Chapter 10 Flashcards
1
Q
The three types of cells in muscle tissue are
A
- skeletal
- cardiac
- smooth
2
Q
What function do all three muscle tissue types share in common?
A
generating a force called muscle tension
3
Q
- create movement
- maintain posture
- stabilize joints
- generate heat
- regulate the flow of materials through hollow organs
A
other functions of muscle tissue
4
Q
due to their length and appearance muscle cells are known as
A
fibers
5
Q
- made up of long muscle cells arranged parallel to one another; some are quite long, extending nearly the entire length of the muscle
- they are multinucleated cells whose contractions arevoluntary (controlled by conscious thought)
A
skeletal muscle
6
Q
- muscle cells are found only in the heart
- Each cell is short and highly branched, and has one to two nuclei
- Intercalated discs join adjacent cells; they contain gap junctions and desmosomes (modified tight junctions) that both unite the cells and permit them to coordinate contraction
- Contraction is involuntary, or not controlled by conscious thought
A
cardiac muscle
7
Q
- muscle cells are long and flat with “spindle-shaped” pointed ends and a single centrally located nucleus
- muscle cells are found lining most hollow organs in the eye, skin, and some glandular ducts; their contractions are involuntary
A
smooth muscle cells
8
Q
What makes smooth muscle cells different from skeletal and cardiac muscle tissues?
A
consists of nonstriated smooth muscle cells
9
Q
What are the five properties of muscle cells?
A
- contractility
- excitability
- conductivity
- extensibility
- elasticity
10
Q
the ability to contract where proteins in the cell draw closer together; this does not necessarily involve shortening of the cell
A
contractility
11
Q
the ability of a cell to respond to a stimulus (chemical, mechanical stretch, or local electrical signals)
A
excitability
12
Q
the ability of a cell to conduct electrical changes across the entire plasma membrane
A
conductivity
13
Q
the ability of a cell that allows it to be stretched without being ruptured (up to 3 times their resting length without damage)
A
extensibility
14
Q
the ability of a cell that allows it to return to its original length after it has been stretched
A
elasticity
15
Q
or muscle cells, are described using specialized terminology
A
myocytes
16
Q
the myocyte’s cytoplasm
A
sarcoplasm
17
Q
the myocyte’s plasma membrane
A
sarcolemma
18
Q
is modified endoplasmic reticulum that:
Forms a weblike network surrounding the myofibrils
Varies in structure in the three types of muscle tissue (discussed later)
A
sarcoplasmic reticulum
19
Q
- cylindrical organelles found in each of the three muscle cell types
- made up of bundles of specialized proteins that allow for contraction
A
myofibrils
20
Q
the most abundant organelle, are made up of mostly contractile proteins
A
myofibrils
21
Q
surrounds the myofibrils and stores and releases calcium ions
A
The sarcoplasmic reticulum (SR)
22
Q
- are deep inward extensions of sarcolemma that surround each myofibril
- form a tunnel-like network within the musclefiber, continuous with the exterior of the cell, and are therefore filled with extracellular fluid
A
Transverse tubules (T-tubules)
23
Q
enlarged sections of SR found flanking each T-tubule
A
terminal cisternae
24
Q
Two terminal cisternae and their corresponding T-tubule form
A
triad
25
made of hundreds to thousands of myofilaments, including contractile proteins, regulatory proteins, and structural proteins
myofibrils
26
generate tension
contractile proteins
27
dictate when a fiber may contract
regulatory proteins
28
maintain proper alignment and fiber stability
structural proteins
29
what are the three types of myofilaments?
* thick
* thin
* elastic
30
composed of bundles of the contractile protein myosin
thick filaments
31
composed of the proteins actin, tropomyosin, and troponin
thin filaments
32
composed of a single massive, spring-like structural protein called titin that stabilizes the myofibril structure and resists excessive stretching force
elastic filaments
33
a contractile protein that has active sites that bind with the myosin heads of thick filaments
actin
34
a long rope-like regulatory protein that twist around two strands of actin, covering active sites.
tropomyosin
35
a small globular regulatory protein that holds tropomyosin in place and assists with turning contractions on and off
troponin
36
* degenerative muscular disease occurring almost exclusively in boys
* Caused by a defective gene for the protein dystrophin, coded on X chromosome
Duchenne Muscular Dystrophy (DMD)
37
In the absence of normal dystrophin, the sarcolemma breaks down and the muscle fiber is destroyed and replaced with fatty and fibrous connective tissue
Duchenne Muscular Dystrophy (DMD)
38
Multiple muscle fibers (surrounded by extracellular matrix called the endomysium) form a
fascicle
39
Each fascicle is surrounded by a layer of connective tissue called the
perimysium
40
Bundles of fascicles make up a
skeletal muscle
41
a skeletal muscle is surrounded by
epimysium
42
The perimysium and epimysium come together at the end of the muscle to form
tendon
43
binds the muscle to its attaching structure (usually bone)
tendon
44
Skeletal muscles are enclosed by a layer of thick connective tissue called
fascia
45
where only thin filaments are found
light bands
46
where both thin and thick filamentsare found
dark bands
47
in light, mnemonic) is composed only of thin filaments
I bands
48
is a dark line in the middle of the A band made up of structural proteins that hold the thick filaments in place and serve as an anchoring point for elastic filaments
M line
49
contains the zone of overlap, the region where we find thick and thin filaments and where tension is generated during contraction
A bands
50
In the middle of the A band where only thick filaments exist is
H zone
51
is found in the middle of the I band and is composed of structural proteins that:
* Anchor the thin filaments in place and to one another
* Serve as attachment points for elastic filaments
* Attach myofibrils to one another across the entire diameter of the muscle fiber
Z disc
52
explains how tension is generated during muscle contraction
the sliding-filament mechanism
53
due to an unequal distribution of ions near the plasma membrane resulting in a polarized resting state
membrane potentials
54
When the barrier separating the ions is removed, they follow their gradients, creating a flow of electrical charges, and the potential energy becomes
kinetic energy
55
the electrical potential across the sarcolemma of a resting muscle fiber and it measures 85 mV, meaning the cytosol is 85 mV more negative than the extracellular fluid
the resting membrane potential
56
can then move through the sarcolemma using protein channels and carriers
sodium and potassium ions
57
how is the concentration gradient maintained?
