Bio Lecture Exam 3

Bone's Role in Calcium Homeostasis

- 99% body calcium is stored in bone - blood level calcium ions (Ca2+) are very closely regulated - nerve and muscle cells depend on stable Ca2+ level in extracellular fluid - blood clotting and many enzyme activities require Ca2+ - osteoblasts and osteoclasts help 'buffer' blood Ca2+ level by bone remodeling - Ca2+ ions are important, tightly regulated - produced in thyroid gland - high blood Ca2+ levels can trigger CT secretion - inhibits activity of osteoclasts - speeds uptake and deposition in to bone

migratory phase

- blood clot becomes scab - epithelial cells bridge wound beneath scab - fibroblasts synthesize scar tissue (collagen, glycoproteins) - damaged blood vessels begin to grow - granulation tissue fills wound

Inflammatory phase

- blood clot forms in wound, seals edges - vasodilation and increased permeability of blood vessels - white blood cells (neutrophils, macrophages) and mesenchymal cells (become fibroblasts) arrive

cardiac muscle

- branched, striated fibers - usually only one nucleus in the center of cell - intercalated discs - blood pumping to body adjusting by hormones and autonomic (voluntary) nervous system - autorythmicity - located only in heart

anaerobic glycolysis

- catabolism of glucose to generate ATP when creatine phosphate deleted (produces enough ATP for ~2 minutes' exercise) - glucose enters muscle fibers via facilitated diffusion of breakdown of glycogen - if no oxygen, pyruvic acid converts to lactic acid - most lactic acid diffuses into blood - liver cells take up lactic acid and convert it back to glucose

2. growth of cartilage model

- condroblasts -> chondrocytes - chondrocytes divide and secrete ECM - interstitial growth - cartilage model begins to calcify - chondrocytes within calcified ECM begin dying (leaves lacuna behind)

periosteum

- connective tissue sheath and associated blood supply - protection, repair, nourished, attachment for ligaments and tendons

histology of bone (osseus tissue)

- connective tissue, few cells, much ECM - ECM- 15% water, 30% collagen, 55% mineral salts - calcium phosphate + calculate hydroxide = hydroxypatite crystals - also calcium, carbonate, magnesium, fluoride, potassium, sodium

3. bone remodeling phase

- dead portions of fracture resorbed by osteoclasts - compact bone replaces spongy bone where needed - osteoclasts remodel bone to original shape

osteoclasts

- derived from fusion of monocytes - ruffled border on bone-surface slide bone-resorption: releases lysosomal enzymes and acids into bone - concentrated in endosteum

structure of skeletal muscle tissue

- each skeletal muscle is separate organ (own individual cell) - myocyte cell = muscle fibers - connective tissue surrounding muscle fibers (in hypodermis, areolar connective and adipose tissue separate skin from muscle) - blood vessels - nerves

hypertonic scar

- elevated above epidermal surface - within original wound boundaries

maturation phase

- epidermis restored to normal thickness - scabs sloughs off - fibroblasts presence decreases - blood vessels return to normal

bone growth in length

- epihpyseal chondrocytes stop dividing - growth plate cartilage is completely replaced by bone - bone growth ends - injury can also stop bone growth

myofilaments

- even smaller filaments within myofibrils - muscle contraction occurs as filaments slide past each other - do not extend length of myofibril - sarcomeres - z discs - thin filaments - thick filaments

connective tissue components of muscle

- fascia - lines body walls and limbs - supports and surrounds muscles and organs - holds muscles with similar functions together (compartments) - carries nerves, blood vessels, and lymphatic vessels - 3 layers of connective tissue extend from fascia 1. epimysium 2. perimysium 3. endomysium

sarcoplasma reticulum

- fluid-filled membranous sacs surrounding each myofibril - stores Ca2+ in redting muscle fiber - release of Ca2+ triggers muscle contraction - terminal cisterns - triad

