Muscle Tissue Flashcards
functions of muscle tissue
movement, posture maintenance, and generation of body heat
special properties of muscle tissue
contractility, excitability, extensibility, and elasticity
sarcolemma
plasma membrane of muscle cells
sarcoplasm
cytoplasm of muscle cells that contains organelles like:
- mitochondria
- glycogen (for energy production)
- myoglobin (for oxygen storage)
skeletal muscle
- striated
- voluntary movements
- attached primarily to bones
- multiple nuclei per cell
cardiac muscle
- striated
- involuntary control
- forms most of the heart
- single nucleus
smooth muscle
- nonstriated
- involuntary
- walls of hollow internal structures (visceral)
- single nucleus
fibrous connective tissue
makes up skeletal muscle alongside muscle cells
fascia
a sheet or band of fibrous connective tissue that is deep to the skin and surrounds muscles and other organs of the body
superficial fascia (subcutaneous layer)
separates muscle from skin and functions to provide a pathway for nerves and blood vessels, stores fat, insulates, and protect muscles from trauma
deep fascia
lines the body wall and limbs and holds muscles with similar functions together, allows free movement of muscles, carries nerves, blood vessels, and lymph vessels, and fills spaces between muscles
epimysium
extension of the deep fascia covering the entire muscle
perimysium
extension of the deep fascia covering the fascicles
endomysium
extension of the deep fascia covering individual fibers
tendon
a cord of dense connective tissue that attaches a muscle periosteum of a bone
aponeurosis
a tendon that extends as a broad, flat layer
origin
attachment of muscle tendon to stationary bone
insertion
attachment of other muscle tendon to movable bone
tendonitis
inflammation of tendons and synovial membranes surrounding certain joints
intramuscular injections
used to administer relatively large doses (up to 5 mL) of drugs that could be dangerous or even fatal if injected into the bloodstream; cause less tissue irritation than subcutaneous injections and are absorbed more quickly
fascicle
single bundles of cells (fibers)
muscle fiber
a single muscle cell
- long, cylindrical, multinucleate cells formed by the fusion of embryonic myoblasts
- number of these cells is set before you are born
- most last a lifetime
hypertrophy
muscle growth occurs this way, an enlargement of existing muscle fibers
myofibrils
- specialized contractile organelles in skeletal muscle tissue
- parallel and threadlike
- contain contractile proteins (myofilaments)
- form the light and dark striations
T tubules
tiny invaginations of the sarcolemma that quickly spread the muscle action potential to all parts of the muscle fiber
sarcoplasmic reticulum
encircles each myofibril and is similar to smooth endoplasmic reticulum
stores calcium ions
myofilaments
- composed of thick (myosin) and thin (actin) filaments (proteins)
- arranged in units called sarcomeres
sarcomere
- repeating subunit along myofibrils
- basic unit of contraction in skeletal muscle
myosin
- main component of thick filaments
- functions as a motor protein (converts energy from ATP into mechanical energy of motion or force)
actin
- main component of thin filaments
- connects to the myosin for the sliding together of the filaments
contractile proteins
actin and myosin
regulatory proteins
tropomyosin and troponin
tropomyosin
blocks myosin-binding sites on actin, preventing myosin from binding there
troponin
holds tropomyosin in place
structural proteins
titin and dystrophin
- keep thick and thin filaments in alignment, give myofibril elasticity and extensibility, link myofibrils to the sarcolemma and ECM
titin
elastic protein that helps a sarcomere return to its resting length after a muscle has contracted or been stretched
dystrophin
enormous protein located between the sarcolemma and outermost myofilaments that links actin filaments to a peripheral protein on the inner face of the sarcolemma
somatic motor neurons
nerve cells with cell bodies in the brainstem and spinal cord that stimulate muscle fibers via their axons, called somatic motor fibers
motor unit
a single motor fiber and all the muscle fibers it innervates
- small motor units present where fine control is needed (like eye movement)
- large motor units present where strength is more important that fine control (like gastrocnemius)
neuromuscular junction
synapse between a somatic motor neuron and a skeletal muscle fiber
action potential
nerve impulse that travels down the motor neuron to the axon terminal and causes release of the neurotransmitter acetylcholine
acetylcholine
neurotransmitter that binds to receptors on the sarcolemma of the muscle fiber and causes muscle contraction
acetylcholinesterase
enzyme that is attached to the sarcolemma and breaks down acetylcholine into acetyl and choline fragments to stop stimulation of the muscle fiber
muscle depolarization
travels along the sarcolemma, down T-tubules, causing release of calcium from sarcoplasmic reticulum into the sarcoplasm
sliding filament mechanism
the sliding of filaments and shortening of sarcomeres causes the shortening of the whole muscle fiber and ultimately the entire muscle
rigor mortis
a state of muscular rigidity following death that results from a lack of ATP to split myosin-actin cross bridges
curare
- plant poison used on arrows and blowgun darts
- causes muscle paralysis by blocking ACh receptors and inhibiting sodium ion channels
- derivatives used during surgery to relax skeletal muscles
botulinum toxin
- blocks release of ACh from synaptic vesicles
- used as a medicine (Botox) for cosmetic and noncosmetic procedures
myoglobin
an oxygen-storing reddish pigment found in muscle fibers
slow oxidative (slow twitch) fibers
- red in color
- resistant to fatigue
- least powerful, smallest diameter
- make ATP aerobically
- lots of mitochondria
- prolonged, sustained contractions
- postural muscles
fast oxidative-glycolytic
- pink in color
- hand and eye muscles
- lots of mitochondria, myoglobin, and blood vessels
- split ATP at a very fast rate
- walking, marathon running
fast glycolytic (fast twitch)
- white in color
- anaerobic activity for short duration
- largest diameter
- make ATP via glycolysis
- fatigue quickly
