Muscle Flashcards
1
Q
What are the 3 types of Muscle tissue found in the body?
A
Skeletal
Cardiac
Smooth
2
Q
Skeletal Muscle has all of the following characteristics except:
- Striated
- Conscious control
- Excitated by Self-depolarization
- Functions in locomotion and heat generation
A
- Excitated by Self-Depolarization is false
- Actually excited by somatic, alpha motor neurons
3
Q
Cardiac Muscle has all of the following characteristics except…
- Unstriated Muscle
- Found in the heart
- Involuntary Control
- Function is to pump blood through the circulatory system
A
- Unstriated muscle is false!
- Cardiac muscole is striated like skeletal muscle
4
Q
Smooth muscle has all of the following characteristics except…
- Nonstriated
- Involuntary control
- Excited by several different mechanisms - stretching, neuronal activity etc…
- Found only in the GI tract
A
- Found only in GI tract would be FALSE
- It is found throughout the body
5
Q
Skeletal muscle is innervated by neurons from the [] [] of the spinal cord
A
Ventral Horn
6
Q
What is the name of 1 skeletal muscle cell?
A
Myofiber
7
Q
What is the organziation of a muscle fiber, from largest “cell to smallest unit”…
A
Myofiber > Myofibril > sarcomere > microfilament (actin/myosin)
8
Q
What is the contractile unit of a myofiber?
A
Sarcomere
9
Q
The sarcolemma is another name for the [] [] of the muscle cell…
A
Plasma Membrane
10
Q
Transverse Tubules
- [] of the sarcolemma
- Connect the myofiber to the []
- Allow for the quick delivery system for the spread of [] [] to the skeletal muscle cell
- Closely associated with the [] [] which spreads throughout the entire cell
A
- Invaginations
- extracellular
- action potentials
- sarcoplastic reticulum
11
Q
What is the thick filament in a myofibril and what is the thin filament?
A
- thick = myosin
- Thin - actin
12
Q
[] [] is the intracellular storage site of Ca2+ for T-tubule usage?
A
Sarcoplastic Reticulum (SR)
13
Q
Myosin is formed by…
2 [] [] of myosin that form the head, neck, and tail
A
Heavy Chains
14
Q
How many heads does Myosin have?
What binding sites are on the myosin head?
A
- 2 heads
- Each head has an actin binding site
- Both have ATPase sites which hydrolyze ATP
- Both have 2 Light chains
15
Q
What are the 2 light chains on each of the myosin heads?
A
- Alkali Light chain - serves a structural role
- Regulatory myosin light chain
- regulates the ATPase capability of the myosin head
16
Q
What molecules make up the double helical actin structure in muscle cells?
A
- G-actin molecules come to gether to make F-Actin molecules
- F-actin chains make the double helix structure
17
Q
What 2 regulatory proteins are on actin that inhibit/prohibit muscle contractions?
A
- Tropomyosin
- Troponin
18
Q
What are the binding sites of Troponin and what does each site bind?
A
- TnC - binds to calcium
- TnT - binds to tropomyosin
- TnI - binds to actin and inhibits actin/myosin interaction
19
Q
Which actin regulatory protein physically blocks the binding of acting to myosin?
Which actin regulatory protein removes the barrier stopping acting/myosin binding?
A
- Tropomyosin
- Troponin
20
Q
What is the sequence of events that removes tropomyosin from the myosin binding sites on the actin molecule?
A
- Ca2+ binds to the TnC subunit of troponin
- Conformational change in troponin
- This conformational change moves tropomyosin out of the way
- Myosin can bind to Actin
21
Q
This portion of the the sarcomere stretches in between adjacent A-Bands…
A
The I band
22
Q
The I-band consists of only [] filament, or [], and stretches between two adjacent []
A
- thin filament
- Actin
- sarcomeres
23
Q
[] - [] anchor points for the thin filaments and the boundaries for the sarcomeres…
A
Z-Discs
24
Q
The []-zone contains only thick filaments and does not overlap with [] filaments
A
- H-Zone
- Thin Filaments
25
The [] - band consists of the full thick filament and does slightly overlap with the thin filament...
