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Z A&P Chapters 7-9 > Lecture #15 Chapter 9 > Flashcards

Lecture #15 Chapter 9 Flashcards

1
Q

What type of neurotransmitter does skeletal muscle respond to?

A

Acetylcholine (ACh)

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2
Q

What is the motor end plate?

A

A specialized part of a muscle fiber membrane at a neuromuscular junction

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3
Q

What are the four steps in nervous control of contraction?

A
  1. An action potential travels down a the length of a motor neuron causing the release of ACh
  2. ACh bind to ACh receptors on the motor end plate
  3. This result in changes in membrane permeability to Na+ and K+ ions which generate muscle impulse (action potential)
  4. This impulse causes sarcoplasmic reticulum to release stored Ca++ ions which cause the muscle to contract
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4
Q

What is the excitation-contraction coupling?

A

The connection between stimulation of a muscle fiber and contraction

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5
Q

What happens during muscle relaxation?

A

Ca++ ions stored in SR, troponin-tropomyosin complexes cover binding sites of actin filaments

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6
Q

What are the five steps that occur upon muscle stimulation?

A
  1. Muscle impulses stimulate the SR to release Ca++ ions into the cytosol
  2. Ca++ bind to troponin causing it to change shape
  3. Tropomyosin protein then become altered
  4. Binding site on actin is now exposed
  5. Myosin head find action resulting in cross-bridge formation
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7
Q

What is the sliding filament model?

A

Where sarcomere shorten and the thick and thin filaments slide past one another

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8
Q

What part of the sarcomere shorten when a muscle contracts?

A

H zones and I bands narrow

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9
Q

What do two Z lines do when a muscle contracts?

A

They move closer together

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10
Q

What is cross-bridge formation?

A

Myosin heads attaching to actin binding-site

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11
Q

What is the powerstroke?

A

When the myosin cross-bridge pulls thin filaments toward the center of the sarcomere (M line) and ADP and Phosphate are released

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12
Q

What breaks the actin/myosin cross-bridge?

A

ATP

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13
Q

What causes the myosin heads to cock?

A

ATP breaks into ADP and Phosphate

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14
Q

What are the 4 steps in muscle relaxation?

A
  1. Acetylcholinesterase decomposes ACh in the synapse (muscle impulses stop causing the stimulus of the sarcolemma to stop)
  2. The Ca++ pump sequesters calcium ions back into the SR
  3. Troponin-tyopomyosin complexes conceal actin binding sites once again (Cross-bride formation is prevented)
  4. The muscle fiber relaxes
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15
Q

What are the tree energy sources availabe for muscle contraction?

A

-ATP (available in small amounts only)
-Creatine phosphate (Enables muscle cells to regenerate ATP for ADP via phosphate transfer)
-Cellular respiration (via mitochondria)

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16
Q

What is creatine phospahte?

A

A molecule in muscle that stores energy

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17
Q

What is ATP?

A

Adenosine triphosphate

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18
Q

What are the two types of cellular respiration?

A

Anaerobic phase and aerobic phase

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19
Q

What happens in the anaerobic phase or cellular respiration?

A

Glycolysis, which occurs in the cytoplasm, produces 2 ATP per glucose sugar

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20
Q

What is glycolysis?

A

The energy releasing breakdown of glucose into 2 pyruvic acid and 2 ATP

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21
Q

What happens in the aerobic phase of cellular respiration?

A

Citric acid cycle + electron transport chain, which occurs in the mitochondria, produce a large of ATP

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22
Q

What is the citric acid cycle?

A

A series of chemical reaction that oxidizes certain molecules (Krebs cycle)

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23
Q

What is the electron transport chain?

A

Series of chemical reaction that high energy electrons from glycolysis and the citric acid cycle and form water and ATP

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24
Q

What is myoglobin?

