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Ch.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 | A connective tissue sheath that surrounds each skeletal muscle |
| Fascia | Another connective tissue located outside the epimysium. Surrounds and separates muscles |
| Perimysium | Loose connective tissue that surrounds muscle fasciculi (fascicle) |
| A muscle is composed of... | Numerous visible bundles known as muscle fasciculi (fascicle) |
| The fasciculi are composed of... | Fibers |
| Fibers | Single muscle cells |
| Endomysium | A connective tissue sheath that surrounds each fiber |
| Myofibrils... | Fill the cytoplasm of each fiber |
| Myofibrils | A threadlike structure that extends from one end of the fiber to the other |
| 2 major kinds of protein fibers that myofibrils consist of | Actin myofilaments, myosin myofilaments |
| Actin myofilaments | Thin myofilaments |
| Myosin myofilaments | Thick myofilaments |
| Form highly ordered units called sarcomeres | Actin and myosin myofilaments |
| Sarcomere is the... | Basic structural & functional unity of the muscle |
| Resting membrane potential | The charge difference across the membrane |
| Action potential | The brief reversal back of the charge |
| Motor neurons | Nerve cells that carry action potentials to skeletal muscle fibers |
| Each branch that connects to the muscle forms a ___________ _________ or ________ near the center of the cell. | Neuromusclular junction or synapse |
| Motor unit | A single motor neuron & all the skeletal muscle fibers it innervates |
| Presynaptic terminal | Enlarged nerve terminal |
| Synaptic cleft | The space between the presynaptic terminal & the muscle cells |
| Postsynaptic terminal | Muscle fiber |
| Each presynaptic terminal contains... | Synaptic vesicles |
| Synaptic vesicles that secrete a neurotransmitter called... | Acetylcholine |
| Every muscle fiber | Cylindrical cell |
| Each muscle fiber... | contains several nuclei |
| Muscles help... | produce heat essential for maintenance of normal body temperature. |
| Action potential reaches nerve terminal | Synaptic vesicles releases acetylcholine into synaptic cleft (by exocytosis) |
| Acetylcholine diffuses across | Synaptic cleft |
| Acetylcholine | binds to receptor molecules in the muscle cell membrane (sarcolemma) |
| Combination of acetylcholine with its receptor | Influx of sodium ions into the muscle fibers |
| The influx of sodium ions into the muscle fibers initiates | Action potential in muscle cell |
| Acetylcholinesterase | The acetylcholine released into the synaptic cleft between the neuron & muscle cell is rapidly broken down by enzymes |
| Name 2 things the enzymatic breakdown ensures | 1. One action potential in the neuron yields only one action potential in the skeletal muscle. 2. Only one contraction of the muscle cell |
| Muscle contraction | Occurs as actin & myosin myofilaments slide past one another causing the sarcomeres to shorten. |
| Sarcomeres shorten | muscle shortens |
| Sliding filament mechanism | Sliding of actin myofilaments past myosin myofilaments during contraction |
| H and I bands | Shorten |
| A bands | Do not change in length |
| Muscle twitch | Contraction of entire muscle |
| Muscle fiber won't respond to stimulus until that stimulus reaches a level called... | Threshold |
| Once the stimulus reaches threshold... | Muscle fiber will contract maximally |
| Reaching threshold and muscles contract maximally known as... | All-or-none response |
| Lag phase | Time between application of a stimulus to a motor neuron & the beginning of contraction |
| Contraction phase | Time of contraction |
| Relaxation phase | Time during which the muscle relaxes |
| Tetany | The muscle remains contracted without relaxing |
| Recruitment | The increase in number of motor units being activated |
| ATP is needed for | Energy for muscle contraction |
| ATP is produced | In mitochondria |
| ATP is | Short-lived and unstable |
| ATP stands for | Adenosine triphosphate |
| 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 | Amount of oxygen needed in chemical reactions to convert lactic acid to glucose & replenish the depleted stores of creatine phosphate stores in muscle cells |
| Muscle fatigue | ATP is used during muscle contraction faster than it can be produced in the muscle cells |
| 2 types of muscle contractions | Isometric & Isotonic |
| Isometric (equal distance) | Length of the muscle does not change, but the amount of tension increases during the contraction process |
| Isotonic (equal tension) | 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. |
| Fast- twitch fibers | Contract quickly and fatigue quickly. Well adapted to perform anaerobic metabolism |
| Slow-twitch fibers | contract more slowly & are more resistant to fatigue. Better suited for aerobic metabolism |
| Points of attachment of each muscle | Its origin & insertion |
| At the attachment points the muscle is connected to | Bone by a tendon |
| Origin (head) | Most stationary end of the muscle |
| Insertion | End of the muscle undergoing the greatest movement |
| Belly | Portion of the muscle between the origin and the insertion |
| Some muscles have | Multiple origins or head |
| I band | Light area on each side of Z line. Consists of actin |
| A band | Darker central region in each sarcomere. Extends the length of the myosin |
| H zone | Center of the sarcomere (another light area.) Consist of only myosin |
| M line | Dark staining band. Myosin myofilament are anchored in the center of the sarcomere |
Created by:
syerrawilson
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