A-band
26
The sarcomere's thick/thin filaments are set up in a [] array - [] thick filaments surrounded by [] thin filaments
1. Hexagonal Array
2. 1 Thick
3. 6 Thin
27
Proteins like dystrophin, titin, nebulin play a key role in maintaining the structure of the []
sarcomere
28
The sarcomere stretches from [] to []
Z-disc to Z-disc
29
During contraction, myosin pulls actin towards the...?
M-line
30
During contraction, do actin and myosin units get smaller or larger?
1. Neither!
2. Actin and myosin filaments do not change size during the contraction
31
During skeletal muscle contraction in which the sarcomere shortens, will the length of each of the following componenets increase, decrease, or stay the same?
1. A-Band
2. I-Band
3. H Zone
4. Z Disc to Zdisc
5. Length of Myosin
6. Length of Actin
1. A-Band - Same
2. I-Band - decrease
3. H Zone - decrease
4. Z Disc - decrease
5. Length of Myosin - same
6. Length of Actin - same
32
What is the smallest function motor unit?
* 1 alpha motor neuron and all of the myofibers that it innervates
33
What would require a more fine motor control - or which of the following would require a greater ratio of motor neurons/myofibers?
Muscles in the eye or Muscles that control posture
* Muscles in the eye receive basically, a 1-to-3 ratio of neuron to myofiber. So their ratio would be larger
* Posture muscles require more motor units becuase it requires more force
34
What is the difference between ligand gated cation channels and nicotinic cholinergic receptors in the Somatic Nervous system?
* Psyche
* There is no difference. They are the same thing on the motor end plate.
35
Are there any fast acting Na+ channels on the motor end plate?
No.
There are cation channels for Na+ influx and K+ eflux
36
At the motor end plate, what is larger at the cation channels, Na+ influx or K+ eflux?
What does this lead to?
* Na+ influx is greater
* **depolarization** of the area
* (Not an action potential though)
37
What enzyme digests acetylcholine in the synaptic cleft?
Acetylcholinesterase
38
T/F
The alpha motor neuron can recycle unused acetcholine from the synaptic cleft?
False!
* The alpha motor neuron has specific channels for the reuptake of **choline**
* ****Choline is left in the synaptic cleft after acetylcholine aceylates its receptor protein
39
Another name for the depolarization of the motor end plate is the [] ?
EPP - End Plate Potential
40
What are the 3 elecrical events that must occur for a muscle cell to be succesfully stimulated?
* Motor Neuron action potential
* EPP, end plate potential at the motor end plate
* Muscle Action Potential
41
What causes the after-hyperpolarization in muscle cell action potentials?
* False
* There is no after-hyperpolarization
42
What causes the difference in the rapid depolarization slope of action potentials and muscle action potentials versus EPPs?
* The steep upwards slope of AP and Muscle AP is caused by the rapid depolarization of membrane causing voltage-gated fast Na+ channels to open.
* The EPP does not have access to fast Na+ channels at the motor end plate.
* It is still caused by Na+ though, just not as rapid
43
What causes the MEPPs (miniature end-plate potentials) on the EPP curve?
* 1 vesiclein the alpha motor neuron randomly releases some Ach into the synaptic cleft.
* This Ach binds to their receptors and triggers a "test" run to make sure everything is working
* at least that is the hypothesis.
44
What are the Safety Factors to ensure neuromuscular Transmission?
1. Motor End plate is flooded with Ach - more than enough to depolarize the end plate
2. Motor end plate contains 4-12 times more ACh receptors than needed to ensure transmission
3. EPP magnitude is 3-4 times greater than required to initiate depolarization of the sarcolemma
45
What structure make up the **triad?**
2 SR regions abut with a T-Tubule in between
46
There is a high concentration of [] and [] in T-tubules because it is extracellular
Na+ and Ca2+
47
[] is a calcium binding protein that helps to maintain a lowe concentraion gradient within the sarcoplastic reticulum?
