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Muscles Terms

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 surrounding skeletal muscle.
fascia connective tissue located outside the epimysium. It surrounds and separates muscles.
perimysium Surrounds muscle fascicles.
fascicles bundles of muscle tissue.
endomysium surrounds each muscle fiber (cell).
muscle cells muscle fibers
myofibrils a threadlike structure that extends from one end of the fiber to the other.
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 units formed by Actin and myosin myofilaments which are joined end to end to form the myofibril. basic structural and functional unit of the muscle.
Z line borders of sarcomeres. attachment site for actin.
cause of banded appearance of muscles arrangement of actin and myosin
I band On each side of the Z line is a light area, [term]. Consists of actin.
A band extends the length of the myosin. It is the darker central region in each sarcomere.
H zone In the center of each sarcomere is another light area called the [term], which consists of only myosin.
M line The myosin myofilaments are anchored in the center of the sarcomere at a dark staining band called the [term].
resting membrane potential The outside of most cell membranes is positively charged compared to the inside of the cell membrane, which is negatively charged. The charge difference across the membrane is called the [term].
action potential When a muscle cell is stimulated the membrane characteristics change briefly. The brief reversal back of the charge is called [term].
motor neurons nerve cells that carry action potentials to skeletal muscle fibers.
synapse neuromusclular junction
neuromusclular junction Axons enter the muscles and branch. Each branch that connects to the muscle forms a [term]. formed by an enlarged nerve terminal resting in an indentation of the muscle cell membrane.
motor unit single motor neuron and all the skeletal muscle fibers it innervates.
presynaptic terminal enlarged nerve terminal.
synaptic cleft space between the presynaptic terminal and the muscle cell.
postsynaptic terminal the receiving part of the connection (synapse) between two nerve cells (neurons). muscle fiber.
synaptic vesicles vesicles that secrete a neurotransmitter called acetylcholine
acetylcholine neurotransmitter which causes muscle contraction.
acetylcholinesterase enzyme that breaks down acetylcholine.
Muscle Contraction 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.
sliding filament mechanism The sliding of actin myofilaments past myosin myofilaments during contraction. The H and I bands shorten, but the A bands do not change in length.
threshold point at which stimulus becomes strong enough for muscle to respond by contracting maximally. This phenomenon is called the 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 where the muscle remains contracted without relaxing.
recruitment The increase in number of motor units being activated.
ATP (adenosine triphosphate) is needed for energy for muscle contraction.
mitochondria produces atp
ADP (adenosine diphosphate) plus phosphate. what atp degenerates into.
creatine phosphate more stable high energy molecule stored in muscles.
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.
Muscle fatigue results when ATP is used during muscle contraction faster than it can be produced in the muscle cells.
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 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. Ex. 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. Ex. dark meat of a duck’s breast or the legs of a chicken).
origin (head) is the most stationary end of the muscle.
insertion the end of the muscle undergoing the greatest movement.
belly The portion of the muscle between the origin and the insertion.
synergists Muscles that work together to accomplish specific movements.
antagonists Muscles that work in opposition to one another.
prime mover Among a group of synergists, if one muscle plays the major role in accomplishing the desired movement.
Occipitofrontalis raises the eyebrows.
Orbicularis oculi closes the eyelids and causes “crows feet” wrinkles in the skin at the lateral corners of the eye.
Orbicularis oris puckers the lips.
Buccinator flattens the cheeks. Trumpeter’s muscle. Orbicularis oris and buccinator are the kissing muscles.
Zygomaticus smiling muscle.
Levator labii superioris sneering
Depressor anguli oris frowning
Mastication chewing
4 pairs of mastication muscles 2 pair of pterygoids, temporalis, and masseter.
Intrinsic Tongue Muscles change the shape of the tongue.
Extrinsic Tongue Muscles move the tongue.
Sternocleidomastoid lateral neck muscle and prime mover. Rotates and abducts the head
Erector spinae group of muscles on each side of the back. Responsible for keeping the back straight and the body erect.
Thoracic Muscles muscles that move the thorax
External intercostals elevate the ribs during inspiration
Internal intercostals contract during forced expiration.
Diaphragm accomplishes quiet breathing. Dome-shaped muscle. Aids in breathing.
Trapezius rotates scapula
Serratus anterior pulls scapula anteriorly
Created by: onjarre
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