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Mammalian Physiology > Exam 3: Chapter 21: Movement and Muscles at Work > Flashcards

Exam 3: Chapter 21: Movement and Muscles at Work Flashcards

1
Q

striated muscle makes up what percentage of tissues in vertebrate?

A

about 50%

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2
Q

Mammalian cardiac muscle contracts _____ times per minutes.

A

30-700

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3
Q

Adult muscle cells are in what state of division. What does this mean?

A

They are in a post-mitotic state. This means that they are capable of adaptation but not division.

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4
Q

Muscles add bulk by _____

A

hypertrophy, addition of proteins

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5
Q

With disuse, muscles will ______

A

atrophy; loss of cells

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6
Q

Strength training muscles will add more ________, result in more __________.

A

Strength training will add more actin and myosin, resulting in the formation of more myofibrils. Can also add more nuclei.

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7
Q

Hypertrophied muscle nuclei are connected to _______/

A

Muscle memory .: Muscles trained at an earlier time, return to earlier strength w/ less effort than before

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8
Q

Leg muscles of distance runners develop…

A

more and larger mitochondria, making more ATP.

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9
Q

Endurance training can cause the formation of more _____ around their muscles.

A

Capilaries

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10
Q

How do muscles from endurance training differ from that of strength training.

A

They (endurance training muscles) do not have the hypertrophy of strength training athletes.

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11
Q

Muscle phenotypes depend on….

A

it’s actions

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12
Q

Slow twitch muscle fiber characteristics:

A

narrow diameters, using aerobic metabolism, predominates in endurance exercise

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13
Q

example of endurance exercise

A

long-distance running, cycling, and swimming

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14
Q

slow twitch muscle fibers action and forces

A

repetitive actions and low forces; economically apply isometric force and involved isotonic contractions

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15
Q

example of strength traning

A

stair running or weight-lifting

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16
Q

strength training uses what type of muscle fibers

A

fast-twitch muscle fibers

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17
Q

Fast-twitch muscle fibers use what type of metabolism

A

anaerobic (without oxygen)

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18
Q

repetition and forces of strength training

A

fewer repetitions and larger forces

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19
Q

different muscle fibers have different _______. What does this influence?

A

isoforms; influence the muscles functional properties

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20
Q

2 important molecules for muscle fibers

A

myosin heavy chain and the thick filament and the Ca2+-ATPase pump of the SR

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21
Q

SO type 1 fibers

A

have many mitochondria and are fatigue resistant

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22
Q

FOG muscle fibers

A

have fatigue resistance

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23
Q

4 main characteristics of FG fibers

A

contract 10x faster than SO, have few mitochondria, large diameters, and fatigue quiclkly