Calsequestrin
48
L-type Calcium channels:
1. L stands for []
2. Also called []
3. Can serve as a [] sensor
4. Or it can act as a Ca2+ []
1. Long
2. Dihydropyridine
3. Voltage Sensor
4. Calcium Channel
49
Calcium Channel Induced Calcium Release (CCICR)
1. DHPR receptor acts as a [] []
2. Linked to a [] release channel in the SR
3. Once DHPR senses depolarization down the sarcolemma, it stimulates the opening of [] channels
1. These receptors are located on the membrane of []
4. In CCICR there is no [] influx of calcium
1. voltage sensor
2. Ca2+
3. RYR, ryanodine Receptors
1. Located on the sarcoplatic Reticulum
4. influx
50
Calcium Induced Calcium Release (CICR)
1. Requires [] of calcium from extracellular fluid
2. DHPR in sarcolemma sense [] and open releasing Ca2+ into []
3. Ca2+ from DHPR binds to [] and opens these channels
4. Ca2+ amounts: [] % from DHPR and [] % from RYR on SR
1. influx
2. depolarization; sarcoplasma
3. RYR (ryanodine)
4. 20% from extracellular, 80% from SR
51
CCICR is normally found in [] muscles
CICR is normally found in [] muscles
1. Skeletal
2. Cardiac
52
The [] head is responsible for the power stroke that moves the thin filaments close to the M-line.
* Myosin
53
What is the cocked state of the cross bridged cycle?
* Myosin head is at 90 degree angle upward
* ATP is cleaved by the ATPase into --\> ADP and Pi are attached to head
* With ADP and Pi - Myosin head has a high affinity for the actin binding site
54
What is the Cross-bridge state of the "cross-bridge cycle?"
* Intracellular Ca2+ is present
* Myosin binds to acting binding sites (after tropomyosin moves out of the way!)
55
What is the power stroke state of the "cross-bridge cycle?"
* The myosin head uses the energy cleaved by ATP.
* ADP and Pi are released and the head goes from a 90 degree angle to a 45 degree angle.
* This moves the actin filament closer to the M-line
56
How does the myosin head remained attached to actin during the "cross-bridge cycle?"
* In order for myosin to release from Actin - ATP must bind to myosin
57
What is the released state of the "cross-bridge cycle?"
* ATP has bound to myosin
* Myosin releases from the actin filament
* Myosin head has a low affinity to actin while ATP is attached.
58
What is the **main** way to resequester calcium from the sarcoplasm to the sarcoplastic reticulum?
* Sarcoplasmic/endoplasmic reticulum calcium ATPase...**SERCA pump**
* Active transport
* Uses ATP
* Pushes Ca2+ against its [] gradient
59
SERCA pumps are associated with [], what does this regulatory protein do?
* phospholamban
* When phospholamband is phosphorylated, it produces an increase in teh activity of the SERVA pump.
60
What protein within the SR helps resequester Ca2+ into the SR?
How does it do this?
* **Calsequestrin**
* Binds to Ca2+ in the SR and lowers the concentration gradient of free Ca2+, also helping out SERCA pumps.
* _Also localizes Ca2+ to the junctional SR for CICR or CCICR_
61
What is the time immediately following an electrical stimulus and before muscle tension begins to build?
The Latent Period
62
A muscle twitch consists of one muscular [] and [] cycle.
What are the 3 main phases of a muscle twitch?
1. Contraction and relaxation
2. latent period, contraction, relaxation
63
T/F
The strength of a muscle contraction does not depend on the initial position of the sarcomere but solely on how many myosin heads are attached to acting during a power stroke.
* False
* Muscle tension does depend on the initial starting position of a sacromere
64
What is the starting optimal length for a sarcomere that will result in **maximal contractile strength?**
2.2 microns (um)
65
Describe the difference between Synchronous Motor Unit Summation and Asynchronous Motor Unit Summation...
* Synchronous - It would be the additional recruitment of motor units to lift/move a heavy load. Think of it like spatial summation...recruiting more than just 1 motor unit.
* Asynchronous - this would be the alternating firing of motor units to allow for a long term, sustained contraction. Multiple motor units, firing at different times
* Posture muscles
66
What would happen if the same motor unit was repeatedly stimulated in quick succession?
It would develop **tetanus** or a fused muscle contraction.
67
T/F
Muscle length shortens during an isometric contraction?
False - muscle length DOES NOT change during an isometric contraction.
68
A body builder decided he was going to try and deadlift 600lbs one day, when his normal maximum lift was 400lbs. He was able to lift the bar one inch off of the ground while keeping his arms perfectly straight.
What type of contraction did his forearms undergo?
