Chapter 10 Flashcards
1
Q
what 3 layers of CT surround the muscle?
A
- Epimysium
- Perimysium
- Endomysium
2
Q
Epimysium
A
dense layer of collagen fibers that covers the entire muscle
3
Q
perimysium
A
covers bundle of muscle fibers called fascicles
4
Q
fascicles
A
collagen + elastic fibers, blood vessels and nerves
5
Q
Endomysium
A
surrounds muscles fibers
-contains elastic fibers, capillaries and nerves
6
Q
Tendon
A
where endomysium, perimysium and epimysium come together
7
Q
names for muscles cells
A
- muscle cell
- myofiber
- muscle fiber
8
Q
myofibril
A
-organelle that contains myofilaments
9
Q
myofilaments
- consists of 2 things
- responsible for
A
- thick (myosin) and think (actin) filaments
- muscle contraction
10
Q
sarcolemma
A
plasma membrane surrounding the cytoplasm
11
Q
Sarcoplasmic reticulum
- what is it similar to
- what does it contain
A
Similar to smooth ER
-contains large amount of Ca++ ions
12
Q
terminal cisternae
A
SR tubules fuse and form an expanded chamber
13
Q
Triad
A
2 terminal cisternae and 1 T-tubule
14
Q
T-tubule
- definition
- what do they form
A
narrow tubes continuous with sarcolemma
-form passage ways through the muscle cells
15
Q
Sarcomere
- definition
- function
A
- functional unit of the myofilament
- gives the appearance of striations under microscope
16
Q
4 components of the sarcomere
A
- thick filaments (myosin)
- Thin filaments (actin)
- Proteins that stabilize these filaments
- Proteins that regulate interactions between filaments
17
Q
in between the I band
A
Z line that connects thin filaments
18
Q
in between the A band
A
H zone that contains think but no thin
19
Q
Thin filament
-composed of 4 things
A
- Troponin
- Tropomyosin
- Actin
- Active site
20
Q
Active site of thin filament
- location
- binds to
- what is it covered by when resting
A
- on actin molecules
- myosin
- tropomyosin
21
Q
Thick filament
-contains
A
-head and tail
22
Q
Sliding filament theory
A
Thin filaments slide toward center of each sarcomere along side of each thick filament
23
Q
During contraction what happens to the length of:
- A band
- I band
- H zone
- Zone of overlap
- Sarcomere
A
- remains constant
- shortens
- shortens
- increases
- Shortens
24
Q
4 principles governing the contraction of skeletal muscle cells
A
- When muscle cells contract they pull on the attached tendon
- Contraction occurs only when skeletal muscle fibers are activated by neurons at a neuromuscular junction
- Tension produced is dependent on the number of motor neurons stimulated
25
motor neurons
neuron and muscle fibers it stimulates
26
How does the size of the motor unit relate to movement controlled
Size of the motor unit relates to how well the movement is controlled
27
small motor units
- 1 neuron stimulates
- allows for
1 neuron stimulates 4-6 muscle fibers
| -fine control
28
Large motor units
| -1 neuron stimulates
1000-2000 muscle fibers
29
Physiology of muscle contraction
| -2 things
1. Control by nervous system: the events of the neuromuscular junction
2. Excitation contraction coupling
30
Events of the neuromuscular junction
| -5 steps
1. Electrical signal travels down the terminal branch of the motor neuron
2. This causes Ca++ to enter the axon terminal
3. Vesicles in axon terminal are going to move to plasma membrane, fuse and discharge contents into synaptic cleft
4. Ach diffuses across synaptic cleft and binds to a receptor on the muscle cell sarcolemma
5. This initiates an electrical signal along sarcolemma of muscle cell (the muscle is now excited)
31
electrical signal=
action potential
32
what are neurotransmitters made up of
acetylcholine
33
Excitation contraction coupling
- definition
- 7 steps (continuation)
- link between generation of an action potential in the sarcolemma and start of muscle contraction
6. electrical impulse conducted into a T-tubule
7. impulse is going to reach the sarcoplasmic reticulum (at the triad)
8. Sarcoplasmic reticulum releases Ca++ into the sarcoplasm
9. Ca++ diffuses to myofibril and binds to troponin on thin filament
10. When Ca++ binds to troponin, troponin changes its shape (causes tropomyosin to change position)
11. This exposes the active site on actin
12. Myosin head binds to the active site on actin
34
contraction cycle
| -3 steps
1. Cross bridge attachment
2. Cross bridge rotation (pivoting)
3. cross bridge detachment
35
Cross bridge attachment
- -what happens
- allows for
- myosin head acts as am ATPase to hydrolyze ATP to ADP + P
| - binding of myosin head to active site on actin
