Module 4 muscles

When the voltage sensor changes shape what else does it cause to change shape?

Calcium channels because it's a mechanically gated channel. Ca gets released, moves from inside that sarcoplasmic reticulum to outside, travels and binds to troponin molecules.

What factors can influence muscle strength/ production of myofibrils and sarcomeres?

Hormones, stress, and artificial anabolic steroids

What happens to creatine when a muscle cell is resting?

Its going to take creatine and added a phosphate to it to store energy. When the muscle needs energy, We are doing go take creatine phosphate and put it onto and ADP to make energy. A quick way to have a phosphate there so it can transfer the phosphate from the creatine phosphate using creatine kinase to make ATP. -Short term energy not a long term source of ATP

Which myofilament do you find in the H zone in a non-contracted muscle?

Just myosin

What is isotonic eccentric muscle contraction?

Muscle gets longer, for example putting the coffee mug down

When the muscle contracts do the actin and myosin get shorter or stay the same length?

The actin and myosin actually get shorter, they do not they stay the same length but slide past each other to make the muscles shorter.

What is recruitment going to depend on?

The activity of the nervous system, as great force is needed, you will use more motor units and motor units with larger fibers. If your going to start a muscle contraction you will start with the smaller sized myofiber/motor neurons, if that is not enough we are going to get more stimuli coming from the nervous system so these smaller neurons have a lower threshold for stimuli than the larger ones. Your brain learns how many different motor units its going to need for different things that you do.

What is muscle strength directly related to?

The amount of myofibrils and sarcomeres within each fiber.

What is the Sarcoplasmic reticulum:?

The smooth ER of the skeletal muscle/myofiber, its job is to store/relsease Ca+

What happens when a muscle is not contraction?

The tropomyosin is covering up those binding sites. There is no calcium bound to troponin. The myosin is not attached to actin

What are the two steps of aerobic respiration and what it produces?

Two step process within this mitochondria (Krebs cycle and electron transport chain). Outcome yields C02, H20, Heat, ATP. This is much more efficient than our glycolysis because you get 36 ATP molecules per glucose molecule and 100 per fatty acid. Requires a steady stream of O2 so its much slower. For moderate activity like walking or stead job

What is a muscle twitch?

Type of motor neuron stimulation. Tension produced by one action potential.

There are more than one type of muscle fibers, which are the two that we are focusing on?

Types Type 1 (slow) and Type 2 (Fast)

Elasticity

ability to return to normal size & shape after being stretched.

What are Transverse tubules (T-Tubules)?

are extensions of the sacrolemma that penetrate into the interior of the of skeletal and cardiac muscle cells. Dips down in there. Picture little holes on the sacrolemma.

How are contractions classified and what are the two types?@

based on pattern of tension production Isotonic and isometic

What happens when a muscle starts to contract and requires energy, think in terms of ATP?

creatine phosphate transfers its phosphate group back to ADP in a reaction that is catalyzed by the enzymes creatine kinase to form creatine and ATP so the ATP can be used to create a muscle contraction. Quick but only lasts for approximately 15 seconds.

What is creatine phosphate?

is a molecule that can store energy within its phosphate bonds.

What is a motor unit?

is a motor neuron and all of the myofibers that it controls

What is recruitment?

process of increasing the number of active motor units, increasing the tension.

What happens when the muscle cell is relaxed with ATP?

produce more ATP than is required for their resting metabolism. And this excess of ATP transfers a phosphate to creatine producing ADP and creatine phosphate. This acts as a quick energy reserve for creating ATP.

If a motor unit inervates with 10,000 myofibers what is this used for?

produces a larger movement like leg muscles

Motor neuron coming out of the spinal cord and will innervate where?

some myofibers

What is a fascicle?

A group of myofibers succrounded by a sarcolemma

What is located on the myosin head?

ATPase which is the ATP binding site, you know its an enzyme because of the "ase."

What does the A band contain in a non-contracted muscle?

Actin and myosin myofilaments

What are the two myofilamnets?

Actin and myosin which combine and form the myofibrils

What are thin filaments?

Actin filaments

What is aerobic respiration?

Aerobic respiration is the breakdown of glucose in the presence of oxygen to produce Co2 water and ATP

What is oxygen dept.?

