Neural Tissue Flashcards
Proteins that Compact Myelin: PNS vs. CNS
Compaction of myelin sheath occurs with expression of myelin-specific proteins: protein 0, myelin basic protein (MBP) Proteolipid protein (PLP) in CNS myelin
Functions of Neuroglia
Provide structural and metabolic support for neurons
Can divide and reproduce when injured (unlike neurons)
Cannot conduct action potentials so cannot transmit information
Schmidt-Lanterman Clefts
allow nutrient flow to the inner portion of the Schwann cell cytoplasm
Schwann cell is like jelly roll around axon and plasma cell membrane is on each side= myelin sheath in purple
Pink= long strips of cytoplasm called Schmidt lanterman clefts and act as highways for nutrients on outside and inside the axon and allow for nutrients to flow into inner portion
Unmyelinated Axons
Are closely associated with Schwann cells
Protected by pockets and invaginations of Schwan cell membranes
Don’t have the multiple wrappings but are still inside the cell somewhat
Peripheral nerves contain…
Axons of alpha motor neurons and peripheral processes of DRG cells
Mixed: sensory, motor, somatic, autonomic
Perineurium
Several layers of flat contractile cells with tight junctions;
Each layer has basal lamina
forms the blood-nerve barrier
Blood vessels come through epineurium and perineurium; toxic substances in blood that we don’t want in the nerves and cannot get through perineurium to prevent any diffusion of these substances
Substances that can get through must be selectively transported through
See the many layers of cells that go around with basement membrane (type 4 collagen)
PNS Ganglion
A collection of nerve cell bodies outside of the brain and spinal cord. Examples: Dorsal Root Ganglia Sympathetic Chain Ganglia Cranial Nerve Ganglia
PPQRRST
Provocative, Palliative Quality of Pain Region, Radiation Severity Time Course, Onset, Intermittence
Opoid/Opiates
Mechanism exerted through agonism of Mu receptors
Inhibition of neurotransmitter release in the dorsal horn of the spinal cord and activation of descending inhibitory controls in the midbrain.
Hepatic Metabolism(most via cytochrome p4502D6)
Excreted Via Kidney (90%–95%)
First-order Kinetics: Constant Fraction of Drug is Eliminated Per Unit of Time Proportional to the Amount of Drug in the Body
Dosing Immediate Release Opioids
How often can you redose? Based on peak effects Peak effect: point at which you get the most pain control and most risk for toxicity (sedation, respiratory depression) In general, peak effect: PO= 1 hour SC= 30 mins IV= 15 mins (fentanyl= 6 mins)
Axon Characteristics
Diameter (largest to smallest): referred to alpha, beta, deta, and C; C fibers are the only fibers that are not myelinated (in this list) and the rest are myelinated = creates variation of impulse velocity
Larger the neuron is in diameter, the faster the impulse will travel and vice versa
Myelin increases transmission velocity = alpha, beta, and delta (fastest to slowest because going from largest to smallest diameter)
Meissner’s Corpuscle
Two-point discrimination; vibrations
Meissner’s corpuscle: located under skin in dermal ridge (upper portion in red) and is important for touch and are encapsulated (layer of CT)
Very dense in the skin (40% of sensory receptors in hand)
Sense grip, vibration, etc.
Meissner’s are rapidly adapting to stimulus, and will stop sensing stimulus after a while
Merkel’s Disk
Steady-state
Merkel’s disk: steady state impulses/stimulated
Merkel’s are slowly adapting to a stimulus
Merkel’s are good at telling shapes of things (pen vs. pencil)
Pacini’s Corpuscle
Rapid compression; vibrations
Pacini’s corpuscles: sensing pressure and are located deeper in the subcutaneous tissue
Only really hard touches and pressures activate this receptor
Good for sensing vibrations (cutting something with a knife)
Ruffini’s Endings
Continuous compression (prolonged touch/pressure) Ruffini’s are located in the dermis along stretch lines of the skin to tell us about movement Slowly adapting – continuous compression; Pacini’s is rapidly adapting
