Muscular System Flashcards
skeletal muscle
- voluntary control
- multinucleated
- very long and striated muscle cells called muscle fibers or myofibers
- attached to a bone
cardiac muscle
- involuntary control
- found in the walls of the heart and responsible for its contraction
- mononucleated
- short, stumpy, and branched cell shape
- intercalated discs with gap junctions
- striated muscle fibers called myocytes, cardiomyocytes, or cardiocytes
smooth muscle
- involuntary control
- found in the walls of GI tract
- mononucleated
- NONstriated muscle cells called myocytes
- small, short, and fusiform (tapered at ends) shape
- dense bodies link cytoskeleton and membrane
endomysium
a thin sleeve of loose connective tissue that surrounds each muscle fiber; creates room for capillaries and nerve fibers to reach every muscle fiber
- “wraps cell”
perimysium
thicker connective tissue sheath that wraps muscle fibers together in bundles called fascicles (the “grain” in a cut of meat)
- “wraps fascicle”
epimysium
fibrous sheath that surrounds the entire muscle; inner surface projects between fascicles to form perimysium
- “wraps muscle”
sarcomere
the functional unit of muscle contraction
- defined by the region from one Z disc to another
- basic action: when muscle fibers contract, the sarcomeres become shorter and the Z discs are pulled closer together
motor unit (components)
- consists of one motor neuron and muscle fibers it supplies
- behaves as a single functional unit- contracts in unison
motor unit sizes
- fibers from one unit are dispersed throughout an entire muscle, an arrangement that causes a weak contraction over a wide area. It is advantageous to have multiple motor units in a muscle because it helps to prevent fatigue. The muscle as a whole can sustain long-term contraction (stronger)
- smaller motor units are found in areas where we need fine motor control (eyeball movement)
synaptic vesicles
- tiny spheroidal pouches or sacs in the presynaptic axon terminals
- filled with the neurotransmitter: acetylcholine (ACh) which stimulates a muscle fiber to contract
skeletal muscle blood supply
- blood capillaries extend through connective muscle tissues to reach every muscle fiber (tremendous demand for energy)
- muscle is generally well vascularized
share of circulating blood (at rest and exercise)
- at rest: 1/4 of heart’s blood output (1.25 L/min)
- during exercise: as much as 3/4 heart’s total output (11.6 L/min)
most important muscle for opening the mouth
masseter
most important muscle for kissing
most important muscle for blowing out air
- orbicularis oris
- buccinator
4 principal muscles of the abdominal wall
- external abdominal oblique: allow the trunk to twist
- internal abdominal oblique: allow the trunk to twist
- transverse abdominal: stabilize the trunk and maintain internal abdominal pressure (compresses abdominal contents)
- rectus abdominis: flexes waist
muscles important in standing back up after touching your toes
erector spinae: extends the spine and is the main postural muscle
SITS mucles of rotator cuff
The tendons of the rotator cuff insert on the proximal end of the humerus and form a sleeve around it, providing stability for the mobile joint:
- supraspinatus: adbuction
- infraspinatus: lateral rotation
- teres minor: lateral rotation
- subscapularis: medial rotation
muscles that cross your legs while sitting
sartorius: helps you flex and rotate the thigh from the hip joint
quadriceps femoris muscle components
extends the knee and consists of four muscles in the anterior compartment:
- rectus femoris: is the only head that crosses two joints; in addition to extending the knee, it flexes the thigh
- vastus lateralis: (largest & strongest) used in leg extension
- vastus medialis: (smallest) knee extension
- vastus intermedius: knee extension
