MSK summary basic principles Flashcards
SLE antibodies
ANA antiDNA Anti SM anti Ro anti rNP
sjorgens antibodies
ANA
anti RO
anti la
systemic sclerosis limited antibody
anticentromere
systemic sclerosis diffuse anibody
anti scl 70
small vessel vasculitis antibodies
ANCA
what happens when Ca2+ binds to troponin on actin filaments?
tropomyosin is moved to uncover cross bridge binding sites on actin
what happens cellularly in rigor mortis?
no ATP present so myosin head remains attached to actin fibre
example of isotonic contractions?
body movements and moving objects
example of isometric contractions
supporting objects in fixed positions and maintaing body posture
do skeletal muscles have a neuromuscular junction?
yes
do skeletal muscles have a gap junction
no
where do skeletal muscles get CA from
entirely sacroplasmic retinculim
where do cardiac muscels get CA from
ECF and sacroplasmiic reticulum
what are the 3 metabolic pathways which supply ATP in muscle fibres?
creatine phosphate (transfer of high energy phosphate from creatine phosphate to ADP) oxidative phosphorylation (main source when O2 is present) glycolysis (main source when O2 is not present)
describe type 1 muscle fibres
slow twitch
prolonged, low work eg walking
abundance of myoglobin + mitochondria
decsirbe 2a type muscles fibres
fast oxidative
prolonged moderate work eg jogging
uncommon
describe type 2b muscle fibres
fast glycocytic
short term, high intensity work eg jumping
fatigue early
few mitochondria + less myoglobin than T1
what is the sensory receptor of the stretch reflex
muscle spindle
what is the stretch reflex
a negative feedback that resists a passive change in muscle length to maintain optimal resting length of muscle
which fibres are sound in muscle spindle and how do they run
intrafusal fibres
found in muscle belly and run parallel to extrafusal fibres (normal fibres)
what are the sensory nerve endings of muscle spindles called
annulospiral fibres
what is the efferent nerve supply of muscle spindles
gamma motor neurones
which components of hyaline cartialge act as elassticy and reduce friction
water + proteoglycans
what is the definitoin of OA
articular cartilage thinning or loss
early vs late events of OA
early - injury to chondrocytes + matrix, fibrillation
late - inflammaotry changes in synovium + subchondral bone –> bone on bone
which scale is used for OA
kellgren - lawrence
surgical treatment for OA
THA
what causes reactive arthritis
chlamydia, shigella and salmonella
what is the cause of enteric arthritis
organisms with high lipopolysaccharides in cell wall trigger immune reaction
what bug causes infectious arthritis in kids
h influenza
what bus causes infectious arthritis in adults
staph aureus
explain the mechanisms behind increased uric acid synthesis?
diet -> purines -> xanthine -> uric acid
what causes hyperuriacemia?
idiopathic 90%
HGORT enzyme deficiency (lesche nyhans syndrome)
increased cell turn over eg cancer and psoriasis
causes of reduced excretion of uric acid?
thiazide diuretics
definition of gout
inflammatory arthriis caused by deposition of uric acid in joints
>0.42mmol/L
how is uric acid excreted normlally
2/3rds from renal
1/3rds from GI
what causes gout?
joints of lower temperature (decreases solubility of urate)
duration of hyperuricaemia
loop diuretics eg furesomide
what is gouty tophus
deposition in soft tissues
histology findings of tophus
amorphous eosinophilic debris + inflammation (giant cells)
pyrophosphate arthropathy
side effect of colcichine
diarrhoea
how does allopurinol work
xanthine oxidase inhibitor
start it 2-4 weeks after acute attack
which cartilage does calcium pyrophosphate / gout affect
fibrocartilge eg knees, wrists, ankles
which type of pseudo gout causes milwaukee shoudler
calcium hydroxyapatite crystals
females 50-60
grading score for joint hypermobility syndrome
modified beighton score
definitoin of OP
quantitive defect
decreased BMD and increased porosity
features of type 1 OP
post menopausal
colles fracture
features of type 2 OP
secondary / old age / alcohol
femoral neck frcature + vertebral fractures
casues of OP
decreased OB
decreased physcial acivity
biochem of OP
decreased Ca
increased PTH
decreased vit D
what is the causes of osteomalacia
softer bones -> fracture
decreased vit d (vit d sitmulates aborption of ca)
roles of PTH
activates OC (releases calcium from bone)
increases resorption of calcium by renal tubules
increases urinary phosphate excretion
which non-tumour is associated with hyperparathyroidism?
brown tumour
what is the biochem of hypeparathyroidism
increased PTH and increased Ca
what happens in secondary hyperparathyroidism?
overproduction of PTH secondary to hypercalcemia
what happens in tertiary hyperparathyroidism?
chronic secondary >develops an adenoma which continues to produce PTH despite biochemical correction
what happens in pagets disease of bone?
abnormality of bone turn over > thick excess bone > increased metabolism
what are the genetic behind pagets?
SQSTM1 / p62
what are the 3 stages of pagets
osteolytic
mixed (OB and OC activity)
osteosclerotic
what are the extra manifestations of pagets?
warm skin
AV shunt
heart failure
secondary malignnacies of pagets
osteosarcoma
fibrosarcoma
pathophysiolgy of myasthenia gravis
auto-IgG binds with ACH receptors on muscle cells
what can cause myasthenia gravis
thymic tumour 10%
diangosis of myasthenia gravis
anti AChR IgG in serum + NMJ dysfunction
treatment of myasthenia gravis
increase neurotranmission - pyridstigmine
surgery - if thymic tumour
immunosuppression - corticosteroids
where are nuclei found in skeletal muscles
at peripheries of ibres, ust under sarcolemma (cell membrane of muscle fibres)
what are fascices
bundles of muscle fibres
what is epimysium
connective tissue which surrounds whole muscle
what is perimysium
surrounds single fasicle
what is endomysium
surrounds single fibre
where are chondrocytes found
lacuna
describe hyaline cartilage
blue-white
translucent
most common
decsribe elastic cartilage
light yellow
flexible
describe fibrocartialge
T1 collagen
chondrocyytes
cartliaginous Ecm
white
what is the composition of bone
65 % hydroxyapatite
23% collagen
10% water
2% non-collagen proteins
what is the epiphysis
cancellous or trabecular bone
what is diaphysis
cortical bone
what are osteoproginator cells
located on bone surfaces eg under periosteum, pool of reserve OBs
what secretes osteoid
OB
types of pain
transduction
transmission
modualtion
perception
what is transduction pain
translation of noxious stimulus into electrical activity at the peripheral nociceptor
what is transmission pain
propagation of pain signals as nerve impulses through the nervous system
what is modulation pain
hidering of pain by opiates
what is perception pain
concious experience of pain
what are nociceptors
first order neurone / aferent sensory neurones
where are nociceptors found
dorsal horn of spinal cord
what is the neurotransmitter of nociceptors?
glutamate + peptides
what are the 2nd order neurones in the nociceptive pathway?
the spinothalamic tract (pain perception) + the spinoreticular tract (autonomic respone to pain, arousal, emotional response + fear of pain)
A$ subtype nociceptor
mechnical / thermal
thinly myelinated
conduction velocity 6-20ms-1
mediate first / fast pain
C fibres nociceptor
unmyelinted
conduction velocity 0.5-2ms-1
all noxious stimuli (polymodal )
mediate slow or secondary pain eg burning, throbbing, cramping, aching sensations
