skeletal muscle chapter 9

skeletal muscle

attached to bone of skeleton

volunatary

cardiac muscle

makes up most of the wall of the heart

involuntary

resposible for pumping action of the heart

smooth muscle

found in wall of internal organs, such as those of digestive tract

involuntary

how many skeletal muscles

600 skeletal muscles

skeletal muscle are composed of

skeletal muscle tissue

nervous tissue

blood

connective tissue

fascia

thin covering of connective tissue around a muscle

tendon

cord-like mass of connective tissue that connects muscle to a bone

aponerurosis

sheet-ike mass of connective tissue that connects a muscle to bone, skin, or another muscles

epimysium

surrounds whole muscle; lines beneath fascia

perimysium

surrounds facicles within a muscle

endomysium

surrounds muscle fibers within a fasciale

compartment

space containing group of muscles, blood vessels and nerves, enclosed by fascia

compartment syndrome

fluid accumulation within a compartment

results in increase in pressure in compartment

leads to deficiency of oxygen and nutirents

causes sever pain

fascia

fascia of each muscle is part of network of faciae

deep fascia

portion surrounding muscles is __ , which connects to subcuntaneous fascia under skin

subserous fascia

network also connects to __of serous membranes

skeletal muscle fiber

multinucleated

saracolemma

sarcoplasm

many myofrils

SR

transverse

trad

sarcolemma

cell membrane of muscle fiber

sarcoplasm

cytoplasm of muscle fiber

myofribrils

long, parallel structures that run down fiber

consist of thin actin filaments and thich myosin filaments

sacromeres

sacromeres

units that connect end to end, to make up myofilamentss

sacroplasmuc reticulum (SR)

endoplasmic reticulum of muscle; stores calcium

transverse tuble

relays electrical impulses to the sr

traid

unite consisting of 1 tuble and 2 sr cisternae

myofibrils consists of what pattern

stration patttern

I band

light band; composed of thin actin filaments

A band

dark band; composed of thick myosin filaments with portions overlapped with thin actin filaments

H zoneq

center of A band; composed of thick myosin filaments

Z line or Z disc

sacromere boundary; in center of I band anchors filaments in place

M line

center of sacromere and A band; anchors thick dilaments

thick filaments

composed of myosin protein

heads form cross-bridge with thin filaments

thin filaments

composed of actin protein

associated with troponin and tropomyosisn, which prevents cross-brige formation when muscle is not concentrating

contraction of a skeletal muscle fiber

requires interaction from several chemical and cellu;ar componets

results from a movement within the myofibrils, in which the actin and myosin filaments slide past each other, shortening the sacromeres

muscle fiber shortens and pills on attachment points

neuromuscular junction (NMJ)

a type of synapse, also called a myoneural junction, a site where an axon of motor neuron and skeletal muscle fiber interact. Skeletal muscle fibers contract only when stimulated by a motor neruon

parts of neruromuscular junction

motor neurons

moter end plate

synaptic cleft

synaptic vescicles

nuerotransmitter

motor neuron

neuron that controls skeletal muscle fiber

moter end plate

specialized folded portion of skeletal muscle fiber, where fiber binds to neurotransmitter

synaptic cleft

space between neruon and muscle fiber, across neurotransmutter travels

synaptic vesicles

membrane-bound sacs containing neurotransmitters

nuerotransmitters

chemicals released by motor neruon to deliver message to muscle fiber

acetylocholine. (ACh)

is the neruotransmitter

ACh 1

nerve impulse causes release of ACh from synaptic vesicles

ACh 2

binds to the ACh receptors on motor end plate

ACh 3

causes changes in membrane permeability to sodium and potassium ions, which generates. a muscle impulse (action potential)

ACh 4

impulse causes release of calcium ions from SR, which leads to muscle contraction

Myasthenia gravis (MG)

autoimmune disorder where antibodies attack acetyyloline receptors on skeletal muscle fibers (moter end plates) in neuromusuclar junction. The person may have only one-third the norma; number of ACh recpetors. This can lead to wide spread muscle weakness and muscle fatigue

Muscular dystorphy

deficeindy or abnormality/mutation in scarce muscle protein called dystrophin, in absence of normal dystrophin, cells lose normal structure and die

dystrophin

binds to internal side of muscle cell membranes, and holds them together during contraction

clostridum botulinum

anaerobic bactera the produces a toxin that causes food poisoning, grows in food that is not properly perserved, causes digestive, muscular and respiratory symptoms. trated with an antitoxin, used in cmall doeses as botox to smooth wrinkles and treat migrains

excitation-concentration coupling

connection between muscle fiber stimulation and muscle contraction

during muscle relaxation

• ca2 ions are stored in SR

•Troponin-tropomyosin complexes cover binding sites on actin filaments

upon muscle stimulation

•Muscle impulses cause S R to release Ca2 ions into cytosol

•Ca2 ion binds to troponin to change its shape

•Each tropomyosin is held in place by a troponin molecule; change in shape of troponin alters the position of tropomyosin

•Binding sites on actin are now exposed

•Myosin heads bind to actin, forming cross-bridges

Sliding filament model of muscle contration

when sacromeres shorten, thick and thin filaments slide past eachother

H zones and I bands narrow

Z lines move closer togther

Thin and thiclk filaments do not change length

overlap between filaments increase

cross-bridge cycling 1

myosin head attaches to actin binding site, forming cross-bridge

cross-bridge cycling 2

myosin cross-bridge pulls thin filament towards center of sacromere

cross-bridge cycling 3

ADp and phosphate are released from myosin

cross-bridge cycling 4

New ATP binds tp myosin

cross-bridge cycling 5

linkage between actin and myosin cross-bridge break

cross-bridge cycling 6

ATP splits

cross-bridge cycling 7

Myosin cross-bridge goes back to original position, ready to bind to another binding site on actin

