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BIO 201 Exam 3 Questions with Correct Answers
1. What composes the muscular system?: Skeletal muscles only
2. What is the study of the muscular system called?: Myology
3. What are the 4 functions of muscles?: 1. Movement
2. Stability
3. Control of body openings and passages
4. Heat production
4. Muscular
movements also serve various roles in .: Communication
5. Describe stability.: Prevents unwanted movements, there are some muscles known as the antigravity muscles that
fight against gravity that help us not fall over or slump.
6. What percent of body heat is produced by skeletal muscles?: 85%
7. What is the endomysium layer?: Thin sleeve of loose connective tissue that surrounds each muscle fiber.
8. The endomysium layer provides room for two things, what are they?: 1. Blood capillaries
- Nerve fibers
9. The endomysium also provides an
environment for the muscle fiber.: extracellular chemical
10. Relate the endomysium tissue and excitation.: Excitation of the muscle fiber depends on
2 / 16 exchange of calcium, sodium, and potassium ions across the endomysial tissue and the nerve end.
11. What is the perimysium layer?: Thicker connective tissue sheath that wraps muscle fibers together in
bundles called fassicles.
12. What are fassicles?: Bundles of muscle fibers together
13. Are fassicles visible to the naked eye, and if so what do they look like?: Yes fassicles
are visible to the naked eye, and they appear as parallel strands.
14. What does the perimysium carry?: Larger blood vessels, larger nerves, and muscle spindles
15. What is the epimysium layer?: The fibrous sheath that surrounds the entire muscle
16. What is the fascia?: Sheet of connective tissue that separates neighboring muscles or muscle groups from each
other and from the subcutaneous tissue.
17. What are the two types of muscle attachments?: 1. Indirect
- Direct
18. What is an indirect attachment?: The muscle ends short of its bony destination and the gap is bridged
by a tendon.
19. What is a tendon?: Fibrous band or sheet
20. What is direct attachment?: There is so little separation between muscle and bone that to the naked eye, the
red muscular tissue seems to emerge directly from the bone.
21. What is the origin?: The bony site of attachment at the relatively stationary end.
22. What is the insertion?: Attachment site at its more mobile end
23. What is the belly?: The thicker middle region between the origin and insertion.
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4. Extensibility
5. Elasticity
35. Which property has been developed by the highest degree?: Responsiveness (ex-
citability)
36. What sends an electrical change across the plasma membrane?: 1. Chemical
signals
2. Stretching
3. Other stimuli
37. What is unique about the contractility of muscles?: The ability to shorten
38. What is extensibility?: Capability of being stretched between contractions.
39. Muscles can stretch as much as times
contracted length.: Three (3)
40. What is elasticity?: Returns to original length after being stretched.
41. What is skeletal muscle?: VOLUNTARY STRIATED muscle that is usually attached to one or more bones.
42. Is skeletal muscle voluntary?: Yes!
43. What is voluntary?: Subject to conscious control
44. What are striations?: Skeletal muscle exhibits light and dark transverse bands.
45. What is the cause of striations?: The overlapping arrangement of their internal contractile proteins.
46. What is involuntary?: Not under conscious control and is never attached to bone.
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47. What are other names for skeletal muscles?: 1. Muscle fibers
- Myofibers
48. What are the three connective tissues in skeletal muscle?: 1. Endomysium
2. Perimysium
3. Epimysium
49. Collagen is not & .: Excitable & Contractile
50. Collagen is somewhat & .: Extensible and Elastic
51. What is the sarcolemma?: Plasma membrane of the muscle fiber.
52. What is the sarcoplasm?: Cytoplasm of the muscle fiber.
53. What are myofibrils?: Long protein bundles that occupies main portion of sarcoplasm.
54. What two things are stored in myofibrils and what are their functions?: 1.
Glycogen - provides energy during heightened exercise.
- Myoglobin - red pigment that stores oxygen until needed for muscular activity.
