A&P Chapter 9 Flashcards
1
Q
What are the three types of muscles?
A
Skeletal, Cardiac, Smooth
2
Q
Where are skeletal muscles located?
A
Attached to bones or skin
3
Q
Which skeletal muscles are attached to skin?
A
Some facial muscles
4
Q
Where are cardiac muscles located?
A
Walls of the heart
5
Q
Where are smooth muscles located?
A
Unitary muscle in the walls of hollow visceral organs (other than the heart) Multiunit muscle in intrinsic eye muscles, airways, and large arteries
6
Q
What is the cell shape and appearance of skeletal muscle?
A
Single, very long, cylindrical, multinucleate cells with obvious striations
7
Q
What is the cell shape and appearance of cardiac muscle?
A
Branching chains of cells; uni or binucleate; striations
8
Q
What is the cell shape and appearance of smooth muscle?
A
Single, spindle shaped, uninucleate, no striations
9
Q
Which of the three muscle types are involuntary?
A
Cardiac and smooth
10
Q
Which muscle type is under voluntary control?
A
Skeletal
11
Q
All muscles share four main characteristics, what are they?
A
Excitability / Responsiveness = ability to receive and respond to stimuli
Contractility = ability to shorten forcibly when stimulated
Extensibility = ability to be stretched
Elasticity = ability to recoil to resting length
12
Q
What are the four important functions of muscles?
A
Produce movement, maintain posture and body position, stabilize joints, and generate heat as they contract
13
Q
Muscles are responsible for all locomotion and manipulation, what are some examples?
A
Walking, digesting, body position
14
Q
Where is skeletal muscle tissue?
A
Packaged into skeletal muscles, which are attached to bones and skin
15
Q
What fibers are the longest of all the muscles?
A
Skeletal muscle fibers
16
Q
Do skeletal muscle fibers have striations?
A
Yes
17
Q
Are skeletal muscles voluntary?
A
Yes, they can be consciously controlled
18
Q
What are characteristics of skeletal muscle?
A
Contracts rapidly, tires easily, and are powerful
19
Q
What is the hierarchy of muscle?
A
A whole muscle contains many fascicles, and a fascicle consists of many muscle fibers
20
Q
What is a muscle fiber?
A
A muscle cell
21
Q
What does skeletal muscle contain?
A
Nerves, blood vessels, and connective tissue
22
Q
What are the connective tissue sheaths of skeletal muscle?
A
Epimysium, perimysium, and endomysium
23
Q
What is the epimysium?
A
Dense irregular connective tissue surrounding the entire muscle
24
Q
What is the perimysium?
A
Surrounds fascicles (groups of muscle fibers)
25
What is the endomysium?
Areolar connective tissue surrounding each muscle fiber
26
Muscles attach to bone in at least two places, what are they?
Insertion and orgin
27
What is the insertion of a muscle?
Attachment to moveable bone
28
What is the origin of a muscle?
Attachment to immovable or less moveable bone
29
Attachments can be direct or indirect, what is a direct / fleshy attachment?
Epimysium fused to periosteum of bone or perichondrium of cartilage
30
Attachments can be direct or indirect, what is a indirect attachment?
Connective tissue wrappings extend beyond the muscle as ropelike tendons or sheetlike aponeurosis
31
What is the microscopic anatomy of skeletal muscles?
Long multiple nuclei, sarcolemma, sarcoplasm, glycosomes, myoglobin, and myofibrils
32
What is the sacrolemma?
Muscle fiber plasma membrane
33
What is the sacroplasm?
Muscle fiber cytoplasm
34
What the glycosomes?
Glycogen storage
35
What is myoglobin?
O2 storage
36
What are myofibrils?
The contractile units
37
What are the characteristics of myofibrils?
Densely packed, rodlike elements
38
What percentage of muscle cell volume is made up of myofibrils?
~80%
39
A single muscle fiber can contain how much myofibrils?
1000s
40
What are the features of myofibrils?
Striations, sacromeres, and myofilaments
41
What are sacromeres?
Repeating contractile units
42
What are the two types of myofilaments in myofibrils?
Actin and myosin
43
What are myofilaments?
Orderly arrangement of actin and myosin myofilaments within the sarcomere
44
What are actin myofilaments?
Thin, extend across I band and partway in A band. They are anchored to Z discs
45
What are myosin myofilaments?
Thick, extend the length of the A band and are connected at the M line
46
What are A bands?
Myosin, dark regions
47
What is the H zone?
Lighter region in the middle of the dark A band
48
What is the M line?
Line of protein (myomesin) that bisects the H zone vertically
49
What are I bands?
Actin, lighter regions
50
What is the Z disc/line?
Coin-shaped sheet of proteins on the midline of light I band
51
Each thick filament consists of what?
Many myosin molecules whose heads protrude at opposite ends of the filament
52
A thin filament consists of what?
Two strands of actin subunits twisted into a helix plus two types of regulatory proteins
53
What are the two types of regulatory proteins in a thin filament?
Troponin and tropomyosin
54
What is the elastic filament?
Composed of the protein titin, holds thick filaments in place; helps recoil after stretching; resists excessive stretching
55
What is dystrophin?
Links thin filaments to proteins of sacrolemma
56
Other proteins bind what together?
Filaments or sarcomeres
57
Other proteins maintain the alignment of what?
Sarcomeres
58
What is Duchenne Muscular Dystrophy?
Genetic disease caused by a defective gene for dystrophin. The sarcolemma of DMD patients tear easily, allowing the entry of excess calcium which damages contractile fibers, causing inflammation and cell death
59
How often does DMD appear in births?
1 in 3600 births
60
DMD appears almost exclusively in which sex?
