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;
67 Cards in this Set
- Front
- Back
|
What is thermogensis?
|
by-product of muscles contraction is head production and is therefore important in homeostasis of body termperature
|
|
|
What is the sarcoemma? What is the Sarcoplasmic Reticulum? What are transverse tubules?
|
Sarcoemma - a membrane that covers the muscle fiber; The Sarcoplasmic Reticulum is the internal tubular structure for Ca2+ storage. transverse tubules are a way for the action potential to spread; it is a network of sarcolemmal membrane that penetrates deep into the muscle fibers. It carries electrical impuses from the sarcolemma to depth of each muscle cell. it is located at the junctions of A and I bands
|
|
|
What is a myofibril?
|
cylindrical rods of contractile and regulatory proteins (actin/myosin filaments running along the axis of the cell)
|
|
|
What is the z-line; m-line, a band, h zone, I band? What does each one contain? Which ones shorten with contraction? Which ones do not?
|
Z-Lines - delineates 1 sacromere
M-Lines - center of the bare zone A-Band - no change in length, the center of the sarcomere H-Zone - bare zone that contains thick filaments (shortens with contraction) I band - contains thin filaments that shorten with contractions |
|
|
What are the 2 main regulatory proteins found in muscle?
|
Tropomyosin - filamentous protein that at rest covers attachment sites
Troponin - globular protein complex, TnC with binds Ca2+, TnT which binds tropomyosin, TnI inhibtion |
|
|
Describe the Myosin Filament Structure? What are cross bridges? Bare Zone? What happens at the head?
|
has 6 polypeptide chains; 2 heavy chains; 4 light chains; Cross bridges are connection of heads to the thick filaments. , the bare zone is the thick filament part that contains no heads and contracts. The head is the part that has the ATPase activity.
|
|
|
What does Dystrophin do? What happens when this does not work anymore?
|
Dystrophin anchors myofibrils to the sacrolemmal membrane;
In Musclular dystrophy - dystrophin is defective or absent |
|
|
What do transverse scaffolding proteins do?
|
They help align thick and thin filaments correctly.
|
|
|
What does Titin do?
|
Large MW protein from M to Z disk which helps center the thick filaments in the sarcomere
|
|
|
What does nebulin do?
|
along the thin filament guides the actin lenght.
|
|
|
what does alpha actin do?
|
anchors the thin filaments to the Z disk.
|
|
|
Steps in stimulating muscle fibers? From action P to snyaptic space.
|
1. Action potential arrives
2. the electrical impluse causes the Ca2+ ion gated channels to open. 3. Ca2+ comes into the cell, possibly attracting the the acetylcholine vesicles. 4. These vessicles fuse with the neural membrane and empty their acetylcholine into the synaptic space via exocytosis |
|
|
After the stuff enters the snyaptic space what happens to get the muscle to move?
|
Once acetycholine is in the synaptic space, it causes Acetylcholine channels to open that allows Na+ and K+ and Ca2+ to enter the muscle. Negative ions cannot enter the cleft because of negative charges at the mouth of the opening. Mostly Na+ flows through because it is in much highher concentration outside. The K+ does not really flow out because the inside of the Cell is so negative Maybe.
-All these Na+ ions cause a positive charge inside the muscle fiber membrane which is now called the end plate potential. This causes an action potential that spreads along the muscle membrane and thus causes muscle contraction |
|
|
What does acetylcholinesterase do?
What does choline acetyltransfersase do? |
It breaks down acetylcholine to choline and acetate. if not the muscle would be in constant contraction mode.
choline acetyltransfersase takes a choline and adds an acetyl CoA to it creating acetylcholine. |
|
|
What is Miniature EPP (MEPP)?
|
the smallest possible charge in the membrane potential of motor end plate by the content of one synaptic vesicle. rigth around 0.4 mv
|
|
|
To generate an EPP the resting potential must go from what to what?
|
it must go from -90 to -50 mv
|
|
|
So once the EPP has fired what happens in the muscle?