1. reactive phase

- formation of fracture hematoma, swelling and inflammation, brings extra white blood cells, blood supply is cut off, nearby bone cells die, there is live bone on either side of the injury but dead bone tissue next to injury

fibrosis

- formation of scar tissue - dense collagen fibers - decreased elasticity - fewer blood vessels - may have reduced sensory structures, hairs, and/or glands

sarcomere

- functional unit of myofibril A band- barker middle part of sarcomere, extends length of thick filaments H band- area within A band with only thick filaments M line- supporting proteins hold thick filaments together at center of H band - zone of overlap I band- remaining thin filaments, no thick filaments - Z disc passes through center of I band

proliferation phase

- growth of epithelial cells beneath scab - collagen fibers secreted by fibroblasts deposited randomly - growth of blood vessels continues

6. formation of articular cartilage and epiphyseal growth plate

- hyaline cartilage covering epiphyses becomes articular cartilage epiphyseal (growth) plate- hyaline cartilage remaining between diaphysis and epiphysis until maturity

enchondral ossification

- hyaline cartilage develops from mesenchyme, then replaced by bone

intramembranous ossification

- in membrane, done in sheets - bone develops directly with mesenchyme

excitation-concentration coupling

- increased Ca2+ concentration in sarcoplasm: start muscle contraction - decreased Ca2+ concentration in sarcoplasm: stops muscle contraction - excitation - contraction - occurs in triads voltage-gated Ca2+ channels - excitation of muscle fibers cause action potential to travel along t tubule - triggers opening of Ca2+ release channels in terminal cisternal membranes when skeletal muscle fiber is excited - Ca2+ released to bind with tropomyosin in contraction cycle

low blood Ca2+ triggers secretion

- increases number and activity of osteoclasts - increases Ca2+ reabsorption in kidney - stimulates formation of calcitrion (active form of Vitamin D), promoting Ca2+ absorption from gastrointestinal tract

3. development of primary ossification

- inward from surface - artery penetrates the perichondrium and cartilage model - stimulates osteoprogenitor cells in perichondrium -> osteoblasts - perichondrium -> periosteum - periosteal capillaries grow into calcified cartilage - induces growth of primary ossification center in center of bone - trabeculae form in calcified cartilage

acetylcholine (Ach) receptor: ligand-gated ion channel

- ligand- gated channel opens/closes in response to ligand building - diffuse through channel

Spongy (trabecular/canellous) bone

- located in epiphysis of long bones and interior of short, flat, sesamoid, and irregular bones - always found in outer layer of compact bone - no osteons - have lamellae, bone lacunae, osteocytes, bone canaliculi - spaces filled with red/yellow marrow/blood vessels

skeletal muscle

- long, cylindrical fibers with striations - multinucleated with nuclei at periphery of cell - voluntary movement controlled by neurons of somatic nervous system - some unconscious control (diaphragm in breathing, posture) - heat production - protection - located usually attached to bones with tendons, some attached to skin

contractile muscle: myosin

- main component of thick filaments - motor protein (undergoes movement) in all 3 types of muscle tissue - converts ATP chemical energy into mechanical energy - myosin tail and head

contractile muscle proteins: actin

- main component of thin filaments - actin molecules twist together to form helix-shaped filament - myosin-binding sites to bind myosin heads together

exercise and bone tissue

- main strain on bone is pull of skeletal muscles and gravity - mechanical strain causes increase deposition of minerals and collagen fibers - athletes have thicker and stronger bones

osteocytes

- mature bone cells - main cells of bone tissue - carry out bone metabolism

1. development of cartilage model

- mesenchymal cells gather and differentiate into chondroblasts - chondroblasts secrete hyaline cartilage - perichondrium surrounds the cartilage model

sliding filament mechanism of muscle contraction

- myosin heads attach to and 'walk' along thin filaments, pulling thin filaments toward M line - total length of sarcomere shortens Z discs: distance between Z discs shortens I band and H zone: narrow and eventually disappear during contraction A band: no change in width - lengths of individual thick and thin filaments does NOT change, simply sliding past each other

