ap lecture t3 p1

Question Answer
how do skeletal muscle tissues replenish from satellite stem cells
cardiac muscle tissues contain and form by cardiocyte and form branching networks connected at intercalated dics. regulated by pacemaker cells
6 functions of skeletal muscle movement, posture, support for soft tissues, guard entrances/exits, temp, store protein
myofibril is surrounded by sacroplasmic reticulum
one sarcomere is from z-line to z-line
thick vs thin filaments of sarcomere A band is also called the thick band and it towards the inside part. the thin filament is the titin
difference between f and g actin f-actin is the whole strand while the g-actin is the individual balls
where is nebulin in f-actin strand runs through the middle
thick filament contains the myosin
the z-line in muscle is between the two titin thingys
skeletal muscles characteristics voluntary muscles, controlled by CNS, supplies nutrients, carry away wastes and supply large amounts of oxygen
muscles are surrounded by a fascia/epimysium
fascia a band of sheet of collagen-based connective tissue that attaches, stabilizes, encloses and separates muscles and other internal organs
perimysium surrounds muscle fibers bundles (fascicles)
endomysium surrounds individual muscle cells (muscle fibers). contains capillaries and nerve fibers contacting muscle cells. contains mysatellite cells (stem cells) that repair damage. blood vessel and nerve supply to fascicles
what three mysiums come together to form tendons (bundle) or aponeurosis (sheet) endomysium, preimysium and epimysium
what are myoctes packed with myofibrils that stretch the entire length of the cell.
what leads to the muscle contraction the active shortening of myofibrils
myofibrils are composted of thin filaments and thick filaments
thin filaments contain actin
thick filaments are made of myosin and titin ( elastic filament
where are myofibrils anchored to the inner surface of the sarcolemma at either end of the myocyte (tendon or aponeurosis)
myocytes characteristics very long. develops through fusion of mesodermal myoblasts (contain hundreds of nuclei)
myosatellite cells become incorporated into endomysium and respond to injury/loading
sarcolemma the cell membrane of a muscle fiber/myocyte and surrounds the sarcoplasm
how does a myocyte coordinate contraction along its length fluid filled transverse tubules (t tubules) are continuous with the sarcolemma and aid in the conduction of electrical impulses across the muscle which are called action potentials
membranes of the sarcoplasmic reticulum form a network of tubules around the myofibrils
when t- tubules encircle the myofibrils the SR exampands and forms the terminal cisterna
the terminal cisterna contains t-tubules and SR that remain distinct. also stores Ca at a 1000x (or 40,000) higher conc than the cytosol
terminal cisterna is able to store Ca because of Ca binding to calsequestin
sarcomeres are contractile units of muscle and structural units of myofibrils that form the striped or striated pattern within myofibrils
each myofibril has how many sarcomeres 10,000
sarcomeres process thick and thin filaments. Proteins that stabilize position of filaments. Proteins that regulate the interaction of filaments
thick filaments are what type of bands A bands
thin filaments are what type of bands I bands and have f-actin
filamentous actin have what shape twisted strands of 300-400 individual globular actin (g-actin) molecules
myosin binds to the active site of g-actin
(thin) nebulin extends between the two g-acti rows, holding them together
(thin) tropomyosin covers the active sites and prevent actin-myosin interaction
troponin subunits has 3 subunits. 1- binds to the tropomyosin molecules together to form troponin-tropomyosin complex. 2- binds the TTC complex to g-actin. 3- has calcium ion receptors that can bind up to two Ca ions
(thin) contraction can only occur when calcium ions bind to tropinin changing the config of TTC complex exposing the active sites
thick filament may contain 300+ myosin molecules twisted together. the tails always orient towards the m-line. H-line contains no heads. myosin heads projects outwards to the thin filaments to form a bridge. myosin hinge allows the head to pivot (contraction)
each thick filament has a core of titin which extends out the end of the thick filament and connects to actinin of the z-line. capable of elastic recoil
what happens during a contraction thin filaments of sarcomere slide towards the M-line, alongside thick filaments. The width of A zone stays the same, the z-line moves closer together
contractions require what electrical sig transmembrane potential. the inside of the cell is slightly negative
extracellular vs intracellular before a contraction extra – excess Na and intra – excess K
An influx of sodium ions leads to depolarization
An outflow of sodium ions leads to hyperpolarization
during a contraction what does the ion pump do transports 3x Na out and 2x K in
skeletal muscle and neural cells have excitable membranes which allow for rapid depolzarization
ions that flow during a contraction are controlled by voltage-gated channels which are responsible for the action potential
when the threshold potential is reached what happens voltage-gated channels open which leads to depolarization
what happens during the refractory period only allows the signal to be propagated in one direction
ach does what acetylcholine is a neurotransmitted which changes the permeability of the cell's plasma membrane
muscle excitation lasks 0.03 seconds
excitation-contraction coupling what happens action potential reaches a triad. releasing Ca and triggering contraction
the contraction cycle 1. begins. 2. active-site exposure. 3. cross-bridge formation. 4. myosin head pivoting. 5. cross-bridge detachment 6. myosin reactivation
1. during the contraction cycle what happens at the beginning involves a series of interrelated steps. Ca arrive within the zone of overlap in sarcomere
2. during the contraction cycle what happens during the active-site exposure Ca binds to troponin weaking the bond between actin and troponin-tropmyosin complex. change in position by rolling away from the active site
3. during the contraction cycle what happens during cross-bridge formation the energized myosin heads bind to them, forming the cross bridges
4. during the contraction cycle what happens during the myosin head pivoting the energy stored in the resting state is released as the myosin head pivots towards the M-line. Power stroke. ADP + Pi is released
5. during the contraction cycle what happens during bridge detachment ATP binds to the myosin head which breaks the link between the myosin head and active site.
