Muscular System #1

Fascia

Thin covering of connective tissue around muscle

Tendon

Cord-like mass of connective tissue that connects muscle to a bone

Aponeurosis

Sheet-like mass of connective tissue that connects a muscle to bone, skin, or another muscle

Epimysium

Surrounds whole muscle; lies beneath fascia

Perimysium

Surrounds fascicles within muscle

Endomysium

Surrounds muscle fibers within a fascicle

Muscle Fibers

Name for muscle cells

Compartment

Space containing group of muscles, blood vessels, and nerves; enclosed by fascia

Compartment Syndrome

Fluid accumulation within a compartment; results in increased pressure in compartment and causes deficiency of oxygen and nutrients

Deep Fascia

Portion of fasciae surrounding the muscles

Subcutaneous Fascia

Portion of the fasciae that is under the skin

Subserous Fascia

Portion of fasciae that is in serous membranes

Myofibrils

Made of sarcomeres; consist of actin and myosin

Triad

Unit consisting of one T tubule and 2 SR cisternae

I Band

Light band; composed of only thin actin filaments; between A Band and Z line

A Band

Dark band; composed of myosin with portions overlapped with actin; spans all of the myosin filaments

H Zone

Center of A band; made of only myosin

Z Line

Sarcomere boundary; in the center of the I band; anchors actin in place

M Line

Center of sarcomere and A band; anchors myosin

Myoneural Junction

Another name for a neuromuscular junction

Motor End Plate

Specialized folded portion of skeletal muscle fiber where it bind to the neurotransmitter

Acetylcholine

Neurotransmitter that causes skeletal muscle contraction

Sodium and Potassium Ions

When ACh binds to motor end plates, the membrane permeability to these ions changes to generate an impulse

Calcium Ions

Particles that the sarcoplasmic reticulum stores

Troponin

Protein that Ca+2 binds to during muscle contraction

Troponin

Holds tropomyosin in place on actin

Tropomyosin

Covers the binding sites on actin

H Zones, I Bands

Two areas that narrow during sarcomere contraction

Creatine Phosphate

Initial source of energy to create ATP in muscle; stores energy in phosphate bond; can only fuel abt 10 secs of intense activity

Myoglobin

Red molecule that stores oxygen in muscles

Muscle Fatigue

Inability to contract muscle; caused by decreased blood flow, ion imbalances, loss of desire

Muscle Cramp

Sustained, involuntary muscle contraction; may be caused by changes in electrolyte concentration

Threshold Stimulus

Minimum strength of stimulation of a muscle fiber required to cause contraction

Twitch

Contractile response of a single muscle fiber to a single impulse

Latent Period

Period of twitch; delay between stimulation and start of contraction

Period of Contraction

Period of twitch; fiber pulls at attachments

Period of Relaxation

Period of twitch; pulling force decreases

Summation

Process by which the force of individual muscle fiber twitches combine when frequency of stimulation increases; produces sustained contractions; can lead to partial or complete tetany

Partial Tetany

Occurs at higher frequencies of stimulation; time spent in relaxation between twitches becomes very brief

Complete Tetany

Does not occur outside of lab; occurs at very high stimulation frequency; forceful sustained contraction with no relaxation between twitches

Recruitment

Increase in the number of motor units activated to produce more force

Muscle Tone

Continuous state of partial contraction in resting muscles

Isotonic

Type of contraction in which the muscle contracts and changes length

Concentric

Type of contraction in which shortening occurs

Eccentric

Type of contraction in which lengthening occurs

Isometric

Type of contraction in which the muscle contracts but does not change length

Slow Twitch Fibers, Type 1 fibers

Always oxidative, fatigue resistant, red fibers, abundant myoglobin, good blood supply, many mitochondria, slow ATPase activity, slow to contract

Fast-twitch fatigue-resistant fibers, Type 2a

Intermediate twitch fibers, oxidative capacity, and myoglobin; white fibers, resistant to fatigue, rapid ATPase activity

Fast-twitch Glycolytic fibers, Type 2b

Glycolysis, white fibers, poorer blood supply and fewer mitochondria than S-T fibers, more SR than other fibers, susceptible to fatigue, fast ATPase, contract fast

Hypertrophy

Enlargement of skeletal muscle that is exercised

Atrophy

Decrease in size and strength of skeletal muscle that is unused

Smooth Muscle

Shorter, single nuclei, elongated with tapered ends, myofilaments randomly organized, no striations, no T-tubules, SR not well developed

Multi-Unit

Type of smooth muscle; cells less organized, function as separate units, fibers function independently, stimulated by neurons and hormones

Multi-Unit

Type of muscle found here: iris of eye, walls of blood vessels

Visceral

Type of smooth muscle; cells respond as a unit, sheets of spindle-shaped muscle fibers, fibers held together by gap junctions, exhibit rhythmicity, conduct peristalsis

Visceral

Type of smooth muscle found in the walls of hollow organs

Calmodulin

What smooth muscle uses instead of troponin

Norepinephrine and acetylcholine

2 neurotransmitters that contract smooth muscle

Skeletal

Up to 30cm in length; 10-100 um in diameter; don’t include the word muscle in answer

Smooth

30-200 um in length; 3-6 um in diameter; don’t include the word muscle in answer

Cardiac

50-100 um in length; 14 um in diameter; don’t include the word muscle in answer

Skeletal

Striations, multiple nuclei, transverse tubule system well developed; don’t include the word muscle in answer

Smooth

Absent striations, single nucleus, no t-tubules; don’t include the word muscle in answer

Cardiac

Striations, single nucleus, t-tubules well developed, intercalated disks; don’t include the word muscle in answer

Skeletal

Contracts and relaxes relatively rapidly; don’t include the word muscle in answer

Smooth

Contracts and relaxes relatively slowly; some types self-exciting; rhythmic; don’t include the word muscle in answer

Cardiac

Network of cells contracts as a unit; self-exciting; rhythmic; remains refractory until contraction ends; don’t include the word muscle in answer