smooth muscle

- non-striated spindle-shaped cells with single, central nucleus (gap junctions common) - motion (usually involuntary), some autorythmicity to cells of digestive tract - located in iris, walls of internal hollow structures (blood vessels, airways to lungs, stomach, intestines, gall bladder, urinary bladder, uterus, attached to hair follicles in skin, arrector pilli muscle is smooth muscle

osteoprogenitor cells

- only bone that divides - differentiate into osteoblasts - found in inner osteogenic layer of periosteum, in endosteum, and in canals within bone that have blood vessels

aging and bone tissue

- over time, resorption by osteoclasts outpaces deposition by osteoblasts - loss of bone mass from demineralization (especially significant to aging in women) - brittleness from decreased protein synthesis with age - slowing down of metabolic processes (ex. protein synthesis)

regulation of blood calcium levels

- parathyroid hormone - negative feedback system with parathyroid cells acting as receptors - low blood Ca2+ triggers PTH secretion - Calcatronin

regulatory muscle protein

- part of thin filament - tropomyosin - troponin - in contraction, Ca2+ binding troponin changes its shape, moving tropomyosin out of way

blood and nerve supple of bone

- periosteal arteries/veins with nerves enter diaphysis through perforating canals - nutrient artery/vein enter diaphysis of long bones through nurtient foramen (supply inner compact bone, spongy bone, and bone marrow) - metaphyseal and epiphyseal artery/vein supply metaphyses and epiphyses

factors affecting bone growth and remodeling

- poor diet - minerals, large amounts needed, especially calcium and phosphate vitamin A- stimulates ostroblasts vitamin C- collagen synthesis vitamin D- calcium absorption in intestines vitamins K1B12- synthesis of bone proteins hormones (insulin-like growth factor, thyroid hormones)

4. development of medullary cavity

- primary ossification center grows toward the ends - osteoclasts break down some trabeculae, creating medullary cavity - wall of cavity eventually replaced by compact (cortical) bone

creatine phosphate

- relaxed muscle fibers produce more ATP than needed - creatine is synthesized in liver, kidneys, and pancreas and transported to muscle cells throughout body - creatine phosphate is 3-6 x more plentiful than ATP in sarcoplasm of resting muscle fibers - rapid reaction - creatine kinase (CK)

aerobic respiration

- sources of oxygen in muscle tissue 1. diffusion from blood (gas exchange in lungs when we breathe) 2. from myoglobin within muscle fibers - glygolysis forms pyruvic acid from glucose (like anaerobic respiration)

5. development of secondary ossification centers

- usually around time of birth - arteries entering the epiphyses stimulate formation - spongy bone in center of epiphyses - no medullary cavity in epiphyses - outward from center to surface

muscle metabolism

- very high amounts of ATP - 3 ways to produce ATP in muscle fibers 1. creatine phosphate 2. anaerobic glycolysis 3. aerobic respiration

excitation-contraction coupling: relaxation

- voltage-gated Ca2+ channels blocking Ca2+release channels - Ca2+ - ATPase pump continuously, moves Ca2+ into sarcoplasmic reticulum (SR) - high Ca2+ in SR, low Ca2+ in sarcoplasm - Ca2+ released from troponin, myosin-binding sites on actin blocked

excitation-contraction coupling: contraction

- voltage-gated Ca2+ channels move, Ca2+ release channels open Ca2+ ATPase pump continuously, moves Ca2+ into sarcoplasmic reticulum (SR)

enchondral ossification

1. development of cartilage model 2. growth of cartilage model 3. development of primary ossification center 4. development of medullary cavity 5. development of secondary ossification center 6. formation of articular cartilage and epiphyseal growth plate

contraction cycle 2: attachment of myosin to actin

1. energized myosin head attaches to myosin-binding site on actin 2. phosphate group released from myosin head - myosin head at this stage = cross-bridge - only one head hinds to actin at a time