|
1. The AP propageates along the sarcolemma and down the t-tubules
2. the AP causes the Ca2+ to be released from the SR 3. Ca2+ binds to the troponin exposing myosin binding sites 4. the cross bridge cycle begins 5. Ca2+ is actively brought back into the SR following the AP 6. Tropomyosin blocks myosin-binding sites and the muscle relaxes. |
|
|
What is the name of the protein in the SR that binds to Ca2+?
|
that would be calsequestrin
|
|
|
What is Myasthenia gravis
|
it is an autoimmune disease where antibodies target Ach receptors and you get sever muscle weakness
|
|
|
What are Esterase Inhibitors? What is an example?
|
prolonged and enchance action of Ach at the motor end plate; Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft, thus slowing down the breakdown of acetylcholine.
|
|
|
what does the botulinum toxin do?
|
it blocks Ach release from presynaptic terminals, total blockade, paralysis of respiratory muscles
|
|
|
what does D-Tubocurarine do?
|
competes with Ach (Nicotinic receptors on the motor end plate used to cause muslce relaxation during anesthesia.
|
|
|
What is angonist? What are 2 Ach receptor agonistss?
|
an angonist is something that modifies a receptor. we have M1 - Vevimeline used for the management of dry mouth in Sjorgen syndrome. and M3 Aceclidine and Pilocarpine that are used to treat glaucoma.
|
|
|
What does Ryanodine do?
|
it mediates the release of Ca2+ from the SR
|
|
|
What does SERCA do?
|
it pump Ca2+ back into the SR
|
|
|
what are the steps involved in the cross bridge cycle
|
1. binding of myosin to actin once the Ca2+ comes in causing the troponin tropomyosin, to leave exposing the binding site for myosin
2. you get the power stroke -> actin gets pulled towards the middle of the sarrcomere; ADP is released. 3. rigor (myosin is on the low energy form). -> new ATP binds to the myosin head. 4. atp binding causes the myosin to unbind from the actin. 5. you get cocking of the myosin head (myosin is in the high energy form). the ATP isx turned into ADP + Phosphate ion |
|
|
why do you get rigor mortis
|
the muscles contract and become rigid even without action potentials. this is caused by a lack of ATP, which is required to cause the seperation of the cross bridges from the actin filaments during the relaxation process.
|
|
|
Sliding Filament Model of Muscle Contraction. What happnes
|
the z lines come closer together
the width of the I band and H zone decreases; the A band stays the same. |
|
|
What does creatine phosphate do?
|
stores energy for sketeltal muscle to contract maxiimally for about 15 seconds. used for short bursts of activity.
|
|
|
What are the 3 main sources of (ATP) energy used for muscle contraction?
|
ATP - immediate source of energy; It is replenished in 3 main ways:
1. Creatine Phosphate - see the other card but basically a really short term storage of ATP; used in short bursts 2. Glycogen - used when both ATP and Creatinine phosphate are depleted, the cell catabolizes glucose to create 2 ATP in glycolysis and does so without O2; 30 to 40 more seconds of energy 3. Cellular respiration - for continued activity with O2. the mit. completely catabolizes glucose to CO2 and H20 with alot of ATP 32 or 36; when no more 02 glucose turns into lactic acid - leads to fatigue. |
|
|
What is a twitch
|
contraction as a result of one single action potential
|
|
|
what is a motor unit?
|
a single motorneuron and the muscle fibers that innervates it
|
|
|
What is the period called that is needed to restore the resting potential? How is the resting potential restored
|
it is called the refractory period.
it is restored by an outflow of K+ ions |
|
|
Frequency Stimulation- Summation?
|
when a 2nd stimulus is applied to an excited muscle cell after the refractory period, the 2nd contraction will be greater than the first. also called wave summation
|
|
|
Frequency Stimulation - Clonus?
|
Clonus (also incomplete tetanus) muscle receives multiple stimuli very quickly and therefore can only relax partially before its next wave summation. the result is sustained contraction where the muscle is contracting maximally but relaxing only partially.
|
|
|
Frequency Stimulation Tetanus
|
stimulation goes to 80 to 100 per second; no relaxation period occurs; Both clonus and tetanus happen because of continued addition of calcium ions to the sarcoplasm without the benefit of sequestering calcium between contractions.
