Muscular System Lecture Flashcards
0
Q
Moving upward toward the skin, the tissue thickens and changes names. What is the new name and what does it eventually become right under the skin?
A
Epimysium turns into fascia, which separates adjacent muscles. As it extends upward, it becomes the hypodermis of the skin.
1
Q
What is the name of the CT surrounding a whole muscle?
A
Epimysium. Dense irregular CT
2
Q
Muscles are made up of fascicles. What is a fascicle? What is the CT covering each fascicle?
A
Skeletal muscle is made of fascicles which are bundles of cells. The perimysium covers each fascicle. Loose aeriolar.
3
Q
What is the CT that holds muscle fibers together within a fascicle?
A
Endomysium. Loose aeriolar.
4
Q
What type of CT are these four structures made of?
A
Loose aeriolar and dense irregular CT
5
Q
Each cell is made up of around 1000 strings/cylinders. What are these called?
A
Myofibrils
6
Q
What is the repeating pattern of lines on the myofibrils called?
A
The sarcomere is the repeating pattern of lines found inside the myofibrils of the muscle cell.
7
Q
What is the name of a muscle fibers cell membrane?
A
Sarcolemma
8
Q
What is the name running vertical down?
A
Transverse tubules or T-tubules.
9
Q
What is the purpose of the T-Tubules in helping the muscle contract?
A
They carry the action potential produced by the nerves from the surface of the muscle cell into its interior. This ensures that all of the myofibrils contract.
10
Q
What is the thing covering the muscle cell?
A
Sarcoplasmic reticulum. SR.
11
Q
The SR stores a substance needed to start the muscle contraction. What is the substance and what causes it’s release?
A
The SR stores calcium, and it’s release is caused by the electrical currents that nerves create. They enter the T-Tubules and make the SR release it’s calcium.
12
Q
How is the SR important in ending a muscle contraction?
A
The calcium must be returned to the SR to stop the contraction.
13
Q
What are the zig zag lines on the ends of each sarcomere?
A
Z lines.
14
Q
What is the space in the middle of the sarcomere called?
A
H zone.
15
Q
(Use picture on page 3)
What is the blue part called?
A
I band.
16
Q
(Use picture on page 3)
What is the green and yellow part called?
A
A band.
17
Q
(Picture page 3)
What is the thick line in the H zone called? Two names.
A
Myosin or thick filament.
18
Q
(Picture page 3)
What are two names for the blue ropes in the A band?
A
Actin or thin filament.
19
Q
Which areas of the sarcomere are visible on a microscope slide of skeletal muscle as a pattern of stripes? What is another name for these stripes?
A
The A band is visible as a dark stripe and the I band is visible as a light stripe. The stripes are called striations.
20
Q
What happens to the sarcomere during a contraction?
A
The sarcomere gets shorter.
21
Q
Have the thick and thin filaments (myosin and actin) shortened because of the contraction?
A
They have NOT shortened.
22
Q
What happens to the I band during a contraction?
A
The I band shortens.
23
Q
What happens to the H zone during contraction?
A
The H zone disappears because the actin filaments slide toward the center of the sarcomere.
24
What happens to the A band during contraction?
There is no change in the appearance of the A band.
25
Explain the lack in change of the A band.
The A band doesn't change because the myosin filament doesn't slide or shorten during the contraction.
26
Which filament slides toward the center of the sarcomere during the contraction?
The actin filaments slide toward the center of the sarcomere in the contraction.
27
What causes the sliding to occur?
Myosin is responsible for the sliding of actin filaments. Myosin heads attach to the actin "beads" and swing, pulling the actin filaments.
28
In this contraction the sliding of filaments causes the sarcomeres to shorten, which shortens the muscle. What is the more specific name for this contraction?
When a muscle shortens, it's called a concentric contraction rather than the normal, isotonic contraction.
29
The sliding of filaments can also cause the sarcomeres to lengthen, which lengthens the muscle. What is the more specific name for this contraction?