Amount of oxygen needed to compensate for ATP produced without oxygen during muscle contraction. Oxygen is required to restore ATP and creatine phosphate levels, convert lactic acid to pyruvic aic, and in the liver to convert lactic acid into glucose or glycogen.

What is isometric muscle contraction?

-Iso means same metric means length -produces force but does not produce movement -example a plank or a wall sit -postural contractions are isometric contraction -lifting something up that is too heavy where you aren't able to move it, is isometric

Conductivity

-Refers to a muscle's ability to transmit nerve impulse

Irritability

-Refers to the ability of the muscle to respond to a stimulus

What are the different frequency of motor neuron stimulation?

-The nervous system changes how frequently it sends out stimuli Twitch contraction Staircase effect/treppe Wave summation Incomplete and complete tetanus

What occurs during the relaxation period during twitch muscle contraction?

-The tension goes down on the graph -Ca2+ is actively being transported back into the SR

What is isotonic contractions?

-"Iso" means same, "tonic" means tension -produces tension and moving a load. -tension remains the same, the muscle length changes -think of picking up a mug and putting it down, lifting mug up and putting mug down -Two different kinds of isotonic contractions: Concentric and Eccentric Isotonic concentric: Muscle gets shorter Isotonic eccentric: Muscle gets longer

What can decrease too much and contribute to muscle fatigue?

-ACH (neurotransmitter): motor neuron cant send the message to tell the muscle to contract -creatin phosphate (CP), wont have enough ATP -oxygen, wont be able to make enough ATP -Glycogen, not able to feed into the ATP systems, wont be able to make enough ATP -Calcium, needed for the motor neuron and SR production

What is the reaction of a muscle at rest and in an active muscle?

-ATP+creatine=Creatine phosphate & ADP catalyzed by creatine kinase = creatine + ATP (energy for muscle contraction) -When a muscle cell is resting its going to take creatine and add a phosphate to it. -When the muscle needs energy, We are doing go take creatine phosphate and put it onto and ADP to make energy. A quick way to have a phosphate there so it can transfer the phosphate from the creatine phosphate using creatine kinase to make ATP. -Short term energy not a long term source of ATP

Explain how the motor neuron sends stimulus to the muscle?

-An action potential arrives a the axon terminal of the cholinergic motor neuron -It reaches the ligand-gated calcium channel -This causes exocytosis by Synaptic vesicles release ACH into the synaptic cleft. -ACH diffuses across the cleft towards the motor end plate. -ACH binds to the end portion of the sarcolemma at the ACH receptors/ligand-gated -Na+ ion channels in the motor end plate. -This opens and Na+ enter the muscle fiber. -Entry of Na+ depolarizes the sarcolemma locally, producing an end-plate potential. -The end-plate potential stimulates an action potential -This end-plate potential moves down the sarcolemma -The action potential is propagated down the T-tubules. -Goes down one side up the other side and continues on all the T Tubules that are in the sarcolemma. -T-tubule depolarization leads to the opening of Ca+ channels (ligand-gated calcium channels) in the SR and CA+ enter the cytosol -Ca+ binds to troponin -Tropomyosin moves, and the active stite of actin are exposed -Myosin binds to actin and the sliding filament theory occurs

In length of tension in a sarcomere, what happens if we have too little overlap between the actin and myosin myofilaments?

-cant form cross-bridges because the myosin cant reach the actin which means the sarcomere wont shorten -This happens in congestive heart failure. The heart muscle gets really stretched out and floppy so the actin and myosin cant reach eachother, so the heart cannot contract with enough strength to move blood.

What are the different phases/periods that occur during twitch muscle contraction and describe each one?

1.Latent phase (period) -no change in tension -what is happening: action potential moving down sarcolemma down the T tubules -calcium to release from the SR 2. Contraction period -increase tension myofilaments sliding past eachother (increasing part of the graph) 3. Relaxation period: -The tension goes down on the graph -Ca2+ is actively being transported back into the SR

What is produced with anaerobic glycolysis?

2 ATP, 2 Pyruvate molecules from 1 glucose molecule.

Which is faster glycolysis or ATP creatine phosphate in energy production?

ATP creatine phosphate. Fast but not sustained

Myosin is bound to actin until what is added?

ATP which is hydrolyzed and the process repeats until we stop motor input.

If no oxygen in available after glycolysis, what occurs?

