, and axons (send output). Cell bodies and dendrites can be stained via Nissl substance (stains RER). RER is not present in the axon.
What happens if axon is injured? What might this allow, and in what particular context?
If an axon is injured, it undergoes Wallerian degeneration - degeneration distal to the injury and axonal retraction proximally; allows for potential regeneration of axon (if in PNS).
What are 6 functions of astrocytes?
(1) Physical support, (2) repair, (3) K+ metabolism, (4) removal of excess neurotransmitter, (5) component of blood-brain barrier, (6) glycogen fuel reserve buffer.
How do astrocytes respond to injury?
Reactive gliosis in response to injury
What is an astrocyte marker?
GFAP
What are microglia? From which germ layer are they derived?
CNS phagocytes. Mesodermal origin.
Explain the use of Nissl stain in astrocytes versus neurons.
Astrocytes - Not readily discernible in Nissl stains. Recall: Neurons - Cell bodies and dendrites can be stained via the Nissl substance (stains RER). RER not present in the axon;
Describe the nuclei and cytoplasm in microglia.
Have small irregular nuclei and relatively little cytoplasm.
What role do microglia play, and in what part of the nervous system?
CNS phagocytes. Scavenger cells of the CNS. Respond to tissue damage by differentiating into large phagocytic cells.
What occurs when microglia are HIV-infected?
HIV-infected microglia fuse to form multinucleated giant cells in the CNS.
What is the major function of myelin? What two properties does this affect?
Increased conduction velocity of signals transmitted down axons. Wraps and insulates axons: (1) increased space constant and (2) increased conduction velocity.
What is the embryological origin of astrocytes?
Derived from neuroectoderm.
What process results from myelin? Name and describe a key location to associate with this process.
Results in saltatory conduction of action potential between nodes of Ranvier, where there are high concentrations of Na+ channels.
What cells form myelin in the CNS versus PNS?
CNS - oligodendrocytes; PNS - Schwann cells