BIOL: Skeletal Sys

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Function of Skeletal Sys in general and 2 Division of Mammalian Skeleton: Primarily=physical support
Divisions:
[Axial] Skeleton: Protects delicate vital organs; comprised of skull, vertebral column, rib cage
[Appendicular]: meant to provide lever upon which skeletal muscles act
OTHER purp: skel bone houses marrow-->blood-forming house
Major components of skeleton: Cartilage
Bone
Tissue Type and Characteristics of Cartilage: Connective tissue; flexible, soft; nerveless; avascular (receives nourishment from capillaries in nearby connective tissue and bone
Cartilage is composed of....which is composed by....: Chondrin: a firm but elastic matrix.
Chondrocytes
Cartilage is the principal component of __skeletons: embryonic (in higher animals)... in mammals most cart hardens and calcifies to bone
Locations of cartilage in humans: external ear, nose, walls of larynx, trachea, skeletal joints
Tissue Type and Characteristics of Bone: Mineralized connetive tissue w/ ability to withstand connective stress; bone tissue is hard and strong while being somewhat elastic and lightweight
MACROSCOPIC Q: 2 basic types of bone and detailed descriptions: [COMPACT] bone: dense bone that to the naked eye has no cavities
[CANCELLOUS/spongy] bone: nuch less dense w/ interconnecting lattice of bony spicules (tribeculae). cavities of lattice (b/t spicules) contain red and/or yellow marrow.
yellow vs red marrow?: yellow is inactive and filled with adipose tissue
red is involved in blood cell formation
MACROSCOPIC Q: Overall bone structure of appendages: think dog bone
DIAPHYSIS: long shaft, mostly made of compact bone with a core of marrow, which connects...
EPIPHYSES: dilated ends of bone, composed of spongy bone surrounded by thin layer of compact.
EPIPHYSEAL PLATE: disk of _cartilagnous_ cells that sep diaphy from epiphy, and site of longitudinal growth
PERIOSTEUM: surrounds long bone, site of muscle tissue attachment
MICROSCOPIC BONE STRUCTURE Compact Bone Composition: dense, hardened bone matrix w/ organic and inorganic componenets.
ORGANIC: includes protein (mostly collagen fibers and glycoproteins)
INORGANIC: CA, P (phosphate), OH- (combine to form _hydroxyapatite_ crystals) and Na, K, MG ions
What gives bones their characteristic strength?: hydroxyaptite crystals combine with collagen fibers
Osteo____ build bone Osteo____ destroy bone: Blasts builds

