Musculoskeletal Flashcards
What makes up a motor unit?
Single motor neuron and muscle fibres innervated by it
What makes up a motor neurone pool?
All motor neurones that supply one whole muscle
What is the neurotransmitter and receptor always found at a neuromuscular junction?
Acetylcholine
Nicotinic receptors
What is the sarcolemma of a muscle fibre?
The muscle fibre membrane
What part of the muscle fibre releases calcium on stimulation?
Sarcoplasmic reticulum
What are T tubules of the muscle fibre and what do they allow?
Deep invaginations of sarcolemma
Allow for quick depolarisation of interior
What causes depolarisation at the neuromuscular junction?
Influx of Na+
What are the thick filaments of the muscle fibre also called?
Myosin
What are the thin filaments of the muscle fibre also called?
Actin
What happens to myosin when the muscle fibre is contracting?
Binds with actin and uses ATP to ‘recock’ heads
What does tropomyosin do when not stimulated?
Lies over the actin filaments and blocks the myosin binding sites
What does troponin do when it is activated?
Binds to calcium, causing a change in shape so that it pulls tropomyosin out of the way
Which are the A bands and what happens to them during contraction?
The dark bands (myosin)
Stay at constant length
Which are the I bands and what happens to them during contraction?
The light bands (actin)
Shorten during contraction
What are the four ATP sources in skeletal muscle?
Phosphocreatine
Anaerobic respiration
Aerobic respiration
Free fatty acid oxidation
What are the three types of muscle contraction and briefly describe each.
Isotonic - shortening
Isometric - remains same length
Eccentric - lengthening
What type of muscle fibre is type I?
Slow twitch, oxidative fibre
Red in colour
What type of muscle fibre is type IIa?
Fast twitch, oxidative fibre
Red in colour
What type of muscle fibre is type IIb?
Fast twitch, glycolytic fibre
White in colour
Which muscle fibre is most resistant to fatigue and which fatigues most rapidly?
Most resistant - type I
Fatigues rapidly - type IIb
What is the red colour of muscle fibres due to?
High content of myosin
What is the recruitment order of muscle fibres types?
1st - type I (smallest neurons - depolarise quicker)
2nd - type IIa
3rd - type IIb
What does contraction strength depend on?
Number of motor units recruited
Frequency of impulses
What is the difference in cartilage in the young, adults and elderly?
Young - hypercellular, no zones, no tidemark
Adult - hypocellular, high matrix, tidemark
Elderly - even fewer cells, matrix degradation
What are responsible for degradation of cartilage?
Matrix metalloproteinases
What type of collagen is articular cartilage primarily made of?
Type II
What is the major proteoglycan of articular cartilage?
Aggrecan
What type of collagen is primarily found in bone?
Type I
What causes osteogenesis imperfecta?
Mutation in DNA coding for collagen type I
What are the three development stages of bone matrix development?
Osteoid
Woven bone
Lamellar bone
What happens in the osteoid stage of bone matrix development?
There is a collagen meshwork without mineralisation
Collagen is secreted by osteoblasts
What happens in the woven bone stage of bone matrix development?
Bone is produced quickly, occurs in new bone formation or repair
Randomly organised collagen fibres
Mechanically weak
What happens in the lamellar bone stage of bone matrix development?
End-stage, well organised and strong bone
Collagen organised in lamellae
Describe compact (cortical) bone.
Solid, hard and dense
Forms outer layer of most bone
Is protective
Describe spongy (trabecular/cancellous) bone.
Network of thin trabeculae separated by marrow space
Remodels in response to stress and mineral homeostasis
What is the most common type of shoulder dislocation?
Anterior
What is the treatment for shoulder dislocation?
Manipulation/surgery
Painkillers
Sling
What sign would a torn rotator cuff show?
Loss of initial elevation of arm
What is frozen shoulder and how would it present?
Adhesive capsulitis
Complete immobile shoulder
What is a Bankart lesion?
Anterior part of labrum separated from glenoid, so anterior gleaned bare and more likely to dislocate at again
What is a Hill-Sachs lesion?
A dent in the posterosuperior humeral head due to impact against the anteroinferior gleaned during dislocation
Change in shape makes more likely to dislocate again
What signs are seen on X-ray in osteoarthritis?
Reduced joint space
Osteophytes
Subchondral stenosis
What are the two phases of the gait cycle and what percentage of the full cycle do they make up?
Stance phase (60%) Swing phase (40%)