Anaerobic glycolysis

What are the three ways muscles get ATP?

Anaerobic respiration Glycolysis Aerobic respiration

What mechanism provides the muscle with more sustainable energy?

Anaerobic respiration and Aerobic respiration

What are sarcomeres?

Are what give skeletal and cardiac muscle their striated appearance. The smallest functional unit of the muscle fiber. Interactions between thick and thin filaments of sarcomeres are responsible for muscle contraction, will get shorter.

What is a myofibril?

Arrangement of myofilaments actin and myosin of the skeletal muscle cell

What is muscle tension?

As the sarcomere shortens, the muscle pulls together and create tension

At rest, why cant the myosin head attach to actin and how does it allow itself to attach?

At rest, the tropomyosin is blocking the binding sites on actin preventing the myosin head from attaching. A nerve impulse moves down the efferent motor neuron allowing calcium to get released from the sarcoplasmic reticulum The calcium binds to troponin, changing its shape and changing the shape of tropomyosin which moves the tropomysin exposing the myosin head binding sites on actin allowing myosin to attach itself.

In order to contract, what is every skeletal muscle fiber innervated by?

Axon terminal of a motor neuron

What does it mean when you are phosphorylating the myosin head?

Basically means you are energizing the myosin head with ATP. The ATPase breaks the ATP into ADP and phosphate.

Why does the muscle look striated?

Because of the arrangement of myofilaments. The strips of the muscles have different names, the H zone, A zone, and I zone.

What is the ATPase of the myosin head?

Binding site for ATP. Is an enzyme that hydrolyzes ATP into ADP and phosphate. Basically it phosphorylates the myosin head (adding energy to it.

What is the energy source for anaerobic respiration?

Blood glucose Glycogen muscle (store glucose) is a polysaccharide so it has a ton of glucose molecules

Compare and contrast Treppe/staircase effect versus Wave summation of motor neuron stimulation?

Both relying on an increase of calcium levels Both increase tension Maximal tension in wave summation is greater- sarcomere already partially contracted

How can pyruvate be used for energy?

Can be used if there is no oxygen available, it is broken down from pyruvate into lactic acid in a redox reaction ( ½ of rx being reduction/gain of electrons and the other half being oxidation loss of elections). Pyruvate gains electrons and becomes lactate (reduction) NADH loses electrions and becomes NAD+ (oxidation). The importance of NAD+ is that it allows glycolysis to continue. Ultimately glycolysis does come to an end because it cant be sustained for very long because of its inefficiency. So after about 1 min the anarobic respiration has completely depleted so its not good for long distance races.

Refers to a muscle's ability to transmit nerve impulse

Conductivity

Refers to the muscle's ability to shorten in length

Contractility

What happens in muscle tissue atrophy?

Decrease use of skeletal muscle, number of sarcomeres and myofibrils disappear (but not the number of muscle fibers).

What does total tension (strength) produced depend on in regards to motor units you active?

Depends on the number and size of the motor units

What is titin?

Elastic fibers

ability to return to normal size & shape after being stretched.

Elasticity

What connective tissue surrounds a myofiber?

Endomysium

What is the name of the connective tissue covering that is outside the sarcolemma?

Endomysium (between fibers)

What connective tissue surrounds the muscle?

Epimysium

Refers to the muscle's ability to extend in length

Extensibility

What occurs during oxygen dept?

Extra O2 is needed to restore energy reserves to metabolize lactic acid and turn it into pyruvate. You are paying back the oxygen dept.

True or False: The ATPase on myosin only grab ATP when the myosin heads are exposed?

False, The ATPase on the myosin molecule will always grab ATP and that means that the myosin head is always energized

What does a group of myofibers form?

Fascicle

What occurs during the latent phase/period during twitch muscle contraction?

First phase No change in tension Action potential is moving down the sarcoleema down the T tubules Calcium releases from the SR

If a motor unit innervates with 1 myofiber what would be its use?

For more precise movements because it needs to activate fewer myofibers

What determines the number of muscle fibers in a given muscle?

Genetically determined and does not change.

What is glycolysis?

Glucose is broken down to produce 2 ATP and 2 Pyruvate. In anaerobic respiration, lactic acid is produced. In aerobic respiration, H20, Co2, heat and ATP is produced.

