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Physiology lecture > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

What does it mean when muscle tissue is excitable?

A

It responds super quickly to stimuli. It responds to electrical impulses and makes a mechanical response

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2
Q

What does it mean when muscle tissue has conductivity?

A

It responds to electrical excitation and sends the signal throughout the plasma membrane and initiates contraction

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3
Q

What is the structure of the sarcolemma? (what is it and what is it made of kind of thing)

A

It is the plasma membrane of the muscle cells that contain T-tubules

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4
Q

What is the structure of the t-tubules? (what is it and what is it made of kind of thing)

A

The are invaginations of the sarcolemma (tunnel looking things), that run deep into the muscle cell

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5
Q

What is the structure of the sarcoplasmic reticulum? (what is it and what is it made of kind of thing)

A

It is the modified form of the smooth ER found in muscle cells that store Calcium

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6
Q

What is the structure of the terminal cisternae? (what is it and what is it made of kind of thing)

A

It is where the sarcoplasmic reticulum ends from and make an expanded chamber

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7
Q

What is the structure of the Triad? (what is it and what is it made of kind of thing)

A

It is where there is a t-tubule sandwiched in between 2 terminal cisternae

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8
Q

What is the structure of the Myofibrils? (what is it and what is it made of kind of thing)

A

They are hundreds and thousands of cylindrical structures made of actin and myosin (myofilaments). Contain proteins responsible for contraction. Bundles of myofilaments

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9
Q

What is the structure of the myofilaments? (what is it and what is it made of kind of thing)

A

Bundles of protein filaments within myofibrils.
Actin- thin protein filament
Myosin- Thick protein filament
Titin- elastic protein filament

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10
Q

What is the function of the sarcolemma and t-tubules?

A

Sarcolemma: Receives electrical impulses and depolarizes
T-tubules: They effectively depolarize the muscle cell WITHOUT touching the cytoplasm of the cell and allow Acetylcholine to go in and depolarize the muscle cell effectively

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11
Q

What is the function of the sarcoplasmic reticulum and terminal cisternae?

A

sarcoplasmic reticulum: It stores calcium
terminal cisternae: It is a reservoir at the ends where there is A LOT of calcium stored there ready to be released to the sarcoplasm to be stimulated by contraction.

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12
Q

What is the function of the triad?

A

plays a crucial role in the process of excitation-contraction coupling by allowing the action potential to quickly get to the terminal cisternae to release the calcium to do the muscle contraction

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13
Q

What is the function of myofibrils and myofilaments?

A

Myofibrils: To produce muscle contraction
Myofilaments: Generate force and movement through (cross-bridging cycle), and contraction of muscle through (sliding filament theory), MOSTLY JUST CONTRACTING THE MUSCLE

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14
Q

What is the purpose of the sarcoplasmic reticulum and terminal cisternae in the muscle cell?

A

Sarcoplasmic reticulum: To store and release calcium

Terminal cisternae: Store large amounts of calcium

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15
Q

What is the purpose of the triad in the muscle cell?

A

plays a crucial role in the process of excitation-contraction coupling by allowing the action potential to quickly get to the terminal cisternae to release the calcium to do the muscle contraction

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16
Q

What is the purpose of the myofibrils and myofilaments in the muscle cell?

A

Myofibrils: To produce muscle contraction
Myofilaments: Generate force and movement through (cross-bridging cycle), and contraction of muscle through (sliding filament theory

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17
Q

What is the location and function of actin?

A

Location: In the zone of overlap of in the A band AND in the I band

Function: G actin has an active site that can bind to the head of a myosin molecule THEY ARE THE TRACK IN MUSCLE CONTRACTION

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18
Q

What is the location and function of Myosin?

A

Location: The A band and H band

Function: The myosin head interacts with actin and form a cross bridge

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19
Q

What is the location and function of Titin?

A

Location: It goes through the core of each thick filament and anchors it to the Z discs on one end and M line on the other end

Function: Helps with the stretching and recoiling of the muscle. HELPS THE MUSCLE FIBER RETURN TO ORIGINAL LENGTH AFTER BEING STRETCHED

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20
Q

What is the location and function of Dystrophin?

A

Location: It is under the sarcolemma in the I band

Function: Links the actin filaments to the transmembrane proteins in the sarcolemma. WHEN IT CONTRACTS IT TAKES THE PLASMA MEMBRANE WITH IT.

