Musculoskeletal System Flashcards
Slow, Oxidative Fibers (Type 1) mitochondria, capillaries, myoglobin content, and glycogen content
Mitochondria: Numerous
Capillaries: Numerous
Myoglobin content: High (red fibers)
Glycogen content: Low
Fast, Oxidative-Glycolytic Fibers (Type 2a) mitochondria, capillaries, myoglobin content, and glycogen content
Mitochondria: Numerous
Capillaries: Numerous
Myoglobin content: High (red fibers)
Glycogen content: Intermediate
Fast, Glycolytic Fibers (Type 2b) mitochondria, capillaries, myoglobin content, and glycogen content
Mitochondria: Sparse
Capillaries: Sparse
Myoglobin content: Low (white fibers)
Glycogen content: High
Slow, Oxidative Fibers (Type 1) rate of fatigue, speed of contraction, and major locations
Rate of fatigue: Slow
Speed of contraction: Slow
Major location: Postural muscles of back
Fast, Oxidative-Glycolytic Fibers (Type 2a) rate of fatigue, speed of contraction, and major locations
Rate of fatigue: Intermediate
Speed of contraction: Fast
Major location: Major muscles of legs
Fast, Glycolytic Fibers (Type 2b) rate of fatigue, speed of contraction, and major locations
Rate of fatigue: Fast
Speed of contraction: Fast
Major location: Extraocular muscles
Red fibers
Well vascularized and have lots of myoglobin, which stores oxygen. Myoglobin is an iron- and oxygen-storage protein found in cardiac and skeletal muscle.
Red fibers contract slowly and resist fatigue.
White fibers
Low in myoglobin; they contract quickly, but tire easily.
Three different motor units in the human body
Type 1, type 2a, type2b
Type 1 motor unit
Highly fatigue resistant, has a lower activation threshold, contains fewer muscle fibers, and has low force generation during contraction.
Type 2 motor unit
Resistant to fatigue, has a higher activation threshold, and the force produced is higher compared to type 1
Type 2b motor unit
Fatigable, has a high activation threshold, innervates the most muscle fibers, and generates the greatest force during contraction
The structural unit of a muscle is a _______
muscle fiber
The functional unit of a muscle, consisting of a motor neuron and the muscle fibers it controls, is a _______
motor unit
Fascia
A band or sheet of connective tissue, that attaches, encloses, and separates muscles and other internal organs. It interpenetrates and
surrounds the muscles, bones, nerves, and blood vessels of the body.
How is fascia classified?
Fascia is classified by layer as superficial fascia, deep fascia, and visceral or
parietal fascia, or by its function and anatomical location.
Deep fascia
Associated with, bone (periosteum and endosteum), cartilage (perichondrium), blood vessels (tunica externa), muscles (epimysium, perimysium, and endomysium), nerves (epineurium, perineurium, and endoneurium)
High density of elastin fiber for extensibility and resilience
Fascia function
Often surrounds groups of muscles, forming compartments.
Fasciae also reduce friction between muscles and blood vessels and nerves.
Muscle functions (broad sense)
Prime mover or agonist, fixators, synergist, antagonist
Prime mover or agonist
The main muscle responsible for producing a specific movement of the body (e.g., concentric contraction).
Fixators
Steady the proximal parts of a limb while movements are occurring in distal parts.
Synergist
Complements the action of prime movers—for
example, by preventing movement of the intervening joint when a prime mover passes over more than one joint.
Antagonist
A muscle that opposes the action of a prime mover. As a prime mover contracts, the antagonist progressively relaxes, producing a smooth movement.
Functions (narrow sense)
Flexors and extensors, abductors and adductors
What muscles shorten the most during contraction?
When muscles contract, the fibers shorten to about 70% of their resting length. Muscles with a long parallel fascicle arrangement shorten the most, providing considerable range of movement at a joint, but are not powerful.
Muscle power
Muscle power increases as the total number of muscle cells increases. Therefore, the shorter, wide pennate muscles that “pack in” the most fiber bundles shorten less but are most powerful.