When the muscle lengthens, it's called an eccentric contraction, rather than a normal isotonic contraction.
30
The sliding of actin filaments inside the sarcomere doesn't always occur in all types of contractions. What is the contraction called is there is no sliding of actin at all?
When sliding of actin doesn't occur it is called the isometric contraction. Isometric means "same length" since the sarcomere doesn't change in length.
31
In isometric contraction, what does happen?
The myosin heads still attach to the actin beads, which creates tension. The isometric contraction is also known as a muscle tone contraction.
32
(Use picture on page 6)
| Name parts E and F.
E is the myosin heads
| F is the myosin filaments
33
(Use picture on page 6)
Structure D is named after it's chain of protein beads called actin. What is A in the diagram? What happens at A during a contraction?
A is the active site on the actin. The active site is a sticky spot on the actin that the myosin heads can attach to during a contraction.
34
(Use picture on page 6)
| Name parts B through D.
B is troponin.
C is tropomyosin.
D is the actin filament.
35
Troponin and tropomyosin have control over whether the myosin heads are attached or not. What is tropomyosin's role in this job?
Tropomyosin helps control when myosin can attach to the actin in muscle because it covers the active sites on the actin filament.
36
Calcium that is released from the SR attaches to the troponin to begin a muscle contraction. What does this calcium cause to happen that allows the muscle contraction to start?
The calcium is released from the SR. Calcium attaches to the troponin and lifts it and the tropomyosin up so that the active sites are revealed and the myosin heads can attach to them and swing, causing a contraction.
37
(Use picture on page 7)
| The entire structure A represents the knobby end of a nerve cell. What two names is this structure called?
A is the presynaptic terminal or synaptic knob. It's part of the neuron.
38
(Use picture on page 7)
| The entire structure I represents the surface of a muscle cell. What is it called?
I is the post synaptic terminal. It is part of the sarcolemma, or covering of the muscle cell.
39
(Use picture on page 7)
| What is G called?
G is the synaptic gap. It is a small space between nerve and muscle.
40
(Use picture on page 7)
| What is substance C, the neurotransmitter released by the nerve cells presynaptic vesicles, D?
C is acetylcholine. Or ACH.
41
(Use picture on page 7)
| What must happen first in the nerve cell to allow ACH to be released?
Calcium enters the synaptic knob of the nerve through the calcium channels (B). Which triggers the release of the ACH.
42
(Use picture on page 7)
| ACH binds to a specific receptor (E) causing it to open. What substance (F) enters the muscle cell through (E)?
E is the sodium receptor.
F is the sodium.
The ACH receptor is a sodium channel that allows sodium to enter the muscle.
43
Once sodium has entered the muscle cell, what has been started in the muscle cell?
Once sodium enters the muscle an action potential has now been started that flows into the muscle and causes it to contract.
44
What happens if ACH stays in the synaptic gap for too long?
Action potentials will continue to be made, causing a constant contraction in the muscle. (Spastic paralysis)
45
What enzyme, (H) prevents ACH from remaining in the synaptic gap too long?
H is cholinesterase (ACHE). It breaks down ACH as soon as it is used and sends the pieces of ACH back to the presynaptic terminal where they are reused to make more ACH.
46
What two types of enzymes prevent ACHE from working? What is the result in the muscle?
Insecticides and military nerve gasses kill by preventing ACHE from breaking apart ACH quickly enough. The result is that ACH stays in the synaptic gap causing synaptic paralysis of the muscle.
47
What specific part of the synapse is affected by curare and in the disease myasthenia gravis?
They both affect the ACH receptor.
48
With curare poisoning and MG what type of paralysis results?
Flaccid paralysis results, the muscle can't contract.
49
Explain exactly what happens in the synapse with MG and curare poisoning?
MG the WBC slowly destroy the ACH receptors over time.
