Download Muscular System – Chapter 9

Muscular System – Chapter 9
I. Four characteristics of muscles
A. contraction – ability to shorten
B. extensibility – ability to stretch or extend
C. irritability – response to a stimulus
D. elasticity – allows contraction and extension
II. Three main body shapes in reference to muscles
A. ectomorph – person with long, slender muscles
B. endomorph – person with rounded muscles and fatty tissue
C. mesomorph – sturdy, compact muscles
III. Refer to muscle types in tissue notes.
IV. Facts about muscles
A. skeletal muscle makes up 40% of body weight
B. 40% of food we eat is converted into muscle energy
C. main source of energy is carbohydrate
D. muscle is made of protein – main component
V. Structure of skeletal muscle
A. connective tissue coverings
1. fascia – layers of fibrous connective tissue that separate muscles and hold
them in place
2. tendons – connective tissue around muscle that connects to bone
3. aponeuroses – connective tissue that forms a broad, flat sheet(on abdomen)
4. connective tissue layers:
a. epimysium – connective tissue that surrounds the entire muscle
b. perimysium – extends inward from the epimysium and separates muscle
into small compartments
c. fascicles – bundle or groups of skeletal muscle fibers
d. endomysium – surrounds each fiber within the fascicles(closest to the
individual muscle fiber)
B. Skeletal muscle fibers(requires a nerve impulse to contract0
1. skeletal muscles are made of myofibrils
a. actin – made of protein
b. myosin – made of protein
2. bands are made of different concentrations of actin and myosin
3. What is in the bands?
a. The A band contains myosin and some actin
b. The H band contains myosin and in center of sarcomere
c. the I band contains actin
d. the Z band contains actin which passes from one unit of muscle to
another
4. a sarcomere is the basic unit of measurement of a muscle—from one Z band
to another(smallest functional unit)
5. construction of a sarcomere
a. the large band is the dark A band
b. in the middle of the dark A is the light H
c. on each side of the dark A is a light I
d. in the middle of the light I is a dark Z
6. muscles are made of muscle fibers and muscle fibers are made of myofibrials
7. sarcoplasmic reticulum – a network of membranous channels that surround
the myofibril
8. traverse tubules – extend inward and function in activating the muscle
contraction
C. neuromuscular junction
1. site where the nerve fiber and muscle fiber meet
(all muscles must have a nerve to work)
2. motor neuron – the nerve fiber which stimulates the muscle
3. motor end plate – specialize membrane of muscle
4. neurotransmitters – substances produced by the nerve which initiates
contraction(acetylcholine-crosses neuromuscular gap)
D. motor units – when one nerve branches and sends several fibers to several
muscle fibers(neuron plus muscle fiber )
VI. Materials found in striated muscles
A. water
B. protein
C. minerals
D. organic compounds
1. creatine
2. creatine phosphate
3. ATP(directly supplies energy to myosin )
4. glycogen
5. protein
VII. Steps in muscle contraction
A. nerve impulse reaches the neuro-muscular junction
B. neuron releases acetycholine which sets up an electrical charge in the
Sarcoleumma(fiber cell membrane)
C. charge travels over the surface of the sarcolemma to the T-tubules
D. the charge goes from the T-tubules to the sarcoplasmic reticulum
E. the sarcoplasmic reticulum releases calcium ions into the sarcoplasm
(protoplasm inside muscle cell)
F. How does calcium cause the contraction?
1. proteins tropomyosin and troponin prevent any interaction between actin and
myocin
2. calcium ions combine with troponin and render it inactive
3. tropomyosin molecules move
4. actin and myosin are now free to interact(main force of contraction)
G. The sliding filament hypothesis:
1. myosin in intercepted by several cross bridges
2. when calcium is released, the cross bridges pull the action filament of each
sarcomere (1 Z band to another) inward toward each other
3. as actin slides in among myosin the Z bands are drawn inward toward the A
band; the sarcomere shortens and the muscle contracts
H. cholinesterase (enzyme) produced by the nerve will break up acetycholine and
themuscle relaxes
VIII. Blood suppl y to the muscle
A. for every 2 rows of muscle cells, there is a row of capillaries
B. capillaries carry nutrients, gases and wastes to and from the muscle
IX. Energy for muscle contraction
A. the main source of energy is ATP from cellular respiration
B. muscle cells store ATP on myosin
C. another source of energy is the chemical creatine phosphate
1. CP + ADP → ATP + C
ATP + C → ADO + CP
D. glucose is the main source of energy
1. stored sugar in the liver is called glycogen
2. lactic acid is also stored in the liver (not enough oxygen)
X. Muscle twitch(single contraction of a muscle)
A. the latent period is a series of chemical changes taking place or when troponin is
Broken
B. contraction period – breakdown of chemicals like ATP
C. relaxation period – chemicals are reconstructed like ATP
D. refractory period – loss irritability (cannot respond) until more oxygen is
Supplied
XI. Definitions:
A. all or none response – fiber responds fully or it doesn’t at all
B. summation – continued stimulation
C. tetanic contraction – a sustained contraction(cannot relax)
Tetany of a muscle – jams up on you; cramps
D. muscle tone – a certain amount of contraction even when the muscles are relaxed
E. threshold – minimum stimulus needed to cause a contraction
F. contractions:
1. isotonic – when muscle shortens
2. isometric – increasing tension (force increase) but muscle does not move
XII. Use and disuse of skeletal muscle
A. muscular hypertrophy – increase in the size of muscle fiber (building muscle)
B. atrophy – muscle decreases in size due to lack of use(degeneration)
XIII. Smooth muscle (visceral)
A. two types:
1. multi-unit smooth muscle – single fibers found in the eyes and walls of blood
vessels
2. visceral – sheets of spindle-shaped fibers that are found in the stomach,
intestine, urinary bladder, uterus
B. facts about smooth muscle contraction
1. slower to contract but can sustain longer
2. stretch much further than skeletal muscle
3. contains actin and myosin but does not have sarcomere arrangements
XIV. Cardiac muscle
A. striated and occurs only in heart
B. intercalated disks form cross-bands(transmits impulses faster)
C. involuntary
D. rhythmic
XV. Disorders of muscles:
A. fatigue – when muscles refuse to respond
B. gangrene – death of a muscle
C. sprain – involves a ruptured (not torn) ligament
D. spasm -abnormal contraction of a muscle
E. cramp – involuntary complete tetanic contraction
F. convulsion – involuntary contraction of a group of muscles
Tetany – a state of spasmodic contractions
I. Body Movements – movement is produced by pulling on tendons which pull on
bones
A. Parts of the muscle:
1. origin – immovable end or attachment of muscle tendon to stationary bone
2. insertion – movable end of muscle or attachment of tendon to movable bone
3. belly – gaster or body – middle of the muscle
4. some muscles have more than one origin or insertion
5. sometimes a muscle will change its function
B. Muscles enable bones to act as levers (pulley system)
II. Muscle action
A. Muscles work in pairs
1. prime mover is the agonist
2. opposite is antagonist
3. synergist – assist the prime mover
III. Naming Muscles
A. By direction of fiber – to the midline
1. parallel
2. perpendicular
3. diagonal