Muscular System Flashcards
(186 cards)
1
Q
Types of Muscle Tissue
A
- Skeletal muscle
- Cardiac muscle
- Smooth muscle
2
Q
elongated muscle cells eg. Skeletal and smooth muscle
cells
A
Muscle fibers
3
Q
both are word roots meaning “muscle”
A
Myo or mys
4
Q
meaning flesh
A
sarco
5
Q
attach to and cover the bony skeleton
A
Skeletal Muscle
6
Q
the longest muscle cells and have obvious stripes called
A
striations
7
Q
the longest muscle cells
A
Skeletal Muscle
8
Q
the longest muscle cells and have obvious stripes called striations
A
Skeletal Muscle
9
Q
Skeletal muscle is a ________________ because it is subject to
conscious contro
A
voluntary muscle
10
Q
responsible for overall body mobility
A
Skeletal Muscle
11
Q
tires easily and must rest after short periods of activity
A
Skeletal Muscle
12
Q
occurs only in the heart
A
Cardiac Muscle
13
Q
cardiac muscle cells are
A
striated
14
Q
is cardiac muscle voluntary or involuntary?
A
involuntary muscle
15
Q
contracts at a fairly steady rate set by the heart’s pacemaker
A
Cardiac Muscle
16
Q
found in the walls of hollow visceral organs, such as the stomach, urinary bladder, and respiratory passages
A
Smooth Muscle
17
Q
Smooth Muscle is found in the walls of hollow visceral organs, such as the
A
stomach, urinary bladder, and respiratory passages
18
Q
Special Characteristics of Muscle Tissue
A
Excitability, Contractility, Extensibility, Elasticity
19
Q
capacity of muscle to respond to a stimulus
A
Excitability
20
Q
ability of a muscle to shorten and generate pulling force
A
Contractility
21
Q
muscle can be stretched back to its original length
A
Extensibility
22
Q
ability of muscle to recoil to original resting length after stretched
A
Elasticity
23
Q
Muscle Functions
A
- Body movement (Locomotion)
- Maintenance of posture
- Respiration
- Communication (Verbal and Facial)
- Constriction of organs and vessels
- Heart beat
- Production of body heat (Thermogenesis)
24
Q
stimulate muscle fibers to contract
A
Motor neurons
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neuron axons branch so that each muscle fiber (muscle
cell) is innervated
Motor neurons
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form a neuromuscular junction
Motor neurons
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neuromuscular junction =
myoneural junction
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muscles require large amounts of energy
Capillary beds surround muscle fibers
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extensive vascular network delivers necessary oxygen and nutrients and carries away metabolic waste produced by muscle fibers
Capillary beds surround muscle fibers
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Dense regular connective tissue surrounding entire muscle
Epimysium
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Separates muscle from surrounding tissues and organs
Epimysium
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Connected to the deep fascia
Epimysium
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Epimysium is connected to the
deep fascia
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Collagen and elastic fibers surrounding a group of muscle fibers called a fascicle
Perimysium
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Collagen and elastic fibers surrounding a group of muscle fibers called a
fascicle
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Loose connective tissue that surrounds individual muscle fibers
Endomysium
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Endomysium contains
blood vessels, nerves and satellite cells
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embryonic stem cells function in repair of muscle tissue
satellite cells
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Collagen fibers of all 3 layers come together at each end of muscle to form a
tendon or aponeurosis
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consists of hundreds to thousands of muscle cells, plus connective tissue wrappings, blood vessels, and nerve fibers.
