Muscle Tissue Flashcards
1
Q
What does skeletal muscle attach to?
A
bone, skin, or fascia
2
Q
What is Fascia?
A
Fascia is a fibrous connective tissue that surrounds muscles, groups of muscles, blood vessels, and nerves, binding some structures together, while permitting others to slide smoothly over each other.
3
Q
Are there striations on fascia?
A
Yes, there are striations on fascia
4
Q
Are skeletal muscle voluntary or involuntary?
A
voluntary
5
Q
What are some functions of muscle?
A
Give shape, produce movement, maintain posture, support other structures, generate heat, regulate organ volumes (sphincters)
6
Q
What are some properties of muscle tissue?
A
excitability conduction contraction extension elasticity
7
Q
Skeletal muscles are composed of bundles of muscle fibres called what?
A
Fascicles
8
Q
What are fascicles made up of?
A
fascicles are made up of MUSCLE CELLS that are elongated and striated (aka MUSCLE FIBRES)
9
Q
What is the membrane called that surrounds the entire muscle?
A
Epimysium surounds the whole entire muscle
10
Q
What is the membrane that surrounds individual fascicles?
A
Perimysium surounds individual fascicles
11
Q
What is the perimysium?
A
Perimysium is a membrane that surounds individual fascicles
12
Q
What is the Epimysium?
A
Epimysium is the membrane that surounds the whole entire muscle
13
Q
Name the order in which structures of a muscle reside?
A
MUSCLE made up of FASCICLES that contain MUSCLE FIBRES made up of MYOFIBRILS made up of SACROMERE made up of MYOFILAMENTS
14
Q
What are the 3 connective tissue components of muscle tissue
A
epimysium
perimysium
endomysium
15
Q
Define innervate
A
to supply with nerves
16
Q
Each muscle is supplied by what (3) things?
A
artery, vien, & nerve
17
Q
Each muscle fibre is supplied by what (2) things?
A
(1-2) capillaries & motor neuron
18
Q
How many muscle cells does a motor neuron innervate?
A
a motor unit
several muscle cells about 150 that contract together
19
Q
In the formation of muscle cells during embryotic development what fuses together to create the muscle fibre?
A
myoblasts
20
Q
What are 2 characteristics of mature muscle cells?
A
- multinucleated
- cannot divide
21
Q
Some myoblasts remain unfused, what are they called?
A
satellite cells
22
Q
What are satellite cells?
A
myoblast cells that maintain their ability to divide; aren’t very many
23
Q
What is the sarcoplasm?
A
The cytoplasm of a muscle cell
24
Q
What is the sarcoplasm composed of?
A
- mainly myofibrils
- glycogen
- myoglobin (red coloured protein that binds to oxygen; and releases it when it is needed by the mitochondria)
25
What are transverse tubules?
invaginations of sarcolemma, filled with interstitial fluid, that carry muscle action potentials deep into sarcoplasm; the arrangement ensure that is excited the whole muscle fibre
26
Define invaginations.
the action or process of being turned inside out or folded back on itself to form a cavity or pouch.
• a cavity or pouch so formed.
27
What is the sarcoplasmic reticulum?
It's like an endoplasmic reticulum of a regular cell; stores calcium
28
What is an endoplasmic reticulum of a non muscle cell?
a network of membranous tubules within the cytoplasm of a eukaryotic cell, continuous with the nuclear membrane.
29
What is the role of calcium in muscle contraction?
binds to troponin which frees up the binding site on actin so myosin heads can bind
30
What triggers calcium to be released
acetycholine (ACH)
31
Whats another name for the sarcolemma?
cell membrane of muscle fibre
32
What is a myofibril?
contractile element of skeletal muscle that extend the entire length of a muscle cell
33
What makes up myofibrils?
long chains of sarcomere
34
What are sarcomere?
the region between z disc to z disc that the basic structural unit of a muscle cell
35
What is the basic functional unit of a muscle cell
sarcomere
36
How many types of myofilaments are there?
2; myosin (thick filament) and actin, troponin, tropomyosin (the thin filament)
37
The bands that make the dark and light striations are called...
```
I bands (light); along the z line
A bands (dark); along the m line
```
38
How many types of proteins do myofibrils contain?
3 types:
- contractile
- regulatory protein
- structural protein
39
What are the 2 contractile proteins?
myosin and actin
40
What are the 2 regulatory proteins?
troponin and tropomyosin
41
What are the 4 structural proteins?
titin, myomesin, nebulin, and dystrophin
42
What are thick filaments?
composed of myosin which resemble 2 golf clubs twisted together;
they form the cross bridge that extend toward the thin filaments;
held in place by m line protein
43
What are thin filaments?
composed of actin, troponin, & tropomyosin;
| in a relaxed muscle, myosin binding sites on each actin are covered by tropomyosin supported by troponin
44
What are some characteristics on titan the structural protein?
- the third most abundant protein in skeletal muscle
- large molecule
- *anchors thick filaments to the z disc and m line
45
What are some components of sliding filament mechanism of contraction?
- myosin cross bridge pulls on filaments
- thin filaments lide inward
- z disc come toward each other
- this means sarcomere shortens thus muscle fibre shortens thus the muscle shortens
46
What is a neuromuscular junction?
the synapse between a motor neuron and muscular fibre
47
What are the 6 mechanisms of contraction (the signal of the contraction)?
