Skeletal and Smooth Muscle Flashcards
(78 cards)
1
Q
types of muscle cells
A
- skeletal
- smooth
- cardiac
2
Q
which types of muscle cells are striated
A
- skeletal
- cardiac
3
Q
what is a skeletal muscle cell called?
A
- muscle fiber
- myofiber
4
Q
myofibers are composed of
A
- myofibrils
5
Q
myofibrils contain
A
- myofilaments
- thick and thin
6
Q
what is the functional unit of the myofibril called?
A
- sarcomere
7
Q
plasma membrane of the myofiber called
A
- sarcolemmea
8
Q
what are T tubules
A
- infoldings that bring plasma membrane deep into myofibril
9
Q
thick filament is made of
A
- myosin
10
Q
thin filament is made of
A
- actin
11
Q
what is on top of actin
A
- tropomyosin and troponin
12
Q
z lines define
A
- a single sarcomere
13
Q
Triad is composed of
A
- T-tubular system and sarcoplasmic reticulum
14
Q
neuromuscular junction is the synapse between
A
- somatic motor neuron
- skeletal muscle fiber
15
Q
post synaptic region of the skeletal muscle at the NMJ
A
- motor end plate
16
Q
all the motor fibers innervated by one somatic motor neuron
A
- motor unit
17
Q
a somatic motor neuron innervates
A
- more than one muscle fiber
18
Q
a muscle fiber is innervated by
A
- ONLY ONE SOMATIC MOTOR NEURON
19
Q
start of somatic motor neuron events
A
- post synaptic potentials summate to exceed threshold
- action potential initiated
20
Q
what happens after the action potential is initiated
A
- AP conducted along axon to terminal
- terminals depolarize
21
Q
what happens when the terminals depolarize?
A
- voltage gated calcium channels open
22
Q
what happens after voltage gated calcium channels open?
A
- calcium enters the presynaptic terminal
23
Q
what happens after calcium enters the presynaptic terminal
A
- vesicles containing acetylcholine undergo exocytosis
- acetylcholine diffuses across synaptic cleft
24
Q
what does acetylcholine bind to
A
- nicotinic acetylcholine receptor channels
25
what happens after acetylcholine binds to nicotinic acetylcholine receptor channels
- receptor channels open which increase the permeability of synaptic membrane to Na and K
26
what happens after receptor channels open
- Na influx exceeds K+ efflux
| - produces a depolarizing graded potential called EPP
27
what happens after the EPP is generated
- EPP exceeds threshold and initiates muscle action potential
28
what happens after the EPP initiates the muscle action potential
- voltage-gated Na+ channels open as the sarcolemma depolarizes
29
muscle action potential is conducted along
- the sarcolemma and into T tubules
30
what happens after the muscle action potential is conducted along the sarcolemma and T tubules
- voltage gated L-type calcium channels in T tubules open
31
voltage gated L-type calcium channels in T tubules have what kind of receptor
- DHP receptor
32
what happens after voltage gated L-type calcium channels in T tubules open
- causes calcium release channels in SR to open
33
what kind of receptors do calcium release receptors in SR have?
- Ryanodine receptors
34
what happens after calcium release channels in SR open?
- calcium diffuses out of SR
| - Calcium concentration near sarcomeres increases
35
what happens after calcium concentration near sarcomeres increases
- cross-bridges form
- contraction begins
- sarcomeres shorten
36
what is an abundant source of calcium
- sarcoplasmic reticulum
37
depolarization of sarcolemma is propagated down
which causes
- T tubules
| - opening of the DHP receptors
38
what do the DHP receptors do
- couple to ryanodine receptors
| - causes Calcium move out of SR into cytosol
39
what does calcium bind to
- calcium binds to troponin and removes troponin/tropomyosin complex blocking actin
40
what does calcium binding to troponin and blocking of tropomyosin allow to happen
- cross bridge formation
| - power stroke
41
calcium binding from the SR in response to a single action potential
- sufficient to bind all sites on troponin to expose actin binding sites for maximum cross bridge binding
42
what happens with decreased calcium in the muscle
- troponin complex blocks myosin binding sites on actin
| - results in relaxation
43
calcium is taken up into the SR by
- Calcium ATPase (SERCA)
44
how does muscle contraction compare to the action potential
- muscle contraction extends far beyond the action potential
45
smooth muscles are what kind of shape?
- spindle shaped
46
do smooth muscles have actin and myosin?
- yes
47
do smooth muscles have sarcomeres?
- no
| - they have dense bodies
48
filaments in smooth muscles are organized how
- diagonally
49
sliding filaments during contraction causes
- cell to ballon out
50
do smooth muscles fire action potentials
- may or may not
51
what regulates degree of contraction of smooth muscle
- cytosolic calcium
52
smooth muscles surround
- hollow structures and organs that undergo changes in volume
53
result of cell contraction in smooth muscle (in regard to lumen)
- shrinks lumen diameter
54
vascular smooth muscle is under what kind of control?
- involuntary control
55
what can control vascular smooth muscle
- hormones
- neurotransmitters from ANS
- local stimuli
56
multiunit smooth muscle electrical coupling between cells
- little electrical coupling between cells
57
multiunit smooth muscle contractions
- may contract independently of its neighbor
| - finer control
58
multiunit smooth muscle contraction example
- iris and ciliary body of eye
59
single unit smooth muscle electrical coupling between cells
- extensive electrical coupling between cells
60
single unit smooth muscle contraction
- coordinated contraction of many cells
61
single unit smooth muscle contraction example
- bladder
62
two sources of calcium in smooth muscle
- extracellular
| - sarcoplasmic reticulum
63
calcium binds what in smooth muscle
- calmodulin
64
calcium binding calmodulin does what
- activates myosin light chain kinase
65
role of MLCK
- phosphorylates myosin
- cross bridge formation
- contraction
66
roles of MLCP (myosin light chain phosphatase)
- dephosphorylates myosin
- cross bridges uncouple
- relaxation
67
activity of MLCP
- constitutive
68
cross bridge activation in smooth muscle compared to skeletal muscle
- slow and energy efficient
69
smooth muscle form of myosin ATPase activity versus skeletal muscle
- low rate of ATPase activity
70
shortening in smooth muscle versus skeletal muscle
- slower
71
fatigue of smooth muscle
why
- do not fatigue during prolonged activity
| - due to low rate of energy utilization
72
role of nitric oxide in smooth muscle
- smooth muscle relaxation
| - most potent vasodilator
73
nitric oxide produced by
- endothelial cells
74
nitric oxide stimulates
enzyme involved
- GTP -> cGMP
| - through guanylate cyclase
75
cGMP activates
- protein kinase G
76
protein kinase G stimulates
- reuptake of cytosolic calcium
| - opening of calcium activated potassium channels
77
result of protein kinase G
- cysotolic calcium levels fall
- MLCK activity decreases
- decreased cross bridge formation
- relaxation
78
smooth muscle contraction graded based on
- amount of cytosolic calcium available