Muscle (organ)
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Connective Tissue Wrappings of Muscle (organ)
covered externally by the epimysium
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is a discrete bundle of muscle cells, segregated from the rest of the muscle by a connective tissue sheath
Fascicle
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a portion of muscle
fascicle
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Connective Tissue Wrappings of Fascicle
surrounded by perimysium
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is an elongated multinucleate cell
Muscle Fiber (cell)
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it has a banded (striated) appearance
Muscle Fiber (cell)
47
Connective Tissue Wrappings of Muscle Fiber (cell)
surrounded by endomysium
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Skeletal muscles span joints and attach to bones (or other structures) in at least two places:
Insertion and Origin
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the movable bone when a muscle contracts
Insertion
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immovable or less movable bone where the movable bone moves towards
Origin
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cell membrane
Sarcolemma
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Surrounds the sarcoplasm
Sarcolemma
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cytoplasm of fiber
sarcoplasm
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Contains many of the same organelles seen in other cells
Sarcolemma
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Has an abundance of the oxygen-binding protein myoglobin
Sarcolemma
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oxygen-binding protein
myoglobin
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Punctuated by openings called the transverse tubules (Ttubules)
Sarcolemma
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Carcolemma is punctuated by openings called the
transverse tubules (T-tubules)
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Narrow tubes that extend into the sarcoplasm at right angles to the surface
Transverse tubules (T-tubules)
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Filled with extracellular fluid
Transverse tubules (T-tubules)
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cylindrical structures within muscle fiber
Myofibrils
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Are bundles of protein filaments
Myofibrils
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protein filaments
myofilaments
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Two types of myofilaments
1. Actin filaments (thin filaments)
2. Myosin filaments (thick filaments)
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At each end of the fiber, ________________ are anchored to the inner surface of the sarcolemma
myofibrils
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When myofibril _________________, muscle ______________
shortens; shortens
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a segment of a myofibril
Sarcomere
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is the contractile unit
Sarcomere
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composed of myofilaments made up of contractile proteins
Sarcomere
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Extended macromolecular structure
Myofilament or filament
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Two types of Myofilament or filament
thick filament and thin filament
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Contain bundled myosin molecules
thick filaments
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Consists of many myosin molecules whose heads protrude at opposite ends of the filament
thick filaments
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Contain actin molecules (plus other proteins)
thin filaments
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Consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins
thin filaments
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thin filaments consists of two strands of actin subunits twisted into a helix plus two types of regulatory proteins which are
troponin and tropomyosin
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The sliding of the thin filaments past the thick filaments
Muscle shortening
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Maintain the organization of the A band
Elastic Filaments
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Provide elastic recoil when muscle contraction ends
Elastic Filaments
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a dark band
A bands
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full length of thick (myosin) filament
A bands
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protein to which myosins attach
M line
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has thick but NO thin filaments
H zone
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a light band
I bands
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from Z disks to ends of thick filaments
I bands
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has thin but NO thick filaments
I bands
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Extends from A band of one sarcomere to A band of the next sarcomere
I bands
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filamentous network of protein
Z disk
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Serves as attachment for actin myofilaments
Z disk
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elastic chains of amino acids
Titin filaments
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keep thick and thin filaments in proper alignment
Titin filaments
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is an elaborate, smooth endoplasmic reticulum
Sarcoplasmic Reticulum
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runs longitudinally and surrounds each myofibril
Sarcoplasmic Reticulum
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Form chambers called terminal cisternae on either side of the T-tubules
Sarcoplasmic Reticulum
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Chambers formed by sarcoplasmic reticulum on either side of the T-tubules
terminal cisternae
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stores Ca++ when muscle not contracting
Sarcoplasmic Reticulum
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when stimulated, calcium released into sarcoplasm
Sarcoplasmic Reticulum
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Sarcoplasmic Reticulum release ______________ into sarcoplasm when stimulated
calcium
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has Ca++ pumps that function to pump Ca++ out of the sarcoplasm back into the SR after contraction
Sarcoplasmic Reticulum Membrane
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Formed by a single T-tubule and the 2 terminal cisternae
triad
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run near the aligned A- and I-band boundaries of sarcomeres
T-tubules
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In a relaxed muscle fiber, the thin and thick filaments overlap only at the ends of the ___________________
A band
103
When the muscle shortens:
1. The I-bands shorten
2. the distance between successive Z discs shortens
3. the H zones disappear
4. the contiguous A bands move closer together but their length does not change
104
Events before the muscle fiber contraction
1. The fiber must be activated, that is, stimulated by a nerve ending so that a change in membrane potential occurs.
2. Next, it must generate an electrical current, called an action potential, in its sarcolemma.
3. The action potential is automatically propagated along the sarcolemma.
4. Then, intracellular calcium ion levels must rise briefly, providing the final trigger for contraction.
105
The Nerve Stimulus and Events at the Neuromuscular Junction
1. When a nerve impulse reaches the end of an axon, the axon terminal releases ACh into the synaptic cleft.
2. ACh diffuses across the cleft and attaches to ACh receptors on the sarcolemma of the muscle fiber.
3. ACh binding triggers electrical events that ultimately generate an action potential.
106
After ACh binds to the ACh receptors, its effects are quickly terminated by
acetylcholinesterase
107
breaks down ACh to its building blocks, acetic acid and choline
acetylcholinesterase
108
Involves a shortage of Ach receptors
MYASTHENIA GRAVIS
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Myasthenia Gravis is characterized by
- drooping upper eyelids
- difficulty swallowing and talking
- generalized muscle weakness
110
Autoimmune disease of Myasthenia Gravis:
antibodies are formed against ACh receptors
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Generation of an Action Potential Across the Sarcolemma
1. An end plate potential is generated at the neuromuscular junction
2. Depolarization: Generating and propagating an action potential (AP)
- The local depolarization current spreads to adjacent areas of the sarcolemma. This opens voltage-gated sodium channels there, so Na+ enters following its electrochemical gradient and initiates the AP. The AP is propagated as its local depolarization wave spreads to adjacent areas of the sarcolemma, opening voltage-gated channels there. Again, Na+ diffuses into the cell following its electrochemical gradient.