What type of contraction did his glutes undergo?
1. Isometric
2. Isotonic
69
T/F
In an isotonic contraction, muscle length changes while the weight remains constant...
True
70
During an isometric twitch, the tension generated is [] to move the load.
The sarcomeres shorten and pull on the [] [] but this does not actually shorten the muscle
Insufficient
Elastic Elements
71
In a [] [], the muscle first contracts in an isometric fashion until the tension generated is sufficient to move the load.
Isotonic twitch
72
What is more prevalent in causing muscle fatigue:
Loss of Glycogen Stores
Lactic Acid
Loss of Neurotransmitter (ACh)
* The main two that studies now point to are the loss og glycogen stores and the loss of ACh/neurotransmitters.
73
T/F
Hypertrophy causes the body to start producing more myofibers.
False
* Repeated constant use, causes the myofibers to swell in size. Now, these myofibers are filled with more actin/myosin/sarcomeres.
74
What is the term used to describe and increase in the number of muscle fibers per muscle?
Hyperplasia
75
What are the 3 ways for muscle cells to get ATP?
Creatine phosphate
Glycolysis
Cellular Respiration
76
During a marathon - which method of energy supply would a muscle cell prefer, creatine phosphate energy or ATP from Cellular Respiration?
ATP from Cellular Respiration
77
T/F
Creatine phosphatase adds a phosphate group to creatine, allowing creatine-phosphate to phosphorylate ADP. Thus, creating ATP.
False.
Everything was correct except that creatine phosphatase would remove a phosphate. Creatine kinase **adds** a phosphate.
78
Type 1 (red) - Slow muscle has all of the following characteristics except:
1. High amounts of myoglobin
2. Many mitochondria
3. Fast SERCA
4. Slow myosin ATPase isoform
5. Dense capillary network
1. Fast SERCA pumps is the incorrect statement
2. Type 1 muscle has **slow** SERCA pumps, which would make sense becuase they are meant to sustain contractions for a long time.
79
Type 2 (white) - Fast Muscle has all of the following characteristics except:
1. Fast SERCA
2. Fast myosin ATPase isoform
3. Many mitochondria
4. Low amounts of myoglobin
1. Many mitochondria would be the correct answer.
2. Type 2 muscle predominately uses the glycolytic energy pathway. Glycolysis does not require mitochondria.
80
81
Which type of muscle uses cellular respiration and which type uses glycolysis for their energy needs?
* Type 1 - Cellular Respiration
* Type 2 - Glycolysis
82
T/F
1 Motor unit is able to stimulate Type 1 and Type 2 muscles at the same time?
* False
* 1 motor unit can only stimulate 1 type of muscle.
* Now, one muscle can have both type 1 and type 2 fibers.
83
Cardiac Muscle Anatomy:
1. [] - [] nuclei
2. Adjacent cells are connected by [] []
1. [] tightly anchor cells together to prevent separation during contraction
2. [] Electrically connect adjacent cardiac cells
3. Sarcomeres give cardiac muscle a [] appearance
4. Composed of a [] which has 1 T-tubule and 1 junctional SR
1. 1-2 nuclei
2. intercalated Discs
1. Desmosomes
2. Gap Junctions
3. striated
4. Dyad
84
What is the term used to describe the ability of the heart to beat as 1 unit?
What connection structure allows the heart to do this?
1. Electrical Synctium
2. Gap Junctions
85
T/F
L-type calcium channels in the heart and their corresponding RYR channels located on the T-tubule membrane, are not as closely associated as seen in skeletal muscle.
* False.
* This would be true, except that RYRs are not located on the T-Tubule membrane, but on the SR membrane
86
Cardiac muscles require the [] of [] Ca2+ to initiate a contraction.
Influx of extracellular
87
Do Cardiac muscles use CCICR or CICR?
Cardiac muscles use both CCICR and CICR.
However, cardiac muscles MUST HAVE the influx of extracellular Ca2+ to use CICR.
88
How do cardiac muscles resequester Ca2+ to following regions:
Sarcoplastic Reticulum
Extraceulluar
1. SR - SERCA pumps, Phospholamban, Calsequestrin
1. same as skeletal muscle
2. Extracellular
1. Na+ /Ca2+, Secondary Active Transport
2. Sarcolemmal Ca2+ pump, Primary Active Transport
89
In the sarcolemmal Na+/Ca2+ transporter, of cardiac cells, which molecule is transported against its concentration gradient?