types of skin wound healing

1. epidermal wound healing 2. deep wound healing

Phases of deep wound healing

1. inflammatory phase 2. migratory phase 3. proliferative phase 4. maturation phase

intramembranous ossification

1. mesenchymal cells -> osteoprogenitor cells -> osteoblasts 2. calcification 3. formation of trabeculae 4. development of periosteum

contraction cycle 1: ATP Hydrolysis

1. myosin head binds ATP 2. ATP hydrolyzed into ADP, energy to myosin 3. energized myosin head moves perpendicular to filaments - ADP and phosphate group still attached to myosin head

contraction cycle 3: power stroke

1. myosin head pivots 2. thin filament is pulled along thick filament toward center of sarcomere - generates muscle tension (force) - energy required for his action is from energy stored in myosin head from ATP hydrolysis 3. at end, ADP is released from myosin head

nerve impulse generates muscle action potential

1. nerve impulse arrives at synaptic end bulbs - stimulates voltage-gated channels to opne 2. Ca2+ flows through open channels - stimulates synaptic vesicles to release Ach into synaptic cleft 3. Ach diffuses to Ach receptors - opens ion channel in Ach receptor, Na+ (positive ion) and other cations flow into cell - cell gains positive charge, changes membrane potential 5. change in membrane potential triggers muscle action potential - action potential propages along sarcolemma (membrane) to t-tubule - causes Ca2+ release from SR into sarcoplasm CONTRACTION 6. Ach broken down by acetycholinesterase (Ache), activity terminated

fractures and repair of bone

1. reactive phase 2a. reparative phase 2b. reparative phase 3. bone remodeling phase

initiation of contraction cycle

1. sarcoplasmic reticulum releases calcium ions (Ca2+) into sarcoplasm 2. released Ca2+ bind to troponin 3. troponin moves tropomyosin away from myosin-binding sites on actin 4. binding sites are free and contraction cycle begins

functions of bone

1. skeletal framework 2. protection of internal organs 3. work with muscles to produce movement 4. mineral homeostasis- store and release minerals 5. hemopoiesis 6. triglyceride storage in adipose cells of yellow bone marrow

neuromuscular junction (NMJ) parts

1. synaptic end bulbs 2. synaptic cleft 3. motor end plate

osteoblasts

BUILD bone

osteoclasts

CARVE out bone

voltage-gated Ca2+ channels

Channels located in the membrane of T-tubules which open in response to an action potential and allow extracellular calcium to enter the cytosol

movement

through interaction of skeletal muscles, bones, and joints

transverse tubules (T tubule)

tunnels of sarcolemma toward center of muscle fibers - filled with interstitial fluid - allows fast spread of action potential along sarcolemma

inflammation

vascular and cellular response

vertebral compression fracture

vertebral body compressed into wedge shape

to synthesize creatine

what is excess creatine used for?

accumulation of lactic acid in muscle fibers and blood stream

what is muscle soreness from?

aerobic respiration (question)

what is slower than anaerobic glycolysis but produces much more ATP?

contractility

ability to conctract when stimulated by nerve impulse

electrical excitability

ability to reproduce muscle action potentials (impulses) in response to specific stimuli (chemical stimuli, autorhythmic response to electrical signals ex. heart)

elasticity

ability to return to original length and shape after contraction and extension

extensibility

ability to stretch, within limits, without being damaged

thin filaments

actin protein (8 nm in diameter, 1-2 um long)

zone of resting cartilage

anchors epiphyseal place to epiphysis

bone growth in thickness

appositional growth... 1. bone forms at surface in ridges on either side of periosteal blood vessels 2. ridges around blood vessels from tunnels 3. osteoblasts in endosteum secrete ECM, form new rings of concentric lamellae

metaphysis

between diaphysis and epiphyses

myosin head

binds ATP and actin - ATP binding site hydrolyzes ATP to generate energy

myoglobin

binds O2 that diffuses into muscle fiber - found only in muscle - releases O2 when needed

osteoblasts

bone deposition- synthesize and secrete components of ECM including collagen - initiate calcification - differentiate into osteocytes

