Exam 2 Flashcards
1
Q
what is the definition of an action potential
A
brief, rapid, large changes in the distribution of charges across a membrane in a non decremental fashion
2
Q
what are the electrical events taking place during an action potential
A
a slow depolarization till the threshold potential is reached, then an explosive depolarization takes place, the membrane repolarizes back to its resting place, finally a transient hyperpolarization occurs
3
Q
what type of channels are responsible for the occurance of action potentials
A
voltage gated channels
4
Q
what happens during the resting phase of an action potential
A
Na+ and K+ voltage gated channels are closed
5
Q
what happens during the threshold potential of an action potential
A
Na+ channels open causing a depolarization then at the peak of the action potential those channels are deactivated
6
Q
what happens at the peak of the action potential
A
K+ gates open allowing K+ ions to leave resulting in a repolarization
7
Q
what happens after the action potential returns to the threshold potential
A
K+ continues to move out causing a hyperpolarization once the K+ channel is fully closed the resting membrane potential is returned
8
Q
what re-establishes and maintains the concentration gradients of Na and K
A
the Na+ K+ pump
9
Q
what is an absolute refractory period (RP)
A
when another action potential can not be generated no matter how depolarized the membrane is to avoid the offset balance of Na and K
10
Q
what is a relative refractory period (RP)
A
when an action potential can be generated but it requires a stronger than normal stimuli due to the membrane being hyperpolarized
11
Q
what is the propagation of unmyelinated axons
A
the charges in the membrane continues to flow to neighboring axons
12
Q
what are schwann cells
A
neuron associated cells that have myelin sheaths wrapped around the axon- in the peripheral system
13
Q
what is the purpose of myelin sheaths
A
to support and propagate action potentials moving down the axon
14
Q
what type of cell does the peripheral nervous system contain
A
Schwann cells
15
Q
what type of cell does the central nervous system contain
A
Oligodendrocyte
16
Q
what does the layers of myelin provide the axons
A
insulated pockets
17
Q
do nodes of roaniver have myelin sheets
A
NO
18
Q
what is the interaction between unmyelinated axons and schwann cells
A
the schwann cell supports several axons that are separated from its neighbor by thin cytoplasmic extensions of the schwann cell
19
Q
what is unique about an action potential occuring in myelinated cells
A
those spots of insulation provides a pocket that allows the action potential to move from one insulated spot to another allowing the rate of passage to increase
20
Q
do myelin sheets create a distance between the ICF and the ECF fluid membrane
A
yes
21
Q
what is saltatory propagation
A
an action potential propagation in myelinated axons
22
Q
what determines the rate of action potentials
A
size and diameter
23
Q
how can an myelinated cell differ from a unmyelinated one in terms of passage rate
A
an myelinated cell can be smaller but move an action potential 3.5x faster
24
Q
does the velocity of an action potential differ between myelinated and unmyelinated cells
A
yes myelinated tend to have a faster velocity
25
are graded potentials depolarizations or hyperpolarizations
this is dependent on the stimulus
26
action potentials always lead to what
depolarization of a membrane and the reversal of the membrane potential
27
what is the amplitude of a graded potenial based off of
the stength of the stimulus
28
what type of amplitude do action potentials have
an all or nothing amplitude
29
what does the strength of stumulus change in an action potential
frequency
30
what size is the general amplitude of a graded potential
small
31
what is the general amplitude of an action potential
large (100mV)
32
what is the typical duration of a graded potential
a few milliseconds to seconds
33
what is the typical duration of an action potential
3-5 minutes
34
what channel is typicall responsible for graded potentials
ligand gated channels
35
what ions are typically involved w/ graded potentials
Na+, K+, or Cl-
36
what ions are typically involved w/ action potentials
Na+ and K+
37
is the there a refractory period w/ graded potentials
NO
38
is summation possible w/ graded potentials
yes both temporal summation and spatial summation
39
is summation possible w/ action potentials
NO due to them being all or nothing
40
how do graded potentials spread
through passive spread to neighboring membrane regions
41
how do action potentials spread
to neighboring membrane regions that regeneration of a new action potential at every point
42
does the amplitude of graded potentials deminish over time
yes the are decremental
43
how are graded potentials created
either by an external stimuli or by the release of neurotransmitters in synapse
44
what is the sarcoplasm
the cytoplasm of muscle cells
45
what is the sarcoplasmic reticulum
endoplasmic reticulum in muscle cells
46
what is the sacolemma
the cell membrane of muscle cells
47
what are myofibrils
what muscle cells are contained of
48