3. Repolarization: Restoring the sarcolemma to its initial polarized state (negative inside, positive outside)
- Repolarization occurs as Na+ channels close (inactivate) and voltage-gated K+ channels open. Because K+ concentration is substantially higher inside the cell than the extracellular fluid, K+ diffuses rapidly out of the muscle fiber.
112
the sequence of events by which transmission of an action potential along the sarcolemma causes myofilaments to slide
Excitation-Contraction Coupling
113
Excitation-Contraction Coupling
1. The action potential (AP) propagates along the sarcolemma and down the T-tubules
2. Calcium ions are released.
- Transmission of the AP along the T tubules of the triads causes the voltage-sensitive tubule proteins to change shape. This shape change opens the Ca2+ release channels in the terminal cisterns of the sarcoplasmic reticulum (SR), allowing Ca2+ to flow into the cytosol.
3. Calcium binds to troponin and removes the blocking action of tropomyosin.
- When Ca2+ binds, troponin changes shape, exposing binding sites for myosin (active sites) on the thin filaments.
4. Contraction begins:
- Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins. At this point, E-C coupling is over.
114
Is the series of during which myosin heads pull thin filaments toward the center of the sarcomere.
Cross Bridge Cycling
115
Cross Bridge Cycling
1. Cross bridge formation.
- Energized myosin head attaches to an actin myofilament, forming a cross bridge.
2. The power (working) stroke.
- ADP and Pi are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result, it pulls the actin filament toward the M line.
3. Cross bridge detachment.
- After ATP attaches to myosin, the link between myosin and actin weakens, and the myosin head detaches (the cross bridge “breaks”).
4. Cocking of the myosin head.
- As ATP is hydrolyzed to ADP and Pi, the myosin head returns to its prestrike high-energy, or “cocked,” position.
116
Types of Muscle Contraction
- Isotonic contraction (concentric)
- Isometric contraction
117
On stimulation, muscle develops enough tension (force) to lift the load (weight). Once the resistance is overcome, the muscle shortens, and the tension remains constant for the rest of the contraction.
Isotonic contraction (concentric)
118
Two types of Isotonic contraction (concentric)
Concentric contractions and Eccentric contractions
119
muscle shortens and does work
Concentric contractions
120
muscle generates force as it lengthens
Eccentric contractions
121
occur when a muscle attempts to move a load that is greater than the force (tension) the muscle is able to develop.
Isometric contraction
122
Muscle is attached to a weight that exceeds the muscle’s peak tension-developing capabilities. When stimulated, the tension increases to the muscle’s peak tension-developing capability, but the muscle does not shorten.
Isometric contraction
123
Pathways for regenerating ATP during muscle activity:
- Direct phosphorylation
- Anaerobic pathway
- Aerobic pathway
124
Coupled reaction of creatine phosphate (CP) and ADP
Direct phosphorylation
125
Energy source of Direct phosphorylation:
Creatine Phosphate
126
Oxygen used in Direct phosphorylation:
None
127
Products of Direct phosphorylation:
1 ATP per CP, creatine
128
Duration of energy provided in
15 seconds
129
Glycolysis and lactic acid formation
Anaerobic Pathway
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Energy source of Anaerobic Pathway:
Glucose
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Oxygen used in Anaerobic Pathway:
None
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Products of Anaerobic Pathway:
2 ATP per glucose, lactic acid
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Duration of energy provided in Anaerobic Pathway:
30-40 seconds, or slightly more
134
Aerobic cellular respiration
Aerobic Pathway
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Energy source of Aerobic Pathway:
glucose; pyruvic acid; free fatty acids from adipose tissue; amino acids from protein metabolism
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Oxygen used in Aerobic Pathway:
Required
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Products of Aerobic Pathway:
32 ATP per glycose, CO2, H20
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Duration of energy provided in Aerobic Pathway:
Hours
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The fastest pathway is
Direct Phosphorylation
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The slowest pathway is
Aerobic Pathway/Aerobic Respiration
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Energy sources used during short-duration exercise and prolonged-duration exercise:
Short-duration exercise
6 seconds:
ATP is stored in muscles used first
142
Energy sources used during short-duration exercise and prolonged-duration exercise:
Short-duration exercise
10 seconds:
ATP is formed from creatine phosphate and ADP (direct phosphorylation).
