Musculoskeletal Flashcards
What are the characteristics of cerebral ataxia? What kind of problem is it?
Slow pace and wide based stance due to loss of balance and coordination. Central neurological problem.
Give three examples of glycoproteins
Osteonectin, fibronectin, laminin
Give five examples of proteoglycans
Versican, aggrecan, biglycan, decorin, hyaluronan
What are the visible signs 10 days post-tenotomy?
Nuclei becomes more round so tenocytes can grow and divide. White space between collagen fibres filled with proteoglycans which bind to water and cause swelling.
What does the cross-banding pattern of collagen fibrils suggest?
Organisation of protein molecules is in a crystalline structure. It is difficult to elongate, which allows for precise movement.
What does a tendon under pressure result in?
Increased proteoglycans
For normal tenocytes under tension, what is the percentage of PG’s? What PG is likely to be found here?
0.15% Decorin containing dermatan sulphate chains.
For tendons under pressure, what is the percentage of PG’s? What PG is likely to be found here?
2-4% Versican/Aggrecan containing chondroitin sulphate chains.
In pressure-bearing regions, what happens to tendon?
Tenocytes turn into chondrocytes. Fibrocartilage
What is the percentage of proteoglycans in the load bearing regions of hyaline cartilage?
10%
What increases the strength of hyaluronan?
GAG side chains are attached to collagen electrostatically.
More PG results in __________
More resistance to pressure
What were the results of the swing, straight, bent leg conditions experiment?
No movement and no weight bearing leads to 40% loss of PG in 4 weeks. Movement alone maintains PG’s.
What does the epidural space contain?
Fat, arteries, and veins. Most arteries and veins transcendant.
What does the subdural space contain?
Virtual space and veins (mostly going across)
What happens when fat pads behind the dura are lost?
Increases space for veins. This can pull on them and they can rupture. Small bleeds can happen, leading to confusion or loss of consciousness.
What is the epineurium?
A sheath around the nerve containing the best qualities of the three maters.
What is the purpose of the denticulate ligament?
Holds arachnoid and pia mater apart.
What does the subarachnoid space contain?
CSF
Which intermuscular septum in the thigh is the strongest?
Lateral
What does the fascia lata attach to superiorly, laterally, and posteriorly?
Superior: pubic tubercle, pubis, inguinal ligament
Lateral: iliac crest
Posterior: sacrum, coccyx, ischial tuberosity
Where is the femoral nerve formed?
Psoas major
What does the adductor canal contain?
Femoral artery, vein, nerve to vastus medialis, saphenous nerve
What is the adductor canal bound by medially, posteriorly, and laterally?
Medial: Sartorius
Posterior: Adductor longus and magnus
Lateral: Vastus Medialis
What are the two uses of the femoral artery in a clinical setting?
1) For arterial samples when unable to collect peripheral samples when shut down in shock.
2) Cardiac angiography, where a catheter is passed up the femoral artery to the aorta and coronary arteries and contrast inserted.
What is are the clinical uses for the femoral vein?
Cannulation. Used for central access. Long catheter inserted into femoral vein as it passes through the femoral triangle and blood samples or pressure measurements form the right side of the heart. Also used to give someone a lot of fluid.
True or false: bone has a lot of PG?
False. Bone has very little PG so collagen and minerals give it strength
How much decorin does bone contain? What is its function?
Very little. Holds together collagen fibres.
What is the purpose of osteonectin in bone?
It is a small molecule that binds together other molecules such as fibronectin and laminin.
What sends the signal to stop growing in primary osteon formation?
Blood vessel
Which compartment is most susceptible to compartment syndrome? Why so?
Anterior compartment of the leg. It is bounded on 3 sides by fairly rigid structures (tibia, IO membrane, anterior intermuscular septum)
Which bone can be removed for bone graft?
Fibula
What are the three points of attachment of the inferior extensor retinaculum?
Lateral: Upper surface of calcaneus
Medial proximal: Medial malleolus
Medial distal: Plantar aponeurosis
Where is the superior peroneal retinaculum?
Above to the lateral malleolus
Below to the lateral surface of the calcaneus
What is the inferior peroneal retinaculum attached to?