6. during the contraction cycle what happens during myosin reactivation myosin reactivation occurs when the free myosi head splits ATP and the energy released recocks the head
7. muscle relaxation what happens when the Ach is broken down Ach is broken down by acetylcholinesterase (AchE) ending the action potential generation
8. muscle relaxation what happens during sarcoplasmic reticulum reabsorbs Ca As the calcium ions are reabsorbed, their conc in the cytosol decreases
9. muscle relaxation, active sites covered and cross-bridge formation ends w/o Ca ions, the tropomyosin returns to its normal position
10. muscle relaxation when contraction ends w/o cross-bridge formation, contraction ends
11. muscle relaxation occurs returns passively to its resting length
Rigor mortis w/o ATP the SR cannot pump Ca out of the cytosol. w/o atp the myosin remain bound to the active sites. remains for about 36 hours
tetanus (rusty nail) bacteria: Clostridium tatani which produces tetanospasmin which inhibits the motor neuron inhibitor
within a muscle fiber, your body cannot control the number of sarcomeres that contract within a muscle fiber
tension of muscle as a whole is determined by tension produced by individual muscle fibers and the total number of muscle fibers stimulated.controlling the number of muscle fibers stimulated and freq of stim
at the molecular lvl, muscle tension depends on the number of pivoting cross bridges
sarcomere tension depends on the the length-tension relationship; the amount of overlap between thick and thin filament
treppe when a second stimuli arrives immediately after relaxation phase. multiple ( up to 50) stimuli will gradually increase tension. this is rare
tetanic contraction all cross bridges form. complete muscle contraction. rare.
motor units (muscle organizational unit) each motor neuron controls 100s of muscle fibers. the size of the motor unit determines how fine of control you have. a sensible twitch, a faciculation involved act. of multiple motor units
the lower the number the more refined the fine motor control. what is the lowest and highest muscle for control the one with the lowest innervation ratio is dorsal interosseous (foot) and the highest is the medial gastrocnemius (calfs)
smooth activation of muscles reqs act of smaller motor units first recruitment. peak tension is reached when all motor units are act.
motor units cycle between active and resting states asynchronous motor unit summation
muscle tone some are always under tension. stabilizes positions of bone and organs, maintains balance and posture. higher muscle tone leads to higher muscle metabolism. loss = neurological disorder
bells palsy disruption/inflammation of the 7th cranial nerve. loss of facial muscle tone
isotonic contraction tension increases and muscle length changes. two types; concentric and eccentric
concentric muscle tension > load
Eccentric muscle tension < load, controls speed
example of isometric contractions carrying a bag of groceries, holding your head up, standing upright on a hillside
muscle contraction speed load and speed of contraction are inversely related. the heavier the load (resistance) the long it take for shortening to begin (recruitment of cross bridges) and less the muscle will shorten
to contract one fiber req 2500 atp molecules/sec
in abundance the muscle does what with ATP ATP -> creatine and becomes creatine phosphate. during muscle contractions the phosphate group "recharges' spend ADP to return it to ATP
creatine kinase used up in 15-30 seconds.