Clasts destroy!
Structural unit of bone?: Osteon OR Haversian system
Describe the layout of an osteon: consists of a central microscopic channel called a __Haversian canal__, surrounded by many concentric circled of bony matrix called lamellae
Haversian canals contain...: blood vessels, nerve fibers, and lymph vascularizing and innervating bone tissue
The lamellae matrix houses....: Mature bone cells, Osteocytes, within the _lacuna_ (spces in the matrix); Canaliculi interconnect each other&lacunae&Haersian canal, exhcanging nutrients and wastes
2 Methods of Ossification: (aka Bone Formation) occurs in two ways: endochondral ossification or intramembrance ossification
Endochondral Ossification: cartilage is replaced by bone; how most long bone form
Intramembrance Ossification: Mesenchymal (embyrionic, undifferentiated) is transformed into and replaced by bone
Talk about bone remodeling: continuous process. bone reformation: inorganic ions Ca and P are absorbed from the blood for use in bone formation. Bone resorption: tohse same ions are released into the blood
Regulation of Bone Remodeling?: By PTH (parathyroid hormone) and calcitonin.
also bone use and stress. PTH raises blood calcium levels by stimulation Ca2+ release from bones and decreasing kidney Ca2+ in kidneys. PTH also converts vitamin D to its active form, which stimulates intestinal calcium absorption.
Movable joint consists of....: a _synovial_ capsule, which has an articular (joint) cavity. Movement of the joint is facilitated by the synovial fluid which lubricates the joint; and also by the articular cartilage on the apposing bone surface which is smooth
Function&Control: Skeletal Muscle: Voluntary Movement; controlled by the Somatic nervous system
Skeletal Muscle: Makeup of Muscle: Long parallel fibers--> muscle fibers.
Skeletal Muscle: Muscle Fibers?: Multinucleated cell created by the fusuion of many mononucleate enbryionic cells. Nuclei are usally on the periphery of the cell. Embedded w/in the fibers are _MYOFIBRIL_ filaments.
cytoplasm of muscle fibers: sarcoplasm.
Cell membrane: sarcolemma
Skeletal Muscle: Unit of Myofibrils: sarcomeres... divided by transverse tubules
Skeletal Muscle: Covering of Myofibrils: Sarcolemma, can propagate an action potential
Skeletal Muscle: T system: transverse tubules that are oriented perpendicularly to myofibrils. T sys provides channels for ion flow throughout muscle fibers & can also prop an axn potential
Skeletal Muscle: Looks like?: striated.. has light and dark bands. Also typified as red or white.
Skeletal Muscle: Red vs white: Red Fibers: slow-twitsh, high myoglobin content (protein that resembles hemoglobin) and many mitochondria--> long dist runners, aerobic activity
White fibers: fast-twitch, abaerobic--> less myoglobin and fewer mitochondria, greater rate of contraction but more
MUSCLE: Smallest 'thread': The _Myofibril_ filaments are divided into contracticle units: Sarcomeres
MUSCLE: Main "threads" surrounded by?: Myofibrils enveloped by _sarcoplasmic reticulum_(stores Ca2+ ions)
MUSCLE: Composition: Thin and Thick Filaments of Sarcomere: THIN filaments are chains of globular actin covered with threads of troponin and tropomyosin. THICK filaments are bundles of myosin molecules w/ organized head and tail region
SARCOMERE: Boundary line of single sarcomere?: Z LINE

also anchors the thin filaments
SARCOMERE: Line down the center (thick) of the sarcomere: M Line
SARCOMERE: Region with only Thick filaments?: H Zone
SARCOMERE: Region with only Thin Filaments?: I Zone
SARCOMERE: Region that spans entire length of thick filaments inc overlap: A Zone
SARCOMERE: Which portions contract? Which do not?: A Zone is not reduced in size but I Zone and H Zone are.
MUSCLE: How initiated?: Msg from SNS sent via motor neuron. Depolarization of the motor neuron results in release of neurotrans which diffuse across synaptic cleft and bind to recptor sites on _sarcolemma_. If enough sites stimmed, all-or-nthing axn potential stimmed
MUSCLE: Structure of Link b/t SNS and muscle: The NEUROMUSCULAR JUNCTION is composed of the _nerve terminal_/_synaptic bouton_ and the sarcolemma. The space b/t is the synaptic cleft
MUSCLE: After initiation of a muscle contraction is...: SHORTENING of the sarcomere... Axn potential conducted along sarcolemma and T-sys.. into interior of muscle fiber. SR (SarcRet) releases Ca ions into Splasm. Ca binds to Trop...leaving actin binding sites free for myosin heads to bond. Thus thin filaments drawn to center of H zone
MUSCLE: What allows for dissoc of myosin molecules?: ATPase activity; ADP&Pi are initially attached to myosin (ATP is hydrolyzed) but after powerstroke occurs ATP binds to myosin to allow for detachment of myosin from actin
MUSCLE: What stage occurs after contractions?: Relaxation... when sarcolemmic recptors cease being stimulated, Ca ions returm to SR. Products of ATP hydrolysis are released from the myosin head, and new ATP binds to mysoin->myosin dissociates from THIN fil and sarcomere extends back. In absence of Ca ion Actin again covered by tropomyosin.
MUSCLE: Stimulus Response?: Indiv fivers are all-or-nothing; must exceed threshold value. ..however more fibers mean graded response of muscle.
MUSCLE: Continual low-grade contractions?: TONUS
MUSCLE: Simple Twitch: the response of a SINGLE muscle fber to a brief stimulus

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