epiphyseal line

bone has replaced cartilage in epiphyseal plate, bones cease growth

comminuted fracture

bone is splintered, crushed, or broken into pieces at site of impact

bone remodeling

bone resorption, bone deposition

enlargement of medullary cavity

bone tissue lining medullary cavity is destroyed by osteoclasts in endosteum

2b. reparative phase

bony callus formation - osteoprogenitor cells develop into osteoblasts - osteoblasts produce trabeculae - fibrous cartilage callus

open (compound) fracture

broken ends of bone protrude through skin

creatine kinase (CK)

catalyzes transfer of high-energy phosphate groups - phosphate group from ATP to creatine = creatine phosphate + ADP - phosphate group from creatine phosphate to ADP = creatine +ATP

inner osteonic layer

cell layer enables bone growth

zone of proliferating cartilage

chondrocytes divide and secrete ECM

common fractures

closed (simple), open (compound), comminuted, greenstick, impacted, pott, colles, vertebral compression

concentric lamellae

concentric rings in osteon bone lacunae (little lakes), contains osteocytes

interosteonic (Volkman's, perforating) canal

connect blood vessels/nerves in medullary cavity, periosteum, and osteonic canals

bone lacunae (little lakes)

contains osteocytes

myofibrils

contractile organelles in skeletal muscle fibers, appear as thread-like structures within sarcoplasm (diameter = ~2 um), extend entire length of a muscle fiber - striation in myofibrils is source of muscle fiber striation

calcification

crystallization of mineral salts hardens bone - initiated by osteoblasts

contraction cycle

cycle repeats as long as ATP and Ca2+ is available

sarcoplasm

cytoplasm of muscle fibers - lots of glycogen: macromolecule made of glucose, sugar storage - glucose used in ATP synthesis

calcitronin (CT)

decreases blood Ca2+ level

junctional folds

deep grooves in motor end plate that provide surface area

outerfibrous layer

dense irregular connective tissue

Z discs

dense protein separating sarcomeres

structure of bone

diaphysis, metaphyses, epiphyseal plate, epiphyseal line

terminal cisterns

dilated end sacs found on both sides of T tubule

closed (simple) fracture

does not break skin

muscular tissue properties

electrical excitability, contractility, extensibility, elasticity

action potential

electrical signal that propagates along membrane of neuron or muscle fiber

mesemchyme

embryonic connective tissue (flat bones of skull, facial bones, mandible, and medial parts of clavicle)

axon terminal

end of motor neuron, divides into synaptic end bulbs

keloid (cheloid) scar

extends beyond wound boundaries

2a. reparative phase

fibrous cartilage callus formation - blood vessels grow into fracture hematoma - fibroblasts from periosteum enter fracture site, produce collagen fibers - cells from periosteum develop into chondroblasts and produce fibrous cartilage - callus of fibrous cartilage (collagen fibers and cartilage) - soft cells, but protect

rapid reaction

first energy source for contraction - enough ATP for about 15 seconds

trabeculae (little beams)

flat plates with network of thin, bony columns, lined with endosteum

triad

formation of T tubules on either side of terminal cisterns

pott fracture

fracture of distal end of fibula

colles fracture

fracture of radius where distal fragment is displaced posteriorly

synaptic cleft

gap between cells in synapse - cells communicate across synapse with chemical neurotransmitters (muscle action potentials arise such as NMJs)

troponin

holds tropomyosin in place

medullary/ marrow cavity

hollowspace within diaphysis - contains fatty yellow bone marrow and blood vessels

outward to inward

how does bone develop un enchondral ossification?

cartilage model

hyaline cartilage

epiphyseal (growth) plate

hyaline cartilage allows diaphysis to grow in length

tropomyosin

in relaxed muscles, blocks myosin from binding to actin

muscle fatigue

inability of muscle to maintain force of contraction after prolonged activity

parathyroid (PTH)

increases blood Ca2+ level

Deep wound healing

injury extends to dermis and subcutaneous layer, scar tissue forms (fibrosis)

