musculoskeletal system

primary function of musculoskeletal system

stability and movement

main components of musculoskeletal system

muscles, bones, joints, cartilage, tendons

what tissues make up skeletal system ?

bone and cartilage

key functions of bone

protects vital structures

stores calcium

produces blood cells

how is cartilage described structurally ?

semi-rigid, resilient connective tissue

what are the 3 types of muscle ?

skeletal, cardiac, smooth

what muscle types are involuntary ?

cardiac and smooth

what muscle types are striated ?

skeletal and cardiac

what neurotransmitter is released at neuromuscular junction ?

acetylcholine (ACh)

what enzyme breaks down ACh at NMJ ?

acetylcholinesterase

what does curare do at NMJ ?

blocks ACh receptors causing muscle paralysis

curare

plant derived (arrowhead) poison

causes muscle paralysis

what is the basic contractile unit of a myofibril ?

sacrcomere

what proteins regulate actin-myosin interaction ?

troponin and tropomyosin

what does calcium bind to during muscle contraction ?

troponin

muscle

muscle fibres + connective tissue

motor unit

single motor neurone and fibres that innervate it

motor neurone pool

all motor neurones innervating one muscle

skeletal muscle shapes

flat, fusiform, parallel, pennate, convergent, circular

neuromuscular junction

site where axon terminal meets muscle fibre

muscle structure hierarchy

Myofilament → Myofibril → Muscle Fibre → Bundle → Muscle

what are the 4 steps of cross-bridge cycle ?

Attachment → Power stroke → Detachment (ATP binds) → Re-cocking (hydrolysis)

what causes rigor mortis ?

lack of ATP prevents detachment of actin-myosin cross-bridges

ACh binds to what receptors ?

nicotinic

what are the 2 types of isotonic contraction ?

concentric - shortening

eccentric - lengthening

what is tonic muscle contraction ?

slight, constant contraction eg. posture maintenance

which muscle fibre type is most fatigue resistant ?

type I - slow oxidative

which muscle fibres are white and fatigue quickly ?

type IIb - fast glycolytic

which muscle fibre type uses both aerobic and anaerobic pathways ?

type IIa - fast oxidative

what are the 4 main sources of ATP in skeletal muscle ?

phosphocreatine

fatty acid oxidation

aerobic glucose metabolism

anaerobic glycolysis

which type of fibre primarily uses anaerobic glycolysis ?

type IIb - fast glycolytic

what does resistance training do to muscle fibres ?

increases size of fast glycolytic IIb fibres (hypertrophy)

boosts glycolytic enzymes

what adaptions occur with endurance training ?

increased mitochondria, capillaries and oxidative capacity

what is the order of motor unit recruitment ?

type I - slow oxidative

IIa - fast oxidative

IIb - fast glycolytic

what determines recruitment order of motor units

size of motor neurone - smallest first

what is peripheral fatigue ?

caused by changes within muscle eg. lactic acid, ADP build up

central fatigue

failure of brain to send excitatory signals to motor neurones

common causes of muscle cramps

ischaemia

metabolic disturbance

electrolyte imbalance

what does EMG measure ?

electrical activity of muscle fibres during APs

fibrillations

spontaneous APs in denervated muscle fibres

fasciculations

visible muscle twitches due to random motor unit discharge

what neurones are affected in MND ?

upper and lower motor

is the sensory system affected in NMD ?

no

drug used in NMD treatment

riluzole

what nerve is compressed in CTS ?

median

3 symptoms of CTS

tingling, hand weakness, thenar muscle atrophy

treatments for CTS

splits, steroids, surgical release

what causes Myasthenia Gravis ?

autoantibodies against ACh receptors

common symptom of MG

ptosis (drooping eyelid)

muscle fatiguability

what class of drug improves MG symptoms ?

acetylcholinesterase inhibitors

what gene is mutated in DMD ?

dystrophin

what is the inheritance pattern of DMD ?

x-linked recessive

primary symptom of DMD in children

difficulty walking and standing

role of calcium in contraction

binds troponin causing conformational change

allows myosin to bind to actin forming cross-bridge

role of calcium in relaxation

actively pumped back into SR