55. Muscle
fibers have multiple nuclei pressed up against .: Sarcolem- ma
56. What are myoblasts?: Stem cells that fuse together to form each muscle fiber.
57. What are satellite cells?: Unspecialized myoblasts that remain in between the muscle fiber and endomy- sium.
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72. What is a thin filament made up of?: Composed of two intertwined strands of a protein called fibrous
(F) actin.
73. What does fibrous (F) actin look like?: Beaded necklace.
74. What makes up fibrous (F) actin?: String of subunits called globular (G) actin.
75. What is on a globular (G) actin?: Active site that binds to the head of myosin.
76. What other molecule does a thin filament have?: Tropomyosin
77. What does a tropomyosin do?: Each blocks 6 or 7 active sites on the G actin subunits.
78. What protein does tropomyosin have?: Troponin.
79. What is troponin?: Small calcium binding protein that is on each tropomyosin.
80. What are elastic filaments made up of?: Made of a springy protein called titin.
81. What does an elastic filament do?: Flank each thick filament and anchor it to a Z disc.
82. What three things does anchoring a thick filament to a Z disc do?: 1. Stabilizes the thick
filament.
2. Center between the thin filaments.
3. Prevents over stretching.
83. What are contractile proteins and what do they do?: Actin & myosin.
They "do all the work" and shorten muscle fibers.
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84. What do regulatory proteins and what do they do?: Tropomyosin & troponin.
Like a switch they determine when the fiber can and cannot contract.
85. What activates the regulatory proteins to contract?: Activated by release of calcium into
sarcoplasm and its binding to troponin.
86. What three things do accessory proteins do?: 1. Anchor myofilaments.
2. Regulate their length.
3. Align myofilaments for maximum effectiveness.
87. What is the most clinically important accessory protein?: Dystophin.
88. Explain dystrophin.: Links actin in outermost myofilaments to transmembrane proteins and eventually to fibrous
endomysium surrounding entire cell.
89. If dystrophin has genetic defects what can occur?: Muscular dystrophy.
90. What is an A band?: Darker striation that is formed by thin filaments overlapping.
91. What is an I band?: Lighter striation.
92. What is a H band?: Lighter middle region of A-band.
93. What is the M line and where is it located?: Located in the middle of the H band and it is the dark line
where the thick filaments originate.
94. A
skeletal muscle never contracts unless stimulated be a ?: - Nerve.
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110. What do synaptic vesicles undergo & what happens?: They undergo exocytosis and release
ACh into the synaptic cleft.
111. What is the synaptic cleft?: The tiny gap that separates the synaptic knob and the sarcolemma.
112. What is a Schwann cell?: Envelops entire junction and isolates from surrounding tissue fluid.
113. What are ACh receptors and how many of them are there in a muscle fiber?: ACh
receptors respond to the release of acetylcholine. There is 50 million of these receptors in each fiber.
114. What is the purpose of junctional folds and it's numerous infoldings?: 1. Reach max # of
ACh receptors.
- Increase the sensitivity.
115. What is the basal lamina?: Surrounds entire muscle fiber and Schwann cell of the NMJ.
116. What is the basal lamina composed of?: Glycoproteins & collagen.
117. What important enzyme does the basal lamina have?: Aceylcholinesterase (AChE)
118. What does AChE do?: Breaks down the ACh after it has stimulated the muscle - this is important in turning ott
contraction and allowing the muscle to relax.
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119. What are muscle fibers and neurons electrically excitable cells?: Plasma mem- branes
exhibit voltage changes in response to stimulation.
120. What is electrophysiology?: Study of the electrical activity in cells.
121. What is the voltage electrical potential?: A ditterence in electrical charge from one point to another.
122. What is the resting potential about?: -90 mV
123. How is the resting membrane potential maintained?: Sodium-potassium pump.
124. What is the action potential?: The quick and up down change in voltage shift from the negative RMP to a
positive value and then back to a negative value.
125. What is excitation?: The process in which action potentials in the nerve fiber lead to action potentials in the muscle
fiber.
126. What is the first step of excitation?: The nerve arrives at the synaptic knob and then stimulates the calcium
gates to open and calcium is pumped into the synaptic knob.
