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Chapter 6: Muscles
| Question | Answer |
|---|---|
| What are the four major functional characteristics of the skeletal muscles? | Contractility, Excitability, Extensibility, and Elasticity. |
| The ability of skeletal muscle to shorten with force is... | Contractility. |
| The capacity of skeletal muscle to respond to a stimulus is... | Excitability. |
| The ability to be stretched is... | Extensibility. |
| The ability to recoil to their original resting length after they have been stretched... | Elasticity. |
| What do muscles do? | Muscles help produce heat essential for maintenance of normal body temperature. |
| Each skeletal muscle is surrounded by a connective tissue sheath called the what? | Epimysium. |
| What is another connective tissue located outside the epimysium that surrounds and separates muscles? | Fascia. |
| What are the numerous visible bundles that compose muscle? What loose connective tissue are they surrounded by? | Fasciculi, and they are surrounded by the perimysium. |
| What are the single muscle cells that fasciculi composed of? | Fibers. |
| What is each muscle fiber? | A single cylindrical cell containing several nuclei. |
| Each muscle fiber is surrounded by a connective tissue sheath called the what? | Endomysium. |
| The cytoplasm of each fiber is filled with what? | Myofibrils. |
| What are myofibrils? | A threadlike structure that extends from one end of the fiber to the other. |
| What 2 major kind of protein fibers do myofibrils consist of? | Actin myofilaments and myosin myofilaments. |
| What are actin myofilaments? | Thin myofilaments, that resemble two strands of pearls twisted together. |
| What are myosin myofilaments? | Thick myofilaments, that resemble bundles of minute golf clubs. |
| Actin and myosin myofilaments form highly ordered units called... | Sarcomeres, which are joined end to end to form the myofibril. |
| What is the sarcomere? | It is the basic structural and functional unity of the muscle. |
| Each sarcomere extends from what to what? | From one Z line disc to another Z line disc. |
| Each Z line is an attachment site for what? | Actin. |
| What gives a banded appearance? | The arrangement of actin and myosin. |
| On each side of the Z line is a light area called the what? What does it consist of? | The I band, and it consists of actin. |
| The A band... | Extends the length of the myosin, and is the darker central region in each sarcomere. |
| In the center of each sarcomere is another light area called... | The H zone, which consists of only myosin. |
| The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the what? | The M line. |
| The inside of the cell membrane is charged how? | Negatively. |
| The outside of the cell membrane is charged how? | Positively. |
| The charge difference across the membrane is called the... | Resting membrane potential. |
| The brief reversal back of the charge is called the... | Action potential. |
| What are nerve cells that carry action potentials to skeletal muscle fibers? | Motor neurons. |
| Each branch that connects to the muscle forms a what? Near what? | Neuromuscular junction, or synapse, near the center of the cell. |
| What is a single motor neuron and all the skeletal muscle fibers it innervates called? | A motor unit. |
| What do many motor units form? | A single muscle. |
| How is a neuromuscular junction formed? | By an enlarged nerve terminal resting in an indentation of the muscle cell membrane. |
| What is the enlarged nerve terminal? | Presynaptic terminal. |
| What is the space between the presynaptic terminal and the muscle cell? | The synaptic cleft. |
| What is the muscle fiber? | The postsynaptic terminal. |
| Each presynaptic terminal contains what, and what do they secrete? | Synaptic vesicles that secrete a neurotransmitter called acetylcholine. |
| The acetylcholine released into the synaptic cleft between the neuron and the muscle cell is rapidly broken down by an enzyme called what? | Acetylcholinesterase. |
| Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten. When the sarcomeres shorten, it causes the muscle to shorten. | Muscle contraction. |
| The sliding of actin myofilaments past myosin myofilaments during contraction is called what? During this, the H and I bands shorten, but the A bands do not change in length. | The sliding filament mechanism. |
| What is a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers? | Muscle twitch. |
| A muscle fiber will not respond to a stimulus until... | Threshold, or when the muscle fiber will contract maximally. This is also called the all-or-none response. |
| The time between application of a stimulus to a motor neuron and the beginning of a contraction is the what? | Lag phase. |
| The time of contraction is... | Contraction phase. |
| The time in which the muscle relaxes is the... | Relaxation phase. |
| Where the muscle remains contracted without relaxing is called... | Tetany. |
| The increase in the number of motor units being activated is called what? | Recruitment. |
| What is needed for energy for muscle contraction? | ATP (Adenosine Triphosphate). |
| Where is ATP produced? | In the mitochondria. |
| ATP is... | Short lived and unstable, and degenerates to the more stable ADP (Adenosine Diphosphate) plus phosphate. |
| Anaerobic respiration... | Without oxygen. |
| Aerobic respiration... | With oxygen (more efficient). |
| The oxygen debit is what? | 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. |
| What results when ATP is used during muscle contraction faster than it can be produced in the muscle cells? | Muscle fatigue. |
| What are the 2 types of muscle contractions? | Isometric (equal distance) and Isotonic (equal tension). |
| The length of the muscle does not change, but the amount of tension increases during the contraction process? | Isometric. |
| The amount of tension produced by the muscle is constant during contraction, but the length of the muscle changes? | Isotonic. |
| Refers to constant tension produced by muscles of the body for long periods of time, and keeps the head up and the back straight... | Muscle tone. |
| What contracts quickly and fatigues quickly, and is well adapted to perform anaerobic metabolism (ex. white meat)? | Fast twitch fibers. |
| What contracts more slowly and is more resistant to fatigue, and is better suited for aerobic metabolism (ex. dark meat)? | Slow twitch fibers. |
| The points of attachments of each muscle are its... | Origin and insertion. |
| At these attachment points the muscle is connected to a bone by a what? | Tendon. |
| What is the most stationary end of the muscle? | The origin (head). |
| What is the end of the muscle undergoing the greatest movement? | The insertion. |
| What is the portion of the muscle between the origin and insertion? | The belly. |
| Some muscles have multiple... | Origin or head. |
| Muscles that work together to accomplish specific movements are called what? | Synergists. |
| Muscles that work in opposition to one another are called what? | Antagonists. |
| Among a group of synergists, if one muscle plays the major role in accomplishing the desired movement, it is the what? | Prime mover. |
| Most muscles have names that are... | Descriptive. |
| Some are named according to their what? | Location, size, orientation of fibers, shape, origin, insertion, and function. |
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jessicamitchell