MUSCULAR SYSTEM Flashcards
Cytoplasm of the muscle cells
Sarcoplasm
Plasma membrane covering each cell
Sarcolemma
Contractile protein myosin molecules, shaped like a golf club head.
Thick Filaments
Contractile protein actin molecules also contains the regulatory proteins tropomyosin and troponin
Thin filaments
Titin and connectin keep thick and thin filaments aligned over one another for proper contraction to occur; comprise the “Z” line
Elastic filaments
Energy-storing polysaccharide abundant in muscle
Glycogen
Oxygen-storing red pigment
Myoglobin
Tunnel-like extension of the sarcolemma extending from one side of the muscle fiber to the other
T tubule
Dilated ends of sarcoplasmic reticulum adjacent to a T tubule
Terminal cisternae
A bundle of protein microfilaments
Myofibril
A threadlike complex of several hundred contractile protein molecules
Myofilament
A protein with a long shaftlike tail and a globular head; constitutes the thick myofilament
Myosin
A fibrous protein made of a long chain of G actin molecules twisted into a helix; main protein of the thin myofilament
F actin
A globular subunit of F actin with an active site for binding a myosin head
G actin
Troponin and tropomyosin, proteins that do not directly engage in the sliding filament process of muscle contraction but regulate myosin-actin binding
Regulatory proteins
A regulatory protein that lies in the groove of F actin and, in relaxed muscle, blocks the myosin-binding active sites
Tropomyosin
A regulatory protein associated with tropomyosin that acts as a calcium receptor
Troponin
A springy protein that forms the elastic filaments and Z discs
Titin
Alternating light and dark transverse bands across a myofibril
Striations
Dark band formed by parallel thick filaments that partly overlap the thin filaments
A band
A lighter region in the middle of an A band that contains thick filaments only
H band
A light band composed of thin filaments only
I band
A disc of titin to which thin filaments are anchored at each end of a sarcomere; appears as a narrow dark line in the middle of the I band
Z disc
Functions of muscle
Movement, stability, communication, control of body openings and passages, heat production
Property of muscle: respond to chemical, mechanical, or electrical stimuli
Excitability(responsiveness)
Property of muscle: initiate events that lead to contraction
Conductivity
Property of muscle: ability to shorten substantially
Contractility
Property of muscle: able to stretch between contractions
Extensibility
Property of muscle: ability to return to original length after stretching
Elasticity
3 muscle tissues
Skeletal, cardiac, smooth
contractile unit of skeletal muscle; defined as the distance between 2 Z discs
Sarcomere
Areolar CT covering each muscle fiber and binding it to its neighbors
Endomysium
Dense irregular CT covering muscle fascicles
Perimysium
Bundles of muscle fibers surrounded by perimysium
Fascicles
Covering of dense irregular CT surrounding the entire muscle
Epimysium
Skeletal muscle fascicle arrangement in which it is thick in the middle and taper at the ends
Fusiform
Skeletal muscle fascicle arrangement in which all muscle fibers are parallel
Parallel
Skeletal muscle fascicle arrangement in which fascicles are short and attach obliquely to a central tendon
Pennate
Skeletal muscle fascicle arrangement spreading out as a fan or converging to a point
Convergent
Skeletal muscle fascicle arrangement in which muscle fibers arranged concentrically
Circular
Type of muscles that are localized to a specific area and function only within that area
Intrinsic muscles
Type of muscles that extend into other areas and are responsible for movements of areas other than where they are attached
Extrinsic muscles
Muscle whose contraction is responsible for a particular movement
Prime mover or agonist
Muscles that assist the movement of the prime mover or agonist
Synergists
Muscle whose action opposes that of the prime mover or agonist
Antagonist
Stabilizes the origin of the prime mover so it can move more efficiently
Fixators
Point of attachment where least movement occurs
Origin
Point of attachment with greatest movement
Insertion
Is controlled by a nerve impulse transmitted by the motor nerve from the brain or spinal cord
Skeletal muscle contraction
Consists of all the muscle fibers controlled by a single motor neuron
Motor unit
Have fewer muscle fibers/nerves(2:1)
Fine control muscles
Initiated by an action potential and followed by the release of a chemical neurotransmitter at the neuromuscular junction
Contraction
Neurotransmitter for skeletal muscle
Acetylcholine
Functional connection between a nerve fiber and its target cell
Synapse
Synapse between a motor nerve and a muscle fiber
Neuromuscular junction
Bulbous swelling at the end of a motor nerve above the motor end plate on the muscle fiber
Synaptic knob, terminal or bouton
Gap between the synaptic knob and the motor end plate
Synaptic cleft
Small packets of neurotransmitter chemical
Synaptic vesicles
Theory in which muscle fibers are composed of many contractile units. Changes in the amount of overlap between thick and thin filaments allows for contraction and relaxation of muscle fibers
Sliding filament theory
Type of muscle contraction where myofilaments are able to slide past each other during contractions; muscle shortens
Isotonic contractions
Type of muscle contraction in which the tension in the muscles increases; muscle unable to shorten
Isometric contractions
A decrease in the angle of a joint
Flexion
An increase in the angle of a joint
Extension
The bicep muscle is shortening while contraction
Concentric muscle contraction
The bicep muscle is lengthening while contracting
Eccentric muscle contraction
A movement that brings the thumb closer to the radial bone of the forearm
Radial deviation or flexion
Draws the little finger closer to the ulnar bone, or outside of the forearm
Ulnar deviation or flexion
Moving a bone away from the midline of the body
Abduction
Moving a bone towards the midline
Adduction
Lifting upward
Elevation
Moving downward
Depression
Movement of the radius around the ulna to turn palm up
Supination
Turning the palm downward
Pronation
Moving a bone around its long axis
Rotation
Function of corrugator supercilii
wrinkles forehead
function of medial rectus
Adducts eye
Function of pelvic muscle
Support of abdominopelvic viscera through their tonic contraction. Resistance to increases in intrapelvic/abdominal pressure during activities such as coughing or lifting heavy objects. chuchu
First described in 1881; deficiency of dystrophin, resulting in progressive loss of muscle fibers
Dystrophinopathy
An autoimmune disease due to an antibody mediated attack directed against nicotinic AchR at neuromuscular junction
Myasthenia gravis
Lack of immunostaining of dystrophin in muscle biopsy specimen; demonstration of deletion in the dystrophin gene
Duchenne muscular dystrophy
The child assumes the hands-and-knees position and then climbs to a stand by walking his hands progressively up his shins, knees, and thighs
Gower’s sign
Involuntary twitches of muscles
Tic
Rhythmical, involuntary contractions of opposite groups of muscles
Tremor
Involuntary, short twitches on motor unit visible under the skin
Fasciculations
Spontaneous contractions of fibers of one muscle that aren’t visible under the skin
Fibrilace
Involuntary contraction of one muscle
Spasm
Painful spasm
Cramp
Multiple spasms of skeletal muscles
Tetanus
Inherited, muscle enlarge due to increased fat and connective tissue, but fibers degenerate and atrophy
Muscular dystrophy
An autoimmune disease due to an antibody-mediated attack directed against nicotinic AchR at neuromuscular junction
Myasthenia gravis
Functions of the pelvic muscles
Support of abdominopelvic viscera through their tonic contraction. Resistance to increases in intrapelvic/abdominal pressure during activities such as coughing or lifting heavy objects. Urinary and faecal continence
Function of corrugator supercilli
Wrinkles forehead