the molecule from glycolysis used by muscles during a contraction pyruvate
excess lactate is converted to pyruvate and glucose by the liver; Cori effect
major types of skeletal muscle fibers fast, slow and intermediate fibers
fast fibers white muscle. most common. rapid contraction. large diameter, large glycogen reserve and few mitochondria. strong contraction, fatigue quickly
slow fibers red muscles. slow to contract and fatigue. small diameter, more mitochondria surrounded by high density of capillaries. have high oxygen supply and contain myoglobin (red pigment, binds oxygen). less dependent on anaerobic metabolism
intermediate fibers are mid-sized. have low myoglobin. have more caplliaries than fast fibers, slower to fatigue
as we age which muscle fibers increases decline in fast-twitch fibers and increase in slow-twitch fibers
ratios of fast vs slow switch nonathletic 50/50. power athletes and sprinters higher father-twitch. endurance athletes higher slow twitch. all in all is genetically determined
muscle growth due to exercise is called hypertrophy
hypertrophy is due to increased number of myofibrils, not myofibers. each muscle fiber increases in diameter
skeletal muscle that is not stimulated loses muscle tone; atrophy. may become irreversible over time, needs for PT and electrical stimulation during rest endurance
anaerobic endurance refers to the time that a muscle can be supported by glycolysis and by the use of existing ATP stores. fatigue sets in within 2 mins
aerobic endurance length of time muscles can contract using mitrochondrial metabolism. fatigue determined by the reserves needed for aerobic respiration
warming muscles up stimulates blood flow and prevents fatigue. breaks down glycogen to glucose. Carb-loading increases glucose reserves
cardiocytes small. single nucleus. branch. Their t-tubules are short and broad and the SR lacks terminal cisternae. Sarcolemma is permeable to calcium ions. Cardiocytes are more sensitive to change in calcium than skeletal muscle. Sarcolemma is permeable to ca ions
cardiocytes are sensitive to changes in Ca even more than skeletal muscle.
Cardiocytes number of mito extremely large and rely on aerobic respiration
intercalated discs connects cardiocytes and allows transfer of action potentials between cells. intertwined sarcolemmas desmosomes gap junctions (allow communication, one big muscle)
automaticity cardiac tissue contracts w/o neural or hormonal stim. action potential set by pacemaker
Pacemaker potential pacemaker current. slow, positive increase in voltage across the cell's membrane. driven by the uptake of Na ions w/o release of K
threshold potential the voltage that must be reached for the cell to fire. results in spontaneous depolarization. SA node reaches potential first, it establishes the heart rate, the natural pacemaker
in cardiac muscle, an influx of calcium ions sustains the depolarization so that is lasts longer. creates a plataeu phase in which the cells charge stays slightly positive (depolarized) for longer.
due to differences in what will cardiac muscles do not experience wave sstimulation or treppe sarcolemma. or else would interfere with the pumping of blood
smooth muscle forms around integumentary system (arrector pili or goose bumps), blood vessels and airways, reproductive and glandular system, and digestive and urinary systems (sphincters)
smooth muscle characteristics single nucleus, never unite to form tendons, nonstriated, diff internal organization of actin and myosin. dense bodies (desmin) bind adjacent smooth muscle together
smooth muscle length-tension relationships plasticity – ability to respond over a range of lengths
smooth muscle control of contractions multiunit smooth muscle cells – organized in motor units (iris, rector pilli). Visceral smooth muscle cells – no contact w/ motor axons
smooth muscle tone influenced by hormones and chemical factors
is tropinin found in smooth muscle no, and tropomyosin does not cover the active sites
in smooth muscle calcium interacts with calmodulin (caM)
with smooth muscle calcium after caM is activated what happens myosin light chain kinase (MLCK) is activated
what are the patterns for fascicle organization parallel, convergent, pennate, circular
parallel muscle fibers parallel to the long axis of the muscle (most common). ex: biceps, rectus abdomins, wrapping muscle
convergent muscle a braod area converges on attachment site (aponeurosis). ex: pectoralis muscles. different areas of themuscle can be stimulated to adjust direction of pull
Pannate muscle unipennate (digitornum muscle), bipennate (rectus femoris), multipennate (deltoid muscle)
circular also called sphincters, open and close to guard entrances of the body. ex: orbicularis oris muscle
in the body what is the lever and what is the fulcrum bone = lever (a rigid, moving structure) and joint = fulcrum (a fixed point). muscle provide applied the force (AF) required to overcome load (L)
three classes of levers 1 2 3 -class lever. depends on the relationship between applied force, fulcrum and resistance
trapezius moves scapula and clavicle (shoulder girdle)
pectoralis major moves moves arm anteriorly
serratus anterior pulls pulls scapula anteriorly
deltoid abducts raises the arm at the shoulder
latissimus dorsi moves adducts (lowers) and extends the arm and shoulder
pectoralis minor moves depresses the shoulder
dorsal interosseus moves extends and abduct the proximal and distal interphalangeal joints of digits 2-4
abductor digiti minimi abducts the 5th digit
lumbricals move flex the metacarpophalangeal joints, extend the proximal and distal interphalangeal joints of digits 2-5