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1st anatomy Ch.6
muscles - Ch. 6
Question | Answer |
---|---|
the four major functional characteristics of skeletal muscles | contractility, excitability, extensibility, and elasticity. |
contractility | the ability of a muscle to shorten with force. |
excitability | the capacity of skeletal muscle to respond to a stimulus. |
extensibility | the ability to be stretched. |
elasticity | the ability for muscle to recoil to their original resting length after they have been stretched. |
**important note on characteristics** | muscles help to produce heat essential for maintenance of normal body temp. |
epimysium | connective tissue sheath that surrounds skeletal muscle. |
fascia | connective tissue located outside of the epimysium, that surrounds and separates muscles; most superior. |
fascicle | bundles of muscle fibers. |
perimysium | loose connective tissue surrounding the fascicles. |
muscle fibers | muscle cells; what makes up the fasciculi. |
endomysium | connective tissue sheath surrounding the muscle fiber. |
myofibrils | thread-like structure that extends from one end of the fiber to the other; within the cytoplasm. |
2 major types of protein fibers in myofibrils | actin and 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 | highly ordered units formed by actin and myosin myofilaments. |
sarcomere | basic structural and functional unit of muscle. |
Z line | a sarcomere extends from one to the other |
I band | light area on each side of the Z line; consists of actin |
A band | darker central region in each sarcomere; extends length of myosin |
H zone | another light area in center of sarcomere; consists of only myosin |
M line | myosin anchored in center of a sarcomere; dark staining band |
resting membrane potential | outside of cell membrane positively charged, inside is negatively charged |
action potential | reversal; outside negatively charged, inside positively charged |
motor neurons | nerve cells carrying action potentials to skeletal muscle fibers |
neuromuscular junction | synapse |
neuromuscular junction/synapse | branches connecting to muscle, near center of cell |
motor unit | single motor neuron and all muscle fibers it innervates; many together form a single muscle |
formation of neuromuscular junction | enlarged nerve terminal resting in an indentation of muscle cell membrane |
presynaptic terminal | enlarged nerve terminal |
synaptic cleft | space between presynaptic terminal and muscle cell |
postsynaptic terminal | muscle fiber |
synaptic vesicles | located in presynaptic terminal; secretes acetylcholine |
acetylcholine | neurotransmitter secreted by the synaptic vesicles |
acetylcholine is released into synaptic cleft through exocytosis when... | action potentials reach the nerve terminal |
acetylcholine diffuses across synaptic cleft and... | binds to receptor molecules |
combination of acetylcholine and receptors causes and influx that... | initiates an action potential into muscle cells, causes it to contract |
acetylcholinesterase | enzyme that rapidly breaks down the acetylcholine that is released |
muscle contraction occurs as... | actin and myosin myofilaments slide past one another, causing sarcomere to shorten; which causes the muscle to shorten |
sliding filament mechanism | sliding of actin myofilaments past myosin myofilaments during contraction |
in the sliding filament mechanism... | H and I bands shorten, but the A bands do not change in length |
muscle twitch | contraction of an entire muscle in response to stimulus that causes action potential in one or more muscle fibers |
threshold | the level a stimulus has to reach for the muscle fiber to respond to a stimulus, will not happen if threshold isn't reached |
threshold | point the muscle fiber will contract maximally |
all-or-none-response | phenomenon for when the fiber will contract maximally |
lag phase | time between application of a stimulus to a motor neuron and the beginning of a contraction |
contraction phase | time of contraction |
relaxation phase | time during which the muscle relaxes |
tetany | muscle remains contracted without relaxing |
recruitment | increase in number of motor units being activated |
ATP (adenosine triphosphate) | needed for energy for muscle contraction; produced in mitochondria; short lived and unstable |
