Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
73 Cards in this Set
- Front
- Back
|
What is the basic principle on which muscles work?
|
A lever system
|
|
|
What types of proteins make up muscles?
|
-Contractile
-Structural |
|
|
What are the contractile proteins in muscle?
|
-Troponin
-Tropomyosin -Actin -Myosin |
|
|
What are the main structural proteins in muscle?
|
-Cap-Z
-Alpha actinin -Nebulin -Tropomodulin -Titin |
|
|
What does Titin do?
|
Maintains the spacing between thick filaments and structural alignments of the sarcomere
|
|
|
What does Nebulin do?
|
Controls the width of thin filaments
|
|
|
What do Cap Z and Alpha Actinin do?
|
They tie the thin filaments to the Z line.
|
|
|
What is the functional unit of a muscle?
|
Sarcomere
|
|
|
What fuzz covers a muscle cell on micrograph?
|
Connective tissue
|
|
|
What does connective tissue do to muscle?
|
Gives it elastic passive force so that if you stretch the muscle it will generate a lot of force just by nature of its passive elasticity.
|
|
|
In the sarcomere, what is the Z-line?
|
The boundary where Actin is attached
|
|
|
What is the I band?
|
Region of thin filaments only
|
|
|
What is the A band?
|
The region where thick/thin filaments overlap
|
|
|
What is the H zone?
|
The region of only thick filaments
|
|
|
What is the M line?
|
The center of the H zone where there are structural proteins.
|
|
|
What line disappears when the muscle contracts?
|
The I band
|
|
|
What is each myosin filament composed of?
|
Many myosin molecules.
|
|
|
What is a myosin molecule like structurally?
|
Consists of 6 components:
-2 Heavy chains (helical) -4 light chains |
|
|
How are the heavy chains arranged?
|
Into a tail and head
|
|
|
How many light chains area associated with each head of a myosin molecule?
|
2
|
|
|
What are the light chains called?
|
2 = regulatory
2 = essential |
|
|
What makes the essential light chains essential?
|
They are essential for the sliding filament mechanism.
|
|
|
Are regulatory light chains very important in skeletal muscle?
|
No
|
|
|
What 3 molecules make up the thin filament?
|
-Actin
-Tropomyosin -Troponin |
|
|
What is the structure of Actin like?
|
It is a helical filamentous molecule, made up of 2 globular actins.
|
|
|
Why is Actin important?
|
Because the active sites for crossbridge formation are on Actin.
|
|
|
How many molecules make up the Actin filament (not molecule)?
|
4
-2 Actins (2 gs -> f) -2 Tropomyosins -1 Troponin |
|
|
What is absolutely essential for the sliding mechanism to work?
|
Calcium
|
|
|
How does Calcium cause muscle contraction?
|
It binds Troponin-C, which allows tropomyosin to move out of the way of the active sites on Actin so crossbridges form.
|
|
|
What happens when Calcium binds troponin-C?
|
Crossbridge formation occurs, then phosphate and ADP are released from myosin.
|
|
|
What must happen after ADP is released from myosin during the sliding filament mechanism?
|
ATP must bind and be hydrolysed again in order to prevent rigor mortis.
|
|
|
So what are the 3 roles of ATP in skeletal muscle?
|
1. Providing the chemical energy that ultimately gets converted to muscle force
2. Preventing Rigor mortis and stopping contraction 3. Pumping calcium back out into the SR via maintaining ionic gradients. |
|
|
What is the sarcolemma?
|
The external cell membrane of a muscle fiber
|
|
|
What are the internal membrane systems in striated muscle?
|
-Transverse tubules
-sarcoplasmic Reticulum |
|
|
What is a Triad?
|
A t-tubule with the SR's terminal cisternae on either side.
|
|
|
What important exchanger resides in the sarcolemma?
|
Na/K ATPase
|
|
|
What is the T-tubule system?
|
An invagination of the external cell membrane
|
|
|
Why is the SR important?
|
That's where calcium is stored for muscle contraction.
|
|
|
At the NMJ for skeletal muscle what is the:
-NT -Receptor |
NT = Acetylcholine
Receptor = nicotinic cholinergic |
|
|
What is the receptor on smooth muscle for impulses transmitted by the vagus nerve?
|
Muscarinic cholinergic
|
|
|
What happens for every motor nerve Action potential that crosses the NMJ?