Also the refractory period is much briefer than the time needed to complete a cycle of contraction and relaxation; the amount of contraction is greater in clonus and tetanus than in a single twtich |
|
|
Frequency Stimulation - Staircas effect- Treppe
|
when a skeletal muscle has been fully rested and is thhen stimulated repeatedly by identical stimuli too far apart to cause wave summation. the first few contractions are a little stronger than the last.
|
|
|
What is muscle tone? How is it maintained?
|
Muscle tone - when sketetal muscles are in a state of partial contraction called tonus -
tonus is maintained by activation of a few motor units at all times even in resting muscles. they rotate when they are on and off. |
|
|
What is recruitment? Howw does it fit in with the size principle?
|
recruitment is the process of increasing the number of active motor units within a given skeletal muscle; it increases muscle strength and also works with short term tetanic contraction to produce smooth movements rather than a series of jerky ones;
The size principle - as motor unirs are recruited larger motoneurons progressively get involved and a larger force is generated. |
|
|
What does preload mean? What does it do to the muscle?
|
preload is the load on a muscle in the relaxed state prior to contraction;
It causes the muscle to stretch; the greater the the preload the greater the stretch on the sarcomere; This causes the muscle to generate passive tension - the higher the preload the greater the passive tension After load - the load the muscle is working against. |
|
|
What is an isometric Contraction?
|
an isometric contraction is does not shorten; but the tension at the preload lenght greatly increases; no motion; pressure nerve exceeds resistance.
|
|
|
What is total tension equal to?
|
It is equal to the active tension (proportional to the number of cross bridges taht cycle) and passive tension (the force generated by preload stretching the muscle)
|
|
|
What are some factors that affect the force of contraction?
|
basically it depends on the length of the sacromere:
1. if the sarcomere is too short the actin filaments interfere with each other 2. with just a little stretch you get "the ideal" relationship between actin and myosin so you can use all the cross bridges 3. preload - overstretches the sarcomere, so you get fewer cross bridges available 4. Overstretched - no actin myosin interactions. muscle does not work |
|
|
What is an isotonic contraction?
|
happens when you move a constant load through a range of motions; the tension stays the same but the length of the fibers shortens.
|
|
|
What are the characteristics of Type I Fibers?
Mitochondria Fatigue Color why? Motor neurons? Purpose in life? ATPase Activity |
-loaded with mitochondria
-depend on cellular respiration for ATP production -rich in myoglobin (red color) -slow twitch because activated by small diameter (slow conducting) motor neurons -dominant muslces that depend on tonus; those responsible for posture -lower ATPase activity |
|
|
What are the characteristics of Type II fibers?
Mitochondria Fatigue Color why? Motor neurons? Purpose in life? ATPase Activity |
-few mitochondria
-fatigue easily -low in myoglobin -fast twitch - activated by large diameter motor neurons; - found in muscles used for rapid movement -high ATPase activity |
|
|
What happens when a muscle loses it nerve supply? What is contracture?
|
it no longer receives the contractile signals so atrophy begins immediately. Contracture is the fact that fibrous tissue that replaces the muscle fibers during denervation atrophy has a tendency to continue shortening for many months.
|
|
|
Why are does smooth muscle allow the walls of hollow organs to stretch without increasing the tension within the cells?
|
because SMC do contain thin and thick filaments they are arranged into sarcomeres.
|
|
|
What is a functional Syncytium? Is this a unitary or multiunit SM
|
it is a way all the SMC are linked together by gap junctions sot taht stiumulation of one results in stimulation of the entire network.
|
|
|
What is a multiunit SM?
|
multiunit consists of individual smooth muscle cells each with its own motor neuron, so that each can contract independently of the others; not that common. found in the arrector pili of hair follicles, ciliary muscle in the eye aand in the iris of the eye
|
|
|
What are the differences between SK and SM?