3. endomysium

inner layer, separates individual muscle fibers, mostly reticular fibers

bone growth in length

interstitial growth

initial bone formation

intramembranous ossification and endochondral ossification

autorythmicity

involuntary alternating contraction and relaxation (heart's natural pacemaker)

zone of hypertrophic cartilage

large maturing chondrocytes

acetylcholine receptors

ligand-gated ion channels found in motor end plate

medullary cavity

madullary/marrow cavity, endosteum

ossification (osteogenesis)

mainly 4 situations... 1. initial formation of bones in embryos and fetuses 2. growth of bones during infancy, childhood, and adolescence 3. remodeling bone 4. repair/fractures

2. perimysium

middle layer, surrounds muscle fascicles (bundles of 10-100+ muscle fibers), dense irregular connective tissue

contact inhibition

migration stops when cells meet together

ligand

molecule that binds to receptor

muscular tissue function

movement, posture, sphincters, thermogenesis

excitation

muscle action potential

contraction cycle 4: detachment of myosin from actin

myosin head detaches from actin when ATP binds to myosin

thick filaments

myosin protein (16 nm in diameter, 1-2 um long)

The site where a somatic motor neuron releases acetylcholine to stimulate a skeletal muscle fiber is called the

neuromuscular junction

acetylcholine (ACh)

neurotransmitter, found in synaptic vesicles in cytosol of synaptic end bulbs

frequency of stimulation

number of impulses per second

impacted fracture

one end of bone firmly driven into interior of other end

greenstick fracture

one side of bone is fractured, other side bends

bone deposition

osteoblasts add minerals and collagen

bone resorption

osteoclasts remove bone minerals and collagen fibers

compact (cortical) bone

osteon, osteonic (haversion, central) canal, concentric lamellae, interstitial lamellae, bone canaliculi, interosteonic (volkman's/perforating) canals

1. epimysium

outer layer, encircles entire muscle, dense irregular connective tissue

motor end plate

part of muscle opposite synaptic end bulbs

sarcolemma

plasma membrane of muscle fibers (cells), nuclei located next to sarcolemma

myosin tail

points toward M line in center of sarcomere

mitochondria

produce ATP to provide energy for muscle fibers

thermogenesis

regulation of heat

osteon

repeating unit within bone

zone of hypertonic cartilage

replacement by bone in progress

sphincters

rings of smooth muscles at exit of hollow organs

osteonic (haversion, central) canal

runs through center of osteon - contains blood vessels, lymphatic vessels, nerves

diaphysis

shaft (body)

contraction

sliding filaments

sarcomeres

smaller compartments of myofilaments

motor unit

somatic motor neuron and all skeletal muscle fibers it stimulates

posture

stabilize body positions (storage and movement)

epidermal wound healing

stem (specialized) cells detach from basement membrane, stem cells enlarge, migrate across wound

osteoprogenitor cells

stem cells derived from mesenchyme, bone stem cells, located in the bone that play a role in bone repair and growth

epidermal growth factor (EGF)

stimulates division and replacement of basal stem cells (ex. abrasions, minor burns, edges of deeper wounds)

neuromuscular junction

synapse between somatic motor neuron and skeletal muscle fiber

synapse

the region of communication between 2 neurons or neuron and target cell

intercalated discs

thick areas of membrane, attach cells together, contain gap junctions and desmosomes

perforating fibers

thick bundles of collagen extend from periosteum into bone extracellular matrix (attach collagen to bone)

bone canaliculi (small channels)

thin channels connect bone lacunae - allows nutrients to diffuse to osteocytes - osteocytes extend processes through canaliculi and communicate with each other via gap junctions

articular cartilage

thin layer of hyaline cartilage covering articulation part of epiphysis - lacks perichondrium and blood vessels - reduces friction and absorbs shock

endosteum

thin membrane lining medullary cavity - contains bone-forming osteoprogenitor cells and connective tissue