127. What is the second step of excitation?: Calcium stimulates the exocytosis of the synaptic vesicles, which
releases acetylcholine in the synaptic cleft.
128. One action
potential cause the exocytosis of about synaptic vesi- cles.: 60
129. How many molecules of ACh is released by each vesicle?: 10,
130. What is the third step of the excitation?: ACh dittuses across the synaptic cleft and then binds to the
receptors on the sarcolemma.
13 / 16 head and "cocks" into a high energy position. Keeps ADP and phosphate group bound to it.
143. What is the second step of contraction?: The cocked myosin head binds to the active site of the thin
filament and forms a cross bridge between the myosin and actin.
144. What is the third step of contraction?: Myosin releases the ADP and phosphate and flexes into a bend,
then tugs the thin filament along with it creating the power stroke.
145. What is the last step of contraction?: Until another ATP binds, myosin releases actin and prepares to repeat
the entire process over again.
146. What is the first step of relaxation?: Nerve signals stop arriving at the NMJ, so the synaptic knob stops
releasing ACh.
147. What is the second step of relaxation?: As ACh dissociates from the receptors, the enzyme AChE breaks it
down to where it cannot stimulate muscle.
148. What is the third step of relaxation?: Active transport pumps calcium back into the SR, the calcium then binds
to the calsequestrin protein and stored for later use.
149. What is the fourth step of relaxation?: As the calcium ions dissociate from troponin they are pumped
in the SR and not replaced.
150. What is the final step of relaxation?: Tropomyosin moves back into the position to block active sites of the
actin filament. Myosin can no longer bind to actin and the muscle fiber ceases all tension.
151. What is the length tension relationship?: Amount of tension generated by a muscle, and therefore
the force of its contraction, depends how stretched or contracted it was before stimulated.
152. What is muscle tone?: Central nervous system continually monitors and adjusts length of the resting muscles,
maintain a state of partial contraction.
153. What does muscle tone maintain?: Maintains optimum length and makes the muscles ideally ready for
action.
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154. What is a myogram?: Chart timing and strength of the muscle's contraction.
155. What does a weak sub threshold electrical stimulus give?: No contraction.
156. What is a threshold?: Minimum voltage necessary to generate an action potential in the muscle fiber and produce
a contraction.
157. What is the latent period?: Delay between onset of the stimulus and onset of twitch.
158. What is internal tension?: Force generated during the latent period.
159. What is the contraction phase?: Phase in which filaments slide and the muscle shortens.
160. What produces external tension?: Once elastic components are taut.
161. What 6 factors do twitches strength affect them?: 1. Stimulus frequency
2. Concentration of Ca 2+
3. How stretched muscle was before stimulus
4. Temperature
5. pH
6. State of hydration
162. What is isometric contraction?: Muscle produces internal tension while an external resistance causes it to
stay the same length or become longer.
163. What is isotonic contraction?: Muscle changes in length but the tension stays the same.
164. What is concentric muscle contractions?: Muscle shortens while tension stays the same.
165. What is eccentric muscle contractions?: Muscle lengthens as it maintains tension.
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177. As the phosphagen system is exhausted what happens?: Muscles shift to anaerobic
fermentation.
178. In
the absence of oxygen, glycolysis can generate a net gain of ATP for every glucose molecule consumed.: 2
179. Where do muscles obtain glucose from?: Blood and their own stored glycogen.
180. Aerobic respiration produces ATP molecules
per glucose.: 36.
181. What are the 6 causes of muscle fatigue?: 1. ATP synthesis declines as glycogen is consumed.
2. ATP shortage slows down Na(+) and K(+) pumps.
3. Lactic acid lowers pH of sarcoplasm.
4. Accumulation of extracellular K(+)
5. Motor nerve fibers use up their ACh
6. Less signal output to skeletal muscles
182. What is endurance determined by?: Large part by one's maximum oxygen uptake.
183. What is the maximum oxygen uptake?: The point at which the rate of oxygen consumption reaches a
plateau and does not increase with an added workload.