-Cycling of Cross bridges -Energy Requirement -How fast the onset of contraction is -High force of contraction -Presence of Latch Mechanism -Regulatory Protein |
Smooth muscles have the following:
-Slow cycling of cross bridges -low energy requirement -slow onset of contraction -high force of contraction -does have a latch mechanism -uses calmodulin not troponin |
|
|
What are the steps in SM contraction?
|
1. Ca2+ enters the cell
2. Ca2+ binds to calmodulin 3. Ca2+ bound to calmodulin activates Myosin light chain kinase (MLCK) - a phosphorylating enzyme which phosphorlates myosin 4. Once this happens myosin can then bind to actin and the SM contracts. |
|
|
How do you stop contraction of SM?
|
You use myosin light chain phosphatase which spits the phosphate from the regulatory light chain.
|
|
|
What is the latch mechanism?
|
-it allows long term maintenace of tone in many smooth muscle organs without much expenditure of energy
-unknow how it works but deactivation of the enzymes causes the myosin to remain bound to the actin; |
|
|
what are 2 neurotransmitters that work on smooth muscle?
|
acetylcholine and norepinephrine
|
|
|
describe the role of Ca2+ and smooth muscle?
|
bc SMC have many more ports for Ca2+ than Na+, Na+ plays a small role. Ca2+ flowing into smooth Muscle cells plays a big role in the creation of the action potential. bc Ca channels open and close much slower than you get the long plateau. Ca2+ is also directly causes contraction through calumodin.
|
|
|
What are 3 ways calcium can cause contraction in SMC?
|
1. Voltage gated Ca2+ Channel
2. A hormone or neurotransmitter causes a ligand-gated Ca2+ to open. 3. a hormone or neurotransmitter causes a 2nd messanger such as IP3 to cause Ca2+ to be released from the SR. |
|
|
In cardiac muscle how is a functional syncytium created?
|
intercalated discs (a thicken area where adjacent cell membranes contact one another, it is through these structures that adjoining cells communicate though gap junctions. The stimulation can pass to all of the cells this way.
|
|
|
How is the heart innervated?
|
the action potential that triggers the heartbeat is generated within the heart itself.
-motor nerves do run to the heart but their effect is simply to modulate the intrinsic rate and the strength of the heartbeat |
|
|
What is inotropism?
|
coontractility or inotropism is the intrinsic ability of myocardial cells to generate froce at a given muscle length.
|
|
|
What is one cause of fibrillation?
|
anything that interferes with the synchronous wave (such as the damaged part of the heart caused by a MI) may cause the fibers of the heart to beat
|
|
|
Why is the heart so easily damanged with no blood flow going to it?
|
because it has fewer mitochondria than sketetal muscle; greater dependenance on cellular repiration for ATP. it also has little stores of glycogen and gets little benefit from glycolysis when the supply of O2 is limited.
|
|
|
describe the importance of Ca2+ in the heart muscle cell.
|
In order for the heart to contract you need extracelluar Ca2+; Ca2+ enters the cell which causes Ca2+ to be released from the SR, Ca2+ binds to troponin; relaxation happens when Ca2+ goes back into the SR.
|
|
|
How do cardiac glycosides work?
|
They block the Na/K atpase pump which pumps Na out and K+ in. This causes the Na/Ca exchnager not work because Na does not want to come into the cell because there is too much Na in the cell. therefore Ca2+ is not pumped out.
|
|
|
what is a dihydropyridine receptor?
|
it is a voltage sensitive protein, deploarization causes a conformational change in this receptor.
|
|
|
what is action tension proportional to?
|
it is proportional to the number of cross bridges formed. tension will be at the maxium when there is maximum overlap of thick and thin filaments.
when the muscle is stretched to its maxium the number of cross bridges is reduced because there is less overlap. when muscle lenght is decreased, the thin filaments collide and tension is reduced. |
|
|
what is the force velocity relationship with isotonic contractions
|
this measures the velocity of shortenting of isotonic contractions when the muscle is challenged with different afterloads.
the velocity of shortening decreases as the afterload increases. |