What step must stored muscle glycogen go through first in order to make glucose available for glycolysis?

Glycogenolysis

What process turns ADP+P unit ATP?

Glycolysis and aerobic respiration is used to attach that phosphate back onto an ADP to make an ATP

What is the first step in both anaerobic and aerobic respiration?

Glycolysis. This is the process of taking one glucose sugar molecule and breaking it down into 2 ATP and 2 pyruvate.

What is a motor unit?

Group of muscle fibers in a muscle that is innervated by a single motor neuron. The size of a motor unit is variable depending on the nature of the muscle.

What occurs to your body when you are in Oxygen Debt?

Heavy breathing even after you have discontinued activity

What is the muscle triad/what forms it?

In skeletal muscle, consists of ` T tubule with and 2 terminal cisternae from the sarcoplasmic reticulum. These structures work together.

Where does aerobic respiration occur?

In the mitochondria

In energy, where is the first place you muscles will take energy and how is it produced?

In your muscle cells there is a reserve of ATP that gets used. In addition that that there is a molecule called creatine phosphate. In a muscle there is 3-6 x more creatine phosphate than ATP in a cell Muscle cell uses ATP which gets hydrolyzed to ADP+P

What is hypertrophy in muscle tissue?

Increase mass and bulk in a skeletal muscle (meaning increased production of sarcomeres and myoribrils).

When you increase the number of active motor units in recruitment what is that going to do?

Increase tension

Is anaerobic glycolysis efficient or inefficient?

Inefficient as 1 glucose molecule makes 2 pyruvate and 2 ATP. Anaerobic respiration is depleted after about 1 min. Not good for long distance races

Refers to the ability of the muscle to respond to a stimulus

Irritability

The 4 characteristics of muscle properties?

Irritability -Refers to the ability of the muscle to respond to a stimulus Contractility -Refers to the muscle's ability to shorten in length Elasticity -ability to return to normal size & shape after being stretched. Extensibility -ability of a muscle and muscle cell to be stretched. Conductivity -Refers to a muscle's ability to transmit nerve impulse

Holding a plank is an example of what kind of muscle contraction?

Isometric muscle contraction

What is it called when the muscle gets shorter?

Isotonic concentric contraction

What are the two different kinds of isotonic contractions?

Isotonic concentric: Muscles get shorter Isotonic eccentric: Muscle gets longer

What is it called when your muscle gets longer?

Isotonic eccentric contraction

Why is lactic acid not good for muscle cells and what do we do with it?

It makes the cell acidic which will interfere with other metabolic pathways. So what we need to do is send that lactic acid to the blood, ship it off to the liver. The liver is going to convert that into pyruvate and eventually glucose which is part of the cori cycle. Lactic acid is one of the things that contribute to muscle fatigue.

What product is the result of anaerobic respiration?

Lactic acid broken down from pyruvate

What can build up too much of and contribute to muscle fatigue?

Lactic acid/lactate Too much build up of ADP, interfers with the actin of calcium and ATP production

What happens once ACH/acetylcholine binders with the motor end plate?

Ligand-gated Na+ ion channels opens and Na+ enter the muscle fiber which causes the sarcolemma to depolarize locally, producing an end plate potential

What is the shape of the myofiber/skeletal muscle cell?

Long

How many myofibrils is there in 1 myofiber?

Many

What are fine control motor units?

More precise movement. Fewer myofibers, for example in the eyes

How to motor units vary?

Motor units vary 1. # of myofibers 2. Size of myofibers and size of motor neuron

Frequency of motor neuron stimulation: Explain the Treppe/staircase effect myogram?

Multiple stimuli Relaxes completely between stimul Tension increases, Example in warming up muscle Stimulus Ca2+ releases Relaxation pumped Ca2+ back into the sarcoplasmic reticulum Not enough time in between these stimuli to completely pump all of the Ca+ back into the SR so you leave a little bit of calcium out there, so everytime we have a stimulus, we have an increase in calcium

What is formed when you get a bunch of myofibrils combined?

Myofiber (the cell that is surrounded by the sarcolemma) builds the muscle

Name the muscle structures from largest to smallest?

Myofiber- myofibrils- myofilments

What are the individual muscle cells called?

Myofibers which group together to for fascicle's which group together to form muscles.

