Musculoskeletal System Flashcards
Produce movement of the skeleton
Maintain posture and body position
Support and control soft tissues (and circulation)
Regulate orifices
Maintain body temperature
Store nutrient reserves
Most prevalent type, somatic, striated, multi-nucleated, and voluntary
Structure from combined tissue types (muscle, connective tissue, and nerves)
Skeletal muscle
Limited to heart (myocardium), visceral, striated, involuntary
Cardiac Muscle
Lining of gut, blood vessels, and glands, visceral, non-striated, and involuntary
Smooth Muscle
Contract to expel contents of secreting glands
Myoepithelial cells
Epimysium
Muscle. Dense layer of collagen fibers
Perimysium
Fascicle. Collagen and elastin fibers.
Contain branching blood vessels and nerves.
About 100 microns diameter
Endomysium
Surrounding muscle fiber cells. Elastin connective tissue.
Formed from collagen fibers of perimysium and epimysium
Attach skeletal muscle to bone
Collagen fibers extend into bone matrix to provide firm attachment
Tendons
Relatively long (up to 30cm long)
Multinucleated (myoblasts fuse into muscle fibers)
Rich in mitochondria
Stem cells replace damaged fibers
Skeletal muscle fibers
Compose skeletal muscle fiber
Consist of bundles of protein filaments called myofilaments
Thin (actin)
Thick (myosin)
Actively shorten to produce overall muscle contraction
Myofibrils
Basic contractile unit of a muscle
Boundaries are the Z-lines
Center is the M-line
I-band composed of myosin filaments - overlaps actin except in H zone
Sarcomere
During a contraction
H-zone and I-bands get smaller
Zones of overlap increase
Z-lines move closer together
A-band width remains constant
Motor Unit
Motor neuron and all the muscle fibres it supplies
The amount of tension produced depends on the number of these units stimulated to contract
Large motor units
Erector spinae posture muscles
Small motor units
Fingers, eye muscles; fine motor control
Electrical impulse transmitted to neuromuscular junction at synaptic terminal
Release of neurotransmitter (acetylcholine) across synaptic cleft - signals al myofibrils in range to contract
Muscle Contraction
Cross bridges
form when myosin binds to actin
Myosin head pivots towards M-line
ADP + P released
Muscle tension exceeds load
Muscle shortens
(contraction - example: upwards movement of bicep)
Concentric muscle contraction
Load exceeds muscle tension
Muscle lengthens
(elongation - example: downwards movement of bicep)
Eccentric
Muscle tension equals load
Muscle length as a whole does not change
Typically oppose the force of gravity
No overall joint movement
Isometric
Tension constant as length changes
Isotonic
The movement of large numbers of calcium ions through membranes set up an electrical field, which is measured by this.
Electromyography
Types of muscle fibers
parallel, convergent, pennate, circular
Example of parallel muscle fiber
Biceps brachii. Adds force and contraction to one direction of movement.
Example of convergent muscle fiber
Pectoralis major. Muscle fibers go in different directions, and converge on a point of action on the skeleton.
Example of pennate muscle fibers
Rectus femoris (bipennate), deltoid (multipennate), extensor digitorum (unipennate)
Example of circular muscle fibers
Around eyes or mouth
Fascicles parallel to long axis of muscle - efficient motion and force
Most common type
Contraction: muscle gets shorter and belly (middle of muscle) gets wider
Parallel muscle fibers
Fascicles originate over wide area and converge on common attachment site - not as much force
Direction of pull can be changed depending on which fascicles contract
Convergent muscle fibers
Tendon runs into muscle
Fascicles form oblique angles to tendon
Contain more muscle fibres than parallel of same size - generates more tension
Unipenate - on one side of tendon
Bipenate - on both sides of tendon
Multipenate - tendon branches within
Pennate muscle fibers
Fascicles concentrically arranged around opening of recess
Form sphincters
Contraction reduces diameter of opening
Circular muscle fibers
tendons
bone to muscle
ligaments
bone to bone
Fulcrum between force and resistance
Relatively large range of movement, but requires large force
Face hanging off where the neck attaches at the occipital bone is resistant by muscles in the back of the neck.
First class lever
Resistance is between the force and fulcrum
Force is farther from the fulcrum than the resistance
Therefore a small force can move a larger weight
Resistance moves slowly and covers a short distance
Chewing a jawbreaker: Muscles in the jaw pulling up at the side of the face. Fulcrum is at temporal mandibular joint, load is at the back of the molar, and forces are on the mandible of the jaw.
Second class lever
Force applied between resistance and fulcrum
Speed and distance traveled increases at the expense of effective force
Muscles must generate greater tension to support resistance/weight at end of lever
Most common lever type in the body
Jaw for a load at the incisors
Third class lever
Agonist
Prime mover muscle
Synergist
Assists agonist muscle
Antagonist
Opposes the movement of an agonist muscle
Fixator
Steadies joint
Moves and stabilizes the trunk
Facilitates breathing
Divided into anterior (hypaxial) and posterior (epaxial) musculature
Trunk Musculature
Moves ribs
Supports abdominal viscera
Maintains inter-abdominal pressure (key for breathing and digestion)
Anterior (hypaxial) musculature
Maintains body position
Supports head and neck
Erector spinae group composed of longissimus, spinalis, and illiocostalis
Shoulder musculature
Stabilize scapula during arm movement, rotate glenohumeral joint
Posterior (epaxial) musculature
Muscular covering of the abdominal cavity
Compress abdomen, rotate/flex trunk, stabilize trunk on the pelvis
Originate on ribs/vertebral column
Abdominal Wall
Parts of abdominal wall
External oblique, internal oblique, transversus abdominis (rectus sheath formed by the aponeuroses of the above muscles), rectus abdominis (6-pack, originates on pubis, inserts on ribs and xiphoid process)
Breathing musculature
Raise/lower the ribs to change thoracic volume (occupy space between ribs)
External and internal types
Intercostal Musculature
Controls position of the scapula
Ascending, transverse, descending
Trapezius
Rhomboids
Major, minor
Serratus anterior
Protracts the scapula
Vertebral, scapular, costal, iliac components
Latissimus dorsi
Designed for flexibility and mobility
Sometimes sacrifice stability
Muscles at glenohumeral, cubital, and radiocarpal joints act to stabilize and rotate arm and hand
Muscles of limb divided into functional compartments by fascia (anterior and posterior)
Upper Limb Musculature
Rotate and stabilize the humerus
Tendons contribute to the shape of the glenoid cavity - originate on scapula (anterior and posterior parts) and insert on the humerous (greater and lesser tubercule), and inctease stability about the joint
Rotator Cuff
Muscle groups of the rotator cuff (SITS)
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
Goes from the shoulder to the elbow
Permit movement about the glenohumeral and cubital joints
Anterior parts:
Biceps brachii
Brachialis (from humerus across elbow joint)
Coracobrachialis (from scapula to humerus)
Posterior parts:
Triceps brachii
Arm
Elbow to wrist
Control fingers
-origin on humerus, ulna, and radius
-Insertion on carpals and phalanges
Anterior parts (origin from medial epicondyle)
-Flexor carpi (radialis, ulnaris)
-Flexor digitorum (superficialis or profundus)
Posterior (origin from lateral epicondyle)
-Extensor carpi (ulnaris, radialis brevis, radialis longus)
-Extensor digitorum
-Extensor indicus
Forearm
Extensors of wrist and hand originate from the
Lateral epicondyle of the humerus near the elbow