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21
Q

What is the location and function of Nebulin?

A

Location: Large non elastic protein that runs alongside the thin filament

Function: Attaches the actin (thin filament) to the Z line and keeps the actin nice and stiff and straight

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22
Q

What is the location and function of Myoglobin?

A

Location: In the sarcoplasm

Function: Stores oxygen needed for muscular activity (red pigment)

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23
Q

Define all of the structural elements in the sarcomere?
1. Z line (disc)
2. M line
3. A band
4. I band
5. H band
6. Zone of overlap

A
  1. Z line (disc) - Protein discs that define the boundaries of a sarcomere (where it can be in)
  2. M line- Myosin disc in the center of the sarcomere in the middle of the A band
  3. A band- Dark band that has both thin and thick filaments
  4. I band- light band that only consists of actin and go from one A band to the next A band
  5. H band- Lighter region on either side of the M line that contains only thick filaments (myosin)
  6. Zone of overlap- where Actin and Myosin overlap
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24
Q

What happens the these structures of the sarcomere when the muscle is at rest? (do they lengthen, shorten, stay the same)
1. Z line (disc)
2. M line
3. A band
4. I band
5. H band
6. Zone of overlap

A
  1. Z line (disc)- Stay the same length (just are farther apart from each other)
  2. M line- Stays the same length
  3. A band- Stays the same length
  4. I band- Lengthens
  5. H band- Lengthens
  6. Zone of overlap- Decreases
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25
Q

What happens to these structures of the sarcomere when the muscle is at contracts? (do they lengthen, shorten, stay the same)
1. Z line (disc)
2. M line
3. A band
4. I band
5. H band
6. Zone of overlap

A
  1. Z line (disc)- Move closer together (stays the same length)
  2. M line- Stays the same length
  3. A band- Stays the same length
  4. I band- Shortens
  5. H band- Shortens
  6. Zone of overlap- Lengthens
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26
Q

What is the role of troponin and tropomyosin? (functions)

A

Troponin: attaches to tropomyosin and Blocks the binding of actin to myosin

Tropomyosin: Wraps around the actin and controls the movement of troponin and blocks the myosin active site when relaxed

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27
Q

How does calcium play a role in the functions of troponin and tropomyosin?

A

When calcium binds to troponin then it moves the tropomyosin away from the binding site of actin. When the calcium leaves the troponin the tropomyosin moves back onto the active sites of the actin.

28
Q

What is the difference between calcium in the axon terminal and calcium in the sarcoplasmic reticulum?

A

Axon terminal: calcium causes the voltage gates channels to open and release of the neurotransmitter acetylcholine.

Sarcoplasmic reticulum: It is stored there and released to attach to troponin and allow crossbriding to happen. (where the tropomyosin moves off the active site of the actin and allows muscle to contract)

29
Q

How does acetylcholine and acetylcholinesterase contribute in muscle contraction?

A

acetylcholine: It binds to the receptors on the sarcolemma and opens the sodium gated channels to open so sodium can create an action potential to get the release of calcium to get the muscle to contract.
acetylcholinesterase: It quickly removes and breaks down acetylcholine from the receptor so we do not have a constant muscle contraction and get a disease like tetanus. Allows the muscle to be at a resting state.

29
Q

How does acetylcholine and acetylcholinesterase contribute in muscle relaxation?

A

acetylcholine: Doesn’t really contribute to relaxation only helps the muscle contract by opening sodium channels and getting a release of calcium

acetylcholinesterase: This helps muscle relaxation by breaking down and removing acetylcholine from its receptors.

29
Q

What is the difference between acetylcholine and acetylcholinesterase?

A

acetylcholine: helps with muscle contraction by binding to the receptors on the sarcolemma and opening sodium gated channels and getting the calcium to release
acetylcholinesterase: Helps with muscle relaxation by removing acetylcholine and breaking it down

30
Q

Is a nicotinic receptor ionotropic or metabotropic?

A

Ionotropic

30
Q

How does the absence of acetylcholine and acetylcholinesterase affect muscle contraction?

