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Chapter 6: Muscles

Contractility The ability of skeletal muscle to shorten with force
Excitability The capacity of skeletal muscle to respond to stimulus.
Extensibility The ability to be stretched
Elasticity Ability to recoil to their original resting length after they have been stretched.
Yes Do muscles help to produce heat essential for maintenance of normal body temperature
Epimysium connective tissue sheath that surrounds each skeletal muscle
Fascia connective tissue located outside the epimysium. surrounds and separates muscles
fascicle numerous visible bundles
perimysium loose connective tissue surrounds fascicle
fibers single muscle cells
endomysium connective tissue sheath surrounding each fiber
myofibrils threadlike structure that extends from one end of the fiber to the other
2 major kinds of protein actin myofilaments myosin myofilaments
actin myofilaments thin myofilaments - resemble 2 minute strands of pearls twisted together
myosin myofilaments thick myofilaments - resemble bundles of minute golf clubs
sarcomeres joined end to end to form the myofibril basic structural and functional unity of the muscle
resting membrane potential the charge difference across the membrane
action potential brief reversal back of the charge
motor neurons nerve cells that carry action potentials to skeletal muscle fibers
neuromuscular junction branch that connects to the muscle near the center of the cell
synapse another name for neuromuscular junction
motor unit a single motor neuron and all the skeletal muscle fibers it innervates
presynaptic terminal the enlarged nerve terminal
synaptic cleft the space between the presynaptic terminal and the muscle cell
postsynaptic terminal muscle fiber
synaptic vesicles located in the presynaptic terminal;secretes a neurotransmitter called acetylcholine
acetylcholine secretion from the synaptic vesicles
sarcolemma acetylcholine diffuses across the synaptic cleft and binds to receptor molecules in the muscle cell membrane
acetylcholinesterase the acetylcholine released into the synaptic cleft between the neuron and muscle cell is rapidly broken down by an enzymes
sliding filament mechanism sliding of actin myofilament past myosin myofilaments during contraction
muscle contraction occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten
muscle twitch a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers
threshold point the muscle fiber will contract maximally
all-or-none response threshold phenomenon
lag phase the time between application of a stimulus to a motor neuron and the beginning of a contraction
contraction phase the time of contraction
relaxation phase the time during which the muscle relaxes
recruitment the increase in number of motor units being activated
ATP (adenosine triphosphate) needed for muscle contraction;produced in the mitochondria; short lived
Yes is it necessary for muscle cells to constantly produce ATP?
creatine phosphate when at rest they can't stockpile ATP but they can store another high-energy molecule
anaerobic respiration without oxygen
aerobic respiration with oxygen (more efficient)
oxygen debt the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the depleted stores of creatine phosphate stores in muscle cells
muscle fatigue results when ATP is used during muscle contraction faster than it can be produced in the muscle cells
isometric(equal distance) the length of the muscle does not change, but the amount increases during the contraction process
isotonic(equal tension) the amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes
muscle tone muscle tone refers to constant tension produced by muscles of the body for long periods of time. keeps head up and back straight
fast-twitch fibers contract quickly and fatigue quickly;well adapted to perform anaerobic metabolism
slow-twitch fibers contract more slowly and are more resistant to fatigue. better suited for aerobic metabolism
Ex. white meat of a chickens breast fast-twitch fibers
Ex. dark meat of a duck's breast or the legs of a chicken slow-twitch fibers
origin(head) the most stationary end of the muscle
insertion the end of the muscle undergoing the greatest movement
belly portion of the muscle between the origin and the insertion
synergists muscles that work together to accomplish specific movements
antagonists muscles that work in opposition to one another
prime mover synergists;the major role in accomplishing the desired movement
erector spinae group of muscles on each side of the back; responsible for keeping the back straight and the body erect.
thoracic muscles muscles that move the thorax
external intercostals elevate the ribs during inspiration
internal intercostals contract during forced expiration
diaphragm accomplished quiet breathing; dome-shaped muscle
abdominal wall muscles the muscles of the anterior abdominal wall flex and rotate the vertebral column, compress the abdominal activity, and hold in the abdominal viscera
linea alba tendinous area of the abdominal wall which consists of white connective tissue rather than muscle
rectus abdominis on each side of the linea alba
tendinous inscriptions cross the rectus abdominis at three or more locations, causing the abdominal wall of a well-muscled person to appear segmented
trapezius rotates scapula
serratus anterior pulls scapula anteriorly
pectoralis major and latissimus dorsi muscles attatches arm to the thorax
pectoralis major adducts and flexes the arm
latissimus dorsi medially rotates, adducts, and powerfully extends the arm "swimmer arm"
deltoid attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb
triceps brachii extends forearm
biceps brachii flexes the forearm
brachioradialis flexes and supinates the forearm
tetany where the muscle remains contracted without relaxing
Created by: jaaybroooke



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