In front: continuous with cruciate crural ligament
Behind: lateral surface of calcaneus
Some fibres attached to peroneal trochlea, forming a septum between the tendons of peroneal longus and brevis.
Which nerve can be used for a nerve biopsy?
Sural nerve
What are the 5 clinical signs of compartment syndrome?
Pain, pallor, pulselessness, paraesthesia, paralysis
What are osteoclasts derived from?
Blood lineage (precursors of blood cells). Not from connective tissue.
What are the two steps of degradation of mineralised bone?
1) Focal decalcification by organic acids
2) Digestion of ECM by acid hydrolases
Give an example of an acid hydrolase
Cathepsin, which digests collagen
How do osteoblasts prepare the surface for osteoclasts?
They digest the osteoid (clear zone). Signal tells osteoblasts to move and osteoclasts come in to fresh bone surface.
How does PTH affect bone removal?
Increases osteoblast and osteoclast activity. Decreases bone mass.
How does calcitonin affect bone removal?
Decreases osteoclast activity, membrane ruffling, number of osteoclasts and movement of osteoclasts. Decreases SA for secretion of acids and enzymes.
Where is calcitonin produced?
By the C cells in the thyroid gland.
What does OPG stand for? What is it produced by?
Osteoprotegerin
Produced by osteoblasts
What are the stages of growth of long bone from cartilage?
Resting, proliferating, maturing, hypertrophy, calcification, new bone
What are the steps for healing of bone fractures?
- Periosteum and endosteum provide source of new bone
- Blood vessels grow slower than cells
- Osteoblasts under low O2 become chondrocytes so cartilage formed
- Capillaries grow in
- Oxygen concentration rises
- Osteoblasts form bone around cartilage
- Cartilage degenerates
- Bone invades
- Osteoclasts dig out channels
- New secondary osteons knit bone ends together
- Remodelling
- Thickness reduced
What can be done to reduce callus size?
Metal plates and screws carry load so the callus size is reduced and help align. Fractures are weaker when removed and takes longer to heal.
Where does the medial collateral ligament attach? Describe it
Medial femoral epicondyle to medial tibia
Broad ligament blends with underlying joint capsule
Where does the anterior cruciate ligament attach?
Anterior tibial spine to lateral condyle of femur
Where does the posterior cruciate ligament attach?
Posterior tibial spine to medial condyle of femur
What is the function of menisci?
Increases the articulation between the femur and tibia
Describe the medial meniscus
Attached to the joint capsule and medial collateral ligament. Less mobile
Describe the movement of the lateral meniscus
More mobile so reduced risk of damage
What can cause gluteal/Trendelenburg gait? Describe what happens.
Injury to Gluteus medius or superior gluteal nerve. Weak thigh abduction. Pelvis tilts down on unaffected side. When walking, must lean to affected side during swing through phase.
Describe the normal function of the gluteus medius when walking
Contracts to support pelvis and stop it tilting to lifted side when standing on one leg.
What are the possible hamstring injuries that may occur? What are they usually caused by?
Midsubtance strains/tears or avulsion from ischial tuberosity. Kicking/running sports.
What is piriformis syndrome?
Sciatic nerve compressed by piriformis. Results in pain, tingling, numbness in buttocks and down leg.
What does trochanteric bursitis result from?
Gluteus maximus fibres rubbing over greater trochanter.
Where is the joint capsule of the hip attached to proximally and distally?
P: Acetabulum and transverse acetabular ligament
D: Intertrochanteric line
What reinforcement does the iliofemoral ligament provide? What does it prevent? What is it attached to proximally and distally?
Superior anterior reinforcement
Prevents hyperextension by corkscrew effect
P: AIIS and acetabular rim
D: Intertrochanteric line
What reinforcement does the pubofemoral ligament provide? When does it tighten? What is it attached to proximally and distally?
Inferior anterior reinforcement
Tightens in extension and abduction to prevent over-abduction
P: Pubis
D: Joint capsule
What reinforcement does the ischiofemoral ligament provide? What does it prevent? Where is it attached proximally and distally?
Posterior reinforcement
Prevents hyper-extension by corkscrew effect
Ischial part of acetabular rim and spirals to base of greater trochanter
What can pes anserinus be used for?
Reconstruct ACL
What is the myotome for adduction and abduction of hip?
