HIsto BSC 10/22

Question 1

kinesthesia

Answer 1

sense of proprioception

Question 2

cryesthesia

Answer 2

sensation of cold

Question 3

anesthesia

Answer 3

total or partial loss of sensation

Question 4

synesthesia

Answer 4

stimulation evokes a sense of another (i.e. sound produces color visualization)

Question 5

paresthesia

Answer 5

skin sensation with no cause - i.e. tingling, itching, prickling

Question 6

what effect would loss of innervation have on the muscle cells?

Answer 6

• atrophy = reduction in size
• occurs in denervation injuries
• cells lose cytoskeletal structure b/c they no longer have innervation
• fillaments degrade and sarcoplasm wastes away
• causes NO myonecrosis –> rabdomyelisis would occur if the muscle cells are atrophying (muscle contents found in blood)

Question 7

dystrophy

Answer 7

wasting away, related to a disease

Question 8

myopathy

Answer 8

muscular disease in which muscle fibers do not function (for one or many reasons)

Question 9

what is the primary cause of myofilament degradation in denervation atrophy?

Answer 9

• increased proteosome activity: ubiquitin-proteosome system: involves two steps:
  [1. target protein is polyubiquinated 2. 26S proteasome recognizes ubiquitin and degrades the substrate]
  –> this results in small, weakened, atrophic cells (just a bag of nuclei with a little cytoplasm associated)
• protein synthesis suppression is not sufficient to eliminate most of cytoplasmic content so quickly

Question 10

Case 2: progressive weakness: fatigue in jaw that worsens with chewing, trouble swallowing, weakness in face muscles that worsens, diplopia that comes on in evening (or after eye strain events). What is the cause of this?

Answer 10

• -> disease is myasthenia gravis
• symptoms suggest a myopathy.
• noted ptosis = drooping eyelids
• weakness in muscles associated with facial expression
• EMG (shows progressive weakness in upper arm, as muscles are continually shocked… contraction amplitude is decreasing - this tells us that muscles aren’t able to recapture functionality quickly) & NCS (shows normal nerve conduction velocities)
• these two tests together show that it is a muscle problem
• tested with AChase inhibitor - reduces the muscular weakness

Question 11

amyetrophic lateral sclerosis

Answer 11

• damage to spinal cord, resulting in weakness, debilitation and atrophy: the cause is nerves. You would not have a normal nerve conduction velocity, because you are losing motor nerves. Would not see high levels of antiAChR in the blood, because this is not an autoimmune disease

Question 12

Multiple Sclerosis

Answer 12

• autoimmune disease, however the Abs would not be specific anti-ACHR abs
• would have an abnormal NCV test

Question 13

WNV Polio-like syndrome

Answer 13

• degradation, death of Central motor neurons - not an autoimmune disease, rather a neurotoxicity effect
• abnormal NCS

Question 14

Myasthenia Gravis

Answer 14

• autoimmune response to AChR on muscle cell membrane
• produces anti-AChR Abs
• b/c of whats happening with Abs there is a lessened degree of infolding of the motor end plate
• both of these result in blockage of binding of ACh, thus muscle won’t contract as well
• anti-AChR binding stimulates degradation of AChR on muscle cell (the receptors are internalized and degraded, thus don’t need as much membrane - results in smoothing of motor end plate)

Question 15

Why does myasthenia gravis result in increasing muscle weakness?

Answer 15

• • build up of ACh, ACh initially released binds up the small amount of AChR that are not bound by ABs. As ACh is continued to be released, there are fewer AChR open to bind. Because there is so few AChR it takes a long time for the receptors to recover. The channels tend to stay open –> progressive fatigue
• not able to recover available muscle fibers because of decreased AChR

Question 16

ocular myasthenia gravis? why this connection to the eyes?

Answer 16

• ptosis and diplopia because eye musculature isn’t working.
• Ocular MG = strictly ocular symptoms because this is noticed immediately
• concentration of AChR in eye muscles are significantly lower than in skeletal muscles- results in significantly reduced function of eyes first.
• test: have patient blink as fast as they can for 20 seconds: Ocular MG will result in ptosis

Question 17

general myasthenia gravis

Answer 17

• patient develops generalized muscle weakness. normally experiences ocular MG first
• 85% of ocular develop into general MG within 2 years.

Question 18

Case 3: boy began walking on his toes. no progression in speech. at age 2 he was referred for speech and language therapy. had a CK level over 10,000 (normal t have hip strength to stand up, uses strait legs, hands strait, walks hands backward to use center of gravity), trendelenburg gait (one side unaffected- one side experiences loss of abduction, must tip in order to swing the leg out).

Answer 18

• no indication of denervation. not MS (onset is usually middle age). not nutritional deficiency (no evidence to support this). not rhabdomyolysis (no kidney failure)
• it is a primary myopathy: see muscle function loss
• his primary myopathy is Duchenne-muscular dystrophy

Question 19

Duchenne-Muscular Dystrophy

Answer 19

• how is contraction transmitted through a tissue? coastameres (constitutive cytoplasmic transmembrane protein complex that ties the filaments to the muscular cell membranes. it contains dystrophin protein)
• mutated dystrophin protein - muscle contraction is not tied with the binding of filaments - don’t get transmission of force out of the muscle cell into the connective tissues
• X linked recessive genetic disease: though many cases are spontaneous
• cells that don’t have dystrophin atrophy and are replaced by fat in the belly of the muscle
• high levels of CK because the muscle is slowly breaking down and releasing its products into the blood