* Ca2+ is transported out of the muscle cell and into the extracellular due to the energy created by Na+ traveling down its concentration gradient.
90
Smooth Muscle Anatomy:
1. Small, [] shape
2. No [] - [],
3. Contain [] which are small indentation in the sarcolemma
4. Actin filaments attach to [] [] and [] instead of Z-discs.
1. fusiform/spindle shape
2. t-tubules
3. caveolae
4. Dense Bodies and the plasma membrane
91
T/F
Even though the actin filaments attach to dense bodies in smooth muscle, the actin/mysoin still aranage themselves in a sarcomere like in skeletal muscle.
False
Smooth muscle does not arrange their actin/myosin within sarcomeres.
92
What are the 2 types of smooth muscle?
Unitary Smooth Muscle
Multi-Unit Smooth Muscle
93
Unitary Smooth Muscle:
1. Several cells operate in a [] fasion
2. Connected [] by Gap junctions
3. Exhibit slow waves, or spontaneous [] activity
1. coordinated
2. electrically
3. pacemaker
94
[] are a form of self depolarization and are rhythmic patterns of depolarization with a subsequent contractions.
Slow Waves
95
What type of smooth muscle is less common?
Where are some examples of where it can be found?
* Multi-unit Smooth Muscle
* Eyes and Vas Deferns
96
The [] Nervous System innervates the Multi-unit Smooth Muscle cells
* Autonomic
* Sympathetic/Parasympathetic
97
All types of smooth muscle depend on Ca2+ from either [] or [] sources for contraction
extracellular or Sarcoplatic Reticulum sources
98
T/F
Some smooth muscle can contract without action potentials?
True!
They rely on a graded potential.
99
Smooth Muscle can acquire Ca2+ in many different ways...list them
1. **Voltage Gated calcium channels** in the plasma membrane
2. **CICR in the Sarcoplastic Reticulum**
3. **Ligand Gated Ca2+ channels**
4. **Ip3-mediated release**
1. G-protein causes IP3 to release Ca2+ from SR
5. **Store operated calcium channels**
1. activated when SR stores of Ca2+ become low
6. **Stretch-operated calcium channels**
1. embedded in plasma membrane and open when smooth muscle is stretched.
100
Instead of binding to troponin, like in skeletal muscles, Ca2+ binds to [] in smooth muscles to initiate the binding of myosin to actin...
Calmodulin
101
Where is calmodulin located?
Where is calsequestring located?
Where is Myosin Light Chain Kinase located?
Where is Myosin Light Chain Phosphatase located?
1. Sarcoplasm
2. Sarcoplastic Reticulum
3. Sarcoplasm
4. Sarcoplasm
102
How does regulation of the cross-bridge cycle differ from skeletal muscle to smooth muscle?
* In skeletal muscle - its regulated at Actin.
* In Smooth muscle - its regulated on the thick filament, myosin.
103
How does phosphorylation of the myosin head effect the cross-bridge cycle?
* The regulatory light chain on the myosin head is phosphorylated
* Once phosphorylated - the myosin head will bind to actin.
104
What enzyme is responsible for the phosphorylation of the myosin head in smooth muscle?
What complex activates this enzyme?
* MLCK - myosin light chain kinase
* Ca2+-Calmodulin complex
105
T/F
Even though it isn't necessary, heart contractions can be stronger if the thin filament gets phosphorylated
False!
* The heart contractions can be stronger if the thick filament, myosin head is phosphorylated.
106
What are the 3 steps for Smooth Muscle relaxation?
1. Intracellular Ca2+ levels must decrease
2. Myosin Light chain kinase must deactived
3. Myosin Light Chain Phosphotase removes phosphate group from the myosin head
107
What is the "Latch" state of the Cross-Bridge Cycle?
What muscle type is it unique to?
* It happens after the myosin head has performed the power stroke
* MLCP removes the phosphate and the myosin head will remained latched to the actin filament.
* No more ATP will need to be used to keep this muscle contracted.
* Unique to smooth muscle
108