Add: L1-4
Abd: L5, S1
What can lead to fractures of the femoral neck?
Trauma, osteoporosis, tumour
What are the possible areas in which the Achilles tendon can be injured?
Muscle belly, MTJ, within tendon, attachment to calcaneus
What do the curvatures in the spine assist?
Assist balance over vertebral column. Pushes tissue to centre of gravity line. Balance with minimum expenditure.
Where is the ligamentum flavum situated? Describe its appearance.
Posterior side of the vertebral foramen. Yellow because of elastic fibres. Stretchy for bending.
Describe the interspinous ligament.
Short. Between spinous processes at an angle. Helps spine open during flexion.
Describe the supraspinous ligament.
Small. Tips of spinous processes. Stretched during bending.
What are the deep back muscles also called?
Erector spinae muscles
Where does multifidus run from and to? What is its action?
Inferiorly to superiorly and posteriorly from transverse process to spinous process. Pulls to side and back. Assists in lateral flexion and rotation.
Where does the nerve supply to intervertebral discs come from?
Ventral rami
What accounts for difficulty locating pain in the back?
Segmental nerves have up to 3 layers of overlap.
Non-segmental nerves have sensory pathways from lower to upper discs.
What are the three types of segmental vessels supplying the intervertebral disc?
Medullary
Posterior intercostal
Lumbar
What are the purposes of the Na-K pump and the Na-Ca exchanger?
Na-K: restores ions
Na-Ca: balances Ca2+ recovery
Describe the preparation and method of Otto Loewi’s experiment
Cannula is inserted into the aorta of the donor heart and perfused with solution that mimics plasma. Valves close and solution goes through coronary circulation. Electrodes placed on vagus nerve. Effluent collected from perfusate of RV and added to second heart.
What is meant by size principle?
Small oxidative units recruited first.
Large glycolytic units last
Describe the nicotinic ACh-gated ion channels
Found at NMJ. Different subunits. ACh must bind to both binding sites for channel to open. As region depolarises, driving force for Na+ to come in and K+ to go out decreases.
What do alpha toxins block?
Nicotinic AChR’s
Give two examples of alpha toxins
Snake venoms (alpha-bungarotoxin) Curare (plant extract, paralyses prey)
Where is AChE found?
Anchored to collagen fibres of basement membrane
What is AChE the target of?
Insecticides and military nerve gass
What causes the change in potential of a motor end plate?
Change in current due to the movement of Na and K ions.
Give examples of presynaptic abnormal neuromuscular transmission.
Lambert-Eaton syndrom: autoimmune, reduced Ca channels, 1 AP causes less neurotransmitter release
Diabetes
Naturally occurring toxins: alpha-latrotoxin triggers exocytosis, botulinum and tetanus toxin prevent vesicles docking.
What type of anormality is myasthenia gravis?
Post-synaptic. Weakness and fatiguability of voluntary muscles. Autoimmune, reduced ACh receptors, shallow junctional folds.
What are two ways to improve myasthenia gravis?
1) More NT to ensure all receptors are opened.
2) Prevent function of AChE to increase time ACh bound to receptors to allow sufficient depolarisation.
What can damage of the inferior tibiofibular joint result in?
The talus is free to move around in the joint. Extra movement leads to damage of articular cartilage. Leads to pain and earlier onset arthritis.
What percentage of total muscle volume do muscle fibres make up? What is the other percentage made up of?
75-92%
Other: CT, BV, nerves
What is the purpose of T-tubules?
AP needs to occur quickly and deeply within cell so muscles are not damaged. T-tubules allow propagation of AP throughout the cell. In continuity with EC space.
What are the three major classes of SR Ca2+ regulatory proteins?
1) Luminal Ca2+ binding proteins for Ca2+ storage
2) SR Ca2+ release channels
3) SR Ca2+-ATPase (SERCA) pumps for Ca2+ reuptake. High affinity for Ca2+
What is the purpose of titin?
For tethering thick filaments to Z disc. Adjustable molecular spring. Contributes to passive forces.
Describe the structure of thick filaments
Hundreds of myosin molecules in a repeating staggered array of paired heads 14.3nm apart. Each pair displaced 1/3 of the ways around the filament. Bare zone in the middle.
