Muskoskeletal System Flashcards
Osteoblasts
Bone makers- bone develops from monucleate cell
Osteoclasts
Bone breakers- resorption of bone
Osteocytes
Bone maintainer- mature bone cell maintains the bone and protects it from
Osteocytes function?
Surrounds osteoid
What do osteoclasts secrete snd its function?
Enzymes and acid.
Enzymes degrade osteoid
Acid dissolves calcium phosphate crystals and they are released into blood
Effects of abnormal growth hormone secretion (gh)
Dwarfism- decreased gh secretion in kids
Gigantism- increased GH
Acromegaly- increased GH in adults- affects visual characteristics in adults
Other hormones that affect growth ?
Thyroid hormones- required for synthesis of GH and actions
Insulin- permissive cellular actions of GH
Sex hormones- important for pubertal growth, postmenopausal deficiency
Glucocorticoids- inhibit growth, raise concern when treating children with chronic doses of glucocorticoids in asthma
Bone associated diseases
Osteomalacia- rickets
Osteoporosis
Osteoarthritis
Gout
Rheumatoid arthritis
Osteomalacia
Rickets
Deficiency in bone- softening and weakening of bones this is because of lack of dietary sufficiency vitamin D2 AND vitamin D3 lack of sunlight
Renal disease - decreases calcitriol
How is osteomalacia treated
Vitamin D
Ergocalciferol- vitamin d in found
Calcitriol if renal disease - it is made in kidney binds to and activates vitamin d receptors
Osteoporosis
Low bone density
More common in women
Causes post menopausal
Gout
Deposition of uric acid crystals in joints
Big toe
Triggers acute arthritic symptoms due to inflammatory response
Myofibrils
Give skeletal muscle striated appearance
Orderly arrangement of thick and thin filaments
Actin and myosin filaments
Filaments form sarcomeres
What are the 3 proteins in thin filament
Actin- binding sites for myosin
Troponin- binds to acting, tropomyosin and calcium for skeletal contraction
Tropomyosin- interacts with actin myosin and troponin to regulate muscle contraction and relaxation
2 binding sites of myosin head:
Actin binding site
Atpase- nucleotide binding sites
Cross bridge cycle
Myosin binds to actin causing ATP breakdown into PI and ADP. Pi provides energy for power stroke. Actin is pulled to middle of sacromere where myosin is. ADP is released .
Myosin is in low energy form called rigor mortis- ATP needs new myosin and calcium. ATP binds to troponin.
ATP separates actin from myosin head
To separate actin from myosin head ATP is hydrolysed and Myosin head will close and go into resting state ready for next contraction - myosin is in high energy form
What is excitation-contraction coupling?
Where action potential in sacrolemma causes contraction
Depends on neural input from motor neuron
Requires calcium from sacoplasmic reticulum
What happens during excitation contraction coupling
Release of acetylcholine from axon terminal of motor neurons and binds to receptors. This binding causes a localised change in membrane permeability leading to action potential in muscle cell.
Action potential spreads rapidly along sarcolemma and T tubules
Action potential triggers calcium release from sarcoplasmic reticulum
Ca binds to troponin exposing myosin binding Sites
Cross bridge cycle begins muscle fibre contracts
Ca is Transported back to sacroplasmic reticulum this blocks myosin binding sites and muscle relaxes
How does the contraction terminate ?
Calcium must leave causing tropomyosin to cover myosin binding sites on actin
To remove calcium from cytosol calcium - ATPase in sacroplasmic reticulum trasnports calcium from cytosol back
This ends acetylcholine release ans action potentials
How do muscle cells provide ATP to drive cross bridge cycle ?
ATP used by muscle:
Cross bridge cycle
Splitting of atp by myosin atpase
Binging of fresh atp to myosin
ATP used to maintain ion gradients
Na k pump
Relaxation
Active transport
