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Flashcards in Module 2 Deck (234)
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121

- total mass is decrease
-Seen in denervation
- when a muscle remains unused for many weeks, the rate of degradation of contractile proteins is more rapid than the rate of replacement

Muscle Atrophy

122

- increase in the number of actin and myosin filaments in each muscle fiber, causing enlargement of the individual muscle fibers

Fiber Hypertrophy

123

- actual number of muscle fiber has been observed to increase in addition to the fiber hypertrophy

Fiber Hyperplasia

124

The fibrous tissue that replaces the muscle fibers during denervation atrophy also has a tendency to continue shortening for many months, which is called ___

Contracture

125

o Will have Muscle Fasciculation
- Small, irregular contractions (due to Ach release from degenerating axons)
o Will have Muscle Fibrillation
- Spontaneous, repetitive contractions (Cholinergic receptors spread out over entire cell membrane)
o Function may fully return w/in 3 months due to Reinnervation
o No further return of function after 1-2 years
o Replaced by fibrous-fatty tissue

Muscle Denervation

126

Remaining nerve fibers sprout new axons (innervate many paralyzed muscle fibers) -> macromotor units -> muscles become stronger but w/less control

Poliomyelitis

127

- several hours after death, all the muscles of the body will go into a state of contracture
- the rigidity results from loss of all ATP (required to cause separation of cross-bridges from the actin filaments during the relaxation process)
- Start after 3-6 hours
- End after 15-25 hours; earlier in high temp

Rigor Mortis

128

Anti-Ach receptor antibodies

Myasthenia Gravis

129

- milder form of dystrophy
- is also caused by mutations of the gene that encodes for dystrophin but has later onset and longer survival

Becker Muscular Dystrophy

130

Skeletal muscle fibers are innervated by large, myelinated nerve fibers that originate from large motoneurons in the ____

Anterior horns of the Spinal Cord

131

A junction between a single axon terminal and the muscle fiber membrane. The invaginated membrane is called the ____

Synaptic gutter or synaptic through

132

A space between the terminal and the fiber membrane is called the ___

Synaptic space or synaptic cleft

133

at the bottom of the gutter are numerous smaller folds of the muscle membrane called ____

Subneural clefts

134

- neurotransmitter that excites muscle fiber membrane
-synthesize in the cytoplasm terminal, but is absorbed rapidly into many small synaptic vesicles

Acetylcholine

135

- found in the synaptic space
- enzyme which destroys acetylcholine a few milliseconds after it has been released from the synaptic vesicles

Acetylcholinesterase

136

- initiates an action potential that spreads along the muscle membrane and thus creating muscle contraction

End plate potential

137

drugs that stimulate the muscle fiber by Ach like action

Metacholine, Carbachol, Nicotine

138

drugs that stimulate the neuromuscular auction by inactivating acetylcholinesterase

Neostigmine, Physostigmine, Diisipropyl flurophosphate

139

- smooth muscle cells contain a large amount of another regulatory protein called ___
- this protein initiates contraction by activating the myosin cross-bridges

Calmodulin

140

Special mechanism in the heart cause a continuing succession of heart contraction

Cardiac rhythmicity

141

- dark areas crossing the cardiac muscle fibers
- cell membranes that separate individual cardiac muscle cells from one another

Intercalated discs

142

- Exhibits atrial and ventricular Syncitium (contract together)
- Uses EXTRAcellular and INTRAcellular Calcium
- Atrial and Ventricular AP is different form Conductive
System AP (SA Node)

Cardiac Muscle Contraction

143

- More developed T-tubule, Less Developed SR compared
to skeletal Muscles
- Calcium Regulation of Cardiac muscles
1. Calcium Channels (increases intracellular
calcium)
a. L-Type or Slow Calcium Channel ->predominant; voltage-gated
b. Fast calcium channel
2. 3Na+-1Ca++ Exchanger (decreases
intracellular calcium)
3. Ca-ATPase pump (decreases intracellular
calcium)

Cardiac Muscle Contraction

144

Cardiac Muscle vs Skeletal Muscle

Cardiac Muscles: Electrochemical Coupling (Ca++-
induced release of Ca++)

Skeletal Muscles: Eletromechanical Coupling
(interaction between DHPR and RYR)

145

Cardiac Muscle vs Skeletal Muscle

Cardiac Muscles: T-tubules in the Z lines
Skeletal Muscles: T-tubules at the ends of I-bands

Cardiac Muscles: Syncitium, No Tetany (Due to long refractory period secondary to voltage-gated L-type Calcium Channels)
Skeletal Muscles: Recruitment, may undergo tetany

146

- No troponin
- Contains the following: MLCK (Myosin Light Chain Kinase); Calmodulin; Caldesmon, Calponin
- MYOSIN-based regulation
- Contains DENSE BODIES (Similar to z discs)
SARCOPLASMIC RETICULUM (SR) - rudementary (smooth muscle rely on extracellular Calcium

Smooth Muscle Contraction

147

- Rudimentary t-tubules
- Contains Voltage-gated L-type Ca++
Channel And The 3Na+-1Ca++
Antiporter

Caveoli

148

- Desmin and Vimentin
- Connect dense bodies with cytoskeletal network

Intermediate Filament

149

- Opens slowly and remains open much longer
- Used by hormones, NT

InsP3-gated Ca++ channel

150

- Causes relaxation vascular smooth muscles
- Used by Nitric Oxide, Adenosine, drugs, hormones

cAMP & cGMP mechanisms