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Skeletal Muscles
| Term | Definition |
|---|---|
| Contractility | The ability to shorten with force |
| Excitability | Capacity to respond to a stimulus |
| Extensibility | Ability to be stretched |
| Elasticity | Recoil to their original resting length after they have been stretched |
| Skeletal muscle is surrounded by a connective tissue sheath called what? | Epimysium |
| Fascia | Another connective tissue that surrounds and separates muscles |
| Fasciculi | Numerous visible bundles |
| Fasciculi are surrounded by loose connective tissue called what? | Perimysium |
| Fasciculi are composed of single muscle cells called what? | Fibers |
| Each fiber is surrounded by a connective tissue sheath called what? | Endomysium |
| A threadlike structure that extends from one end of the fiber to the other? | Myofibrils |
| Myofibrils consist of 2 major kinds of protein fibers. What are they? | Actin & Myosin |
| Define actin. | Thin myofilaments. They resemble 2 minute strands od pearls twisted together. |
| Define myosin. | Thick myofilaments. They resemble bundles of minute golf clubs |
| Actin an myosin myofilaments form highly ordered units called what? | Sarcomeres |
| Basic structural and functional unity of the muscle | Sarcomere. |
| .... joined end to end to form the myofibril. | Sarcomeres. |
| Muscles help to produce what? | Heat essential for maintenance of normal body temperature. |
| Each side of the Z line is a light area called what and consists of what? | I Band, and consists of actin. |
| The A band extends the what of the myosin? | The length. |
| In the center of each sarcomere is another light area called what and consists of what? | H band zone, and consists of only myosin. |
| Myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called what? | The M line |
| The charge difference across the membrane is called what? | Resting Membrane Potential |
| An attachment site for actin? | Z line |
| The brief reversal back of the charge is called what? | Action potential |
| Nerve cells that carry action potentials to skeletal muscle fibers? | Motor Neurons |
| Each branch that connects to the muscle forms a what near the center of the cell? | Neuromuscular junction, or synapse |
| A single motor neuron and all the skeletal muscle fibers it innervates are called what? | Motor Unit |
| How is a neuromuscular junction formed? | By an enlarged nerve terminal resting in an indentation of the muscle cell membrane. |
| The enlarged terminal is called what? | Presynaptic terminal |
| Synaptic Cleft | Space between the presynaptic terminal and the muscle cell |
| Postsynaptic Terminal | Muscle Fiber |
| Each presynaptic terminal contains synaptic vesicles that secrete a neurotransmitter called what? | Acetylcholine |
| The acetylcholine released into the synaptic cleft between the neuron and muscle cell is rapidly broken down by an enzymes | Acetylcholinesterase |
| Muscle contractions | Occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten |
| Sliding Filament Mechanism | The sliding of actin myofilaments past myosin myofilaments during contraction |
| 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 stimulus until that stimulus reaches a level called what? | Threshold |
| The phenomenon | All-or-none response |
| Lag phase | The time between application of a stimulus to a motor neuron and the beginning of a contraction |
| Time of contraction | Contraction phase |
| The time during which the muscle relaxes | Relaxation phase |
| Tetany | Where the muscle remains contracted without relaxing |
| The increase in number of motor units being activated | Recruitment |
| Name 3 things about ATP | 1.) It's needed for energy for muscle contraction 2.) It's produced in the mitochondria 3.) It's short-lived and unstable |
| High-energy molecule | Creatine Phosphate |
| Anaerobic Respiration | Without Oxygen |
| Aerobic Respiration | With Oxygen |
| Oxygen Debt | 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 |
| Results when ATP is used during muscle contraction faster than it can be produced in the muscle cells | Muscle Fatigue |
| 2 types of muscle contractions? | 1.) Isometric 2.) Isotonic |
| Isometric | The length of the muscle does not change, but the amount of tension increases during the contraction process |
| Isotonic | 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 | Muscle tone |
| Contracts quickly and fatigue quickly; well adapted to perform anaerobic metabolism | Fast-twitch fibers |
| Contract more slowly and are more resistant to fatigue; they are better suited for aerobic metabolism | Slow-twitch fibers |
| The most stationary end of the muscle | Origin (head) |
| The end of the muscle undergoing the greatest movement | Insertion |
| The portion of the muscle between the origin and the insertion | Belly |
| Synergists | Muscles that work together to accomplish specific movements |
| Antagonists | Muscles that work in opposition to one another |
| Among a group of synergists, if one muscle plays the major role in accomplishing the desired movement, it is the what? | Prime Mover |
| Occipitofrontalis | Raises Eyebrows |
| Orbicularis Oculi | Closes Eyelid (Crows Feet) |
| Orbicularis Oris | Puckers the Lips |
| Buccinator | Flattens the Cheeks |
| Zygomaticus | Smiling |
| Levator Labii Superioris | Sneering |
| Depressor Anguli Oris | Frowning |
| Mastication | Chewing |
| 2 tongue muscles | 1.) Extrinsic 2.) Intrinsic |
| Extrinsic | Moves the tongue |
| Intrinsic | Changes the shape of the tongue |
| 2 Mastication muscles | Masseter and Temporalis |
| 2 Kissing Muscles | Buccinator and Orbicularis Oris |
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hannahxoxo
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