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
What role does oligodendroglia play? Vaguely quantify this role.
Myelinates the axons of the neurons in the CNS; Each oligodendrocyte can myelinate many axons (~30)
What is the embryological origin of oligodendroglia? Name another non-neuron cell in the nervous system that is derived from there as well.
Derived from neuroectoderm; Astrocyte
What is the predominant type of glial cell in white matter?
Oligodendroglia
What kind of appearance do oligodendroglia have on H & E stain?
“Fried egg” appearance on H & E stain
Name 3 conditions/diseases in which oligodendroglia are injured.
Injured in multiple sclerosis, progressive multifocal leukoencephalopathy (PML), and leukodystrophies.
Draw the structure of astrocytes and microglia.
See p. 447 in First Aid 2014 or p. 411 in First Aid 2013 for visuals
Draw an image including the following: Node of Ranvier, Oligodendrocyte, & Axon.
See p. 447 in First Aid 2014 or p. 412 in First Aid 2013 for visual
Draw an image including the following: Schwann cell, Nucleus, Myelin sheath, & Node of Ranvier.
See p. 448 in First Aid 2014 or p. 412 in First Aid 2013 for visual
How many PNS axons can one Schwann cell myelinate? Compare this to oligodendroglia myelination of CNS axons.
Each Schwann cell myelinates only 1 PNS axon.; Each oligodendrocyte can myelinate many axons (~30)
What is the embryological origin of Schwann cells?
Derived from neural crest.
What 2 roles do Schwann cells play?
(1) Each Schwann cell myelinates only 1 PNS axon (2) Also promote axonal regeneration
Again, what process results from myelin (e.g., Schwann cells)? Name and describe a key location to associate with this process.
Increased conduction velocity via saltatory conduction between nodes of Ranvier, where there are high concentrations of Na+ channels
In what syndrome are Schwann cells destroyed?
Destroyed in Guillain-Barre syndrome
What is acoustic neuroma? Where is acoustic neuroma typically located? With what other condition can it be strongly associated, and in what context?
Acoustic neuroma - Type of schwannoma; Typically located in internal acoustic meatus (CN VIII); If bilateral, strongly associated with neurofibromatosis type 2
What are 4 receptor types for sensory corpuscles?
(1) Free nerve endings (2) Meissner corpuscles (3) Pacinian corpuscles (4) Merkel discs
What are 2 types of free nerve endings? Describe the fibers of each.
(1) C - slow, unmyelinated fibers (2) A-delta - fast, myelinated fibers
Describe the fibers and adaptation of the following kinds of sensory corpuscles: (1) Meissner corpuscles (2) Pacinian corpuscles (3) Merkel discs.
(1) Large, myelinated fibers; adapt quickly (2) Large, myelinated fibers; adapt quickly (3) Large, myelinated fibers; adapt slowly
What do each of the following kinds of sensory corpuscles sense: (1) Free nerve endings (2) Meissner’s corpuscles (3) Pacinian corpuscles (4) Merkel’s discs?
(1) Pain and temperature (2) Dynamic, fine/light touch; position sense (3) Vibration, rapid changes in pressure (4) Pressure, deep static touch (e.g., shapes, edges), position sense
Where are each of the following kinds of sensory corpuscles found in/on the body: (1) Free nerve endings (2) Meissner’s corpuscles (3) Pacinian corpuscles (4) Merkel’s discs?
(1) All skin, epidermis, some viscera (2) Glabrous (hairless) skin (3) Deep skin layers, ligaments, and joints (4) Basal epidermal layer, hair follicles
Draw an image depicting the layers of a peripheral nerve, labeling the following: nerve trunk, epineurium, perineurium, endoneurium, and nerve fibers.
See p. 448 in First Aid 2014 or p. 412 in First Aid 2013 for visual
What do Endo, Peri, and Epi mean? Why is this relevant to the peripheral nerve?
Endo = inner, Perio = around, and Epi = outer; Endoneurium –> Perineurium –> Epineurium (i.e., layers surrounding nerve fibers and altogether making up nerve trunk)
What role/function/location does the endoneurium have? In what condition/disease is it affected, and how?
Endoneurium - Invests single nerve fiber layers (inflammatory infiltrate in Guillain-Barre syndrome)
What role/function/location does the perineurium have? What is an important clinical application for it?
Perineurium (Permeability barrier) - surrounds a fascicle of nerve fibers. Must be rejoined in microsurgery for limb reattachment.
What role/function/location does epineurium have?
Epineurium - dense connective tissue that surrounds entire nerve (fascicles and blood vessels).