What is the arrangements of myofilaments of actin and myosin of the skeletal muscle cell called?

Myofibril

What do actin and myosin combine to form?

Myofibrils

What is the sarcomere actually composed of?

Myofilaments actin and myosin

What are the lines you see in the myofibrils?

Myofilaments actin and myosin which combine to form the myofibrils

Frequency of motor neuron stimulation: Explain the twitch contraction myogram?

Myogram of what a muscle does in response to 1 action potential and the tension it produces. Divded into 3 phases: Latent phase/period, contraction period, relaxation period.

What are thick filaments?

Myosin

What does myosin do once the myosin head binding site is exposed from moving tropomyosin?

Myosin attaches to actin, forming the cross-bridge

If your not making cross bridges are you going to be able to shorten the sarcomere?

No

Are our motor units always the same size?

No, motor units can vary in size. Size varies on the number of myofibers that are innervated.

In wave summation, does the muscle completely relax in between twitches?

No, there is an incomplete relaxation between twitches, partially shortened sarcomere.

What does the I band contain in a non-contracted muscle?

On either side of the H and A bands. Only the actin myofilament.

Each muscle fiber is innervated by how many motor neurons?

Only one.

Explain why glycolysis is an anaerobic process?

Oxidative phosphorylation (aerobic respitation) Glycolysis anaerobic Glycolysis is an anaerobic process, non of its steps involve he use of oxygen. However immediately upon finishing glycolysis, the cell must continue respiration in either an aerobic or anaerobic direction. In aerobic respiration, will continue on to the citric acid cycle in the mitocontrain. In anaerobic respiration glycolysis continues and pyruvate acid is brown down into lactic acid in the cytosol

What connective tissue surrounds a fascicle?

Perimysium

What are the 3 important inputs that enter in aerobic respiration?

Pruvate Glucose Fatty Acids ? Amino acids

During anaerobic glycolysis, what is broken down and how much energy is produced?

Pyruvate (end product of glycolysis) is broken down into lactic acid. Anaerobic respiration does not produce ATP itself (all ATP during anaerobic respiration is produced during glycolysis) but keeps glycolysis going, since glycolysis yields 2 ATP, we can say that anaerobic respiration yields 2 ATP for every molecule of glucose.

What happens to pyruvate during aerobic respiration?

Pyruvate enters aerobic respiration.

How is NAD+ produced and why is it important in energy production?

Pyruvate is broken down into lactic acid. Produces NAD+ (oxidation as part of the redox reaction). This allows glycolysis to continue.

Extensibility

Refers to the muscle's ability to extend in length

Contractility

Refers to the muscle's ability to shorten in length

What is each myofiber surrounded by besides connective tissue?

Sacrolemma

What is the smallest functional unit of the muscle fiber?

Sacromere

What is the name of the cytoplasm of the skeletal muscle/myofiber or muscle fiber?

Sacroplasma

What is the name of the plasma membrane of skeletal muscle?

Sarcolemma

Why do we want our sarcomeres to be at a certain length?

Sarcomere have an idea amount of stretch We want our sarcomeres to be at a certain length because sarcomere length determines number of cross bridges that can be formed.

Myofibrils have repeating units of what?

Sarcomeres

What is the smooth ER of the skeletal muscle cell/myofiber called?

Sarcoplasmic reticulum

What occurs during the contraction period during twitch muscle contraction?

Second phase. Increase tension myofilaments sliding past eachother (increasing part of the graph)

Explain the sliding filament theory?

Signal from the nervous system Calcium gets released from sarcoplasmic reticulum (because it stores the calcium). Calcium binds to the troponin. Changes the shape of troponin (conformational change) Troponin changes the shape of tropomyosin. The tropomyosin is than going to move, exposing the myosin binding sites This allows the myosin to attach to the actin forming cross-bridges The gross bridges changes orientation from towards the z discs to the center of the sarcomere, brining those z discs closer together The whole sarcomere gets shorter because those myofilamnets are sliding past each other and the muscle contracts.

Frequency of motor neuron stimulation: Explain the incomplete and complete myogram?

Still temporal summation Incomplete tetanus is kind of like a wave summation our action potentials have just gotten a lot closer together our maximal tension is going greater and pretty soon if you get these stimuli closer together and you wont get any relaxation at all between them in complete tetanus. No time for those sarcomeres to relax. Sometimes complete tetanus is called fused tetanus and incomplete is called unfused tetanus.

