How can we help?

You can also find more resources in our Help Center.

79 terms

Muscles

STUDY
PLAY
Cardiac
heart
skeletal
muscles attached to bone
smooth
organs, lining of blood vessels
muscle tissue characteristic
all muscle cells are elongated
muscle contraction depends on myofilaments:
myofilaments: actin and myosin
Sarcolemma
structure of muscle tissue; cell membrane of muscle cell
Sarcoplasm
structure of muscle tissue; cytoplasm of a muscle cell
excitability
characteristic of muscle tissue; ability to receive and respond to stimuli
contractility
characteristic of muscle tissue; ability to shorten when stimulated
extensibility
characteristic of muscle tissue; ability to be stretched
elasticity
characteristic of muscle tissue; ability to recoil to resting length
cardiac muscle structure
1-2 nuclei, network of fibers, intercalated disks, striations
cardiac muscle characteristics
T-tubules and mitochondria, SR is less developed than skeletal muscle and stores less Ca++,
functions of skeletal muscle tissue
produce movement, maintain body posture and body position, support soft tissues, guard entrances and exits, body temperature, store nutrient reserves
fascia
sheet of fibrous connective tissue, protects and lubricates
tendon
dense regular connective tissue that attaches skeletal muscle to bone
muscle
organ, contains thousands of fibers
fascicle
physically and functionally discrete bundle of fibers, wrapped by perimysium
fiber
muscle cell
epimysium structure
collagen fibers that surround entire skeletal muscle
perimysium structure
collagen and elastic fibers, surrounds fascicles (bundles of muscle fibers)
endomysium
delicate, elastic connective tissue, surrounds individual skeletal muscle cells (fibers) contains capillary networks, satellite cells and nerve fibers
multinucleate
fusion of myoblasts in embryo, have lost ability to undergo mitosis
sarcoplasmic reticulum (SR)
network of smooth ER surrounding each myofibril, pairs of terminal cisternae form perpendicular cross channels, functions in the regulation of intracellular Ca2+ levels
intercalated disks in cardiac muscle tissue
provide very little resistance to the passage of action potential
functional syncytium
a large number of cardiac cells acting as a single cell
cardiac muscle tissue
involuntary control, contracts rhythmically and does not tire easily, self exciting
skeletal muscle characteristics
voluntary control, contracts rapidly and vigorously but tires easily, may exert great force
skeletal muscle structure
multinucleate fibers, long and thin, striations (sarcomeres)
SR
high concentration of calcium ions compared to sarcoplasm, membrane becomes more permeable to calcium ions when stimulated, controls contractions
T tubules
continuous with the sarcolemma, penetrate the cells interior at each A-band - I-band junction, associate with the paired terminal cisternae to form triads that encircle each sarcomere
terminal cisternae
dilated ends of sarcoplasmic reticulum, sit on both sides of a t tubule
muscle contraction occurs when
SR releases Ca++ into the sarcoplasm, signal rapidly distributed by t tubles
myofibrils
physically and functionally discrete parts of a muscle fiber, shorten to produce muscle contractions, composed of myofilaments
sarcomere
region of a myofibril between two successive Z discs, smallest contractile unit of a muscle fiber, composed of thick and thin myofilaments
myosin
thick filament, run the entire length of an A band
actin
thin filament, run the length of the I band and partway into the A band
Z disc
sheet of proteins, anchors thin filaments, connects myofibrils to one another
H zone
lighter midregion where filaments do not overlap
M line
myomesin, holds adjacent thick filaments together
muscles
giant group of muscle fibers
muscle fibers
grouped into fascicles
fascicles
contain hundreds of muscle fibers
muscle fiber
is one long thin cell
structural proteins
nebulin, titin, dystrophin, myomesin
regulatory proteins
part of thin filament along with actin, troponin, tropomyosin
contractile proteins
actin, myosin
nebulin
holds the helix of actin in place, structural protein
titin
holds the myosin in place, thus maintaining the organization of the A band, helps the muscle to resist excessive stretching and helps in muscular recoil, structural protein
dystrophin
cytoplasmic protein that links the cytoskeleton to the extracellular matrix, stabilizes the sarcolemma, structural protein
myomesin
M line of the sarcomere, anchors the myosin in A band, structural protein
troponin
complex of 3 globular proteins, one binds actin, one binds tropomyosin, one binds calcium
tropomyosin
rod-shaped protein, covers myosin-binding site on actin
thin filament (actin)
coiled helical structure, myosin-binding site on each bead of actin
thick filament (myosin)
rod-like tail that ends in two globular heads (cross bridges), cross bridges (head) interacts with active sites on thin filaments
produce movement
skeletal muscle contractions pull on tendons, help move blood through the body
maintain body posture and position
tension in skeletal muscles
support soft tissues
abdominal and pelvic cavity skeletal muscles support weight of visceral organs
guard entrances and exits
opening of digestive and urinary tract surrounded by skeletal muscle
body temperature
thermogenesis
store nutrient reserves
skeletal protein broken down into amino acids if diet is inadequate
epimysium function
separates muscles from tissues/organs
perimysium function
connects blood vessels and nerves to fascicles
skeletal muscle contraction
pull on attached tendons which create tension and tension applied to object overcomes resistance and pulls object towards source of tension, this requires ATP
normal skeletal muscle is under neural control
1. activated by somatic motor neurons 2.neurons stimulate of sarcolemma
sliding filament theory
muscle contraction involves the sliding movement of the thin filaments past the thick filaments, Hugh Huxley 1954
steps in muscle contraction
1. signal from brain/spinal cord 2.excitation-contraction coupling 3.contraction cycle
Neuromuscular Junction (NMJ)
place where a neuron meets the sarcolemma of a muscle cell, usually found in the middle of a muscle cell
pre-synaptic terminal
part if NMJ, neuron coming from the spinal cord and connecting with the sarcolemma, secretes the neurotransmitter Ach
synapse
part of NMJ, gel filled space between the pre-synaptic membranes
post-synaptic membrane (motor end plate)
part of NMJ, region on sarcolemma that contains membrane receptors for ACh
neurotransmitters
chemical substance released from a neuron to send a signal from the brain
Acetylcholine
primary neurotransmitter in motor neurons to skeletal muscle
events at the neuromuscular junction
1.nerve impulse arrives at axon terminal 2.ACh is released and binds with receptors on the sarcolemma 3.Electrical events lead to the generation of an action potential 4. Begins the excitation-contraction cycle
motor unit is composed of
a motor neuron and all of the muscle fibers it supplies
recruitment of motor units
not every fiber of a muscle HAS to contract simultaneously, increase intensity=increase in motor units
small motor units
in muscles that control fine movements (fingers and eyes)
large motor units
in large motor units in large weight-bearing muscles (thighs and hips)
twitch
simplest contraction observable in the lab, response of a motor units to a single, brief threshold stimulus is referred to as this