Chapter 10 - Muscles & Muscle Tissue Flashcards
Skeletal muscle
voluntary, striated muscle attached to & covering skeleton; most abundant type; function: to move bones; length of muscle = length of cell; involved in reflexes–fastest contraction & w/greatest force; downside-gets tired easily;
cells = long, thick, straight cells; striped
Cardiac muscle
involuntary, striated muscle in the heart wall; not as long as skeletal; interconnected & branched; can contract by itself–only tissue that does this; steady rate of contraction–rhythmic
Smooth muscle
involuntary, nonstriated muscle in the hollow visceral organs (except heart & blood vessels); not as long as skeletal muscle tissue; (ex. stomach, intestines, bladder, uterus, blood vessels); slowest rate of contraction–doesn’t tire out
4 Characteristics of Muscle tissue
- Excitability or Irritability
- Contractility
- Extensibility
- Elasticity
Excitability or Irritability
ability to receive & respond to a stimulus
Contractility
ability to shorten
Extensibility
ability to be extended or stretched
Elasticity
can recoil after being stretched & return to original resting length
Muscle fiber
muscle cells
Fascicles
bundles of muscle fibers
Gross anatomy of a muscle (3 CT coverings)
consists of many skeletal fibers; continuous; connected to each other @ the ends
- Endomysium
- Perimysium
- Epimysium
Endomysium
CT sheath which surrounds each muscle fiber
Perimysium
CT sheath which covers each fascicle
Epimysium
CT sheath which surrounds the entire muscle
Insertion
site of attachment of muscle to a movable bone
Origin
site of attachment of muscle to an immovable or less movable bone; always proximal to insertion
2 Main types of muscle attachment
- Tendons - rope-like attachments to bone; most common attachment of muscle to bone; dense regular CT; collagen fibers
- Aponeuroses - flat sheet-like attachments of muscle to other muscle or to bone; dense regular CT; abdominal muscles
Muscle Actions
usually work together to from opposite movements;
- Flexor - muscle which decreases the angle of the joint
- Extensor - muscle which increases the angle of the joint
Sarcolemma
plasma membrane of muscle fibers; can carry electrical signals
Sarcoplasm
cytoplasm of muscle fibers; includes cytosol, organelles & inclusions
Myoglobin
muscle protein that binds oxygen
Myofibrils
organelles in the sarcoplasm which contain contractile elements; structures that shorten (contract); consists of thick filaments & thin filaments;
Sarcomeres
smallest contractile units in muscle fibers; length of a sarcomere is from Z disc to the next Z disc; repeating unit making up myofibril
Thick filament
made of the structural protein myosin; darker region
Thin filament
made of the structural protein actin, and 2 regulatory proteins (not actively involved in muscle contraction): tropomyosin & troponin; lighter region
Sarcoplasmic reticulum
smooth ER of muscle fibers, stores Ca++ ions
Terminal cisterns
end regions of the sarcoplasmic reticulum
T tubule
sarcolemma which penetrates muscle cell interior; found between neighboring sarcoplasmic reticulum; made of same material as sarcolemma; electrical signals can go inside cell
Triad
consists of a T tubule between 2 terminal cistern; 3 structures–terminal cisterns on either side & t-tubule
Functions of Muscles
-Produces movement - of bones, blood, food digestion; applies to all 3 types of muscle tissue
The below 3 apply to Skeletal muscle tissue only:
-Maintains posture
-Stabilizes joints
-Generates heat - transforms chem energy (ATP) to mechanical energy & releases heat
Skeletal muscles are organs
700 muscles; richly vascularized; have all 4 tissue types (CT, muscle tissue, epitheleal & smooth muscle tissue, nervous tissue); plus very specific function
“myo”, “mys” & “sarco”
“muscle”
Example of Flexor muscle
- biceps - decreases elbow joint
2. hamstrings (knee) - bends knee
Example of Extensor muscle
- Triceps
2. Quadriceps - can’t bend knee; can only extend
Microscopic anatomy of skeletal muscle fibers
long, thick cells; many, many nuclei (100s or 1,000s); 2nd longest cells in body–some over 1 foot long; nerve cells are the longest cells
Embryonic development
100s of myoblasts line up to form one long skeletal muscle (cell): fusion of many myoblasts
Special names given to structures inside cell
bc unusual
Inclusions (in sarcoplasm)
stockpile of carbs & O2 built in & can quickly make ATP;
-glycogen granules & myoglobin
Glycogen granules (inclusions)
polysaccharide (carb); stored nutrients right inside cell; allow it to have carbs right there; so not entirely dependable upon blood
Interaction between thick & thin filaments
allows myofibrils to shorten; arrangements of thick & thin filaments give cell striated look
Myosin
fibrous protein w/2 globular regions (myosin heads) @ end; q protein made of amino acids (myosin tail)–thin part
Muscle contraction occurs when
myosin interacts w/actin
Regulatory proteins (in thin filament)
block contraction or release muscle so it can contract;
- Troponin - binds calcium (trigger for muscle contraction)
- Tropomyosin - blocks binding sites on actin
