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Week 8 LOs
Terms in this set (66)
What parts will change length during cross bridge cycling?
Sarcomere, H band, I band but NOT A band
What actions and around what axis occurs at the talocrural joint (ankle)?
plantar flexion and dorsiflexion around the transverse axis
Where is there more stability in the tarsocrural joint (ankle) with dorsiflexion or plantar flexion at the talus bone?
More stability in dorsiflexion because the anterior surface of the talus is wider so more space to articulate with vs. the posterior side is narrower
Think of in ballet how instable it is when on "toes"
what type of joint is the subtalar joint? in the foot
what actions occur here?
subtalar joint is between the talus and the calcaneus
inversion (in) and eversion (out) of the foot occur here around an oblique axis
What actions do the deltoid and calcaneofibular ligaments of the ankle prevent?
deltoid ligament= prevent eversion around the subtalar joint
calcaneofibular ligament= prevent inversion
Adduction/Abduction of the fingers is around what axis vs. what about the does?
fingers= around the AP aixs
toes= around the vertical axis
What unique about adductor magnus with its actions around the transverse axis?
What about its innervation?
anterior fibers pass in front of axis and do hip flexion and the posterior fibers pass in back of axis so do hip extension
Anterior fibers= obturator nerve
Posterior fibers= tibial nerve
How does rotation of the hip aid when walking, what does it do?
Lengthens the stride
Hip adductors help control the position of the lower limb during the swing phase
Also help control the center of gravity from shifting laterally
If someone is having trouble walking down the stairs what nerve might be damaged?
what muscles do this motion?
Knee extension-->rectus femoris, vastus lateralis, intermedius, and medialis
Femoral nerve innervates these muscles
Which muscles made up the pes anserinus?
If someone can't laterally rotate their knee what muscle might be damaged? Innervation?
What other motions can this muscle do and might be affected?
Long head= tibial nerve
Short head= common fibular nerve
Long head can also do hip extension
Short and long head can do knee flexion
1)Describe what happens as the sarcomere stretches to the H zone?
2)what is the I and Z bands?
1)H zone width will increase as the thick/thin overlap decreases
2)I band= contains the Z line and parts of the thin filaments that have
-A band= contains the H zone, M-line and contains the thick filaments that have myosin and the width of the A band will stay constant regardless of the sarcomere length (vs. the I band will change width when the sarcomere moves0
What medication do you want to give someone if they have malignant hyperthermia reaction?
Note: a difference in E-C coupling between skeletal muscle and cardiac is that in cardiac the amount of
Ca2+ that passes through the DHYR is not enough to activate muscle contraction directly but will trigger the RYR on the SR to release its Ca2+ which will
Describe how during an muscle action potential leading to contraction is "terminated"
The Ca2+ need to be put back into the SR and it is done so where is a high conc. of C2+ and the ATPase Ca2+ pump will
What does the Na+/Ca+ exchanger do which is on the surface of the external membrane (sarcolemma)?
: a small amount of Ca2+ enters the cell everytime the heart because and to offset this this pump will exchange (input) 3 Na+ into the cell-->resulting in a net charge of 1+ everytime the heart beats
This doesn't have too much of an effect UNLESS and this can get hyperactive and can result in arrythmias
If you give someone haloperidol and you notice hyperthermia and muscle stiffness what could this be? What other symptoms should you watch out for?
What is the pathophys?
What causes the heat?
What should you give?
Malignant hyperthermia-->other symptoms could be hyperkalemia, metabolic acidosis
RYR1 receptor is skeletal musce (most common receptor defect) is
and results in spewing lots of Ca2+ into the cytosol-->muscle contraction
Heat caused by the ATPase pump on SR trying to pump the excessive amounts of Ca2+ back into the SR
When should you suspect Catecholaminemic Polymorphic Ventricular Tachycardia
Induced by stress or excercise without any structural abnormalities or prolonged QT interval
often occur in childhood or early adolescents
Mutation in RYR2
Hyperactivity of RYR2
Describe how the rate of cross-bridge attachement correlates with rate of force production in muscle
Rate of force production correlates with the amount of cross-bridge attachment and detachment
Passive tension (tension that occurs when stretch muscle) is mainly due to what protein?