Acetylcholinesterase (enzyme)

an enzyme that breaks down the neurotransmitter acetylcholine (ACh) into choline and acetate, thus terminating nerve impulses and ensuring proper signal transmission at synapses

ATP reserves

first source of energy for muscel contraction

muscle cells store only a small amount

creatine phosphate

initial source of energy to regenerate ATP from ADp and P

stores energy in phosphate bone like ATP

ATP + creatine phosphate can only fuel 10 seconds of intense muscle contration

cellular reperation

must be used to fuel longer periods of muscle contraction

breaks down glucose and produces ATP

Glucose stores as glycogen in ,muscle cells

muscle fatigue

inablitiiy to contract muscle

common causes of muscle fatigue

decrease blood flow

ion imbalances across sarcolemma

lose of fesire to continue to excersie

accumulation of lactic acid

muscle cramp

sustained, involuntary muscle contraction

may be caused by changes in electorlyte concentration in extracellular fluid in the area

threshold stimulus

minimun strenght of stimulation of a muscle fiber requred to cause contraction

twitch

contractile response of a single muscle fiber to a single impulse

latent period

delay between stimulation and start of contraction

period of concentration

fiber pulls at attachements

period of relaxation

pulling force decrease

length-tension relationship

length of muscle fiber before stimulation determins amount of force it can develop

optimum starting length

is resting length of the muscle fiber

stretch muscle fibers develop

less force, since some mysoin heads cannot reach binding sites on actin

shorten muscle fibers develope

less force, since compression sacromers cannont shorten further

summation

process by which the force of individual muscle fiver twitches combine, when frequency of simulation increases. produces sustained contractions. and can lead to partial or complete tentanic contractions

partial tetany

occurs at higher frequencies of stimulatioin. time spent in relaxation between twitches becomes brief

complete tetany

occurs at very high frequencies of stimulation. does not occur in body, only laboratory. forceful sustained contraction has no relaxation between twitches

motor unit

a motor neuron plus all the muscle fibers it controls. precise movement are produced with fewer muscle fibers in a moter unit

recruitment

increases in the number of motor units activated, to produce more force. only certain motor units are activated at first then others activate later on. intensity of stimulation increases

sustained contractions smaller motor units

recruited 1st

sustained contractions larger motor units

recruited later 2nd

summation and recruitment can produce

sustaiend contraction of increasing strength

muscle tone (tonus)

continuous state of atrial contraction in resting muscles

isotonic

muscle contracts and changes length

means equal force

isotonic concentric

shortening contraction, occurs when lifting an objecrt

isotonic eccentric

lenthening contraction; occurs when force not sufficent to lift object

isometric

muscle contracts but does not change length, means equal length. tension developes, but parts attached to muscle do not move

fast-twitch fatigue resistant fibers lla

•Intermediate twitch fibers

•Intermediate oxidative capacity

•Intermediate amount of  myoglobin

•White fibers

•Resistant to fatigue

Rapid ATPase activity

fast-twitch glycoltic fibers llb

•Anaerobic respiration (glycolysis)

•White fibers (less myoglobin)

•Poorer blood supply than slow-twitch fibers

•Fewer mitochondria than slow-twitch

•More SR than slow-twitch

•Susceptible to fatigue

•Fast ATPase activity; contract rapidly

hypertrphy

enlargment of skeletal muscle that is excerised

atrophy

decrease in size and strength of skeletal muscle that is unused

smooth muscle fibers are

shorter. single, centrally located nucleus. enlongated with tapering ends. myofilamanets randomly organized. lack stration. lack transverse tubules. sr not well devloped

multi-unit smooth muscle

•Cells are less organized

•Function as separate units

•Fibers function independently

•Iris of eye, walls of blood vessels

Stimulated by neurons, hormones

visceral smooth muscle

•Single-unit smooth muscle; cells respond as a unit

•Sheets of spindle-shaped muscle fibers

•Fibers held together by gap junctions

•Exhibit rhythmicity

•Conduct peristalsis

•Walls of most hollow organs

More common type of smooth muscle

resembles skeletal contractions in these ways

•Interaction between actin and myosin

•Both use calcium and ATP

•Both are triggered by membrane impulses

diffrent from skeletal muscle contractions in these ways

•Smooth muscle lacks troponin; uses calmodulin instead

•Two neurotransmitters affect smooth muscle: Acetylcholine (Ach) and norepinephrine (NE)

•Hormones can stimulate or inhibit smooth muscle

•Stretching can trigger smooth muscle contraction

•Smooth muscle slower to contract and relax

•Smooth muscle more resistant to fatigue

•Smooth muscle can change length without changing tautness

cardiac muscle

•Located only in the heart

•Striated muscle cells

•Muscle fibers joined together by intercalated discs

•Fibers branch, contain a single nucleus

•Network of fibers contracts as a unit (syncytium)

•Self-exciting and rhythmic

•Longer refractory period than skeletal muscle

•No sustained or tetanic contractions

4 basic componets of levers

•Rigid bar or rod (bones)

•Fulcrum or pivot on which bar moves (joint)

•Object moved against resistance (weight)

Force that supplies energy for movement (muscles