Chapter 9 Muscle Study Guide

3 types of muscle tissue

skeletal, cardiac, smooth

what are the two types of muscle tissues that are referred to as muscle fibers

only skeletal and smooth muscles are elongated and referred to as muscle fibers

sarcoplasm

muscle cell cytoplasm

connective tissue layers in skeletal muscle

sheaths that cover the layers of the muscles

what are the 3 connective tissue layers in skeletal muscle

epimysium, perimysium, endomysium

epimysium

made of dense irregular connective tissue, surrounds whole muscle

fascicles

bundles of muscle cells

perimysium

fibrous connective tissue, surrounds fascicles

endomysium

areolar connective tissue that surrounds each individual muscle fiber (cell)

individual cell (muscle fibers)

long cylindrical multinucleated

sarcolemma

plasma membrane in muscle fiber

sarcoplasm

contains glycosomes and myoglobin

glycosomes

store glycogen granules

glycogen

stored glucose

myoglobin

red pigment, stores oxygen

myofibrils

rod like organelles accounting for approx 80% of cell volume and is made of myofilaments

striations

repeating series of dark (A) and light (I) bands

A bands

contain thick (myosin) and thin (actin) filaments; have lighter H-zones (no actin) and M lines (myosin)

I bands

contains thin (actin) filaments; if it has a middle interruption then there is a z-disc or z line

sarcomere

functional unit, smallest contractive unit of muscle fiber; the region of myofibril between 2 successive z discs; contains the A band flanked by ½ band at each end; made of thick myosin filaments

thick myosin filaments

rod like tail attached by flexible hinge to 2 globular heads; the heads form cross bridges (during contraction) linking thick and thin filaments; (h zone) central part is smooth with no myosin heads

what do the myosin heads contain

actin and atp binding sites

thin (actin) filaments

have subunits (globular actin) which contains active sites for myosin heads; contains tropomyosin and troponin

tropomyosin

helps stabilize actin core, and which block myosin minding sites on actin during muscle relaxation

troponin

globular protein complex that binds to actin, binds to tropomyosin and helps position tropomyosin on actin nd binds to calcium ions

elastic filaments

made of titan and extend from z disc through thick filament to m line; holds thick filaments in place and helps muscle cells spring back after shape stretching

dystrophin

links thin filaments to integral proteins of sarcolemma (helps to stabilize it)

Deuchene Muscular Dystrophy (DMD)

lack of dystrophin, fragile sarcolemmas which tear during contraction and allow entry of excess calcium ions which damage contractile fibers, which breaks down and leads to apoptosis and loss of muscle

sarcoplasmic reticulum

(smooth ER) regulates intracellular levels of calcium ions; interconnecting tubules surround each myofibril (run longitudinal)

what 3 organelles are in the SR

terminal cristernae, T-tubules, and triad

terminal cristernae

run perpendicularly at A band - I band junction; occurs in pairs and stores calcium ions

t tubules

internal protrusions of sarcolemma; occur at A band - I band junction; help increase surface area; help conduct impulses to deep regions of muscle

triad

1 tubule and 2 terminal cristernae

activation at neuromuscular junction includes

axonal ending of neuron, synaptic cleft, and junctional folds of sarcolemma

axonal ending of neuron

axon terminal contains synaptic vesicles, which contain neurotransmitter scetylcholine

synaptic cleft

space between the axon terminal and muscle cells’ sarcolemma; filled with collagen fibers and glycoproteins

junctional folds of sarcolemma

increases surface area; and contains millions of ach receptors

motor unit

motor neuron and all muscle cells it supports

muscle twitch

response of motor unit to single action potentioal of its motor neuron; quick contraction and relaxation of muscle fibers

what are the 3 phases of a muscle twitch

latent period, period of contraction, period of relaxation

latent period

events of excitation -contraction coupling (no muscle tension is seen)

period of contraction

cross bridge formation (tension increases)

period of relaxation

calcium reentry into sr (tension declines to zero

muscle tone

slight contraction of relaxed muscles due to spinal reflexes that activate one group of motor units then another in response to activation of stretch receptors in muscles and tendons; keeps muscle firm, healthy, and ready to respond to stimuli which helps stabilize joints and maintain posture; constant, slightly contracted state of all muscles

2 types of contractions

isotonic and isometric

isotonic

same tension: thin filaments slide, does work

what are the two types of isotonic contractions

concentric and eccentric

concentric

muscle shortens, does work

eccentric

muscle lengthens; does work

isometric

same measure: when muscle attempts to move load that’s greater than tension the muscle is able to develop; thin filaments don’t slide even though cross bridges form tension

ATP provides the energy needed for the muscle fiber to…

move and detach cross bridges; pump calcium back into sr; pump sodium our of and potassium back into the cell after excitation-contraction coupling

creatine phosphate

unique molecule located in muscle fibers that donate Pi to ADP to instantly form ATP; muscle cells have enough CP to power the cell for 15 sec

creatine kinase

enzyme that carries out transfer of phosphate

lactic acid

diffuses into the bloodstream, used as fuel by liver, kidney, and heart, converted back to pyruvic acid or glucose by liver; anaerobic respiration only yields 5% as much atp as aerobic but 2.5x faster

aerobic respiration

produces 45% of atp during rest and light to moderate exercise, but is slower than anerobic resp

muscle fatigue

when muscles can no longer perform a required activity, they are fatigued

what does muscle fatigue result in

depletion of metabolic reserves (Ca/ATP); damage to sarcolemma and SR, low pH (lactic acid), muscle exhaustion and pain

muscle hypertrophy

muscle growth from heavy training; increases in diameter of muscle fibers; increases number of myofibrils; and increases mitochondria and glycogen reserves

muscle atrophy

lack of muscle activity; reduces muscle tone, size, and power

smooth muscle

spindle shaped, uninucleate, lines hollow organ walls (respiratory, digestive, urinary, etc.), no striations, no sarcomeres

single unit smooth muscle

visceral muscle (except heart); often have rythmic spontaneous Action potentials; have gap junctions (electrical couplings) so contract as a single unit

multi unit smooth muscle

large air ducts, large arteries, arrestor pili, internal eye muscles; have independent neuromuscular junctions and similar to skeletal muscle

hyperplasia

ability to divide and increase number of cells (uterine smooth muscle puberty and pregnancy)