143
Energy sources used during short-duration exercise and prolonged-duration exercise:
Short-duration exercise
30-40 seconds and End of Exercise:
Glycogen stored in muscles is broken down to glucose, which is oxidized to generate ATP (anaerobic pathway)
144
Energy sources used during short-duration exercise and prolonged-duration exercise:
Prolonged-duration exercise
Hours:
ATP is generated by breakdown of several nutrient energy fuels by aerobic pathway.
145
a state of physiological inability to contract even though the muscle still may be receiving stimuli
Muscle Fatigue
146
Causes of Muscle Fatigue
- ionic imbalances
- accumulation of inorganic phosphate (Pi)
- lactic acid
147
raises the concentration of H+ and alters contractile proteins
lactic acid
148
extra amount of oxygen that the body must take in for these restorative processes
Excess Postexercise Oxygen Consumption (EPOC)
149
reason for hyperventilation during exercises
Excess Postexercise Oxygen Consumption (EPOC)
150
For a muscle to return to its resting state, all the following must occur:
1. Its oxygen reserves in myoglobin must be replenished.
2. The accumulated lactic acid must be reconverted to pyruvic acid.
3. Glycogen stores must be replaced.
4. ATP and creatine phosphate reserves must be resynthesized.
151
moderately weak but sustained muscle activity required for endurance exercise does not promote significant skeletal muscle hypertrophy
Resistance Exercise
152
results mainly from high-intensity resistance exercise (eg. weight lifting or isometric exercise)
Muscle Hypertrophy
153
degeneration and loss of mass
Disuse Atrophy
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begins when muscles are immobilized
Disuse Atrophy
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muscle strength can decline at the rate of
5% per day
156
Thick filaments are fewer but have myosin heads along their entire length.
Smooth Muscle
157
No troponin complex in thin filaments
Smooth Muscle
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a protein that acts as the calcium binding site
calmodulin
159
In Smooth Muscle, thick and thin filaments arranged
diagonally
160
lacks the highly structured neuromuscular junctions of skeletal muscle
Smooth Muscle
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dense body network (serving as the Z disk)
Intermediate filament
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Contraction of Smooth Muscle
1. Calcium ions (Ca2+) enter the cytosol from the ECF via voltage-dependent or voltage independent Ca2+ channels, or form the scant SR.
2. Ca2+ binds to and activates calmodulin.
3. Activated calmodulin activates the myosin light chain kinase enzymes.
4. The activated kinase enzymes catalyze transfer of phosphate to myosin, activating the myosin ATPases.
5. Activated myosin forms cross bridges with actin of the thin filaments. Shortening begins
163
Different autonomic nerves serving the smooth muscle of visceral organs release different neurotransmitters
Neural Regulation
164
Neurotransmitters
- acetylcholine
- norepinephrine
- gastrin
165
smooth muscle location of acetylcholine
bronchioles
166
action of acetylcholine
strong contraction that narrows the bronchioles
167
smooth muscle location of norepinephrine
bronchioles and blood vessels
168
action of norepinephrine
dilates the bronchioles, constriction
169
Hormones and Local Chemical Factors
- Histamine
- excess carbon dioxide
- low pH
- lack of oxygen
170
smooth muscle location of gastrin
stomach
171
action of gastrin
contract, to churn food
172
Types of Smooth Muscle
- Unitary Smooth Muscle
- Multiunit Smooth Muscle
173
Unitary Smooth Muscle is found in
walls of all hollow organs except the heart
174
are arranged in opposing (longitudinal and circular) sheets
Unitary Smooth Muscle
175
Are innervated by varicosities of autonomic nerve fibers
Unitary Smooth Muscle
176
Unitary Smooth Muscle are innervated by varicosities of
autonomic nerve fibers
177
often exhibit rhythmic spontaneous action potentials
Unitary Smooth Muscle
178
Unitary Smooth Muscle are electrically coupled by
gap junctions
179
are electrically coupled by gap junctions and so contract as a unit (for this reason recruitment is not an option)
Unitary Smooth Muscle
180
Respond to various chemical stimuli
Unitary Smooth Muscle
181
Electrical isolation of cells allows finer motor control
Unitary Smooth Muscle
182
smooth muscles in the large airways to the lungs and in large arteries, the arrector pili muscles attached to hair follicles, and the internal eye muscles that adjust pupil size and allow the eye to focus visually
Multiunit Smooth Muscle
183
Consists of muscle fibers that are structurally independent of one another
Multiunit Smooth Muscle
184
Is richly supplied with nerve endings, each of which forms a motor unit with a number of muscle fibers
Multiunit Smooth Muscle
185
Responds to neural stimulation with graded contractions that involve recruitment
Multiunit Smooth Muscle
186
Gap junctions permit coordinated contraction
Multiunit Smooth Muscle