ADP (adenosine diphosphate) | ATP degenerates to this more stable plus phosphate |
creatine phosphate | high-energy molecule, when ATP can't be stored at rest |
anaerobic respiration | without oxygen |
aerobic respiration | with oxygen (more efficient) |
oxygen debt | amount of oxygen needed in chemical reactions to convert lactic acid to glucose... |
muscle fatigue | when ATP is used during muscle contraction faster than it can be produced |
isometric | (equal distance) length of muscle does not change, but amount of tension increases during contraction process |
isotonic | (equal tension) amount of tension produced is constant, but the length of muscle changes |
muscle tone | constant tension produced by muscles of body for long period of time |
fast-twitch fibers | contract and fatigue quickly |
slow-twitch fibers | contract slower and more resistant to fatigue |
origin | (head) most stationary end of the muscle |
insertion | end of the muscle undergoing greatest movement |
belly | portion of muscle between the origin and insertion |
**note on muscle anatomy | some muscles have multiple origins or head |
synergists | muscles that work together to accomplish specific movements |
antagonists | muscles that work in opposition to one another |
prime mover | one muscle that plays the major role in accomplishing the desired movement |
muscle names | descriptive; according to location, size, orientation of fibers, shape, origin, insertion, and function, etc |
occipitofrontalis | raises the eyebrows |
orbicularis oculi | closes the eyelids and causes "crows feet" wrinkles in the skin at the lateral corners of the eye |
orbicularis oris | puckers the lips |
buccinator | flattens the cheeks, trumpeter's muscle |
zygomaticus | smiling muscle |
levator labii superioris | sneering |
depressor anguli oris | frowning |
mastication | chewing |
4 pairs of mastication muscles | 2 pair of pterygoids, temporalis, and masseter |
intrinsic tongue muscles | change shape of the tongue |
extrinsic tongue muscles | move the tongue |
sternocleidomastoid | lateral neck muscle; prime mover |
platysma | sheet-like muscle that covers the anterolateral neck |
erector spinae | group of muscles on each side of the back |
thoracic muscles | muscles that move the thorax |
external intercostals | elevate the ribs during inspiration; most involved in breathing |
internal intercostals | contract during forced respiration; most involved in breathing |
diaphragm | accomplishes quiet breathing; aids in breathing; dome-shaped |
linea alba | tendinous area of abdominal wall |
rectus abdominis | on each side of the linea alba; abs |
layers lateral to rectus abdominis | superficial to deep: external abdominal oblique, internal abdominal oblique, transverses abdominis muscles |
trapezius | rotates scapula |
serratus anterior | pulls scapula anteriorly |
arm attached to thorax by | pectoralis major and latissimus dorsi muscles |
pectoralis major | adducts and flexes the arm |
latissimus dorsi | medially rotates, adducts, and powerful extends the arm; "swimmer's muscles" |
deltoid | attaches humerus to the scapula and clavicle; major abductor of the upper limb |
triceps brachii | extends forearm; posterior compartment of arm |
biceps brachii | flexes forearm; anterior compartment of arm |
brachialis | flexes forearm |
brachioradialis | flexes and supinates forearm |
flexor carpi | flexes wrist |
extensor carpi | extends wrist |
flexor digitorum | flexes fingers |
extensor digitorum | extends fingers |
intrinsic hand muscles | 19 hand muscles located within the hand |
interossi muscles | located between metacarpals; responsible for abduction and adduction of fingers |
gluteus maximus | buttocks; contributes to most of the mass |
gluteus medius | hip muscle; common injection site |
quadriceps femoris | extends leg; anterior thigh muscles |
sartorius | "tailors muscle"; flexes thigh |
hamstring muscles | posterior thigh muscles; flexes leg, extends thigh |
gastrocnemius and soleus | calf muscle; joins to form calcaneal tendon (Achilles tendon); flex foot and toes |
peroneus | lateral leg muscles; primarily everters, aid in plantar flexion |
intrinsic foot muscles | 20 muscles in foot; flex, extend, abduct, and adduct toes |