This statement is not quite correct in a biomechanical sense.
Muscle origin
The origin is usually the proximal end of the muscle, which remains fixed.
Muscle insertion
The insertion is usually the distal end of the muscle, which is movable.
Types of skeletal muscle contraction
Reflexive contraction, tonic contraction, and phasic contraction
Reflexive contraction
A type of skeletal muscle contraction automatic and not voluntarily controlled—for example, respiratory movements of the diaphragm. Muscle stretch evokes reflexive contraction produced by tapping a tendon with a reflex hammer.
Tonic contraction
A type of skeletal muscle contraction which is a slight contraction (muscle tone) that does not produce movement or active resistance but
gives the muscle firmness, assisting the stability of joints and the maintenance of posture.
Phasic contraction
A type of skeletal muscle contraction.
Two types of phasic contraction: Isometric and isotonic
Isometric contractions
A type of phasic contraction where the muscle length remains the same—no movement occurs but muscle tension is increased above tonic levels (e.g., the deltoid holds the arm in abduction).
Force = Mass
Isotonic contraction
A type of phasic contraction where the muscle changes length to produce movement.
Two types:
Concentric contraction: Muscle shortening, Force > Mass
Eccentric contraction: Muscle lengthening/relaxation of a contracted muscle, Force < Mass
Muscular hydrostat
A biological machine
consisting mainly of muscles with no skeletal support.
Ex. human pharynx (throat), elephant trunk
Joint classification
Joints can be classified as synarthroses or diarthroses.
Diarthroses (synovial joints)
Joints that allow free
movement of the attached bones, such as knuckles, knees, and elbows.
Synarthrosis
Permits only limited movement.
Synostoses, syndesmoses, and symphyses
Synostoses
A type of synarthroses joint that allows essentially no movement between bones. In older adults synostoses unite the skull bones, which in children and young
adults are held together by sutures.
Syndesmoses
A type of synarthroses joint that joins bones by dense connective tissue only. E.g., the interosseous ligament of the inferior tibiofibular joint and the posterior
region of the sacroiliac joints.
Symphyses
A type of synarthroses joint that have a thick pad of fibrocartilage between the thin articular cartilage covering the ends of the bones. Examples include
intervertebral discs and the pubic symphysis.
Diarthroses (synovial joints) components
Articular capsule: Composed of fibrous layer and synovial membrane.
Synovial membrane lines the capsule and produces synovial fluid. Continuous with a ligament inserting into the periosteum of both bones;
Joint cavity containing synovial fluid lubricant
Rheumatoid arthritis
Chronic inflammation of the
synovial membrane of the joint causes thickening of
this connective tissue and stimulates the macrophages to release collagenases and other
hydrolytic enzymes.
Articular Cartilage
Proteoglycan aggregates bound to hyaluronan
form a hydrated megacomplex that acts as a biomechanical spring. This spring distributes forces evenly through the cartilage, and also causes movement of water within the cartilage.
When pressure is applied a small amount of water is forced out of the cartilage matrix into the synovial fluid. When pressure is released
water is attracted back into the interstices of the matrix. Such movements of water occur constantly with normal use of the joint, and are also important for nutrition of the cartilage, and for gas and metabolite exchange.
Intervertebral Disc
The disc consists of
concentric layers of fibrocartilage that form the annulus fibrosus, which surrounds the nucleus
pulposus.
The intervertebral discs function primarily as shock absorbers within the spinal column and allow greater
mobility within the spinal column.
Herniated Disc
Within an intervertebral disc, collagen loss or other degenerative changes in the annulus fibrosus are often accompanied by
displacement of the nucleus pulposus, a condition variously called a slipped or herniated disc. This occurs most frequently on the posterior region of the intervertebral disc where there are fewer collagen bundles.
Carpal tunnel syndrome
Results from any lesion that significantly reduces the size of the carpal tunnel or, more commonly, increases the size of some of the structures (or their coverings) that pass through it (e.g., inflammation of the synovial sheaths).
Force generated by a muscle is proportional to its ________
cross-sectional area
(the number of fibers
being fired).
