Skeletal muscle disease/dysfunction

muscle trivia

sartorius - “tailor’s muscle”

stapedius - smallest muscle (in ear)

gluteus maximus - strongest single muscle

zygomaticus major - “smiling muscle”

orbicularis oris - “kissing muscle”

latissimus dorsi - “swimmers muscle”

serratus anterior - “boxers muscle”

psoas - “tenderloin mucles”

injection methods

intramuscular (IM) - large doses, immediate absorption, 90 degree angle

subcutaneous (SubQ) - just under skin, less traumatic, 45 degree angle

intravenous (IV) - penetrates blood vessel, fastest way into body (emergencies), 45 angle

intraosseous (IO) - drill into bone marrow, when speed is necessary/blood vessels compromised

factors affecting skeletal muscle usually involve:

nerve supply to the muscle (neuromuscular diseases), transmission of impulses across myoneural junction (tetanus, botulism), metabolic processes within muscle (hypocalcemia tetany)

neuromuscular junction (NMJ) overview

action potential travels to axon, calcium enters cell, causes what’s in axon (ex Ach) to release, then binds to receptor on receiving neuron, causes Na to flow in, depolarization, action potential

myositis

muscle inflammation, localized is inflammation after injury/overuse, generalized is rare disease involving widespread inflammation and degradation of skeletal muscle tissue

atrophy vs hypertrophy

you have to move your muscles to develop tone, they need to be stimulated; if muscles aren’t used the space fills with loose CT

atrophy=lack of use=muscles get smaller

hypertrophy=overuse=muscles get bigger

anabolic steroids & human growth hormone

both involved in boby building/athletics, anabolic steroids use testosterone to grow muscle size, human growth hormone is more natural but still enhancing (blocks cortisol, less muscle breakage between sessions)

2 types of muscular hypertrophy

sarcoplasmic hypertrophy - change in volume, look big=more reps, more sarcoplasma fluid is stored, appear larger but not actual strength

myofibrillar hypertrophy - change in density/# if cells, use more weight, look big and have strength, more muscle protein synthesis

Ganglion cyst

synovial fluid leaks out under dermis, becomes trapped under palmar aponeurosis, don’t know why it happens, not problematic unless it presses on a nerve

Bells palsy (idiopathic unilateral facial paralysis)

dysfunction of facial nerve VII, inability to control facial muscles on that side of the face, usually self correcting

strabismus

eyes are not aligned with one another, typically lack of coordination of extraocular muscles, can effect depth perception, usually only affects one eye, can cause amblyopia where the brain only sees what is perceived by one eye

compartment syndrom

compression of nerves and blood vessels in enclosed space, leads to muscle/nerve damage, caused by trauma/rapid growth of muscle/tight casts or bandages (young active boys, muscle grows faster than muscle sheath can keep up with)

impingement syndrome

most common shoulder injury, supraspinatus tendon becomes trapped between acromion process and head of humerus, causes tendon and bursa to inflammate, swimmers shoulder/common over head sport injury

electromyography (EMG)

measure neurons and muscles on electrical basis

neurodegenerative/neuromuscular diseases

affect skeletal muscles as well as neurons, gives the name neuromuscular, weakening of muscles from reduced nerve stimulation, eventually muscles related to breathing are impacted (ex amyotrophic lateral sclerosis ALS)

some diseases associated with the myoneural junction

myasthenia gravis - antibodies formed against Ach at neuromuscular junctions, reduces number of receptors available (autoimmune disease), may patients have tumor of thymus gland, treat with acetylcholinesterase inhibitors)

botulism - infection by Clostridium botulinum, botulinum toxin inhibits release of Ach from voluntary motor neurons; botox injected in muscles to cause them to relax

tetanus - Clostridium tetani, produces neurotoxin that mimics Ach, overproducing effects (constant muscle contraction), muscular spasms

muscular dystrophy

any of several hereditary diseases of muscular system characterized by weakness and wasting of skeletal muscle, not a result of nerve supply problems, fat can infiltrate giving the appearance that muscles are there, ex Duchenne’s muscular dystrophy