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Chapter 6: Muscles
| Question | Answer |
|---|---|
| contractility | the ability of skeletal muscle to shorten with force |
| excitability | the capacity of skeletal muscle to respond to a stimulus. |
| extensibility | the ability to be stretched |
| elasticity | ability to recoil to their original resting length after they have been stretched |
| epimysium | connective tissue sheath that surrounds skeletal muscle |
| fascia | connective tissue located outside the epimysium; surrounds and separates muscles |
| muscle fasciculi | numerous visible bundles that compose muscles |
| perimysium | loose connective tissue that surrounds muscle fasciculi |
| fibers | single muscle cells that make up the fasiculi |
| endomysium | connective tissue sheath that surrounds each fiber |
| myofibrils | a threadlike structure that extends from one end of the fiber to another |
| actin myofilaments | thin myofilaments. They resemble two minute strands of pearls twisted together |
| myosin myofilaments | thick myofilaments. They resemble bundles of minute golf clubs |
| actin and myosin myofilaments form? | sacromeres |
| sacromeres: | joined end to end to form the myofibril; basic structural and functional unity of muscle |
| Where does each sacromere extend to? | one z line to another z line |
| Z line | an attachment site for actin |
| I band | consists of actin and is on each side of z line (light area) |
| A band | extends the length of myosin, darker central region in each sacromere |
| H zone | consists of only mysoin and is in the center of each sacromere. (light area) |
| M line | dark staining band in the middle of sacromere where mysoin myofilaments are anchored |
| charge of most outside cell membranes | positive |
| charge of most inside cell membrane | negative |
| 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 fibers |
| axons enter where? | muscles and branches |
| neuromuscular junction/synapse | each branch that connects to the muscle |
| motor unit | single motor neuron and all the skeletal muscle fibers it innervates; form a single muscle |
| neuromuscular junction formed by? | an enlarged nerve terminal resting in an indentation of the muscle cell membrane |
| presynaptic terminal | enlarged nerve terminal |
| synaptic cleft | the space between the presynaptic terminal and muscle cell |
| postsynaptic terminal | the muscle fiber |
| synaptic vesicles | secrete a neurotransmitter; inside presynaptic terminal |
| acetylocholine | neurotransmitter; diffuses across the synaptic cleft and binds to the postsynaptic terminal causing a change in the postsynaptic cell |
| when action potential reaches the nerve terminal | causes the synaptic vesicles to releases acetylcholine into the synaptic cleft by exocytosis |
| the combination of acetylcholine with its receptor | causes an influx of sodium ions into the muscle fiber |
| influx causes | an action potential in the muscle cell, which causes it to contract |
| acetylcholinesterase | enzymes that break down the acetylcholine released into the synaptic cleft between the neuron and muscle cell |
| what does the enzymatic breakdown ensure? | that one action potential in the neuron yields only one action potential in the skeletal muscle, and only one contraction of the muscle cell. |
| muscle contraction | occurs as actin and myosin myofilaments slide past one another causing sacromeres to shorten |
| sliding filament mechanism | sliding of actin myofilaments past mysoin myofilaments during contraction |
| in sliding filament mechanism what happens? | the H and I bands shorten, but the A bands do not change in length |
| 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 | at which point the muscle fiber will contract maximally (aka all-or-none response) |
| lag phase | the 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 muscle relaxes |
| tetany | where the muscle remains contracted without relaxing |
| recruitment | the increase in number of motor units being activated |
| ATP | needed for energy for muscle contraction; produced in mitochondria ; short lived and unstable |
| ADP | plus phosphate |
| creatine phosphate | high-energy molecule that can be stored when atp cant be stockpiled |
| anaerobic respiration | without oxygen |
| aerobic respiration | with oxygen |
| after intense exercise.. | the respiration rate remains elevated for a period of time even though the muscles are no longer actively contracting. |
| oxygen debt | the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and to replenish the muscle cells |
| muscle fatigue | results when ATP is used during muscle contraction faster than it can be produced in the muscle cells |
| two types of muscle contractions | isometric and isotonic |
| isometric | equal distance; the length of the muscle does not change, but the amount of tension 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 | 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. They are better suited for aerobic metabolism |
| 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 |
| anatagonists | muscles that work in opposition to one another |
| prime mover | one muscle plays the major role in accomplishing the desired movement |
| occipitofrontalis | raises the eyebrows |
| orbicularis oculi | closes eyelids; causes "crows feet" |
| orbicularis oris | puckers the lips |
| buccinator | flattens the cheeks |
| zygomaticus | smiling muscle |
| levator labii superioris | snerering |
| depressor anguli oris | frowning |
| mastication | chewing |
| 4 pairs of mastication muscles | 2 pair of pterygoids, temporalis, masseter |
| intrinsic tongue muscles | change shape of tongue |
| extrinsic tongue muscles | move the tongue |
| neck muscle | sternodeidomastoid: lateral neck muscle and prime mover |
| trunk muscles | erector spinae: group of muscles on each side of back |
| thoracic muscles | muscles that move the thorax |
| muscles most involved in breathing | external intercostals and internal intercostals |
| external intercostals | elevate the ribs during inspiration |
| internal intercostals | contract during forced expiration |
| diaphragm | accomplishes quiet breathing; dome-shaped muscle; aids in breathing |
| abdominal wall muscles | flex and rotate the vertebral column, compress the abdominal cavity, and hold the abdominal viscera |
| linea alba | tendinous area of the abdominal wall that 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 |
| lateral to the rectus abdominis are layers of muscles called... | external abdominal oblique, internal abdominal oblique, and transverses abdominis muscles |
| trapezius | rotates scapula |
| serratus anterior | pulls the scapula anteriorly |
| pectoralis major and latissimus dorsi muscles | attach arm to thorax |
| pectoralis major | adducts and flexes arm |
| latissimus dorsi | medially rotates, adducts, and powerfully extends the arm. |
| deltoid | attaches the humerus to the scapula and clavicle, and is the major abductor of the upper limb |
| Triceps brachii | extends the forearm. Occupies the posterior compartment of the arm |
| Biceps brachii | flexes the forearm. Occupies the anterior compartment of the arm |
| Brachialis | flexes forearm |
| Brachioradialis | flexes and supinates forearm |
| Retinaculum (bracelet) | strong band of fibrous connective tissue that covers the flexor and extensor tendons and holds them in place around the wrist so that they do not “bowstring” during muscle contraction |
| Flexor carpi | flexes the wrist |
| Extensor carpi | extends the wrist |
| Flexor digitorum | flexes the fingers |
| Extensor digitorum | extends the fingers |
| intrinsic hand muscles | 19 hand muscles that are located within the hand |
| Interossi muscles | located between the metacarpals, are responsible for abduction and adduction of the fingers |
| Gluteus maximus | buttocks. Contributes most of the mass of the buttocks |
| Gluteus medius | hip muscle and common injection site. |
| Quadriceps femoris | extends the leg; anterior thigh muscles |
| Sartorius | “tailors muscle”; flexes the thigh |
| Hamstring muscles | posterior thigh muscles; flexes the leg and extends the thigh |
| Gastrocnemius and soleus | forms the calf muscle; They join to form the calcaneal tendon |
| calcaneal tendon (Achilles tendon) | flex the foot and toe |
| peroneus muscles | the lateral muscles of the leg; primarily everters (turning the lateral side of the foot outward) of the foot, but they also aid in plantar flexion |
| intrinsic foot muscles | 20 muscles; flex extend, abduct, and adduct the toes |
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