what are myofilaments
filaments found in muscle cells consisted of thin actin filaments and thick myosin filaments
49
what is the relationship between actin filaments and myosin filaments in muscle cells
the actin and myosin filaments slide across each other which is what causes contractions and relaxations
50
what is the I band
actin filaments w/ in a myofibril w/ some myosin
51
what is the A band
myosin filaments w/ in a myofibril w/ some actin on the outer parts
52
what is the H zone
region in the middle of the A band where there is only myosin
53
what does a small H zone equal for a muscle
it means the muscle is fully contracted
54
what is the M line
a protein called myozenin that marks the centre of the sarcomere, primarily role is structurally keeping everything spaced properly
55
what is the Z disc
an anchor point where actin are anchored to each other on both sides of the I band
56
what is a T tubule
an extension of the sarcolemma that extends down in the cell membrane that wraps around myofibrils to relay an action potential
57
what ion allows the SR to be extremely extensive for contraction
Ca
58
what is the terminal cisternae of SR
where the sarcoplasmic reticulum and T tubule meet physically
59
what is the triad in skeletal muscle cells
T tubule, sarcoplasmic reticulum, and terminal cisternae
60
what is tropomyosin
it prevents myosin from binding to actin in the absence of Ca
61
what is troponin
it shifts the position of tropomyosin on the actin filaments, exposing myosin binding sites on actin
62
where are actin filaments oriented w/ their plus end
Z disc
63
where are actin filaments oriented w/ their minus end
the center of the sacromere
64
what is ATP critical for in muscle
both contraction and relaxation
65
what is the difference between channels and gap junctions
channels are material specific while gap junctions will allow anything through that can fit
66
how many nuclei are in each cardiomyocyte
one or two large ones located centrally surrounding the numerous mitochondria
67
how are cardiac muscle cells arranged
distinctly aligned w/ one another
68
what type of muscle cells are striated
cardiac and skeletal
69
does cardiac muscle require a signal for contraction
no
70
what purpose does intercalated disks have for cardiac muscle cells
they join them w/ adjacent cells as well as allowing passage of electrical activity throughout creating a conduit from one cell to the next
71
how are sepearate cardiomyocytes connected
by desmosomes and adherin junctions
72
where in individual cardiomyocytes is the nuclei
in the center of the cell
73
how many nuclei does smooth muscle cells have
one
74
are smooth muscle cells straited
NO
75
what are smooth muscle cells modulated by
autonomic nervous system
76
what do gap junctions in smooth muscle cells do
they allow for coordination of contraction
77
what are actin filaments attached to in the cytoplasm of smooth muscle
dense bodies
78
what are actin filaments attached to in the membrane of smooth muscle
attachment plaques
79
what is the caveolae
folds in the cell membrane that contain aggregates of receptors and ion channels responsible for conveying signals into the cell
80
what is a single unit smooth muscle cell
a buncle or sheet of hundreds to thousands of smooth muscle fibers that contract together as a single unit
81
how are neurotransmitters distributed to both a single unit smooth muscle cell and a multi unit smooth muscle cell
via varicosities
82
what are multi unit smooth muscle cells
these are capable of contracting independently of one another and often are innervated by a single nerve ending
83
what type of contraction does multi unit smooth muscle cells have
spontaneous
84
what type of contraction does single unit smooth muscle cells have
synchronous due to action potentials flowing from one fiber to another thru gap junctions
85
how are action potentials communicated to skeletal muscles
from a motor neuron extending from the ventral root of the spinal cord
86
what is the only way skeletal muscle can be induced for contraction
after interacting with motor neurons
87
what is neurogenic mean for SM
that is when smooth muscle contracts in response to stimulation from neurons, typically w/ multi unit muscles
88
what is myogenic for SM
when the muscle itself generates its own rhythmic contractions, typically w/ single unit muscles
89
where is an action potential initated in skeletal muscle
at a neuromuscular junction
90
what is a dihypropyridine recepors (DHPR)
a voltage dependent Ca channel that acts like a voltage gated sensor that is present in the T tubule
91
what is excitation contraction coupling
idea that an action potential will inevitably lead to contraction that stems from DHPR
92
what is a ryanodine receptor (RYR)
a Ca channel in the sarcoplasmic reticulum that is opened due to depolarization caused conformational change in DHPR, this is initally causes the cross bridge cycle
93
what happens after repolarization of the sarcolemma
DHPR and RYR return to their original conformation, Ca channels close, ATP dependent Ca pumps return Ca to the SR, Ca levels in the sarcoplasm declines, Ca dissociates from troponin, and tropomyosin returns to its "blocking" position on actin