Curare binds to ACH receptors and causes them to close. So no sodium can enter the muscle cells and thus no action potentials can be started so no contraction.
50
Can a muscle fiber contract halfway or incompletely?
No.
51
What is the all or none principle?
A muscle can't contract halfway or incompletely.
52
What does this mean about the way sarcomeres act during a contraction?
When actin slides in the sarcomere it slides as far as it can. The sarcomeres always shorten to their fullest possible extent, which is what creates the strongest possible contraction for the cell.
53
Muscles are made up of many motor units. What is a motor unit?
A motor unit is a group of muscle cells that are under the control of one nerve.
54
If the electrical voltage applied to a muscle is gradually increased what happens to the number of motor units which contract? What does this mean happens to the muscle contraction?
The number of motor units contracting increases as the voltage is increased. This causes the muscle contraction to get stronger.
55
If a subthreshold stimulus is used on a muscle, now many motor units in the muscle will contract?
A subthreshold stimulus will not cause any motor units to contract because it is too weak to cause cells to contract.
56
If a threshold stimulus is used on a muscle, how many motor units will react?
Only one motor unit will contract out of the many more units in the muscle.
57
If a maximal stimulus is used, what happens?
All motor units will contract, producing the strongest contraction possible.
58
A maximal stimulus is one that is strong enough to cause _________ motor units in a muscle to contract.
All.
59
Motor unit summation means that as the stimulus is ________, the _____________ of a muscle contraction increases.
Increased, strength.
60
Motor unit summation explains how one muscle can have contractions if varying or different __________ like a pat slap or punch done by the same muscle.
Strengths.
61
Motor unit summation is also called ________.
Recruitment- because as you increase the electrical current you are getting more and more cells to contract.
62
Sometimes after a period of rest, when a muscle first contracts, not all of its calcium is released from the SR. Since only some of the calcium is released, will the muscle contract fully the the first few times it contracts?
No, the contraction will not be as strong as it should be if all of the calcium isn't released by the SR.
63
Sometimes after a period of rest, when a muscle first contracts, not all of its calcium is released from the SR. What is this concept known as?
The Treppe Effect.
64
Sometimes after a period of rest, when a muscle first contracts, not all of its calcium is released from the SR. What do these contractions look like? Because of this, what is this concept also called?
The Treppe a Effect is a series of contractions that gradually get stronger. The contractions look like steps going up because they increase in size so this concept is also called the staircase phenomenon.
65
Sometimes after a period of rest, when a muscle first contracts, not all of its calcium is released from the SR. What kind of stimuli are used to produce this and how many are given per second?
The shocks should be maximal and be given at low frequency, or 10-20 shocks per second.
66
Wave summation means that several individual muscle contractions can be __________ together so that they create a contraction that is ___________ than a single contraction.
Added or summated
| Stronger
67
How is wave summation created in a muscle?
Wave summation is created when electrical shocks are applied to the muscle while it is already contracting, using 20-40 shocks per second.
68
When many contractions are summated this leads to a type of wave summation caused tetanus. In complete tetanus many contractions fuse together, producing a long powerful contraction. How is complete tetanus created in a muscle?
The muscle is not allowed to relax between stimuli by applying the stimuli at a high frequency using 40-50 stimuli per second.
69
When many contractions are summated this leads to a type of wave summation caused tetanus. In complete tetanus many contractions fuse together, producing a long powerful contraction. What specifically happens in muscle cells that causes complete tetanus?
Calcium can't be returned to the SR between shocks because they can't go that fast. Calcium has to be returned to end any contraction. So you have one big long contraction.
70
Why is complete tetanus not a regular event in the body?
Complete tetanus is 40-50 shocks per second while the normal firing of nerves in the body is usually 25 shocks per second.
71
How fast does a nerve have to fire action potential onto a muscle to cause the Treppe Effect?
10-20 shocks per second.
72
Overall what causes the Treppe effect to occur? What is the main thing that causes the contractions to get stronger?
