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Chapter 9
1. Skeletal, cardiac and smooth
2. Long muscle cells of skeletal and smooth muscle tissue are referred to as “fibers”.
3. These are very long cells compared to other cells in the body, so they are referred to as
“fibers”.
4. Actin (thin filament) and myosin (thick filament).
5. Definitions:
a. Sarcolemma- plasma membrane of a muscle cell. Forms the motor-end-plate
across from the nerve endings and the t-tubules of the cell.
b. Sarcoplasm- cytoplasm of a muscle cell- contains myoglobin for increased
oxygen storing and glycosomes for glycogen storage.
6. myo-, mys- and sarco
7. type:
a. skeletal- multinucleated, striated, long, cylindrical cells that are voluntarily
controlled and found only in skeletal muscle. Their force production is adaptable
and they contract rapidly. They are formed from the fusion of cells that work
together for a common function, so they act as a syncitium. Movement of the
body or things in the environment.
b. Smooth- no striation, one central nucleus and involuntarily controlled. Found in
the walls of hollow organs for movement of substances. Contract slowly.
c. Cardiac- striated, single nucleus, short, fat and branched cells with lots of
mitochondria. Involuntarily controlled and found in the walls of the heart. Moves
blood.
8. Characteristics:
a. Can receive and respond to stimuli. Stimulus is the neurotransmitter from neurons
and the response is the contraction and generation of force.
b. Contractility- ability to shorten forcibly
c. Extensibility- ability to be stretched beyond resting length
d. Elasticity- ability to return to resting length after being stretched.
9. Functions:
a. Movement- locomotion, manipulation of the environment for skeletal. Movement
of a substance through a hollow organ for smooth and movement of blood for
cardiac.
b. Posture
c. Stabilizing joints
d. generating heat
10. Skeletal muscle tissue, CT sheaths, nervous tissue and blood (another CT)
11. Sheaths:
a. Endomysium- surrounds each muscle fiber
b. Perimysium- surrounds groupings of muscles called fascicles
c. Epimysium- out covering of the entire muscle and is continuous with the tendon
of the muscle
12. There is one nerve that brings electrical signal to each muscle, one artery bringing blood
(oxygen and nutrients) to each muscle and there may be more than one vein taking blood
(carbon dioxide and wastes) away from each muscle.
13. Definitions:
a. Origin- end of the muscle that is on the bone that will move least in the action.
b. Insertion- end of the muscle on the bone that will move most in the action. Hint:
the insertion will always move toward the origin in the action.
14. Multinucleated cell with a specialized plasma membrane called a sarcolemma and
cytoplasm called sarcoplasm (contains glycosomes and myoglobin). They are also very
long (several centimeters) and not very wide (several micrometers).
15. Cells fuse together during fetal development to form muscle fibers so they “work
together” = syncitium.
16. Sarcoplasm.
17. A cylindrical unit packed with myofilaments that fill the muscle fibers
18. sarcomere
19. defined from z-disc to z-disc and contains overlapping actin and myosin proteins for
contraction.
20. See drawing on lecture ink. Definitions:
a. Z disc- sheets of protein that span the myofibril and form the boundaries of the
sarcomeres.
b. “Dark” bands. Contains myosin with overlapping actin.
c. “Light” bands. Contain actin only.
d. Myosin only
e. Formed by desmins up the center of the sarcomere
21. Attachments:
a. Actin attached by nebulin
b. Myosin attached by titin
22. thin filament and thick filament, respectively
23. it is a modified smooth endoplasmic reticulum. It specifically stores and releases calcium
into the sarcoplasm for muscle contraction
24. the ends of the sarcoplasmic reticulum (SR) that are coupled to the t-tubule to form triads.
The calcium is released from this part, which is triggered by electricity coming down the
t-tubule.
25. Indentations of the sarcolemma. It carries the electric signal deep into the muscle fiber
and triggers the SR to release its calcium for muscle contraction.
26. two terminal cisternae and one t-tubule between them at the A-I junctions of the
myofibrils.
27. the t-tubule carries the electric signal to the terminal cisternae, which then are triggered to
release calcium into the sarcoplasm for muscle contraction.
28. during muscle contraction, actin is pulled by myosin towards the center of the sarcomere,
so actin “slides” past myosin.
29. the myosin heads “grab” actin to form a crossbridge. Then the myosin heads change
shape in a way that pulls actin towards the center of the sarcomere. This action is called a
power stroke.
30. motor
31. the motor neuron ending contains vesicles filled with the neurotransmitter acetylcholine.
The portion of the muscle sarcolemma across from the motor neuron ending is called the
motor end plate and contains receptors for acetylcholine. The space between the motor
end plate and the motor neuron is called the synaptic cleft.
32. a lipid “bubble” formed by a phospholipid bilayer. Acetylcholine
33. cleft
34. exocytosis
35. an enzyme called acetylcholinesterase. As long as it is in the cleft it can bind to the
receptors and cause muscle contraction. To be able to relax the muscle the
neurotransmitter must be removed.
36. a motor neuron and all of the muscle fibers that it innervates.
37. spindle shaped cells with only one nucleus. Not striated even though it still has actin and
myosin. The actin and myosin are arranged in a cris-cross pattern. There is only a little bit
of endomysium.
38. skeletal muscle cells are cylindrical and centimeters long whereas smooth muscle cells
are spindle and a couple of hundred micrometers long. Skeletal muscle cells contract to
move the body and things in the environment whereas smooth muscle cells contract to
move substances through hollow organs
39. wave-like contractions of smooth muscle in the walls of hollow organs to move
substances through them
40. bulbous swellings called varicosities release neurotransmitter over many smooth muscle
cells at once.
41. in a cris-cross pattern through the cell. This pattern allows the cell to twist and shorten
during contraction
42. intermediate filaments are actin and myosin (see definitions under cytoskeleton
components in chapter 3) and dense bodies hold them together when they cross in the
cell.
43. SR is less developed. Indentations called calveoli hold calcium from extracellular fluid
for contraction. There are no Z-disks or sarcomeres. Smooth muscle responds to stretch
by relaxing, thus allowing a hollow organ to fill with a substance, such as in the stomach,
urinary bladder or uterus.