Describe the structure of thin filaments
Two F-actin filaments twisted around eachother.
Tropomyosin lies along F-actin in groove.
Troponin complex made up of TnT, TnC, TnI
Nebulin helps align actin filaments
Describe the role of calcium in cross brifge cycling activation
At rest, cytosolic calcium is low. As calcium increases, binds to TnC cooperatively. Regulatory proteins on thin filament are activated, releasing inhibition by TnI. Tn-Tm complex moves and exposes myosin binding site on actin. Cross-bridge cycling generates force as long as calcium concentration high and ATP available.
What types of SR have feet?
SR participating in junctions or corbular SR
What is the structure of DHPR?
4 homologous repeats in a diamond shape, forming a tetrad
What does DHPR stand for?
Dihydropyridine receptors
What opposes DHPR tetrad?
4 RyR1 molecules functioning as a single Ca2+ release channel
Describe DHPR’s
L-type, slow, voltage receptor, activated when voltage change sensed, initiates RyR opening
What inhibits and activates RyR1 activation?
I: Cytosolic Mg2+
A: ATP
What are the three ways to increase force of contraction?
1) Summation and tetanus
2) Recruitment of motor units
3) Action of sympathetic nervous system
What does the scapula cover?
Posterior-lateral surface of ribs 2-7
What acts as the fulcrum of clavicular movements?
Costoclavicular ligament
What holds the intraarticular disc of the SC joint in place?
Articular capsule bound to outer edge of IA disc.
What leads to winged scapula?
Severed long thoracic nerve
What are the four shunt muscles of the arm?
Deltoid, short head of biceps, coracobrachialis, long head of triceps.
What is at risk when you have a posterior, inferior dislocation of shoulder?
Axillary nerve and posterior circumflex humeral artery
What is at risk when you have a mid-shaft fracture of the humerus?
Radial nerve and profunda brachii artery.
What are the components of a synarthroses? Give examples
Bone - fibrous tissue - bone
Skull bones, forearm and leg bones
What is a synostosis?
Fused sutures
What is syndesmosis?
Unfused interosseous membrane
What are the components of primary synchondroses? Give examples
Bone - cartilage - bone
Epiphyseal plate, costal cartilage
What are the components of secondary synchondroses? Give examples
Bone - cartilage - fibrocartilaginous tissue - cartilage - bone
Interverteral discs, manubrio-sternal joint
What are the components of diarthroses?
Bone - cartilage - joint space - cartilage - bone
Describe the temporomandibular joint
Where jaw articulates. Started off as meniscus on either side but now joined up to form a complete pad of tissue within the joint space. Under pressure so is fibrocartilage. Lower joint can protrude forwards and backwards, which requires fibrocartilage because hyalin cartilage is not good at sliding forward and backward.
What can set off degenerative arthritis? What prevents this?
Start losing proteoglycans as we age especially at periphery so increased chance of damage. Movement can prevent it.
What are the benefits of having loose articular capsule?
Increases the range of motion. Not supporting unless at extreme range of motion. Far away from articular cartilage, which prevents fouling onto bone at extreme ranges.
When is the humerus likely to dislocate?
When arm is abducted and externally rotated
Which bursa is in contact with the shoulder joint?
Sbscapular bursa
Describe the properties of the coracohumeral ligament during abduction and adduction.
Abd: lax
Add: stretched, allowing passive suspension
What is another name for the fibrous articular disc?
Triangular fibrocartilage complex
What are the three functions of the interosseous membrane between the radius and ulna?
Hinge
Muscle attachment
Force transmission (As force from hand goes through radius, it is transmitted via oblique fibres to the ulna, which has a much broader base than R)
What are the three joints of the wrist?
Radiocarpal joint
Midcarpal joint
Carpometacarpal joint
What is the wrist crease formed by?
Line between the 2 styloids
What are the functions of the carpal tunnel?
Stops tendons bowstringing. Mechanical advantage as they act like pulleys
Between which muscles does the median nerve run?
FDS and FDP
What can pick up the supply of the forearm if the brachial artery supply diminishes?
Collateral anastomoses
What does damage to the radial nerve result in?
Wrist drop, which can affect flexor efficiency. Need to extend wrist to get full efficiency of flexors.
What is the purpose of the intertendinous bands?
