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
most important muscle for smiling
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 in the “up” part of a sit up
rectus abdominis
most important muscles of a push-up
pectoralis major
muscles important in standing back up after touching your toes
erector spinae: extends the spine and is the main postural muscle
what happens when the diaphragm contracts?
diaphragm flattens, slightly enlarging thoracic cavity and causing air intake (respiration)
- quadratus lumborum aids respiration by stabilizing the diaphragm and rib 12
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 supinate the forearm
supinator
- a deep muscle on the posterior proximal forearm
biceps brachii (also flexes elbow and shoulder):
- has two heads that originate on the scapula and converge on a single belly whose tendon inserts on the radial tuberosity.
- The tendon of the long head travels through the intertubercular (bicipital) groove.
muscles that extend the elbow
anconeus
- a small muscle located at the elbow attaching the humerus and ulna
triceps brachii
- has three heads, one of which arises on the scapula, and a strong tendon that inserts on the olecranon process.
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
the thumb
pollex
