LECTURE - Muscle and PNS Flashcards
three types of muscles
- skeletal
- cardiac
- smooth
contraction unit of skeletal muscle
sarcomere
central core disease
ultrastructural disorganization (Z-band streaming)
voluntary control of body movements and sensory
somatic
autonomic
unconscious control of bodily functions
(heart rate, BP, etc.)
- sympathetic (F or F)
- parasympathetic (R & D)
Pacinian corpuscle
an encapsulated ending of a sensory nerve that acts as a receptor for pressure and vibration (skin)
epineurium
outermost protective layer = composed of dense connective tissue
perineurium
surrounding each individual fascicle (by collagenous tissue w a layer of flat epithelial cells)
endoneurium
surrounding individual nerve fiber (by loose vascular supporting tissue)
nerve teasing
technique of manually separating axons following osmication
- used to assess segmental demyelination and other myelin abnormalities
- time-intensive due to fragility of axons
TEDIOUS!
T or F. Cardiac muscle cells can regenerate
F!
Skeletal muscle cells can due to satellite cells and smooth muscle cells can under special conditions
bone is attached to muscle via
tendon
sarcomere structure
- 2 bands, 2 lines, 1 zone
- bands:
> anisotropic (dark); myosin
> isotropic (light); actin - lines:
> Mittelscheibe (middle disc)
> Zwischenscheibe (intercalated disc) - H zone:
> Heller (bright in German)
> absent thin filaments
sarcomere disruption
- central core disease
> ultrastructural disorganization (Z-band streaming)
the link between depolarization of the muscle membrane and contraction
excitation-contraction coupling
rigor mortis
stiffening of the joints and muscles of a body a few hours after death, usually lasting from one to four days
skeletal muscle contraction
- requires ATP to detach myosin head from actin
- rigor mortis occurs if no ATP = no detachment of myosin from actin = stiff muscles
this can be used to select pathological muscle site in difficult cases
MRI
best specific muscles for biopsy
deltoid
biceps
quadriceps
selection of muscle to biopsy
- chronic disease: muscle with moderate, but not severe, weakness
- acute disease: muscle with severe or moderate weakness
AVOId muscles that were site of EMG, injections, or trauma
muscle processing technique
- open biopsy procedure
- do not use cautery, sutures, or clamps
- needle to minimize trauma (may miss patchy or epimysial pathology)
- obtain several samples from biopsy site
muscle processing transportation
- may be saved in saline moistened gauze for several hrs
- keep cool
- should NOT be immersed in saline, fixative, or other liquids
- adequate dry ice = frozen for shipping ‘overnight’
muscle processing preservation
- freeze most tissue in isopentane precooled to -160C in liquid nitrogen
> freezing process should be rapid to prevent artifact
> store frozen muscle at -80C - fix some muscle in 4% glutaraldehyde
> embed momst fixd muscle in plastic = for ultrastructural analysis + good visualization of muscle endomysial capillaries
> paraffin embedded material = useful for surveys for inflammation & morphology of inflammatory cells; gives poor muscle fiber morphology
basic panel of stains in muscle biopsy
- Gomori trichrome
- acid phosphatase: lysosomal activity
- NADH: mitochondrial activity
- ATPase: fiber type (differentiates using different pHs)
- non-specific esterase: denervation
- COX/SDH: mitochondrial activity
- PAS/PASD: glycogen
- oil red O/sudan black: fat
NOTE: many of these are enzyme-based and thus will not work on formalin-fixed paraffin embedded material
basic panel of stains in muscle biopsy
- Gomori trichrome
- acid phosphatase: lysosomal activity
- NADH: mitochondrial activity
- ATPase: fiber type (differentiates using different pHs)
- non-specific esterase: denervation
- COX/SDH: mitochondrial activity
- PAS/PASD: glycogen
- oil red O/sudan black: fat
NOTE: many of these are enzyme-based and thus will not work on formalin-fixed paraffin embedded material
nemaline rod myopathy
congenital, often hereditary neuromuscular disorder with many symptoms that can occur such as muscle weakness, hypoventilation, swallowing dysfunction, and impaired speech ability
T or F. cardiac muscle is not attached to tendon
T! attached to each other by intercalated discs
T or F. Cardiac muscle only has one cell with one nuclei
T! unlike skeletal muscle which has multiple nuclei; this one cannot regenerate; this one has branching connections
pacemaker cells
sinoatrial cells
- produce depolarization and action potentials to drive cardiac cell contraction
voluntary control of body movements and sensory
somatic
autonomic
- unconscious control of bodily functions (heart rate, BP, etc.)
- sympathetic = fight or flight
- parasympathetic = rest + digest
peripheral nerve biopsy
- sural nerve most often sampled > pure sensory nerve (no motor deficit post-biopsy) > easily accessible and identifiable - superficial peroneal - superficial radial
how should a nerve biopsy arrive
- fresh on saline moist gauze
- split into three parts:
> paraffin (FFPE)
> plastic embedded sections for Toluidine blue sections + electron microscopy
> teased nerve fibers
neurofilament IHC
labels axons
Bielschosky stain
silver stain that stains axons black
oligodendrocytes vs Schwann cells
- oligo = myelinates many axons in CNS
- Schwann = myelinates a single axon in PNS
Node of Ranvier
space between myelin sheath which allows saltatory conduction
Masson Trichrome stain (peripheral nerve)
stains myelin fuschia
Toluidine blue stain for peripheral nerve
- highlights myeline sheath with dark blue staining
- assesses myelination and axonal density and myelin loss
types of axons in a peripheral nerve fascicle (3)
- large myelinated axons = fastest conduction
- small myelinated
- unmyelinated axons = slowest
T or F. pain sensors are myelinated
F! they are unmyelinated which is why you feel the heat first and pull way THEN you feel pain; heat sensors (myelinated = faster)
an example of demyelinated peripheral neuropathy
Guillain-Barre syndrome
congo red stain
- for amyloid
- stains amyloid salmon pink
- when polarized, shows apple-green birefringence
dorsal root ganglia
aggregate of sensory neuronal cell bodies
