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Anatomy

Chapter 6 Muscles

TermDefinition
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
Fascia connective tissue located outside the epimysium, it surrounds and separates muscles
Perimysium loose connective tissue
Fibers fasciculi are composed of single muscle cells
Endomysium fibers surrounded by a connective tissue stealth
myofibrils a threadlike structure that extends from one end of the fiber to the other
actin myofilaments type of protein fiber, they resemble 2 minute strands of pearls twisted together
myosin myofilaments thick myofilaments
sarcomeres actin and myosin myofilaments from highly ordered units
resting membrane potential charge across membrane
action potential the brief reversal back of the charge
motor neurons nerve cells that carry action potentials to skeletal muscle fibers
neuromuscular junction each branch that connects to the muscle
synapse near the center of the cell
motor unit a single motor neuron and all skeletal muscle fibers it innervates
presynaptic terminal the enlarged nerve terminal
synaptic cleft the space between the presynaptic terminal and the muscle cell
postsynaptic terminal muscle fiber in the between the presynaptic terminal
synaptic vesicles each presynaptic terminal contains this
acetylcholine that secrete neurotransmitter
acetylcholinesterase it's released into the synaptic cleft between the neuron and muscle cell is rapidly broken down by enzymes
sliding filament mechanism sliding of actin myofilaments past myosin myofilaments during contraction
muscle twitch a contraction of an entire muscle in response to a stimulus that causes the action potential in one or more fibers
threshold a muscle fiber that will not respond to stimulus reaches a level
all-or-none response threshold phenonmenon
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 the time during which
relaxation phase time during which the muscle relaxes
tetany where the muscle remains contracted without relaxing
recruitment the increase in the number of motor units being activated
ATP (adenosine triphosphate) needed for energy for muscle contraction
ATP is produced by mitochondria
ATP is short-lived and unstable
It degenerates to the more stable ADP plus Phosphate
creatine phosphate can store high energy molecule
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
muscle fatigue results when ATP is used during muscle contraction faster than it can be produced
isometric length of muscle does not change, but amount of tension increases during contraction process
isotonic amount of tension produced by the muscle is constant during contraction but the length of the muscle changes
muscle tone constant tension produced by muscles of the body for a long period of time
fast-twitch fibers contract quickly and fatigue quickly
slow-twitch fibers contact more slowly and are more resistant to fatigue
origin (head) most stationary end of the muscle
insertion the end of the muscle undergoing the greatest movement
belly where the portion of muscle between the origin and the insertion
some muscles have multiple origins or head
synergists muscles that work together to accomplish specific movements
antagonists muscles that work in opposition to one another
most muscles have names that are descriptive
some muscles are named according to location, size, orientation of fibers, shape, origin, insertion and function, etc.
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
zygomaticus smiling muscle
levator labii supererioris sneering
62 buccinator flattens the cheeks
orbicularis oris and buccinator kissing muscles
depressor anguli frowning
intrinsic tongue muscle change shape of tongue
extrinsic tongue muscle move the tongue
sternocleidomastoid lateral neck muscle and prime mover
erector spinae group of muscle and prime mover.
external intercostals elevate the ribs during inspiration
internal intercostals contract during forced expiration
diaphragm accomplishes quiet breathing
trapezius rotates scapula
serratus anterior pulls scapula anteriorly
pectoralis major adducts and flexes the arm
latissimus dorsi medially rotates, adducts, and powerfully extends the arm
Created by: drewcyrus_