Muscular Tissue Flashcards
what causes contraction in a muscle
protein actin pulled by protein myosin; only in striated muscles after binding sites are exposed in response to calcium and proteins troponin and tropomyosin
how many nucleuses do skeletal, cardiac, and smooth muscles have
skeletal: multinucleated
Cardiac: 1-2 nuclei
smooth: 1 nuclei
whats the difference between cardiac and skeletal muscle
cardiac has 1 nuclei; muscle fibers are shorter; possess many mitochondria & myoglobin; branched & connected by intercalated disc
intercalated discs
apart of sarcolemma; allow cardiac muscle cells to contract in wave-like pattern so heart can pump
gap junction in cardiac cells
forms channels between muscle fibers that allow depolarizing current produced by cations to flow from cardiac muscle cells
desmosomes
cell structure that anchors ends of cardiac muscle fibers together so cells do not pull apart during stress of individual fibers contracting
what nervous system do pacemaker cells respond to
autonomic nervous system; controls heart rate
functional syncytium
begins w/ pacemaker cells; wave of contraction that allows heart to work as a unit
features of smooth muscle fibers
spindle shaped like football; single nucelus; thousands times shorter than skeletal fibers; produce their own connective tissue endomysium; no striations but do contain actin/myosin
do smooth muscles contain troponin?
no they have protein called calmodulin; Ca++ binds to calmodulin to activate enzyme myosin kinase which attach to thin filaments & when those move past thick filaments it stimulates pull and contraction of muscle
smooth muscle energy
power output low but contractions must continue always, so Ca++ always present to maintain muscle tone
motor units
axon-like swelling called “boutons” from autonomic neurons form motor units through smooth muscle
what are the 2 different smooth muscles & locatoins
single unit: walls of visceral organs; has its muscle fibers joined by gap junctions so that they contract as one unit; aka visceral muscle; has stress-relaxation response meaning they can stretch & fill w/out releasing contents
multi unit: rarely posses gap junctions; contraction does not spread cell to cell; stimuli comes from ANS & hormones not stretching; large blood vessels/resp tract
hyperlasia
smooth muscle can divide to produce more cells, ex. uterus at puberty
epimysium
irregular connective tissue wrapped around each muscle fiber
fascicle
individual skeletal muscle fiber
perimysium
middle layer connective tissue inside each fascicle
endomysium
in each fascicle; encases muscle fiber; thin connective tissue; made of collagen & reticular fibers
aponeurosis
aka fascia; connective tissue between skin & bones; ex. lats
sarcolemma
plasma membrane of skeletal muscle fibers
sarcoplasmic reticulum (SR)
stores releases and retrieves CA++
actin
thin filaments
myosin
thick filament
sarcomere
packet of microfilaments & proteins such as troponin & tropomyosin; bordered by z-discs; run entire length of muscle fiber;
neuromuscular junction
where muscle fiber first responds to signaling by motor neuron; where motor neurons terminal meets muscle fiber
excitation-contraction coupling
process involved in skeletal muscle contraction; skeletal muscle fibers to contract; sweeps through sarcolemma; Ca++ is released from SR; myosin then pulls actin filaments towards center & shortens muscle
t-tubules role
carry action potential into interior cell to trigger opening of calcium channels in membrane of adjacent SR; causes Ca++ to diffuse out into sarcoplasm and trigger muscle contraction
what stimulates muscle contraction
Na+ enters & releases Ca++ from SR sustained by ATP
what is the sliding filament of contraction
signaled by motor neuron; thin filaments are pulled & slide over thick filaments w/sacromeres when Ca++ enters sarcoplasm
tropomyosin
winds around chains of actin filament covers myosin binding sites to prevent actin from binding there; topomyosin binds to troponin & Ca++
cross-bridge formation
tropomyosin exposes myosin binding site on actin filament; Ca++ binds to troponin & move tropomyosin; then thin filaments are pulled by myosin heads to slide past thick filaments toward sarcomere
what are the three ways ATP can be regenerated
creatine phosphate metabolism; anaerobic glycolysis & fermentation; aerobic respiration
creatine phosphate
molecule that can store energy in phosphate bonds; atp transfers energy to creatine & this can be used during first 15 seconds of energy source
anaerobic glycolysis & fermentation
second source of energy; non oxygen dependent process that breaks down glucose to produce ATP; slower than creatine phosphate; breaks down glycogen stores & converts to lactic acid; good for short bursts of energy
aerobic respiration
breakdown of glucose in presence of oxygen produces CO2 H2O and ATP; takes place in mitochondria; this provides ATP for resting/moderate activity; uses circulating glucose in blood stream/pyruvic acid/fatty acids; increases efficiency of circulatory system so o2 can be supplied to muscles longer
what type of molecule is myoglobin
protein
what are the products of atp hydrolyzation
ADP and Phosphate
when muscle atrophies what happens
number of sacromeres & myofibrils decreases
what is two criteria to consider when classifying types of muscle fibers
how fast some fibers contract relative to others & how fibers produce ATP
three main types of skeletal muscle fibers
- slow oxidative fibers contract relatively slowly & use aerobic respiration
- fast oxidative fibers have fast contractions & primarily use aerobic respiration but fatigue quicker than SO fibers
- fast glycolytic fibers have fast contractions & primarily use anaerobic glycolysis; fatigue the quickest
angiogenesis
formation of more extensive capillary networks around the fiber; supply O2 & remove metabolic waste
insertion of a muscle
moveable end of the muscle that attaches to the bone being pulled
origin
end of the muscle attached to a fixed bone
antagonist
maintain body/limb position; control rapid movement
what are the main 6 major fascicle arrangements
parallel, fusiform, circular, convergent, bipennate, unipennate, multipennate
what are the 4 pairs of abdominal muscles
external oblique, internal oblique, transversus abdominis, rectus abdominis
linea alba
fibrous band that is bilateral rectus sheaths that join anterior midline of body; enclose rectus abdominis
