Anatomy & Physiology Flashcards
What are the CNS/PNS origins?
Neuroectoderm, Neural crest & mesoderm
What cells originate from Neuroectoderm?
- CNS neurons
- Ependymal cells
- Oligodendroglia
- Astrocytes
What are Ependymal cells?
Inner lining of ventricles that make CSF
What cells originate from Neural crest?
PNS neurons & Schwann cells
What cells originate from Mesoderm?
Microglia
What are Neurons?
Signal-transmitting cells of the nervous system
Permanent cells–do NOT divide in adulthood
Which cells do Neurons signal-relay w/?
- Dendrites (receive input)
- Cell bodies
- Axons (send output)
What does Nissl substance stain?
RER in cell bodies & dendrites
RER is NOT in axons
What does an axon undergo when it is injured?
Wallerian degeneration
What is Wallerian degeneration?
Degeneration distal to the injury & axonal retraction proximally
What does Wallerian degeneration allow for?
Potential regeneration of axon if in PNS
What do Astrocytes do?
- Physical support
- Repair K+ metabolism
- Removal of excess neurotransmitter
- Maintenance of BBB
What do Astrocytes do in response to injury?
Reactive gliosis
What is the marker for Astrocytes?
GFAP
What are Microglia?
CNS phagocytes w/ Mesodermal origin
Do microglia stain w/ Nissl stains?
No
What is the histology of Microglia?
Small irregular nuceli & relatively little cytoplasm
What do Microglia do?
Scavenger cells of the CNS
Respond to tissue damage by differentiating into large phagocytic cells
What happens to HIV-infected microglia?
Microglia fuse to from multinucleated giant cells in the CNS
What is Myelin?
Wraps & insulates axons→ Inc space constant & inc conduction velocity of signals transmitted down axons
What does Myelin result in?
Saltatory conduction of AP b/w nodes of Ranvier where there are high conc of Na+ channels
What are the Myelin cells of the CNS?
Oligodendrocytes
What are the Myelin cells of the PNS?
Schwann cells
What are oligodendroglia?
Each oligodendrocytes myelinates multiple CNS axons (up to 50 each)
What do Oligodendroglia look like on a Nissl stain?
Appear as small nuclei w/ dark chromatin & little cytoplasm
What is the predominate glial cell in white matter?
Oligodendroglia
What do Oligodendroglia look like on H&E stain?
Fried eggs
When can Oligodendroglia be destroyed?
Multiple Sclerosis
How man axons do Schwann cells myelinate?
1 PNS axon
What do Schwann cells promote?
axonal regeneration
When can Schwann cells be destroyed?
Guillain-Barre syndrome
What is Acoustic neuroma?
Type of Schwannoma
Where are Acoustic neuromas usually located?
Internal acoustic meatus (CN VIII)
What are free nerve endings?
- C–slow, unmyelinated fibers
- A delta–fast, myelinated fibers
Where are free nerve endings located?
All skin, epidermis, some viscera
What do free nerve endings sense?
Pain & temp
What are Meissner’s corpuscles?
Large, myelinated fibers
Adapt quickly
Where are Meissner’s corpuscles located?
Glabrous (hairless) skin
What do Meissner’s corpuscles sense?
Dynamic, fine/light touch
Position sense
What are Pacinian corpuscles?
Large, myelinated fibers
Where are Pacinian corpuscles located?
Deep skin layers, ligaments & joints
What do Pacinian corpuscles sense?
Vibration & pressure
What are Merkel’s discs?
Large, myelinated fibers
Adapt slowly
Where are merkel’s discs located?
Hair follicles
What do Merkel’s discs sense?
pressure, deep static touch & position sense
What is Endoneurium?
Invests single nerve fiber layers
(Inner)
What is the inflam infiltrate in Guillian-Biarre?
Endoneurium
What is Perineurium?
Surrounds a fascicle of nerve fibers
(around)
What must be rejoined in microsurgery for limb reattachment?
Perineurium