|
It causes an AP in the muscle fiber that spreads over the cell and leads to coordinated calcium release from the SR.
|
|
|
What is a motor unit?
|
The combination of the motor nerve and all of the muscle cells that it innervates.
|
|
|
Does one motor nerve innervate just one muscle cell?
|
No; it innervates many muscle cells, in several different fascicles.
|
|
|
Why is it good that motor nerves innervate multiple muscle fibers?
|
It ensures that when the signal is sent from the brain to contract the muscle, it will happen.
|
|
|
What are small motor units used for?
|
Fine-detail tasks like surgery or writing
|
|
|
What are large motor units used for?
|
Nondetailed movements like walking or pushing your car out of the ditch.
|
|
|
What is ACh stored in at the ends of motor nerves?
|
Vesicles
|
|
|
What causes the motor nerve to release ACh for contraction?
|
The opening of voltage-gated Ca channels in the end of the motor nerve axon.
|
|
|
What happens when calcium influxes?
|
It binds calmodulin and results in vesicle docking to the membrane, exocytosis, and spilling of ACh into the synaptic cleft.
|
|
|
What causes calcium to go into the nerve terminal?
|
The fact that there's normally a huge gradient for calcium influx bc intracellular calcium is LOW and extracellular Ca is high.
|
|
|
What happens as a result of ACh release into the NMJ?
|
It binds the ACh receptor, which is a sodium channel that opens, and causes end plate potential to change in the muscle fiber.
|
|
|
Why is such a huge amount of ACh released at the NMJ into such a small area?
|
To ensure that when ACh is released, it will activate the receptors.
|
|
|
What prevents ACh from hanging around and activating the ACh receptors continually?
|
AChesterase
|
|
|
What is an anti-cholinesterase?
|
Nerve gas
|
|
|
Why is nerve gas deadly?
|
Because NMJ transmission continues to occur and is not stopped.
|
|
|
In what disease is Anti-AChesterase an important therapeutic agent?
|
Myasthenia gravis
|
|
|
Why give Anticholinesterase for myasthenia gravis?
|
Because it keeps ACh around longer so that even though receptors are auto-Ab bound and lower in concentration, those that are available WILL get some action.
|
|
|
Do AP's carried by motor nerve axons generate EPPs and IPPs in muscle fibers?
|
NO; every AP guarantees an AP in the muscle.
|
|
|
2 toxins that block APs at the NMJ:
|
-Curare
-Botulinum toxin |
|
|
What exactly does Curare block?
|
The nicotinic cholinergic receptor on the muscle cell
|
|
|
What does Botulinum block?
|
ACh release from the presynaptic terminal
|
|
|
2 things that Excitation-contraction coupling is vitally dependent upon in muscle fibers:
|
-Changes in membrane potential
-Internal membrane systems of the muscle fiber |
|
|
What membrane systems are essential for efficient EC coupling in STRIATED muscle?
|
-SR
-T-tubules |
|
|
Which internal membrane system does an AP generated by the NMJ travel down?
|
The t-tubule
|
|
|
So what drug blocks the ACh receptor? What is it used for?
|
Curare - used as a muscle relaxant for surgery
|
|
|
What drug is used to treat Myasthenia gravis and why?
|
Neostigmine - bc it keeps ACh around longer by blocking ACHesterase
|
|
|
What warfare agent is an Anticholinesterase?
|
Nerve gas
|
|
|
What is the hollywood drug of choice and why?
|
Botulinum toxin - interferes with ACh release from the presynaptic terminal and keeps your face smooth and paralyzed.
|
|
|
What does the T-tubule do for EC coupling?
|
It allows the AP to penetrate deeply into the muscle to allow for coordinated contraction of the whole muscle.
|
|
|
How do the T-tubules couple the AP from the sarcolemma to muscle contraction?
|
When the AP traverses the T-tubule, it opens voltage gated Ca channels which is transmitted by foot proteins to ryanodine sensitive Ca channels in the SR that open and allow calcium influx.
|
|
|
What is calsequestrin?
|
A protien in the SR that binds calcium as it is resequestered during the end of a contraction so that the CA ATPase pump doesn't need as much energy.
|
|
|
What disease results when the SR calcium channels fail to close properly?
|
Malignant hyperthermia
|
|
|
When does Malignant hyperthermia become apparent?
|
Under volatile anesthetic conditions.
|
