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Muscles Chapter 6


Contractility ability of skeletal muscle to shorten with force
Excitability capacity of skeletal muscle to respond to a stimulus
Extensibilty ability to be stretched
Elasticity ability to recoil to their original resting length after they have been stretched
Muscles help Helps produce heat essential for maintenance of normal body temperature
Epimysium connective tissue sheath that surrounds each skeletal muscle directly upon it
Fascia most superficial connective tissue outside the epimysium which surrounds and separates the muscles
Fasciculi numerous visible bundles that compose muscle
Perimysium loose connective tissue which surrounds that fasciculi
Four major functional characteristics of muscles contractility, excitability, extensibility, elasticity
Muscle cells muscle fibers
What fasciculi are compose of muscle fibers (muscle cells)
Single cylindrical cell containing several nuclei each muscle fiber
Endomysium connective tissue sheath that surrounds each muscle fiber
Cytoplasm of each fiber is filled with this myofibrils
Myofibril threadlike structure that extends from one end of the fiber to the other
2 major kinds of myofibrils actin and myosin myofilaments
Actin myofilament thin myofilaments which resemble 2 pearl strands twisted together
Myosin myofilaments thick myofilaments that resemble bundles of golf clubs
Sarcomere highly ordered unit formed by actin and myosin filaments that join end to end and form a myofibril. Basic structural and functional unity of the muscle that Extends from z line to z line
Z line attachment point for actin
I band light area on each side of a z line that consists of actin
A band darker central region in each sarcomere that extends the length of the mysoin
H zone light center of each sarcomere that consists of only myosin
M line myosin myofilaments are anchored in the center of the sacromere at a dark staining band
Resting Membrane Potential the charge difference across the membrane
Positive Charge outside of most cell membranes
Negative Charge inside of most cell membranes
Action Potential Reversal back of the charge when a muscle cell is stimulated that characteristics change briefly
Motor Neurons nerve cells that carry action potentials to skeletal muscle fibers
Where Axons enter The muscles and branch
Neuromuscular Junction (synapse) what forms near the center of the cell when a branch connects to the muscles
Motor Unit a single motor neuron and all the skeletal muscle fibers it innervates. motor units form a single muscle
How a neuromuscular junction is formed when an enlarged nerve terminal resting in an indentation of the muscle cell membrane
Presynaptic terminal enlarged nerve terminal
Synaptic cleft space between the presynaptic terminal and the muscle cell
Postsynaptic terminal the muscle fiber
Acetylcholine diffuses across the synaptic cleft and binds the postsynaptic terminal causing a change in the postsynaptic cell
Synaptic Vessels within each presynaptic terminal and secrete a neurotransmitter called acetylcholine
Acetylcholinesterase rapid enzymatic breakdown when acetylcholine is released into the synaptic cleft between the neuron and the muscle cell which ensures that one action potential in the neuron yields only one action potential in the skeletal muscle, and only one contraction
Muscle contraction 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.
H and I bands during muscle contraction shorten
A bands during muscle contraction do not change length
Threshold when a muscle fiber will not respond to stimulus
all-or-none response when threshold happens and the muscle fiber contracts maximally
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
Successive twitches occur when successive stimuli are given so frequently, the muscle doesn't have time to fully relax
Tetany where the muscle remains contracted without relaxing
Recruitment increase in number of moror units being activated
ATP adenosine triphosphate needed for energy for muscle contraction. Produced through mitochondria, short-lived and unstable.
ADP adenosine diphosphate is was ATP degenerates too. more stable
Muscle cells constantly produce ATP
Creatine phosphate ATP can't stockpile, but is stored as this high energy molecule
Anaerobic respiration with out oxygen
Aerobic respiration with oxygen
oxygen debt 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 when ATP is used during muscle contraction faster than it can be produced in the muscle cells
2 typed of muscle contraction isometric and 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 length of the muscle changes but the tension remains constant
muscle tone refers to constant tension produced by muscles of the body for long periods of time. (keep up and back straight)
fast-twitch fibers contract quickly and fatigue quickly. well adapted to perform anaerobic metabolism (white meat of chicken breast)
slow-twitch fibers contract more slowly and are more resistant to fatigue. They are better suited for aerobic metabolism (dark meat of chicken legs)
Attachment points for muscle origin and insertion
Origin most stationary end of a muscle
Insertion end of a muscle undergoing the greatest movement
Belly portion of muscle between the origin and insertion
Multiple origins 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
Prime mover a muscle that plays a major role in a group of synergist
Nomenclature how muscles are named by location, size, orientation of fibers, shape, origin, insertion, and function
frontalis raises eyebrows
orbicularis oculi closes eyes
orbicularis oris moves mouth
buccinator flattens cheeks
zygomatic smiling
levator labil superioris sneering
depressor anguli oris frowning
mastication chewing
4 pairs of chewing muscles temporalis, masseter, and pterygoid
2 types of tongue muscles intrinsic and extrinsic
Intrinsic tongue muscles changes shape of tongue
extrinsic tongue muscles moves tongue
Soft palate muscles close the posterior nasal cavity to keep liquid and food from entering it
swallowing constriction of the pharynx and larynx, elevation of the pharynx
pharyngeal elevators elevate pharynx
pharyngeal constrictors constrict pharynx
sternocleidomastoid lateral neck muscle that rotates and abducts the head
torticollis twisted/wry neck
sacrolemma oval nuclei that can be seen beneath the plasma
axon neuron process that carries impluses away from the nerve cell body; the conducting portion of a nerve cell
fixators muscles acting to immobilize a joint or bone; fixes the origin of a muscle so the muscle action can be exerted at the insertion
motor unit motor neuron and all the muscle cells it supplies
internal intercostals inhale
external intercostals forced exhale (sigh)
diaphragm dome shaped muscle that divides thoracic cavity from the abdominal cavity (quiet breathing)
Abdominal muscle keeps guts in
lines alba white line down the middle of the abdomen
rectus abdominis abdominals; external obliques; flexes the vertebral column
tendinous inscriptions white connective tissue that crosses the rectus abdominis to give a segmented look (abs)
arrector spinea on each side of the vertebral column; keep back straight and body erect
Face and Neck muscles temporalis, frontalis, orbicularis oculi, zygomaticus, orbicularis oris, sternocleidomastiod, masseter, platysma
arm muscles deltoid, triceps brachii, biceps brachii, brachialis, brachioradialis, flexor carpi radialis
Trunk muscles pectoralis major, rectus abdominis, external oblique, latissimus dorsi, gluteus medius, gluteus maximus
leg muscles quadriceps, satorius, hamstrings, gastrocnemius, soleus, extensor digitorum longus, calcaneal (achilles) tendon
Created by: lucyjw12