Males
61
What age group does DMD appear in?
2-7
62
How does DMD progress?
From extremities upward, affecting the head, chest muscles, and cardiac muscle
63
What is the prognosis of DMD?
With supportive care, people with DMD can live into the 30s and beyond
64
The decision to move is activated by what?
The brain
65
Where does the signal transmit to after the brain makes the decision to move?
Transmitted down the spinal cord to motor neurons which then activate muscle fibers
66
What are the excitable cells capable of action potentials?
Neurons and muscle cells
67
What are excitable cells?
Cells capable of changing resting membrane potential voltages
68
The action potential crosses from neuron to muscle cell via which neurotransmitter?
Acetylcholine (ACh)
69
What is the sarcoplasmic reticulum?
Smooth ER surrounding each myofibril. The terminal cisterns (ends).
70
What does the sarcoplasmic reticulum store and release?
Ca2+
71
What are the T tubules?
Part of the sarcolemma that allows electrical nerve transmissions to reach deep into the interior of each muscle fiber
72
What is the triad?
Terminal cistern, T tubule, and terminal cistern
73
What does the triad mean?
When an electrical impulse passes, T tubule proteins change shape, causing SR proteins to change shape, causing release of calcium into the cytoplasm
74
In the relaxed state, thin and thick filaments overlap ______ at ________
Overlap only slightly at the ends of the A band
75
What is the sliding filament model of contraction?
Thin filaments slide past thick filaments, causing actin and myosin to overlap more
76
How are cross bridges formed, and what process is allowed to begin?
When the nervous system stimulates muscle fibers, myosin heads are allowed to bind to actin, forming cross bridges, which causes the sliding (contraction) process to begin.
77
Cross bridge attachments form and break several time, pulling ____ ______ a little closer toward the center of the sarcomere
Thin filaments
78
The axon terminal (end of axon) and muscle fibers are separated by a gel-filled space called what?
The synaptic cleft
79
Membrane-bound synaptic vesicles are stored within what?
Axon terminals
80
What neurotransmitter do synaptic vesicles contain?
Acetylcholine
81
What are the infoldings of sarcolemma called?
Junctional folds
82
What do junctional folds contain?
Millions of ACh receptors
83
What is the junctional fold region called?
Motor end plate
84
What does the neuromuscular junction consists of?
Axon terminals, synaptic cleft, and junctional folds
85
What do muscle fibers exhibit?
Resting membrane potential
86
What is the fluid like in the Resting Membrane Potential
The fluid inside the cell is negative compared to fluid outside the cell.
87
What is the RMP of a muscle cell?
About -90 mV
88
What is the RMP set by?
Leak channels and Na+/K+ pumps (the voltage-gated channels are closed)
89
What are the events at the Neuromuscular Junction in order?
1. Action potential arrives at the axon terminal
2. Voltage-gated calcium channels open, and calcium enters the motor neuron
3. Calcium entry causes release of ACh neurotransmitter into synaptic cleft
4. ACh diffuses across to ACh receptors (Na+ chemical gates) on sarcolemma
5. ACh binding to receptors opens gates, allowing Na+ to enter resulting in end plate potential
6. Acetylcholinesterase degrades ACh
90
Many toxins, drugs, and diseases interfere with events where?
Neuromuscular junction
91
What is Myasthenia Gravis?
Disease characterized by drooping upper eyelids, difficulty swallowing and talking, and generalized muscle weakness
92
What is the physiology of Myasthenia Gravis?
Shortage of ACh receptors because the person's ACh receptors are attacked by their own antibodies. This suggests that it's an autoimmune disease
93
What is Tetanus?
Spastic paralysis caused by a toxin from Clostridium Tetani
94
What is the physiology of Tetanus?
The toxin, clostridium tetani, blocks the release of inhibitory neurotransmitter in the spinal cord, resulting in overstimulation of muscles
95
How is Tetanus prevented?
Vaccination
96
What is Botulism?
Muscular paralysis caused by a toxin from Clostridium Botulinum
97
What is the physiology of Botulism?
The toxin, Clostridium Botulinum prevents the release of ACh at synaptic knobs
98
What is the toxin Clostridium Botulism used for?
Toxic ingestion can be life-threatening, but careful injections of it can treat spasticity or can be used for cosmetic purposes (Botox)
99
What is Rigor Mortis?
3-4 hours after death, muscles begin to stiffen. Peak rigidity occurs about 12 hours postmortem
100
What is the physiology of Rigor Mortis?
Intracellular calcium levels increase because ATP is no longer being synthesized, so calcium cannot be pumped back into SR. This results in Cross Bridge formation. ATP is also needed for cross bridge detachment. The lack of ATP results in the myosin head staying bound to actin, causing a constant state of contraction.
101
The muscles stay contracted in Rigor Mortis until when?
Muscle proteins break down, causing myosin to release
102
Contractions may/may not ______ _______
Shorten muscle
103
What is an Isometric Contraction?
No shortening; muscle tension increases but does not exceed load
104
What is an Isotonic Contraction?
Muscle shortens because muscle tension exceeds load
105
Muscles must be ____ to remain healthy
Active
106
What is Disuse Atrophy?
Degeneration and loss of mass, due to immobilization or loss of neural stimulation, can begin almost immediately
107
By what percentage does muscle strength decline by per day?
5%
108
Paralyzed muscles can atrophy to how much of its inital size?
One-Fourth
109
What replaces the lost muscle tissue?
Fibrous connective tissue
110
Once fibrous connective tissue replaces the lost muscle tissue, rehabilitation is _______ at this point
Impossible
111
What does aging result in?
Loss of muscle mass and fibrosis. The muscle mass is replaced by dense regular connective tissue, which decreases flexibility