The main cause is a gradual release of calcium by the SR. It takes several contractions for all of the calcium to be released.
73
Why does the amount of calcium released by the SR affect the strength of muscle contractions?
The amount of calcium determines the number of active sites that will be uncovered and thus, the number of myosin heads that can attach to the actin. The more myosin heads that attach, the stronger the contraction.
74
Muscle tone can be described as a ________ contraction because only a _______ number of motor units are contracting at any one time.
Partial
| Limited
75
What term describes the type of contraction that muscle tone is?
Isometric contraction.
76
Can the sliding filament theory be used to explain muscle tone?
No because the actin doesn't slide in a muscle tone contraction.
77
What is happening in muscle tone?
There is an increase in tension in the muscle because myosin heads attach to the actin but they do not swing.
78
Can a muscle tone contraction be used to move your arms and legs?
No.
79
What two things are muscle tone contractions used for?
Keep postural muscles tight, to keep head upright, torso and calf muscles tight.
Used to hold limbs in position.
80
There is an energy production system used in skeletal musical know as the phosphagen system. What is creatine phosphate?
Creatine phosphate is an energy source that is stored in skeletal muscle to prevent muscle from totally running out of ATP. Each CP is a backup energy supply that is rapidly turned into 1 ATP when levels are low.
81
At what point during physical exercise is creatine phosphate used?
At the very beginning of intense, short term exercise. It provides energy for the first fifteen seconds of exercise.
82
Why is creatine phosphate used at this point in physical exercise?
It quickly provides energy for contraction while the slowed processes that create energy from food are not yet producing ATP.
83
What is fatigue?
The deterioration of muscle contraction, leading to the total loss of the muscles ability to contract.
84
What are the main causes of fatigue?
Insufficient energy ATP production, often due to lack of oxygen and lack of sugar in the muscle.
85
What specifically happens in the muscle when fatigue occurs?
Without ATP, the SR is unable to store calcium. Calcium leaks out of the SR causing myosin to attach to actin, producing tetanus.
86
How are cramps or contractures related to fatigue?
Contractures are a type of cramping in a muscle that is the start of fatigue, a temporary state of tetanus that often occurs in the hands.
87
How much ATP is created from one glucose by aerobic metabolism?
Aerobic metabolism creates 36 ATP from each molecule of glucose. Other foods besides sugar, like protein and fat, are also turned into ATP using the aerobic process.
88
What makes aerobic metabolism so good at producing energy?
The use of oxygen allows the greatest amount of energy to be made from foods. The word aerobic means that oxygen is used.
89
What type of skeletal muscle cells are best at producing energy and thus use this method? Aerobic
Slow twitch or slow oxidative cells.
90
What does this mean about how long these cells can contract before fatiguing? Aerobic
Able to contract for long periods of time.
91
What special molecule do these cells contain and how does it help in the energy making process? Aerobic
Slow twitch cells contain myoglobin, a molecule that allows them to store oxygen.
92
What is the alternate method for producing energy? Aerobic
Anaerobic metabolism.
93
Why is it less efficient at making energy? Anaerobic
It doesn't use oxygen.
94
What are the major drawbacks to a muscle cell using this method? Anaerobic
Only a limited amount of energy is produced.
95
What one advantage does it have over aerobic metabolism? Anaerobic
The process of producing ATP by anaerobic respiration is two and a half times faster than producing it by aerobic respiration.
96
What type of skeletal muscle cells use this method? Anaerobic
Fast twitch or fast glycolytic.
97
Even though these cells are not designed for endurance what are they designed for? Anaerobic
Quick powerful contractions that give speed in a short activity.
98
In some people endurance training can cause fast twitch to turn into intermediate fibers. What does this mean happens to these fibers?
When fast twitch turn into intermediate fibers they have the endurance of slow twitch fibers. This means the intermediate fiber is a type of fast twitch that is not only good for speed but also for endurance.