A

acetylcholine: Without it you wouldn’t be able to contract your muscles and you would have weak muscles
acetylcholinesterase: Without it your muscles would be constantly contracting and your muscle would not rest. You would not be able to move

31
Q

What is a nicotinic receptor?

A

A receptor that binds to acetylcholine and opens the ion channels to allow for depolarization in the cell

31
Q

What role does a nicotinic receptor have in muscle contraction?

A

When acetylcholine is bound to it, It allows sodium to flow through the sarcolemma and depolarize the cell which then releases calcium and allows for muscle contraction to occur

32
Q

Describe a motor unit

A

It is a nerve fiber that stimulates ALL of the muscle fibers that is attached to (can have many fibers BUT fibers only have one motor unit). It behaves as a single functional unit

32
Q

What are the 3 steps of the excitation-contraction coupling?

A
  1. Electrical impulses (depolarization) triggers the release of calcium from the sarcoplasmic reticulum into the sarcoplasm
  2. Calcium binds to the troponin changing its conformation and rotates tropomyosin away from the myosin binding sites
  3. Actin and myosin are free to interact and form a crossbridge
33
Q

What are the 3 steps of the sliding filament theory?

A
  1. Stored energy from the resting position allows the myosin head to pivot toward the M-line which pulls the actin filament with it
  2. ATP binds to the myosin head causing it to release and break the crossbridge with the actin filament
  3. Myosin uses ATP to reposition its head to prepare for another cycle
33
Q

What muscle activities require large muscle units and small muscle units?

A

Large: Sitting, Running, Walking, Moving a couch, Powerlifting

Small: Playing the piano, Writing, Reading

33
Q

What does it mean when a motor unit is large? and when it is small?

A

Large: Used for large and powerful movements (1,000-2,000 muscle fibers per motor neuron)

Small: Allows for precise muscle control (10-100 muscle fibers per motor neuron)

34
Q

What step in the muscle contraction cycle (initiation, excitation contraction coupling, and sliding filament) uses ATP? And describe myosin heads as an ATPase in the step.

A

The contraction step (sliding filament theory).

The myosin head is like ATPase in that it hydrolyzes ATP to ADP and !P so that it can bind to the actin and move it again.

34
Q

What are the 5 steps of initiation (excitation)?

A
  1. An action potential arrives at the axon terminal
  2. Triggers Ca2+ voltage gated channels to open and triggers the release of acetylcholine from synaptic vesicles
  3. Triggers Ca2+ voltage gated channels open and triggers the release of acetylcholine from synaptic vesicles
  4. ACh diffuses across the synaptic cleft and binds to its receptors on the sarcolemma, Na+ gated channels open and does depolarization
  5. AChE breaks down ACh to end the electrical current. Acetate and choline is broken down and choline is taken back up to the presynaptic membrane
35
Q

Compare slow and fast muscle fibers in respect to the number of mitochondria each has

A

Slow: A LOT OF MITOCHONDRIA

Fast: FEW NUMBERS OF MITOCHONDRIA

36
Q

Compare slow and fast muscle fibers in respect to vascularization it does

A

Slow: HIGH vascularization (do not fatigue easily)

Fast: LOW vascularization (fatigue easily)

36
Q

Compare slow and fast muscle fibers in respect to size of muscle fiber diameter each has

A

Slow: Half the size of the diameter of fast muscle fibers

Fast: Has a bigger diameter

37
Q

Compare slow and fast muscle fibers in respect to presence of myoglobin and color each has

A

Slow: It is more red because it contains more myoglobin (more oxygen)

Fast: Don’t contain myoglobin more white

37
Q

What is muscle tone?

A

Where muscles are always in a state of slight contraction

38
Q

What is the function of slow and fast muscles?

A

Slow: Made for endurance, low intensity activities, aerobic

Fast: Made for quick sprinting exercises, High intensity, anaerobic

39
Q

What 3 characteristics contribute to muscle relaxation after a muscle contraction?

A
  1. Acetylcholine is broken down
  2. Sarcoplasmic reticulum reabsorbs Ca2+
  3. Active sites are covered again, blocking cross-bridge
40
Q

Why is it healthy to have more muscle tone? (5)

A
  • Helps maintain posture
  • shock absorption
  • prevent uncontrolled changes in body movement or joint movement
  • improve coordination
  • increase resting metabolism
41
Q

How does a muscle dispose of lactic acid?