the Na+/K+ pump
58
how many sodium ions and potassium ions does the pump move?
3 sodium ions out of the cell and 2 potassium ions into the cell
59
brief changes in the membrane potential of a cell from a resting negative value to a positive value, then back to its resting negative value
action potentials
60
open in response to the presence of a chemical
ligand-gated channels
61
open and close in response to changes in the membrane potential of the plasma membrane
voltage gated channels
62
begins when voltage-gated Na+ channels open, allowing Na+ to flow inward
depolarization
63
begins after Na+ channels have closed and voltage-gated K+ channels have opened, allowing K+ to diffuse out of the cell
repolarization
64
* the synapse where a single motor neuron communicates with many muscle fibers
* function is to transmit a signal, called a nerve impulse (an action potential), from the neuron to the sarcolemma of the muscle fiber
The neuromuscular junction
65
are chemicals that trigger changes in a target tissue when released, allowing for cell to cell communication
neurotransmitter
66
the space between axon terminal and muscle fiber, filled with collagen fibers and a gel that anchors the neuron in place
synaptic cleft
67
specialized region of the muscle fiber plasma membrane whose folded surface has many ligand-gated Na+ channels; ACh is the ligand that opens these gates, allowing Na+ to diffuse into the muscle cell
motor end plate
68
begins when an action potential signals the release of acetylcholine from the axon terminal into the synaptic cleft
excitation phase
69
the link between the stimulus and the contraction
excitation-contraction coupling
70
begins when Ca++ ions bind troponin, which pulls tropomyosin away from actin’s active site; the crossbridge cycle then begins
contraction phase
71
diffuses across the synaptic cleft where it can bind to ligand-gated channels found in the motor end plate of the muscle fiber sarcolemma
acetylcholine
72
Ligand-gated channels open when they bind acetylcholine which allows Na+ ions to enter the muscle fiber generating an
end plate potential
73
Motor neurons continue to fire action potentials as acetylcholine is rapidly degraded by the enzyme
acetylcholinesterase
74
The end plate potential is generated by the influx of _______ into the motor end plate.
sodium
75
Acetylcholine is released from the synaptic terminus in response to
An action potential arriving at the synaptic terminus
76
The term “synaptic cleft” refers to
The gap between the neuron and the muscle fiber
77
The sodium channels of the motor end plate are
ligand-gated channels
78
The end plate potential is
a local depolarization
79
leads to the opening of VOLTAGE-gated Na+ channels in the sarcolemma surrounding the motor end plate, which triggers an action potential
end-plate potential
80
The channels that open in the sarcolemma surrounding the motor endplate and generate an action potential are
voltage-gated channels
81
The term “propagate” when referring to an action potential means
spread
82
In order to trigger a muscle contraction, an action potential must reach the
triads
83
a triad consist of
Two terminal cisternae and a T-tubule
84
________ is released from the SR in response to arrival of an action potential
Ca2+
85
Covers actin active sites
tropomyosin
86
Troponin has three subunits. Which of the following does NOT bind to one of these subunits?
myosin
87
Action potential arrives at triad, calcium is released from the terminal cisternae, calcium binds to troponin, tropomyosin exposes the actin active sites
sequence of events that occur in preparation for contraction
88
begins when actin’s active site is exposed, initiating the crossbridge cycle
contraction phase
89
occurs when ADP + Pi are released from the myosin head
power stroke
90
Hydrolysis of ATP is responsible for
Recocking of the myosin heads
91
The binding of ATP to myosin is responsible for
Release of the myosin heads from the actin active sites
92
The release of ADP and Pi from myosin occurs during
the power stroke
93
The myosin heads return to their low-energy (relaxed) state during
the power stroke
94
Pulls the thin filaments toward the M lines
the power stroke
95
During muscle fiber relaxation, calcium channels in the SR close because
The resting membrane potential is restored
96
During muscle fiber relaxation
Calcium is pumped back into the SR
97
Acetylcholinesterase in the synaptic cleft degrades acetylcholine, allowing
Ligand-gated sodium channels to close
98
Sarcolemma repolarization during relaxation
Restores the resting membrane potential
99
Which aspect of muscle relaxation requires ATP?
Pumping calcium ions back into the SR
100
concentration in the cytosol is 5–6 times higher than ATP; it can immediately regenerate enough ATP for about 10 seconds of maximum muscle activity
creatine phosphate
