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Ch 6 Muscles


4 Major Functional Characteristics Contractility Excitability Extensibility Elasticity
Ability of skeletal muscle to shorten with force Contractility
Capacity of skeletal muscle to respond to a stimulus Excitability
Ability to be stretched Extensibility
Ability to recoil to their original resting length after they have been stretched Elasticity
Connective tissue sheath that surrounds the skeletal muscle Epimysium
Superficial to the epimysium Fascia
Fascia Surrounds and separates the muscles
Fascicle Composes a muscle
Loose connective tissue that surrounds the fascicle Perimysium
Muscle cells Muscle fibers
Connective tissue sheath that surrounds the fiber Endomysium
Myofibrils 2 major kinds of protein fibers
Actin myofilament Thin: 2 strands of pearls twisted
Myosin myofilaments Thick: bundles of golf clubs
Sarcomere Basic structural unit and function unity of the muscle
Stretches from one Z line to the next Sarcomere
I band Light area composed of actin
A band Dark composed of myosin
M line Line found in-between the A bands composed of myosin
H zone Space between A bands composed of myosin
Outside of the cell membranes Positively charged
Inside of the cell membranes Negatively charged
Charge difference across the membrane Resting membrane potential
Action potential When a muscle cell is stimulated the membrane characteristics change briefly. This is the brief reversal back
Nerve cells that carry action potentials to skeletal muscle fibers Motor neurons
Each branch that connects to the muscle forms a... near the center of the cell Neuromuscular junction; synapse
A single motor neuron and all the skeletal muscle fibers it innervates Motor unit
Neuromuscular junction Formed by an enlarged nerve terminal resting in an indentation of the muscle membrane
Enlarged nerve terminal Presynaptic terminal
Space between the presynaptic terminal and the muscle cell Synaptic cleft
Postsynaptic terminal Muscle fiber
Each presynaptic terminal contains Synaptic vesicles
Synaptic vesicles Secrete a neurotransmitter caller acetylcholine
Acetylcholine Diffuses across the synaptic cleft and binds to the postsynaptic terminal Causing a change in the postsynaptic cell
Acetycholinesterase An enzyme that rapidly breaks down acetylcholine which is released into the synaptic cleft between the neuron and muscle cell
Sliding filament mechanism The sliding of actin myofilaments slide past myosin myofilaments during contraction
During a contraction, what bands shorten and what band does not change in length H and I bands shorten. A does not change
Muscle Twitch A contraction of an entire muscle in response to a stimulus that causes the action potential in one or more muscle fibers
A muscle fiber will not respond to stimuli until that stimulus reaches a level called Thresh hold
All-or-none response Refers to the threshold thing
Lag phase 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 which the muscle relaxes
Tetany Where the muscle remains contracted without relaxing
The increase in number of motor units being activated is called recruitment
ATP Adenosine triphosphate
Needed for energy for muscle contraction ATP
ATP is produced by Mitochondria
ADP Adenosine diphosphate
Creatine phosphate Stored in place of ATP and is used for energy
Anaerobic Without oxygen
Aerobic With oxygen (more efficient)
Muscle fatigue Results when ATP is used during muscle contraction faster than it can be produced in the muscle cells
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. Oxygen debt
2 types of muscle contractions Isotonic and Isometric
Isotonic (equal tension) The amount of tension produced by the muscle is constant while the distance of the muscle changes (bowling)
Isometric (equal distance) The distance of the muscle stays the same while the tension of the muscle changes
Muscle Tone 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 (chicken breast// white meat)
Slow-Twitch fibers Contract more slowly and are more resistant to fatigue. Better suited for aerobic metabolism (chicken legs// dark meat)
4 pairs of mastication muscles 2 pairs of pterygoids, temporalis, and masseter
Zygomaticus Smiling muscles
Intrinsic Tongue Muscle Change the shape of the tongue
Orbicularis Oris Puckers the lips
Levator Labii Superious Sneering
Depressor Anguli Oris Frowning
Antagonists Muscles that work in opposition to one another
Extrinsic Tongue Muscle Move the tongue
Buccinator Flattens the cheeks. Trumpeter's muscle
Which 2 muscles or involved in kissing Orbicularis oris and the buccinator
Sternocleidomastoid Lateral neck muscle and prime mover. Rotates and abducts the head
Synergists Muscles that work together to accomplish specific movements
Insertion The end of the muscle undergoing the greatest movement
Mastication Chewing
Occipitofrontalis Raises the eyebrows
Prime mover Among a group of synergists, the muscle that plays the major role in accomplishing the designed movement
Orbicularis Oculi Closes the eyelids and causes "crow's feet" wrinkles in the skin at the lateral corners of the eye
Belly Portion of muscle between the origin and the insertion
Origin (head) most stationary end of the muscle
Created by: erharpe2



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