94
what depolarization cause in the sarcoplasm
it causes a conformational change in DHPR that opens the RYR Ca channel on the SR, Myosin/Actin cross bridges which induces sliding of actin filaments
95
what is the Ca induced Ca release seen in the contraction of cardiac muscles
An action potential enters from adjacent cells, voltage gated Ca channels open allowing Ca to enter the cell, Ca induces Ca release through RYR channels which causes Ca spark which create a Ca signal, Ca ions bind to troponin to initate contraction
96
what happens when the cardiac muscle relaxes
Ca unbinds from troponin Ca is pumped back into the sarcoplasmic reticulum for storage, Ca is exchanged w/ Na. The Na gradient is maintained by the Na K ATPase
97
what is the propagation of myelinated axon potentials
Slatatory propagation which is when the ions jump from one insulated pocket to another
98
what type of neurotransmitter is released in muscle cells
acetylcholine
99
describe the cross bridge cycle
ATP binds w/ myosin, after Ca is released from the voltage gated channels Ca binds to troponin pulling tropomyosin from actin allowing myosin binded w/ ADPase to bind to actin, the ADPase then unbinds from the myosin leaving room for another ATP to bind to the myosin to relax and detach from the actin
100
what type of neuron releases norepinephrine
somatic
101
what is the connective tissue surrounding each myofibril
endomysium
102
what connective tissue is surrounding each fascicle
perimysium
103
what connective tissue is surrounding groups of fascicles
epimysium
104
what type of cycle is the cross bridge cycle and how long does it contiune
it is the contractile cycle and it contiunes as long as the Ca and ATP is present
105
how does contraction in a skeletal muscle ends
Ca ATP pumps returns Ca to the sarcoplasmic reticulum resting the membrane polarity
106
what type of stimulus contracts smooth muscle
mechanical, electrical, or chemical
107
what does depolarization cause in smooth muscle cells
contractions from the opening of voltage dependent calcium channel causing an increase of the intracellular concentration of Ca
108
what are neurogenic smooth muscle
smooth muscle that is initated by the stimulus from neurons
109
what is myogenic smooth muscle
smooth muscle that self generates rhythmic contractions
110
what is phasic contractions
rapid alternating contractions and relaxations
111
what is tonic contractions
a degree of tension or tone is maintained at all times
112
describe the release of neurotransmitter at a varicosity
the action potential arrives at the varicosity causing a depolarization opening the voltage gated Ca channels allowing Ca to trigger exocytosis of synaptic vesicles NE then binds to the adrenergic recptor of the target once NE diffuses away from the synapses the activity stops
113
what happens after the snyapses of contraction stops in a smooth muscle cell
the NE is transported back into the axon placed back into the synaptic vesicles to be metabolized by monamine oxidase (MAO)
114
what connects adjacent fibers in smooth muscle
gap junctions
115
how is myosin different in terms of contraction of smooth muscle
in SM the movement of myosin heads is mediated by two small protein chains associated w/ the neck of the myosin molecule
116
what is the role light chains have in smooth muscle contraction
once they are phosphorylated they allow the myosin head to bind to actin
117
what is kinases
enzymes that add phosphate groups
118
what is phosphatases
enzymes that remove phosphate groups
119
what is calmodulin
a Ca binding protein that stimulates SM contraction
120
what is the myosin light chain kinase (MLCK)
it regulates the myosin and actin interaction by binding phosphate to myosin in the presence of calmodulin and Ca allowing it to bind w/ actin
121
where does most Ca come from for SM contraction
the ECF
122
how can cytosolic Ca levels be increased in SM cells
either by voltage dependent activation processes or by receptor mediated processes
123
what is the mechanism for SM contraction
intracellular Ca concentrations increases when Ca enters the cell and is released from sarcoplasmic reticulum then Ca binds to calmodulin activating the MLCK this phosphorylates light chains in myosin increasing myosin ATPase activity inacting the cross bridge slide along actin creating muscle tension
124
how does SM contraction end
Ca decreases and the phosphate unbinds from the light chain of the myosin head through myosin light chain phosphatase (MLCP)
125
what are satellite cells
a ganglia cell that regulates O2, CO2, nutrient, and neurotransmitter levels in the peripheral nervous system specifical the afferent side
126
what are astrocytes cells
they maintain blood brain barrier providing structural support, regulating ion, nutrient, and dissolved gas concentrations while absorbing and recycling neurotransmitters in the central nervous system
127
what are ependymal cells
line ventricles and central canal and assists in producing, circulating, and monitoring of cerebrospinal fluid
128
what are microglia cells
they remove cell debris wastes, and pathogens by phagocytosis
