Muscular System Flashcards
Movement
Contraction pulls on insertion where a tendon attaches to a bone or other tissue
Posture
By producing muscle tone with continuous contractions to stabilize joints
Protection
Muscles support the walls of the abdominopelvic cavity and protectthe visceral organs ex:rectus abdominus, transverse abdominus protect the intestines
Thermogenesis
Metabolism can be regulated to produce heat and warm the body temperature
What are the functions of the muscular system
Movement, posture, protection and thermogenesis
What are the general functions of muscle tissue
excitability and contractility
Excitability
Muscles respond to stimuli
Ex:skeletal muscles stimulus comes from a motor neuron
Contractility
Muscles can shorten when stimulated
Cardiac muscle structure and location
Found in the muscular wall of the heart (myocardium), branching striated cells called cardiomyocytes have a central round nucleus and form cell junctions called intercalated disks that contain desmosomes and gap junctions.
Striations
alternating light and dark bands (stripes)
Cardiac muscle function
Contraction is involuntary, stimulated by an internal pacemaker of the heart, regulated by autonomic nervous system and endocrine system
Smooth muscle structure and location
Found in the walls of hollow organs, Spindle shaped (fusiform) cells with a central nucleus and no striations
Smooth muscles function
Contraction is involuntary, regulated by the autonomic nervous system and endocrine system
Skeletal muscle structure and location
Found attached to skeleton through tendons (dense regular CT), Long striated cells called fibers that contain multiple nuclei
Fascicle
Bundle of skeletal muscle fibers
Aponeurosis
Tendon that forms a thick flattened sheet ex:epicranial aponeurosis
Origin
Location where tendon attaches to bone that remains stationary during the action produced by contraction of that skeletal muscle
Insertion
attachment that moves during the action produced by contraction
Epimysium
Superficial covering of fibrous CT that encloses the skeletal muscle organ and connects to tendon
Perimysium
Fibrous CT covering bundles of muscle fibers called fascicles
Endomysium
Areolar CT covering individual fibers within a fascicle
Sarcolemma
Plasma membrane of muscle fiber
Myofibril
Non-membranous organelles within muscle fibers made of repeating structural and functional units called sarcomeres containing overlapping myofilaments
Sarcoplasmic reticulum
Membranous organelles similar to the smooth endoplasmic reticulum surrounding myofibrils, its primary function is storage and release of calcium
Transverse (T) tubules
Deep indentations in the sarcolemmal surface forming a network of narrow spaces filled with extracellular fluid. The sarcolemma here contains channels that allow facilitated diffusion of sodium ion from the extracellular fluid into the cytoplasm surrounding the sarcoplasmic reticulum
Terminal cisternae
Expanded chambers of sarcoplasmic reticulum adjacent to T-tubules
Sarcomere
structural and functional unit of skeletal muscle cells contains overlapping thick and thin myofilaments
Myofilaments
Fibrous proteins within myofibrils that produce contraction
Thick filaments
contain motor protein called Mysoin ATPase
Thin filaments
contain Actin (cytoskeleton protein supports shape of the cell and contains binding sites for myosin), Troponin (Calcium sensor protein), and Tropomyosin (Fibrous protein covers myosin binding sites of actin)
Z-line
Ends of sarcomere contain proteins that anchor thin filaments in place
A-band
Entire length of the thick filament
I-band
Only thin filaments with no overlap of thick filaments
H-band
Central region of thick filaments with no overlap of thin filaments
M-line
Center of H-band
Skeletal muscle function
Contraction is voluntary, controlled by somatic nervous system, somatic motor neurons excite contraction of muscle fibers
Neuromuscular junction structure
Axon terminal, motor end plate, synaptic cleft, and motor unit
Axon terminal
End of motor neuron that releases neurotransmitters to excite muscle fiber
Motor end plate
Sarcolemmal surface adjacent to axon terminal that has receptors that detect neurtransmitters
Synaptic cleft
Small space between axon terminal and motor end plate
Motor unit
a motor neuron and all of the muscle fibers it excites
Excitation
At the neuromuscular junction, the axon terminal releases acetylcholine (ACh). The motor end plate is the location of the ACh receptors in the muscle fiber sarcolemma. When ACh molecules are released, they diffuse across a minute space called the synaptic cleft and bind to the receptors that stimulate an action potential (brief reversal of the membrane potential)
Contraction
An action potential stimulates the release of calcium ions from the sarcoplasmic reticulum into flood the sarcoplasm. Calcium is the mediator of excitation contraction coupling that binds to troponin exposing the binding sites on actin to allow cross-bridge formation. A cross-bridge forms between actin and the myosin heads triggering contraction. As long as calcium ions remain in the sarcoplasm to bind to troponin, and as long as ATP is available, the muscle fiber will continue to shorten
Parallel (non-fusiform) fascicle arrangement
Fibers run straight from origin to insertion
Ex: sartorius
Parallel (fusiform) fascicle arrangement
Spindle shaped large belly tapers at end
Ex: biceps brachii
Convergent fascicle arrangement
Spread out broadly at the origin but come together to a narrow tendon for insertion
Ex: Pectoralis major
Circular fascicle arrangement
Fascicles form concentric rings that surround an opening
Ex: Obicularis oris
Pennate fascicle arrangement
“featherlike” fibers arranged at an oblique angle to a tendon. Allows the muscle to produce a large force at the expense of producing less movement
Unipennate
all muscle fibers on same side of the tendon
Ex: Extensor digitorum
Bipennate
Fibers on both sides of tendon
Ex: Rectus femoris
Multipennate
Tendon branches within the muscle
Ex:Deltoid
What are the seven criteria commonly used to name muscles?
- Shape Ex: deltoid=triangular
- Origin/Insertion Ex:Sternocleidomastoid=O-Manubrium and clavicle I-Mastoid
- Fiber direction Ex:Rectus abdominus, external and internal abdominal obliques
- # of origins Ex: Biceps brachii(2 heads), triceps brachii (3 heads)
- Location Ex:Biceps brachii (arm), biceps femoris (thigh)
- Size Ex:Extensor carpi radialis brevis (short) and longus (long), adductor magnus (largest)
- Action Ex:Extensor carpi radialis, flexor carpi radialis, adductor magnus, supinator
Prime-mover/Agonist
Main muscle responsible for action
Ex: biceps brachii
Antagonist
Muscle that stretches and stabilizes in support of the action of the agonist
Ex: Triceps brachii
Synergist
Muscles assit by adding additional force for movement or stability
Ex: Brachialis and Brachioradialis assist with flexion of elbow