Titin-->will resist the stretching
Know what short sarcomere, long sarcomere, and optimal length sarcomere is with relationship to the myosin and actin of the thick and thin filaments
Short sarcomere= will have tension at the begining but as muscle shortens the thin filaments will begin to overlap with each other and won't be availbable for myosin to bind
Optimal-length sarcomere: ALL myosin heads are able to bind the actin filaments
Long sarcomere: no overlap between the myosin and actin filaments so will have a decrease in tension generated
If you pick up to hold a 150lb box which reflexes will activate
Inverse myotatic reflex (golgi tendon reflex)-->golgi tendon organ will sense the strain and send info to spinal cord which will
alpha motor neuron and muscle won't contract to try and hold because know it will be too heavy
Identify the main sources of ATP for muscle fibers and infer why aerobic metabolism produces more ATP than anaerobic metabolism
Creatine phosphate: very fast acting (few seconds)
Oxidative phosphorylation: aerobic (during moderate exercise)
Glycolysis: anaerobic (high intensity exercise)-->ATP from glucose (mitochondria)
What are the characteristics of the 3 types of muscle fibers?
Which do you use when standing, sprinters, vs. marathon runners
Which has a high vs. low myosin ATPase activity?
Type I: slow oxidative (RED) Slow twitch used in posture/antigravity (standing) Don't adapt with exercise
Type IIa: fast oxidative (pink-ish) Used in aerobic exercise (marathon runners)
Type IIb: fast glycolytic (white) Used in fast, high power activities
Type IIa & IIb have a high myosin ATPase activity vs. type I has a slow myosin ATPase activity
What is the recruitment of motor units (fiber types) during muscle contraction or exercise?
Slow oxidative (type I)-->fast oxidative (type IIb)-->fast glycolytic (type IIa)
what is the difference between dendrites and axons?
What lines the axons with myelin?
Dendrites= receive information from other nerve cells
Axons= main conducting unit
Schwann cells line the axons with myelin
Know difference between epineurium, perineuriu, endoneurium
Epineurium= surround or fills the space between the fascicles (contain several thousand axons and various supporting cells)
Perineurium= encases each fasicle
Endoneurium= space between the myofibrils?? that is encased in the perimeurium
How does the conduction velocity of peripheral nerves compare to spinal descding tract or CN?
Peripheral nerves have a slower conduction velocity than spinal tract nerves or CN (they have a smaller diameter)?
Neuroplasticity is when neighboring nerves can compensate for damage to one near by but can go wrong and get maladaptive changes such as neuropathic pain, hyperreflexia and dystonia
Nerve injury can affect either axons or the myelination or also invovle neruoplasticity
What does the Seddon type classification for nerve injury classifcations:
How does seddon type and sunderland overlap?
Neuropraxia= transient injury usually caused by demyelination (but intact nerve otherwise
Axonotmesis=interruption of the axon occurring (bulk of nerve intact)
Neurotmesis= laceration, can't conduct
Sunderland II-IV is axonotmesis
Sunderland I is just neuropraxia
Sunderland V= complete nerve transection
What makes sunderland I a better prognosis?
What will you see on testing with neuropraxia?
NO Wallerian degeneration-->retrograde degeneration of distal part of axons
better porgnosis-=->complete functional recovery usually expected
On testing: will see conduction above and below lesion but not across it
If someone wakes up and can't move their right arm what might be the cause to check?
"Saturday night palsy"-->occurs typically to the radial nerve to sustained pressure on medial arm
Persists until local myelin repairs and can take minutes to months (6-8 months)
What is it called when an axon is transected and you have Wallerian degeneraiton distally
Endoneurium and Schwann cell sheath remain intact
Axon can regenerate within endoneurial tube back to target
what does the recovery of this depend on
2nd degress sunderland axonotmesis
Recovery depends on:
-distance to reinnervation (if occurs at wrist vs. be shoulder, should will be faster)
Which nerve injury classifcation is when there is endoneurial tube and axon transection?
What about if the perineurium transected?
3d degree sunderland (perineurium still intact)
If perineurm not intact then 4th degree sunderland
· Describe the stages of Wallerian degeneration.
Degenerative changes in the distal segment of a peripheral nerve fiber (axon and myelin) and occurs when its continuity with its cell body is distrupted by a focal lesion
~24hrs after injury get some myelin debris
~2 weeks after injury: get macrophage recruitment and Wallerian degeneration
~weeks to months: get Schwann cell alignment and axon regeneration
What is synkinesis?
What about a neuroma?
Can occur when have improper rewiring of nerves after they heal
Smile when blink (for example)
: occur from sprouting axons of a cut nerve that bundle together and can cause shooting pain and sensory signals when tapit is injured perineurium
What type of sensation does:
Which occurs first, 2nd, 3d in healing process?
-Merkel cells-->fingertip touch
-Pacinian corpuscle-->vibration, 2 point discrimiination
-Meissner corpuscle: finger stroking, vibration too?
when a nerve is recovering what symptoms do you except to see first and this correlates with what structure?
which is last?