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24
Q

Motor units are made up of…

A

each muscle type with the motor neurons that connect them

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25
How can motor units be converted?
Can be converted from one type to another by cross-innervation
26
Motor units recruit in a fixed order:
SO, FOG, and lastly FG
27
what determines a muscles's contractile performance?
power output, which changes in response to use and disuse
28
how is mechanical power generated determined?
forced produced in a muscle multiplied by the velocity of shortening
29
velocity of shortening _______ as the load _______.
decreases, increases
30
Power output of most muscles is maximal when...
the muscle shortens to 20-40% of Vmax
31
power is measure in what unit?
watts
32
Endurance training elicits....
changes in fiber type, increasing capillary density and mitochondrial density
33
Normal people have what ratio of fast to slow muscle fibers
50/50
34
Marathoners have much higher ________ fibers and few _____.
higher slow fibers and few fast fibers
35
Sprinters have more _______ fibers
fast fibers
36
exercise training can cause...
increases in capillary density, increases in mitochondrial density, a convergence between fiber types, especially types IIa and IIx
37
endurance training leads to what change in capillaries?
can lead to a larger number of capillaries contacting muscle
38
angiogenesis
the vascularizing of the muscle
39
vascular endothelial growth factor
produced by exercised muscles, stimulates angiogenesis
40
Mitochondria in response to endurance training
endurance training increases the number of mitochondria
41
Changes mitochondria that lead to less fatigue
changes in the structural and enzymatic proteins of the mitochondria
42
more mitochondria allow the cells to...
use more oxygen
43
How do new mitochondria get fuel? What does this allow for?
use more fat as fuel instead of glucose; saves glycogen and produces less lactic acid
44
3 types of genes that contribute to muscle phenotypes
- contractile protein genes (myosin isoforms) - angiogenesis genes (growth factors like VEGF) - mitochondrial genes
45
what does transcriptional coactivator PGC-1a do
coactivates a number of transcriptional factors; enhances mitochondrial biogenesis, muscle fiber conversion, and angiogenesis
46
PCG-1a1 is required for
production of VEGF and angiogenesis
47
What does B-adrenergic sympathetic stimulation happen with
happens with exercise, induces PGC-1a1
48
resistance/strength training causes? What does it not cause?
It causes changes in hypertrophy and changes in fiber types and it does NOT cause increases in aerobic capacity or capillary density at muscles
49
strength training can result in? What does this mean? What affect does detraining have?
- fiber type changes, gene expression changes, type IIa over IIx - This means there is a decreased amount in myosin heavy- chain (Mhc) IIX and increased amount of myosin heavy- chain IIa - De training has the opposite effect with Mhc IIx levels increasing beyond pre- training values
50
PGC-1a4 is made with strength training and what does this isoform do?
this isoform downregulates myostatin and upregulates IGF-1
51
combined resistance and endurance training can...
improve performance
52
hypertrophy can also occur in ______ muscles. When else can it occur?
cardiac; occurs during development, but also with exercise and pregnancy
53
how does cardiac muscle hypertrophy occur?
- proteins are added to myofibrils - adds sarcomeres to myofibrils - results in thicker heart walls and larger heart chambers, especially the left ventricles
54
hypertrophy of cardiac muscles result in
1. enhanced cardiac function 2. more oxygen taken up by myocytes 3. higher force and speed and contraction 4. greater stroke volume
55
Effects of endurance exercise on the heart
makes greater wall thickness and internal diameter of the heart
56
Effects of strength/resistance training on the heart
increases wall thickness
57
effects of pregnancy on heart
blood volume may increase by 50%
58
effects of hibernation on heart
decrease in heart rate, ventricular tissues atrophies 26%, and pathological atrophy may occur with high BP
59
unused muscle will
break down
60
major cause of atrophy
enzymatic breakdown of proteins
61
response to muscle atrophy
both mitochondria and nuclei decrease, less actin mRNA, cytochrome C mRNA, and oxidative enzymes
62
humans experience atrophy in
microgravity; disuse atrophy from weightlessness during space travel
63
17 days in space resulted in what changes in muscles (results were taken before and after the trip)
Muscle size and strength decreased: soleus muscle was 70% type I fibers, loss occurred in both thick and thin fibers, decrease in fiber diameters (even though sarcomere length was similar in both samples)
64
161-192 day space flights resulted in
20% decrease in type I fibers, fiber composition changed from slow to fast
65
starting at age 40, humans lose how much muscle mass?
1-2% muscle mass each year
66
What is sarcopenia? What is a key factor?
age related muscle loss, death of motor neurons in the spinal cord is a key factor and debranching is a part of it
67
what percent of motor neurons die by normal aging?
10-15%
68
muscle mass loss can cause issues with
balance and posture, resulting in falls and injury
69
what can help slow muscle mass loss in old age
continued strength training
70
endurance training can lessen
loss of mitochondria, helping with cell metabolism
71
what type of diet can help retain muscle?
nutrition with plenty of protein
72
some animals experience little or no disuse atrophy: how? Muscles lost accounts for what percentage of their strength?
- bears (hibernate 5-7 months and although inactive have little disuse atrophy); may recycle nitrogen from urea into amino acids used in protein synthesis - 25-30% of their strength
73
maintaining muscle mass is important for
controlling homeostasis
74
myostatin
growth factor (GDF-8), controls muscle mass; negative regulator, its inactivity results in more muscle mass
75
animals with GDF-8 mutation
"double muscled", both copies of the gene normal are thin; humans with mutation would be very strongly muscled
76
PI3K-Akt1 pathway
Akt1 controls the balance between synthesis and atrophy a protein kinase cell signaling enzyme with a role in protein synthesis and cell survival; its role can be stimulate by use or not and hormones
77
IGF-1
stimulates PI3K and Akt1
78
Akt1 is activated by
phosphorylation; stimulates protein synthesis and then also acts as a negative regulator in the nucleus
79
GH and androgens
also stimulate protein synthesis
80
When the muscle is inactive and leads to atrophy what is happening?
the PI3K-Akt1 pathway isn't function, Akt1 is suppressed by glucocorticoids from the stress response
81
Mechanical power=
Force produced in a muscle x shortening velocity
82
What is shortened velocity influenced by?
The myosin isoforms expressed by the motor units of the muscle
83
Power is the product of.....
force and velocity
84
What is maximum forced produced by a muscle proportional to?
The cross- sectional area of the contractile elements
85
Steps in P13K- AKt1 pathways
1. Strength work stimulated IGF-1 release: When muscle exerts force on a load, it secretes IGF-1, which binds its receptor and triggers molecular pathways for protein synthesis 2. IGF-1 stimulated P13K and AKt1 3. AKt1 is activated by phosphorylation 4. This stimulates protein synthesis and then also acts a negative regulator in the nucleus

Mammalian Physiology (17 decks)

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