physiology bone/skeletal/muscular

bone

organ made of bone, cartilage, dense connective tissues adipose and nervous tissue working together

functions of skeletal system

provides support, protects internal organs, assists body movements, mineral homeostasis (calcium and phosphorus) blood cell production, stores triglycerides

diaphysis

bone shaft

2 epiphyses

both ends of bone at joint

2 metaphyses

region between diaphysis and epiphysis

articular cartilage

covering both epiphyses

periosteum

connective tissue surrounding diaphysis

medullary cavity

hollow space within diaphysis

endostenum

thin membrane lining medullary cavity

bone is made of what

15% water, 30% collagen, 55% crystallized mineral salts

osteoprogenitor cells

bone stem cells differentiate into other types of cells

osteoblasts

bone building cells that secrete matrix

osteoclasts

remodel bine and release calcium

compact bone

providing protection and support

spongy bone

lightweight and provides tissue support

cartilage

poorly vascularized cartilage tissue with chondrion sulfate and various fibers

fibrocartilage

forms intervertebral disc of spine

articular cartilage

thin layer of hyaline cartilage

periosteum

tough sheath of dense, irregular C.T on the outside of the bone

periosteal arteries

diaphysis through volkmann’s canals

nutrient artery

enters the diaphysis through a nutrient forearm and exits via nutrient vein

bones form

during fetal development, before adulthood, when bones remodel or when fractures heal

bone formation 2 forms

intramembranous and endochondral

intramembranous

how we make flat bones, connective tissue membrane is replaced by bone

endochondral

replaces cartilage with bone in the developing embryo and fetus

organic constituents

collagen fibers provide flexibility and tensile strength

inorganic hydroxyapatite crystals

calcium phosphate, calcium carbonate

trace elements bone

magnesium, floride, sulfate

growth plate

is always actively dividing and causing bone to elongate from each end

reactive phase repair of bone

an early inflammatory phase

reparative phase of repair bone

formation of fibrocaritaginous callus first and a bony callus second

bone remodeling phase

last step and callus is remodeled into spongy bone

open fracture

broken ends of bone, does not break skin

comminuted fracture

bone is crushed into pieces

greenstick fracture

one side of bone is broken, common in children

impacted fracture

one end of fractured bone is forcefully driven into the interior of other

pott fracture

distal end of the lateral bone with serous injury of distal tibial

colles fracture

fracture of distal end of radius

bones role in calcium homeostasis

bones store 99% of body’s calcium

parathyroid hormone

is secreted by parathyroid gland when calcium levels drop

calcitriol

increase calcium absorption in the intestiens

vitamin a

stimulates activity of osteoblasts

vitamin c

needed for synthesis of collagen

vitamin d

essential to healthy bones because it promotes absorption of calcium from foods in the gastrointestinal tract into the blood

vitamin k and b12

needed for synthesis of bone proteins

IGFs (insulin growth factors)

come from liver

thyroid hormones

promote bone growth by stimulating osteoblasts and protein synthesis

sex hormones

estrogen and testosterone, cause dramatic effect on bone growth and occurs during teenage years

hypo secretion during childhood

pituitary dwarfism

hyper secretion during childhood

gigantism

hyper secretion as adult

acromegaly, giant hands feat and facial features

skeletal muscle

striated and voluntary

cardiac

wall of the heart, striated and involuntary

smooth visceral muscle

in viscera; non-striated and involuntary

functions of muscle tissue

body movements, regulating organ volumes, movement of fluid and thermogenesis

excitability

respond to chemicals released from nerve cells

conductivity

propagate electrical signals over membrane

contractility

ability to shorten and generate force

extensibility

ability to be stretched without damaging the tissue

elasticity

return to original shape after being stretched

how are muscles formed?

myoblasts to satelite cell to immature muscle fiber

sacromere

functional unit of myofibrils

contractile proteins

myosin and actin

regulatory proteins

troponin and tropomyosin

structural proteins

provide proper alignment, elasticity and extensibility, titin, myosin, nebulin and dystrophin

thick filaments

myosin heads that extend toward thin filaments help by the M line of proteins

thin filaments

myosin-binding site on each actin molecule

what forms the M line?

myomesin

what helps maintain the alignment of actin?

nebulin

what reinforces sarcolemma?

dystrophin

Contractile proteins

Proteins that generate force during muscle contractions

Myosin

Contractile protein that makes up thick filament; molecule consists of a tail and two myosin heads

Actin

Contractile protein that is the main component of thin filament; each actin molecule has a myosin-binding site where myosin head of thick filament binds during muscle contraction.

Regulatory proteins

Proteins that help switch muscle contraction process on and off

Tropomyosin

Regulatory protein that is a component of thin filament; when skeletal muscle fiber is relaxed, tropomyosin covers myosin binding sites on actin molecules, thereby preventing myosin from binding to actin.

Troponin

Regulatory protein that is a component of thin filament; when calcium ions (Ca2+) bind to troponin, it changes shape; this conformational change moves tropomyosin away from myosin-binding sites on actin molecules, and muscle contraction subsequently begins as myosin binds to actin.

Structural proteins

Proteins that keep thick and thin filaments of myofibrils in proper alignment, give myofibrils elasticity and extensibility, and link myofibrils to sarcolemma and extracellular matrix

Titin

Structural protein that connects Z disc to M line of sarcomere, thereby helping to stabilize thick filament position; can stretch and then spring back unharmed, and thus accounts for much of the elasticity and extensibility of myofibrils.

alpha-Actinin

Structural protein of Z discs that attaches to actin molecules of thin filaments and to titin molecules

sliding-filament mechanism

exposure of the myosin binding sites on actin in the presence of Ca2+ and ATP, the thick and tin filaments slide to another, and the sarcomere is shortened

isotonic contractions

a load is moved

isometric contraction

no movement occurs

Botulinum toxin blocks release of Ach

bacteria in improperly canned food

curare

plant poison, blocks ACh receptors, muscle paralysis

neostigmine

blocks AchE and more ACh strengthens weak muscle contractions

creatine supplementation

gain muscle mass but shut down bodies own synthesis

muscle fatigue

inability to contract after prolonged activity

motor unit

one somatic motor neuron and all the skeletal fibers

myogram

Record of a contraction; 3 periods

latent period

Ca 2+ is being released from SR

contraction period

filaments slide

relaxation period

Ca 2+ into SR

refractory period

muscle cannot respond

wave summation

second stimulus increases strength of a contraction before relaxation

partial relaxation

stimuli is called incomplete tetanus

increasing number of active motor units

prevents fatigue and helps smooth muscle movements

tetanus vaccination

protects against the bacterium clostridium tetani

motor unit recruitment

motor units fire asynchronously and produce smooth muscle contraction

muscle tone

involuntary contraction of small number of moto units, important to maintaining blood pressure

motor unit

motor neuron plus all of the muscle cells it innervates