Miscellaneous MSK stuff Flashcards
What are the functions of muscles?
movement
heat generation
joint stability
posture
What is a pennate muscle?
A muscle with one or more aponeurosis running through the muscle body from the tendon, can be uni, bi or multipennate
Fasicles attach to aponeurosis at an angle (pennation angle)
What is a parallel muscle?
Where the fibres run parallel to the force generating axis
Give the 3 types of parallel muscle, an example and description.
Strap- fibres run longitudinally to contraction direction and the muscle is shaped like a strap or belt. Eg- sartorius
Fusiform- wider and cylindrically shaped with tapered ends (biceps)
Fan shaped- fibres go from small point and spread over broad area at over end (pectoralis)
Describe and give example of circular muscles
concentric fibres
attach to skin, ligaments and fascia rather than bone
act as sphincters
What is the difference between a muscles origin and insertion
origin- bone, usually proximal which has greater mass and is more stable on contraction than insertion
Insertion- tends to be moved by contraction, distal and can be bone, tendon or CT
How does compartment sydrome occur?
trauma to one compartment causes bleeding and swelling and so puts pressures on nerves and vessels in that compartment as it cant move
What are signs and symptoms of compartment syndrome?
- deep, constant, poorly localised pain
- aggravated by passive stretch of muscles in that group
- parasthesia
- tense and firm to touch
- swollen, shiney, bruised
- prolonged capillary refill time downstream
How is compartment syndrome treated?
fasiotomy
What is a synergist?
A muscle that assists the prime mover
What is a neutraliser?
A muscle that prevents unwanted actions that an agonist can perform
What does a fixator do?
acts to hold a body part immobile whilst another body part is moving- they stabilise joints
What is an isotonic contraction?
Where there is constant tension in the muscle and the muscle length changes to move the load- concentric isotonic is muscle shortening, eccentric is where the muscle exerts force on extension
What is an isometric contraction
where the muscle length is constant but varies in tension- eg hand
Describe a first class lever
- a seesaw
- falcrum (joint) is between the load and the effort (muscle)
- Eg in neck extension, load at front (heat), joint in middle ( vertebrae) and muscles at back
Describe a 2nd class lever
- wheel barrow
- falcrum (joint) at front
- load in middle
- effort/ muscle at back
eg calf raise
Describe a 3rd class lever
- Fishing rod
- load at front
- then effort
- then falcrum
- bicep curl
What is a motor unit?
a motor neurone and the muscle fibres that it innervates
the fewer fibres per motor unit the more fine the control will be
What determines the type of muscle fibre?
the isoform of myosin heavy chain that is present
What colour are fast glycosidic and slow oxidative muscle fibres?
fast (type 2)- white
slow (type 1)- red
Will fast type muscle fibres be recruited 1st or last?
last- they are generally large motor units,
What senses contraction and stretching of muscle and position sense?
intrafusal muscle fibres as part of the muscle spindles in the muscle belly- type 1a sensory neurones relay rate of change in muscle length, type 2 sensory neurones provide position sense
What is the use of having motor neurones as well as sensory neurones in the intrafusal muscle fibres?
They can adjust and become more sensitive to changes in stretch
Why do muscles have a tone (never fully relax)?
constant motor stimulation and elasticity
What is the name for loss of muscle tone and give some causes
Hypotonia
muscular dystrophy, legions of lower motor neurones, legions of muscle spindles, legions of cerrebellum, neurone shock (floppy baby syndrome), REM sleep
What is the resting membrane potential of muscles fibres and why?
-90mv
very permeable to cl-
What is myotonia congenita?
Periodic muscle stiffness and hypertophy due to mutation in chloride channel meaning you cannot keep the resting membrane potential low to prevent random muscle contraction. Usually exacerbated by fear, cold, inactivity and relieved by exersize
What is myotonia?
inability to relax muscle at will
give some muscle diseases caused by faulty Na+ channels
pottassium aggravtated myotonia- bought on my eating high k+ foods
paramyotonia congenita
hyperkalaemic periodic paralysis
What marks the pre and post axial boarder of the upper limb?
preaxial boarder- cephalic vein
postaxial- basillic vein
What is a dermatome?
a strip of skin innervated by a single spinal nerve
Where do dermatomes originate from?
the doral part of each somite differentiates into dermamyotome, the myotome proliferates while the dermatome disperses to form the dermis. The dermis associated with the precursor of the limbs is stretched and moved down the limb