A

Lactic acid is released in the bloodstream and converted back to pyruvate in the presence of oxygen in liver tissue

41
Q

What is the role of creatine phosphate during ATP production? And when ATP is not being used?

A

It basically gives its ATP to ADP to get a faster ATP production

When ATP is not being used the ATP gives a phosphate group to creatine for it to be stored and used for later

41
Q

What energy source do muscles use at rest, moderate exercise, and during peak activity?

A

Rest: fatty acids

Moderate exercise: glycogen

Peak activity: creatine phosphate

42
Q

What is lactic acid?

A

It is the buildup of lactate in the muscle cells decreases the pH and leads to muscle fatigue

43
Q

Where does lactic acid come from?

A

When there is a lack of oxygen pyruvate is converted to lactic acid

44
Q

What is the recovery period after exertion?

A

Where the muscle fibers are returned to normal (they are relaxed)

45
Q

What is oxygen debt?

A

It is the amount of oxygen that is needed to restore pre-exertion conditions. NEED TO RECOVER OXYGEN LEVELS TO BE ABOVE NORMAL LIKE BEFORE WE EXERTED THE OXYGEN

46
Q

What is peristalsis? And where does it happen?

A

It is where muscles in the GI tract contract and relax in a way to push food and water through the GI tract. IT IS INVOLUNTARY MOVEMENT.

It happens in the GI tract (esophagus, stomach, small and large intestine)

46
Q

What is excess post- exercise oxygen consumption?

A

Where respiratory and heart rate remain high after exercise so oxygen debt can be repaid and we consume oxygen to restore ATP, CP, and glycogen reserves (physiological variables) to their normal values

47
Q

What is the difference between single-unit smooth muscle and multi-unit smooth muscle?

A

Single: Cells that are connected to each other by gap junctions that function as one unit (small intestine)

Multi: They are not connected by gap junction and they work independently and depend on varicosities to contract and do stuff (the eye)

48
Q

How does smooth muscle store calcium?

A

In the caveolae in the sarcolemma

49
Q

How does calcium trigger smooth muscle contraction? (2)

A
  1. An increase in cytosolic calcium initiates contraction. calcium is released from the sarcoplasmic reticulum and extracellular fluid
  2. Calcium binds to calmodulin and starts the cascade that ends in phosphorylation of myosin light chain
50
Q

What is the difference that calcium has in skeletal vs smooth muscle?

A

Skeletal: It goes in and affects the troponin and does the muscle contraction itself.

Smooth: It is a second messenger and starts a cascade effect of phosphorylation.

51
Q

Based on these characteristics, determine if they belong to skeletal, cardiac, or smooth muscles
1. Sarcomeres present
2. Lines vessel walls
3. Multinucleate
4. Branching cells
5. Slowest contraction cycle
6. Gap junctions present between cells
7. Controlled by somatic motor neurons
8. Controlled by autonomic motor neurons
9. Influenced by epinephrine
10. Contraction controlled by intracellular Ca2+
11. Involuntary
12. Myocardium
13. Visceral muscle
14. T-tubules present
15. Striated appearance

A
  1. Sarcomeres present- Skeletal
  2. Lines vessel walls- Smooth
  3. Multinucleate- Skeletal
  4. Branching cells- Cardiac
  5. Slowest contraction cycle- Smooth
  6. Gap junctions present between cells- Cardiac
  7. Controlled by somatic motor neurons- Skeletal
  8. Controlled by autonomic motor neurons- Cardiac and smooth
  9. Influenced by epinephrine- Cardiac
  10. Contraction controlled by intracellular Ca2+- ALL OF THEM
  11. Involuntary- Cardiac and smooth
  12. Myocardium- Cardiac
  13. Visceral muscle- Smooth
  14. T-tubules present- Skeletal and Cardiac
  15. Striated appearance- Skeletal and Cardiac
52
Q

What is the purpose of the sarcolemma and T-tubules?

A

Sarcolemma: Receives electrical impulses and depolarizes and do be a barrier between extracellular and intracellular stuff
T-tubules: to rapidly conduct electrical signals from the surface of a muscle fiber deep into the cell

53
Q

How many times can myosin pull on actin (during the sliding contraction) before needing ATP to do the cycle all over again?

A

1 ATP

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