36
Cross bridge rotation
powerstroke occurs as ADP + P and is released from myosin head
37
Cross bridge detachment
- what binds
- what does binding do
- ATP binds myosin head
| - disrupts linkage between myosin head and active site on actin
38
All or none principle
After stimulation by a nerve, an individual muscle cell either contracts to its fullest or not at all (does not apply to the entire muscle)
39
Principle of graded strength
strength of the contraction can range from weak to strong
40
Single stimulus
Twitch
41
twitch
- response of a muscle cell to a single stimulus
1. latent phase
2. contraction phase
3. Relaxation phase
42
latent phase of a twitch
begins at stimulation - action potential spreads down sarcolemma and SR releases Ca++
-Ca++ will bind to troponin as soon as its released from SR
43
contraction phase of a twitch
tension rises to peak (crossbridges are forming)
44
relaxation phase of a twitch
Ca++ levels are falling and active sites are covered
45
Summation
- definition
- produces
- 2 types
Adding individual twitches together
- graded contractions
1. multiple motor unit summation
2. Temporal (wave) summation
46
multiple motor unit summation
- increased force of contraction caused by an increase in stimulus strength
- sub-threshold, threshold, sub-maximal, maximal stimulus
47
threshold
minimum stimulus needed to produce a contraction
48
maximal stimulus
Maximum stimulus without any additional force of contraction
49
tension produced by skeletal muscle is determined by:
| -2 things
1. stimulated muscle fibers
| 2. total number of stimulated muscle fibers
50
temporal (wave) summation
increased force of contraction caused by an increase in the frequency of stimulation
51
tetanus
stimulation of a muscle at even higher frequency produces "fusion" of summation twitches
52
Frequency of temporal summation
- definition
- what happens to the strength
next stimulus arrives before relaxation phase has ended
| -strength of stimulus remains the same
53
why does increase in the frequency of stimulation increase the force of contraction (temporal summation)?
- muscle cell has not had a chance to fully relax before the next stimulus arrive
- muscle is still partially contracted and Ca++ stores are still available from last contraction
54
Treppe
- definition
- why?
If a muscle is stimulated a 2nd time immediately after the relaxation phase has ended the force of contraction will be greater than the 1st stimulus
-increased Ca++ availability (in sarcoplasm) and heat increases activity of muscle enzyme
55
Muscle tone
- definition
- why does it occur
- example
- constant tension produced by muscles for extended periods of time
- because some motor units are active even when whole muscle is not contracting
- muscles that keep the back and legs straight, the head upright and the abdomen flat
56
Isotonic contraction
muscle develops tension, overcomes resistance and object is moved
57
Isometric contraction
Muscle develops tension, cannot overcome resistance and object is not moved
58
Muscle fatigue
- lack of O2
- depletion of ATP
- accumulation of lactic acid
- ionic imbalances
59
Fast fibers
- definition
- common?
- color
- capillary supply
- mito
Rapid movements for short periods of time
- most muscle fibers in humans
- white
- scarce
- few
60
Slow fibers
- definition
- type of muscle
- color
- capillary supply
- mito
- high endurance and contracts for an extended period of time
- postural muscle
- red
- dense
- many
61
Oxygen debt (excess post - exercise O2 consumption)
- definition
- 3 examples
- what does rapid breathing do
- Amount of O2 needed to restore homeostasis in the muscle tissue
- 1. ATP stores must be replenished
2. Lactic acid that builds up during exercise must be converted to glycogen
3. Creatine needs to be converted back to creatine phosphate
- helps to replenish O2
62
The role of creatine phosphate
- energy sources
- what is it used for
- formula
- ATP + creatine phosphate
- used to produce ATP in muscle cells
- ADP+ creatine phosphate -> creatine + ATP
63
Muscle hypertrophy
Muscle cell enlargement in response to repeated stimulation
64
Muscle Atrophy
Muscle cells reduce in sixe in response to a lack of stimulation
65
Delayed onset muscle soreness
| -3 proposed mechanisms
1. small tears in muscle tissue (damaged sarcolemma) (permits the loss of enzymes and chemicals that stimulate pain receptors
2. muscle spasm in affected muscles may cause pain
3. tears in connective tissue and tendons of affected muscles