Meissner's corpuscles: fingertip touch, pressure-->easiest reinnervate
Pacinian corpusles: hardest (vibration and 2 point discrimination)
Describe the diagnosis of ALS.
What are some of the symptoms of ALS?
A clincial diagnosis but electrodiagnostic findings also help support this
-UMN: fasiculations, muscle atrophy, weakness cramps
-LMN: slowness to movements, spasticity, Babisnki sign
-can affect 1 segment of body and then spread to adjacent ones
Which medication can trigger inflammatory-mediated necrotizing myopathy?
statins-->may also have antibodies to HMGCoA reductase
If a 60 year old man comes in and can't flex his fingers and and has atrophy of his quadricep muscles what should you think about?
Inclusion body myositis
Which of the myositis is associated with cancer?
Dermatomyositis occurs in about 25% of DM patients within 0-5 years disease onset
If an adolescent is experiencing exercise intolerance with elevated CK, lactate, myoglobinuria and a few others which disease should you look for?
Impairment in glycolysis/glycogenolysis, mitochondrial respiratory chain
If someone has ragged red fibers on muscle biopsy and myoglobinurea what should you think about?
If someone comes in with ptosis and ophthalmoparesis (cant move eyes) what should you think about?
90% of people may also have limb weakness
What are the lab values for mitochondrial dysorders?
-right ratio of lactate to pyruvate (this suggests metabolic block in respiratory chain)
Which muscles of the anterior compartment of the leg do inversion vs. eversion?
NOTE: all do dorsiflexion
Inversion: tibialis anterior and extensor hallucis longus
Eversion= extensor digitorum longus, extensor peroneus (tertius)
Explain how the tibialis anterior interacts with the gait cycle.
Eccentric contraction (muscle elongates): when lowering foot down to ground
Isometric contraction (maintains length): when bringing foot back forward to step, foot swings forward
Concentric contraction: dorsiflexes foot as heel prepares to strike
How does someone try to compensate for footdrop?
Which nerves are involved?
Will elevate hip of affected side and extends the knee and kicks it out in front to plant
Nerves: deep fibular nerve (innervates anterior compartment of leg) or more upstream at the common fibular nerve
How do shin splints work?
overuse injury that involves the muscle pulling on the periosteum that covers the shaft of the tibia and can result in little fractures in the tibia
Need to rest or else can result in more serious fractures
What holds the fibularis longus and brevis to bone?
Know where fibularis longus extends onto the dorsal foot
They are hold onto bone via the fibular retinaculum (vs.
retinaculum holds Tom, Dick, an Harry muscle tendon)
Fibularis longus wraps around the lateral malleus and inserts onto the medial cuneiform and big toe
Which of the posterior leg muscles can't flex the knee?
but the gastrooccnemius and popliteus can
What are the actions of the popliteus?
Lateral rotation: of fixed tibia and rotate femur
Medial rotation: of fixed femur and rotate tibia
If someone is running or jumping which posterior leg muscles is mainly responsible?
What about if just using to stand for posture or walking?
running and jumping= gastrocnemius
posteru & walking=solues
If there is damage to the tibial nerve or the calcaneus tendon which actions will be impaired?
-unable to run or jump
Know what order the deep posterior leg muscles wrap around the medial malleus
Tom: tibialis posterior
Dick: flexor digitorum longus
An: posterior tibial artery & tibial nerve
F= flexor hallicus longus
If someone is having trouble with the "toe-off" motion of the gail cycle which muscles might be affected?
flexor digitorum longus and flexor hallucis longus
Passive arch= ligaments
Active arch= muscles
Which muscle on the dorsal foot cannot be found in the hand?
Extensor digitorum brevis
Someone with plantar fasciatis what is it and nerves involves?
involves the plantar aponeurosis from overuse and get inflammation at the calcaneal branches of the tibial nerve
What is the sensory information nerves of the dorsal foot?
Deep fibular nerve: sensation between big toe and 2nd toe
Superficial fibular nerve: sensation to rest of dorsal foot
What ares of sensation on the plantar food does the medial tibial nerve do?
What muscles does it do?
Sensation of the lateral tibial nerve?
medial sole of foot and plantar side of big toe, 2nd toe, 3d toe, and 1/2 of 4th toe
Muscles of innervation:
-flexor digitorum brevis
-flexor hallucis brevis
Lateral tibial nerve: lateral sole and lateral 1/2 of 4th toe and pinky toe
Blood supply of the foot
NOTE: at rest ATP binds to myosin head groups and is partially hydrolyze to create the high affintiy for actin to bind but actin can't bind unless the troponin/tropoymsin complexs are removed
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