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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 |
Created by:
NatalieSn
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