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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

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