What happens to lactic acid?

Take to the liver. Converted into pyruvate and eventual glucose in the cori cycle.

Where is calcium stored?

Terminal cisterna of the sarcoplasmic reticulum, also called lateral sacs.

What happens to ATP when it attaches to the myosin head?

The ATP will be hydrolyzed by the ATPase on the myosin head. This breaks down to ADP+Pi. At rest the myosin head is cocked and ready to go.

What does it mean that the myosin head is always energized?

The ATPase on the myosin molecule will always grab ATP and what that means is that the myosin head is always energized. It is ready at any time to bind to the myosin binding sites that are exposed.

What zone/band disappears when a sarcomere shortens?

The H zone in the middle

When a muscle is contracted how do the H, I, and A bands change?

The I band and the H band are doing to reduce in size when the sarcomere shortens. The A band is going to increase in size as the sarcomere shortens.

What is the endomysium?

The connective tissue covering that is outside the sarcolemma

What is sarcoplasma?

The cytoplasm of skeletal muscle

What happens once the sarcolemma is depolarized at the motor end plate?

The end plate action potential moves down the sarcolemma down the T-tubules, down one side and up the other side and continues on all the T Tubulues in the sarcolemma. This depolarizes the T tubule membrane opening ligand-gated Ca+ channels in the SR. This Ca+ binds to troponin

What is the tendon made from?

The endomysium plus the perimysium plus the epimysium that extend past the muscle fibers

What is to be used first in our aerobic respiration?

The glucose which is broken down by glycolysis produces our pyruvate. This is what is being use first in our aerobic respiration.

What happens to the voltage sensor protein in the T-tubule membrane?

The membrane potential moving down the T tubules changes the shape of the voltage sensor protein. This change of shape changes the shape of the calcium channel in the SR, allowing Ca+ to be released.

What kind of neuron communicates with the muscle cell?

The motor neuron that are cholinergic (releasing acetylcholine (ACH) as our neurotransmitter in our synaptic vesicle)

What in the skeletal cell is Ca+ stored and released?

The sarcoplasmic reticulum

What happens when ATP produced by creatine phosphate is depleted?

The muscle turns to glycolysis as a method by which it can source its ATP.

What do fascicles combine and create?

The muscle which is than covered in the epimysium (deep fascia)

When the tropomyosin moves what gets exposed?

The myosin head binding sites on actin are exposed

This myosin heads needs to let go and grab another active binding site How do we get the myosin head to unattached from the actin site?

The myosin head needs to let go to grab another myosin head binding site on actin to continue the sliding action. ATP is added, that ATPase in the myosin head breaks it down into ADP+ PI and that myosin head is again cocked and ready to go. The binding sites are still exposed so this myosin head grab onto the binding site on actin and form a cross bridge and results in a power stroke. This is repeated until that sarcomere is shortened.

What is the Sarcolemma?

The plasma membrane of the skeletal muscle cell

When a muscle contracts, which part of the muscle actually gets shorter?

The sarcomere

If the myosin binding sites are exposed, what is happening to the sarcomere?

The sarcomere is shortening and contracting.

How does the sarcoplasmic reticulum in the T tubules get those calcium channels to open?

There is a protein in the T-tubule membrane called a voltage sensor. The membrane potential moving down the T tubule changes the shape of the voltage sensor protein. This change of shape changes the shape of the calcium channel in the SR This allows Ca+ to be released.

How do the tropomysoin prevent muscles from being contracted all the time?

They cover up those binding sites on actin

What is the structure of actin?

They have actin molecules/actin subunits look like little balls. These all form together to create the myofilament. The dark dots on them are the myosin head binding sites. They have two regulatory proteins (tropomyosin and Troponin.) The Tropmyosin looks rope like.

What is attached to the Z disc/Z line of the sarcomere?

Thin myofilament/ actin

Explain why there is an incomplete muscle contraction during wave summation?

This happens because Ca2+ ions, same basic idea as Treppe. Second stimulus causes a release of even more calcium With wave summation you are getting bigger waves and more tension

Where does anaerobic respiration occur in the muscle cell?

This is going to be in your sarcoplasm of the muscle cell.

What is the job of the sarcoplasmic reticulum?

