BIOL 252 1st Edition Lecture 10 Outline of Last Lecture I Skeleton Function II Histology of Osseous Tissue III The Matrix IV Long Bone Structure V Structure of Flat Bone VI Histology of Compact Bone VII Histology of Spongy Bone VIII Bone Formation Outline of Current Lecture I Poll Everywhere II Bone Growth and Remodeling III Calcium Homeostasis IV Hypercalcemia V Osteoporosis VI Muscles basic structure of skeletal muscle Current Lecture I II Poll Everywhere a In which of these locations would you NOT expect to find osteoblasts i Within trabeculae ii Why An osteoblast w in matrix osteocyte iii Osteoblasts are on the surface surrounding trabeculae 1 On outer surface of compact bone and inner surface of compact bone near medullary cavity iv Why can t you build bone from inside the matrix 1 Can only build on the surface 2 Osteocytes would be trapped in the matrix a Matrix is solid v Osteoclasts are on same surfaces as osteoblasts Bone Growth and Remodeling a Bone Growth i Interstitial growth of cartilage bone elongation results from cartilage growth These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 Within 2 Cartilage can do both interstitial and appositional ii Appositional growth of cartilage and bone deposition of new bone cartilage on surface of existing cartilage bone 1 Grows on the outer position surface 2 Make trabeculae fatter like adding rings on a tree b Remodeling i Repairs microfractures ii Reshapes bones iii Releases minerals into blood 1 Calcium and phosphate 2 Phosphate is regulated the opposite of calcium 3 Calcium is important for nervous system function and muscle function 4 Osteoblasts deposit bone matrix making calcium phosphate and collagen to build bone a Where do they get calcium From the blood b Mineralization crystallization process in which calcium phosphate and other ions taken from blood plasma 5 Osteoclasts through secretion of acids dissolve bone matrix into aqueous solution picked up by the blood a Mineral resorption process of dissolving bone and releasing minerals into blood 6 Calcium homeostasis a Sources of calcium b When blood Ca falls body releases Ca from bones increases Ca absorption from intestines increases Ca retention in kidneys c What do we need to absorb calcium i Vitamin D 7 Job of kidney filters blood removes nitrogen compounds a Pulls back the good stuff after filtering everything b So lose calcium to the kidneys but then pull most of it back c Can tweak the amount 8 Ex hypocalcemia a Low calcium b Release more cell type responsible osteoclasts iv Why would you want to change bone 1 Apply different stresses to bone v Wolff s law architecture of bone determined by mechanical stresses placed on it and bones adapt to withstand those stresses vi Osteoclasts tear down bone matrix III IV V VI 1 If add bone matrix to one side in order to turn move it tear down the other side changing the orientation of bone Calcium Homeostasis a Regulators of blood calcium levels b Calcitonin released when Ca is high thyroid gland i Lowers Ca c PTH released when Ca is too low parathyroid gland i Increase Ca d Calcitriol released when Ca is low i Works together w PTH ii Comes from Vitamin D Hypercalcemia a Which explains symptoms of depression sluggishness slow reflexes b Prisoner in solitary confinement hypocalcemia no Vitamin D c Rickets as a child hypocalcemia vitamin D deficiency d Partial thyroidectomy releases Calcitonin which lowers levels of calcium e Kidney removal store calcitriol in kidneys not enough calcitriol cannot absorb Vitamin D hypocalcemia Osteoporosis a Normal spongy bone vs osteoporotic spongy bone has little pits due to activity of osteoclasts i Due to imbalance ii Kyphosis vertebrae curvature iii In females more common bone matrix production stimulated by estrogen 1 Males testosterone estrogen amount of estrogen declines slowly 2 Females less stimulus for bone matrix production because estrogen declines steeply 3 Medication calcium Vitamin D estrogen Muscles basic structure of skeletal muscle a Striated b Voluntary c Multiple nuclei per cell d Each cell fiber has dozens of nuclei e Sarcolemma muscle cell membrane f Sarcoplasm has myoglobin stores oxygen and glycogen stored glucose g Mitochondria produce ATP for muscle contraction h Myofibril i Not membrane bound ii Do the contracting and generate force i Controlling when we contract look superficially at cell membrane j Openings in membrane continue down into cell transverse tubules i ii iii iv Passage way into muscle cell Extension of cell membrane Bring cell membrane deeper into cell Where you have action potentials 1 AP on cell membrane and on t tubules to travel deep w in cell v Alongside each two specializations of SR 1 Triad 2 terminal cisternae and transverse tubule k Endoplasmic reticulum i Same organelle sarcoplasmic reticulum but specialized ii Stores calcium iii In cytoplasm low calcium levels iv Small storage of calcium in SR constantly sucking up calcium ions v W AP SR releases its calcium vi Trigger for contraction calcium l Thick filament i Myosin heads generate movement by converting ATP energy to force ii Each head has ATPase activity using breaking ATP apart into ADP and phosphate iii Tails join w other tails forming thick filament m Thin filament i F actin ii Tropomyosin regulatory iii Troponin complex regulatory iv When calcium comes along from SR binds to troponin changes shape causes tropomyosin to roll out of the way n Sarcomere i Thin filament overlapping thick filament alternating ii Slides past each other to generate force