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Chapter 6 Muscles
Study Notes for Anatomy/Physiology Chapter 6 Skeletal 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 each skeletal muscle |
| Fascia | connective tissue located outside the epimysium that surrounds and separates muscles |
| Fasciculi | numerous visible bundles that compose muscle |
| Perimysium | loose connective tissue that surrounds the fasciculi |
| Fibers | muscle cells each fiber is a single cylindrical cell containing several nuclei |
| Endomysium | a connective tissue sheath that surrounds each fiber |
| Myofibrils | a threadlike structure that extends from one end of the fiber to the other fills the cytoplasm of each fiber |
| 2 Major Kinds Of Protein Fibers | 1. actin myofilaments 2. myosin myofilaments |
| Actin Myofilaments | thin myofilaments they resemble 2 minute strands of pearls twisted together |
| Myosin Myofilaments | thick myofilaments they resemble bundles of minute golf clubs |
| Sarcomeres | highly ordered units formed by actin and myosin myafilaments they are joined end-to-end to form the myofibril |
| The basic structural and functional unit of the muscle | The Sarcomere |
| Z line | an attachment site for actin |
| I band | Consists of actin A light area located on each side of the Z line |
| A band | extends the lenth of the myosin the darker central region in each sarcomere |
| H zone | Consists only of myosin a light area in the center of each sarcomere |
| M line | Dark staining band the center of the sarcomere where myosin myofilaments are anchored |
| Membrane Potential | Resting Membrane Potential Action Potential |
| Resting Membrane Potential | The outside of most cell membranes is positively charged compared to the inside of the cell membrane, which is negatively charged It is the charge difference across the membrane |
| Action Potential | When a muscle cell is stimulated, the membrane characteristics change briefly The brief reversal back of the charge |
| Motor Neurons | nerve cells that carry action potential to skeletal muscle fibers |
| Axons | Enter the muscles and branch |
| Neuromuscular Junction (Synapse) | formed near the center of the cell by each branch that connects to a muscle |
| Motor Unit | a single motor neuron and all the skeletal muscle fibers it innervates Many form a single muscle |
| formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane | Neuromuscular Junction |
| Presynaptic Terminal | the enlarged nerve terminal |
| Synaptic Cleft | the space between the presynaptic terminal and the muscle cell |
| Postsynaptic Terminal | the muscle fiber |
| Synaptic vesicles | in each presynaptic terminal secretes a neurotransmitter called acetylcholine |
| Acetylcholine | accumulates in the neurons causes muscle to contract |
| Acetylcholinesterase | causes the muscle to relax |
| Muscle Contraction | occurs as actin and myosin myofilaments slide past one another causing the sarcomeres to shorten when sarcomeres shorten, it causes the muscle to shorten |
| Sliding filament mechanism | the sliding of actin myofilaments past myosin myofliaments during contraction |
| Bands that shorten | H bands I bands |
| Bands that do not change in length | A bands |
| 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 | the level at which a muscle fiber will respond to stimulus the point the muscle fiber will contract maximally |
| Phenomenon that occurs in the threshold | 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 | the time of contraction |
| Relaxation Phase | the time during which the muscle relaxes |
| Tetany | the muscle doesn't have time to fully relax |
| Recruitment | the increase in number of motor units being activated |
| ATP | Adenosine triphosphate |
| ADP | Adenosine diphosphate |
| Adenosine Triphosphate | needed for energy for muscle contraction produced in the mitochondria short-lived and unstable degenearagtes to the more stable ADP plus phosphate |
| Creatine Phosphate | high energy molecule stored when muscle cells are at rest |
| Anaerobic respiration | without oxygen |
| Aerobic respiration | with oxygen more efficient |
| Oxygen debt | the amount of oxygen needed in chemical reactions to convert lactic acid to glucose and replenish the depleted stores of creatine phosphate stores in muscle cells |
| Muscle Fatigue | results when 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 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 example: white meat of a chicken's breast |
| Slow-twitch Fibers | Contract more slowly and are more resistant to fatigue they are better suited for aerobic metabolism example: the dark meat of a duck's breast of the legs of a chicken |
| Points of Attachment of Muscles | Origin Insertion At these points, the muscle is connected to bone by a tendon |
| Origin | (the head of the muscle) the most stationary end of the muscle example: shoulder |
| Insertion | the end of the muscle undergoing the greatest movement example: elbow |
| Belly | the portion of the muscle between the origin and the insertion example: arm |
| Synergists | muscles that work together to accomplish specific movements |
| Antagonists | muscles that work in opposition to one another examples: bicep and tricep |
| Prime mover | among a group of synergists, it is the one muscle that plays the major role in accomplishing the desired movement |
| Occipitofrontalis | raises eyebrows |
| Orbicularis Oculi | closes eyelid (crows feet) |
| "Kissing muscles" | Orbicularis Oris Buccinator |
| Orbicularis Oris | Puckers the lips |
| Buccinator | flattens the cheeks ("trumpeter's muscle") |
| Zygomaticus | smiling |
| Levator Labii Superioris | sneering |
| Depressor Anguli Oris | Frowning |
| Mastication | chewing |
| Mastication Muscles | Pterygoids (2pairs) Masseter (1pair) Temporalis (1pair) |
| Tongue and swallowing muscles | important in speech and mastication |
| 2 Tongue Muscles | Extrensic Tongue Muscle Intrinsic Tongue Muscle |
| Extensic Tongue Muscle | moves the tongue |
| Intrinsic Tongue Muscle | changes the shape of the tongue |
| sternocleidomastoid | prime mover lateral neck muscle rotates and abducts head |
Created by:
Harmon.jpaige
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