To store and release Ca+

Where is troponin attached to on actin?

Tropomyosin

Which regulatory protein/molecule on actin covers up the myosin binding sites?

Tropomyosin

What are the two regulatory proteins of actin and their funtions?

Tropomyosin: Rope like appearance. Help regulate the function of muscle contraction. Covers up those myosin binding sites on actin. Troponin: Binding site for calcium, attached to the tropomyosin

Once calcium is bound to troponin, what happens to the tropomyosin?

Troponin binding with calcium causes tropomyosin to move

How does your muscle get quick short term energy?

We are doing go take creatine phosphate and put it onto and ADP to make energy. A quick way to have a phosphate there so it can transfer the phosphate from the creatine phosphate using creatine kinase to make ATP. Short term energy not a long term source of ATP

What is it mean to have optimal length of tension in a sarcomere?

We have the ideal amount of overlap between actin and myosin. Here we will have the greatest amount of tension because we can form the most cross-bridges w/o structural interference

How does the powerstroke occur with th myosin molecule?

When ADP+P leave the myosin molecule once attached to the actin, this causes the power stroke. The myosin pulls actin so that it slides past itself.

How are the cross bridges formed?

When the actin and myosin attach

What causes the ACH to exocytose across the synaptic cleft?

When the action potential reaches the ligand-gated calcium channel

What is isotonic concentric muscle contraction?

When the muscle gets shorter, for example picking up a coffee mug

How does the shortening of a sarcomere stop?

When we stop motor input. Once the neuron shuts off, we are going to actively transport calcium back to the sarcoplasmic reticulum so the binding sites are doing to get covered again my tropomyosin.

Explain why rigor mortis occurs?

When you die your ATP production goes down. Calcium starts to leak from your sacroplasmic reticulum. The calcium binds to troponin and the muscles are going to contact and use up all of the internal stores of ATP causing rigor mortis You run out of ATP to uncouple these cross bridges.

What kind of gated channel are you going to find at the synaptic end of the neuron and the end plate potential?

Will have voltage gated channels that is going to cause the synaptic vesicles to exocytose into the synaptic cleft. Ligand-gated calcium channel.

When relaxing a skeletal muscle fiber< where does this process ultimately begin?

With the motor neuron, which stops releasing its chemical signal, Ach, into the synapse. The muscle fiber will repolarize, which closes the gates in the SR where Ca was being released. ATP driving pumps will move Ca out of the sarcoplasm back into the SR. This results in the reshielding of the actin binding sites on the thin filaments. Without the ability to form cross-bridges between thin and thick filaments, the muscle fiber loses its tension and relaxes.

Does size matter in a motor unit?

Yes the smaller the motor unit, the more fine or precise control you will have

In length of tension in a sarcomere, what happens if you have too much overlap of the actin myofilament?

You can have too much overlap, we can get cross bridges but the structure itself cant get that must shorter, so that the structural interference is that physically the sarcomeres are already almost shortened so they aren't going anywhere.

What defines a sarcomere?

Z disc/Z line (same thing). Thin lines. Attached to the z disc is a thin myofilament or actin.

Explain why the motor units are all or none?

either all of these motor units are going to contract or none of them are

The tendons that attached the the periosteum that envelop the bone are extensions of what?

endomysium, perimysium and epimysium that extend past the muscle fibers.

Frequency of motor neuron stimulation: Explain the wave summation myogram?

has to to with temporal/time 1st Stimulus: increase tension 2nd Stimulus: even greater increase in tension The muscle does not completely relax in between twitches Incomplete relaxation between twitches, partially shortened sarcomere This happens because Ca2+ ions, same basic idea as Treppe. Second stimulus causes a release of even more calcium With wave summation you are getting bigger waves and more tension

Explain my the disease polio impacts muscle movements?

it will disconnect motor neurons from their myofibers so motor neurons get destroyed. The second motor neuron can adopt the other myofibers but over the years they get worn out and wont be able to function properly.

What are gross control motor units?

large movement: lots of myofibers, largest- gastric

Why is it important to have enough venous return (enough blood) coming back to the heart?

that will stretch the heart muscle out to get the optimal sarcomere length to increase contraction strength

What are the Terminal cisternae?

the enlarged areas of the sarcoplasmic reticulum surrounding the transverse tubules