A

An oxygen storing pigment in muscle tissue

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25
What is oxygen debt?
The amount of oxygen muscle cells require after physical exercise to restore levels of glucose, ATP, and creatine phosphate
26
What is anaerobic/lactic acid threshold?
Shift in metabolism from aerobic to anaerobic during strenuous muscle activity when insufficient O2 is available
27
What is muscle fatigue?
The inability to contract muscle
28
What are the four common causes of muscle fatigue?
-Decreased blood flow -Ion imbalances across the sarcolemma -Loss of desire to continue exercise -Accumulation of lactic acid (iffy)
29
What is a muscle cramp?
Sustained, involuntary contraction
30
What causes muscle cramps?
Changes in electrolyte concentrations in extracellular fluids near muscle
31
What is the threshold stimulus?
The minimum strength of stimulus required for a muscle to contract (when reached is causes an action potential)
32
What is an action potential?
The sequence of electrical changes in a nerve or muscle cells exposed to a stimulus that exceeds threshold
33
What is a twitch?
A single contraction of a muscle fiber followed by relaxation The contractile response to a single impulse
34
WHat are the three periods of a twitch?
-Latent -Contraction -Relaxation
35
What is one thing that can determine the force a muscle can generate?
The length of the muscle fiber before stimulation
36
Why do stretched muscle fibers generate less force?
Due to myosin head being unable to reach actin binding sites
37
Why do shortened muscle fibers develop less force?
Due to the physical restriction of sarcomeres become further compressed
38
What is summation?
The process of combining the force generated by individual muscle fiber twitches Increased force of contraction by skeletal muscle fibers when a twitch occurs before the previous twitch relaxes
39
What is a motor unit?
Motor neuron + all of the muscle fibers it controls
40
A whole muscle consists of ______ motor units?
Many
41
A large number of fibers within a motor unit provide ____ movements?
Coarse
42
A small number of muscle fibers within a motor unit provide ____ movements?
Precise
43
What is recruitment?
An increase in the number of motor units becoming activated which helps to produce additional force
44
During sustained contractions what type of motor units are recruited first?
Smaller motor units
45
During sustained contraction what type of motor units are recruited later?
Larger motor units
46
Isotonic contraction?
Muscle contracts and changes length, equal force
47
Concentric contraction?
Shortening contraction
48
Eccentric contraction?
Lengthening contraction
49
Isometric contraction?
Muscle contracts but does not change length, change in force
50
5 Facts about slow-twitch fibers?
-Type I -resistant to fatigue -Slower to contract -Stimulated by aerobic exercise -High myoglobin (red)
51
5 Facts about fast-twitch, fatigue-resistant fibers?
-Type IIA -Quicker to contract than type I -Resistant to fatigue -Stimulated by forceful exercise -High myoglobin (red)
52
4 Facts about fast-twitch, glycolytic fibers?
-Type IIB -Contract rapidly -Susceptible to fatigue -Low myoglobin (white)
53
Time frame when each energy system is used?
1-6sec stored ATP 10sec creatine phosphate 30-40sec anaerobic pathway Hours aerobic pathway
54
6 characteristics of smooth muscles?
-Short, elongated fibers with tapered ends -Centrally located nuclei -Myofilaments randomly organized -No striations -No transverse tubules -SR not fully developed
55
Two types of smooth muscles?
Multi-unit and visceral
56
Where can multi-unit smooth muscles be found?
Iris (eye) and walls of blood vessels
57
2 characteristics of multi-unit smooth muscles?
Less organized cells where each fiber functions independently
58
Where can visceral smooth muscle be found?
In the walls of most hollow organs
59
What is the characteristic of visceral smooth muscle?
Sheets of spindle-shaped muscle fibers function as a unit to contract with rhythmicity
60
What does smooth muscle have in place of troponin?
Calmodulin
61
What two neurotransmitters work in smooth muscles?
ACh and norepinephrine (NE)
62
Differences in contraction rate and fatigue between smooth and skeletal muscles?
Smooth muscles contract slower and are more resistant to fatigue
63
What are characteristics of caridac muscle?
-Joined via intercalated discs -Fibers branch but have single nucleus -Contract together as a unit (syncytium) -Self-exciting; rhythmic -Longer refractory periods than skeletal muscle -No sustained/tetanic contractions
64
What two things are the action of a muscle dependent on?
The type of joint and the way the muscle is attached on either side of the joint
65
4 basic components of levers?
-Rigid bar/rod (bones) -Fulcrum/pivot point (joint) -Resistance (weight) -Force (muscles)
66
Organization of first class lever?
Resistance-fulcrum-force
67
Organization of second class lever?
Fulcrum-resistance-force
68
Organization of third class lever?
Resistance-force-fulcrum
69
Agonist?
Prime mover-the muscle that causes movement at a joint
70
Extensor muscles?
Extend the joint and increase joint angle
71
Flexor muscles?
Decrease joint angle
72
6 cells and 5 stages of muscle repair?
Quiescent satellite cell -Activation Activated satellite cell -Proliferation Myogenic progenitor (myoblast) -Differentiation Myocyte -Fusion Myotube -Maturation Myofiber

Z A&P Chapters 7-9 (5 decks)

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