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