Ch 10 Muscles Flashcards
fascicles
bundle of muscle fibers or axons
muscle fibers
muscle cells
tendon
cord of dense regular connective tissue that connects muscle to bone
deep fascia
dense sheet of dense irregular connective tissue, separates muscles, binds together muscles with similar functions, fills spaces between muscles
epimysium
a layer of dense, irregular connective tissue surrounding a skeletal muscle
perimysium
fibrous sheath enveloping each of the fascicles of skeletal muscle fibers
endomysium
areolar connective tissue layer surrounding a muscle cell or fiber
a. Z disc
b. M line
c. I band
d. A band
e. myosin (thick filament
f. actin (thin filament)
a. tropomyosin
b. myosin binding site
c. troponin
d. Ca binding site
explain a twitch
electrical impulse travels from brain down axons to neuromuscular junction to activate muscle. changes to a chemical impulse at the synaptic knob in form of acetylcholene. ACh binds to receptors on sarcolemma, which triggers electrical pulse. this travels down the T-tubes and opens Ca gated voltage channels bringing Ca into cell
explain crossbridge cycling
- Ca bind to troponin on thin filament, causing tropomyosin to move and change and expose myosin binding cites on actin
- myosin heads in cocked position bind to exposed myosin binding site on actin, forming a crossbridge between myosin and actin
- myosin head swivels toward center of sarcomere, pulling attached thin filament, called power stroke. ADP is released
- ATP binds to ATP binding site on myosin head, which causes release of myosin head from the binding site on actin
- ATP is turned to ADP by myosin and provides energy to reset myosin head
sarcoplasmic reticulum
stores calcium, wraps around myofibrils (made of myofilaments) and contains Ca pumps to pump Ca into muscle
two ways muscles use ATP
crossbridge cycling and Ca pump
three ways to generate ATP in skeletal muscle
immediate phosphate transfer, short term supply via glycolysis, long term supply via aerobic cellular respiration
lactic acid
made from pyruvic acid when O2 not available
regenerates NAD+ to feed back through glycolysis (forming NADH)
aerobic excercise
cycling, walking, jogging, swimming
increase in number of mitochondria, surrounding capillaries, myoglobin synthesis (stores little bit of O2)
no noticeable muscle hypertrophy
resistance exercises
weightlifting, isometric exercise
increase in muscle fiber size, number of mitochondria, myofilaments, and myofibrils
store more glycogen
hypertrophy
oxidative fibers
fatigue resistant
high endurance due to aerobic respiration
contractions slower, more powerful
extensive capillaries, many mitochondria
large supply of myoglobin (red fibers)
glycolytic fibers
fatigue-able
ATP is primarily anaerobic
contractions are brief
fewer capillaries, fewer mitochondria
large glycogen reserves
smaller supply of myoglobin (white fibers)
fatigue
inability to maintain desired power output of muscles
sometimes neurologic
low ATP (low O2, run out of energy reserves)
muscle twitch
the response of a motor unit to a single action potential
latent period
time betweeen neural stimulation and muscle contraction
contraction
active bridging of actin and myosin
relaxation
cross bridging stops, returning muscle to resting state
tetany
prolonged contraction caused by many impulses in quick succession
motor unit
a motor neuron and all the muscle fibers attached to it
neurons can be attached to multiple fibers, fibers attached to only one neuron
isotonic contraction
muscle length changes
concentric isotonic
muscle gets shorter as it contracts (picking up baby)
force > resistance
eccentric isotonic
muscle gets longer as it contracts (putting baby down)
force < resistance
isometric contraction
muscle length does not change (holding baby)
DOMS
delayed onset muscle shortage (being sore a day or two later)
agonist
muscle that provides major force of movement
antagonist
muscles that reverse a specific movement
synergist
work w agonist to better produced desired movement
adds more force
stabilizing joints
preloading muscle
using passive tension (in titan) to help generate force
(stretching the muscle, actin and myosin stretched apart)
muscle tone
skeletal muscle almost always slightly contracted
keeps muscles healthy, ready to respond, stabilizes joints, maintains posture
myasthenia gravis
drooping eyelids and muscle weakness
not enough ACh receptors (autoimmune disease where they are destroyed)
muscular dystrophy
destroys muscle (problems in regulating Ca entry)
appears during childhood
cardiac muscle cells
short, branching, striated fibers
one or two nuclei, many mitochondria (aerobic respiration)
intercalated discs join ends of neighboring fibers (desmosomes and gap junctions)
contractions started by heart’s autorhythmic pacemaker cells (influenced by ANS)
where is smooth muscle found
blood vessels, bronchioles, intestines, ureters, uterus
smooth muscle
fusiform shaped cells, smaller than skeletal fibers
sarcolemma has varied Ca tubes and sarcoplasmic reticulum sparse
fatigue resistant (can maintain contraction without ATP through latenbridge mechanism)
frequency
repeated firing of a single motor unit until fused tetanus is reached
recruitment
activating additional motor units to increase force