Links the ED tendons and stops them oversplaying
What does DOMS stand for?
Delayed Onset Muscle Soreness
What is strengthening muscles associated with?
Eccentric contractions. Muscle growth may be aided as a result of the eccentric muscle damage causing the release of cytokines.
What is the most contractile property of muscle that limits maximum sprinting speed?
Force-velocity relationship
When does max power occur?
At 1/3 max force so contraction is most efficient at 1/3 of maximum rate of shortening.
Describe Type I muscle fibres
Slow, oxidative. Reduced rate of ATP turnover. Many mitochondria and myoglobin. Resistant to fatigue. Many in postural muscles and endurance athletes.
Describe Type IIA fibres
Fast, oxidative. Hybrid of type I and II fibres. Red and increased mitochondria. Both aerobic and anaerobic. More prone to fatigue than type I
Describe Type IIB fibres
Fast, glycolytic. White, produce ATP slowly anaerobically. Short, fast bursts of power and fatigue rapidly. Can turn into type IIA by resistance training. Sprinting.
List 3 muscle performance enhancing techniques.
Creatine supplements
Carbohydrate loading
Increased altitude training
What contributes to central fatigue?
Reduced activation from CNS, reduced motor units recruited
What contributes to peripheral fatigue?
Reduced Ca2+ transient, Reduced Ca2+ sensitivity of myofibrils, slow cross bridge cycling
What are the purposes of dystrophin? What happens when there is not enough dystrophin?
Connected to proteins in cell membrane that link ECM to EC actin filaments. Important for controlling receptors for channels allowing Ca2+ influx.
DMD increases membrane permeability. Soluble enzymes such as creatine phosphate leak out. Ions such as Ca2+ enter.
What changes are there to muscle fibers during sarcopenia?
Increased Type I fibers with no change in mean fibre cross-sectional area for type I or type II fibers. Reduced capillary: fibre ratio. Dennervation of fast fibres and motor units and motor unit remodelling.
What type of joint is the metacarpophalangeal joints?
Condyloid/ellipsoid
What are the interphalangeal joints reinforced by?
Collateral ligaments
What is the tunnel of the ulnar nerve called?
Guyon’s canal/ulnar tunnel
What is the ulnar nerve at risk to?
People who handle vibrating machinery or cyclists. It is close to the surface and up next to pisiform so can cause numbness in hand.
What are the three types of physiological movement?
Voluntary
Somatic reflex
Rhythmic motor patterns
Where are muscle spindles found? What is their structure?
Small structures embedded in all muscle fibers except the tongue and diaphragm. Each has a capsule containing muscle fibres and cells that are sensory cells. These fibers have contractile elements (actin and myosin) at peripheral regions innervated by the axons of gamma motoneurons.
What do gamma motoneurons control?
The excitability of stretch receptors in muscle spindles.
What are the 4 components of motor units?
1) Cell body of alpha motoneuron
2) Axon
3) All NM junctions (synapses) formed by a single motoneuron
4) All muscle fibers innervated by a single motoneuron
What are the physiological consequences of the size principle?
1) Some S type motor units fire almost always
2) S type motor units are best suited for carrying sustained but small loads
3) Weak contractions can be graded with greater precision than strong contractions
4) Necessity to exercise hard to prevent atrophy of FF units
What are the synaptic inputs to alpha motoneurons?
1) Descending tracts
2) Spinal interneurons
3) Propriospinal neurons
4) Afferent fibres (type 1a) from muscle spindles
What are the 4 main receptors which control movement?
1) Muscle spindles
2) Golgi tendon organs
3) Pain receptors in the skin
4) Joint receptors
What are the three reflexes?
1) Stretch/ myotatic/ tendon/ monosynaptic reflex
2) Reverse (inverse) myotatic reflex
3) Flexion (withdrawal) reflex and the crossed-extension reflex
What is the process by which antagonists are inhibited called? What is it carried out by?
Reciprocal inhibition
Inhibitory 1a interneuron
What are the functions of the reverse myotatic reflex?
1) Under extreme conditions, it protects muscles from overload
2) Its normal function is to maintain muscle tension in optimal range
What is the purpose of the crossed-extension reflex?
Stabilises the other leg when one is lifted due to the flexion/withdrawal reflex