1. nerve impulse reaches an axon terminal, synaptic vesicles release ACh (acetycholine)
2. ACh opens sodium channels and sodium rushes into the cell
3. a muscle action potential spreads across the sarcolemma, down into the transverse tubules
4. The sarcoplasmic Reticulum releases calcium into the sarcoplasm
5. calcium binds to troponin which causes the troponin tropomyosin complex to expose the myosin binding sites on the actin
6. the contraction cycle begins
48
What is the chemical messenger that stimulates a muscle contraction?
acetycholine
49
What binds to troponin in order to expose myosin binding sites?
calcium
50
What releases calcium in order to bind to troponin for a muscle contraction to begin?
Sarcoplasmic reticulum
51
What role do the t tubules do in order to aid in a muscle contraction?
the neural impulse travels through the t tubles in order to ensure that there is a a full muscle contraction
52
What causes relaxation?
- a lack of calcium; so troponin-tropomyosin complex covers myosin binding sites
- acetycholine enzyme breaks down acetycholine
- muscle action potential ceases
- calcium channels close
- calcium is pumped back into the SR by active transport
53
What is a contraction cycle?
a repeating sequence of events that causes thick and thin filaments to move past each other
54
What are the 4 steps to contraction cycle?
1. Myosin heads are activated by ATP
2. Myosin heads bind to myosin binding sites on actin creating crossbridge
3. Power stroke (myosin heads pull actin toward the centre of the sarcomere
4. Myosin heads bind to ATP and crossbridge detaches
55
What makes the contraction cycle continue?
- If there is still ATP availlable for priming myosin
| - if the calcium level near troponin tropomyosin complex is high
56
Active muscle use _____ rapidly.
ATP
57
______ ___ is used within seconds in the muscles.
Sarcoplasmic ATP
58
What are the three sources of ATP production within the muscle?
1. creatine phosphate (short term)
2. anaerobic cellular respiration (intermediate)
3. aerobic cellular respiration (longer lasting)
59
What is creatine phosphate (typically first go to)?
- produced in resting muscle from access ATP (to store)
- 3-6 times more plentiful then ATP within a muscle cell
- source of rapid ATP production (sustains for a max of 15 seconds)
60
What is anaerobic respiration (typically second)?
- glycolosis splits glucose into pyruvic acid and ATP
- if no oxygen is present then pyruvic acid produces lactic acid which is diffused into the blood
- Can provide ATP for 30-40 seconds in maximal activity
(2 ATP per glucose)
61
What is aerobic respiration (typically last because it takes longer)?
- occurs in mitochondria if oxygen is availlable
- provides ATP for activity lasting over 30 seconds
- 36 ATP per glucose
- source of 90% of ATP for activity after about 10 min
62
Define muscle fatigue.
the inability to contract forcefully after prolonged activity which is preceded by central fatigue
63
Define central fatigue.
feeling of tiredness and desire to stop activity
64
What do they think causes muscle fatigue?
- depletion of creatine phosphate or a decrease in calcium within the sarcoplasm
other contributing factors:
- decreased O2 or glycogen
- increase of lactic acid, ADP
- insufficient acetycholine release from motor neurons
65
What is a motor unit?
one motor neuron that is interfacing with multiple muscle fibres (tyically10-15, but up to 3000 fibres the one muscle neuron)
66
When there is an action potential the _____ contracts.
whole motor unit
67
What is the average amount of muscle fibres in a motor unit?
150 muscle fibres
68
If there is more demand for movement then more _______ are activated.
motor units
69
What is a twitch contraction?
a brief contraction of all fibers in a motor unit in response to a SINGLE action potential in its motor unit
70
What is a myogram
a graph (or record) of a muscle contraction
71
How long does a twitch contraction last?
20- 200 milliseconds
72
How longs does and action potential take?
1-2 milliseconds
73
What is fused tetanus (type of wave summation)?
Stimulation 80 to 100 times per second, it does not relax
74
What is wave summation?
When a second stimuli occurs after the first refractory period, but before skeletal muscle fibre has relaxed.
75
What is unfused tetanus(type of wave summation)?
When a skeletal muscle is stimulated 20-30 times per second
76
What causes wave summation and tetanus?
Calcium remains in the sarcoplasm thus force of second contraction is added to the first.
77
What law do muscle cells obey?
all or nothing
78
What is a graded response?
a varied muscle contraction strength acheived by:
- changing FREQUENCY of muscle fibre stimulation
- changing the NUMBER OF FIBRES stimulated
79
What is muscle tone?
- involuntary muscle contraction of a small number of motor units (alternately active and inactive in a constant shifting pattern)
- keep muscles firm even though they are relaxed
- important for maintaining posture and blood pressure
80
Define Isotonic contraction.
contraction that causes muscle shortening thus MOVEMENT
81
Define isometric contraction.
contraction that increases muscle tension but does not shorten, thus NO MOVEMENT
82
There is a brief delay between stimulus and contraction, what is this time period called.
Latent period (when calcium is released from SR)
83
Peak tension develops in the muscle fibre during which period?
Contraction period (when the cross bridge forms)
84
When calcium is actively transported back into the sarcoplasmic reticulum in a process that takes 10 -100 msec, what period is this?
Relaxation period (muscle relaxes)
85
What are the three periods of a twitch contraction?
Latent
Contraction
Relaxation
86
Define refractory period.
the time following stimulation when a muscle or nerve cannot respond
87
What are some characteristics of cardiac muscle?
- striated branched fibres
- single centrally located nucleus
- cells are connected by intercalated discs
- has the same arrangements of myofilaments as skeletal muscle
- more sarcoplasm and mitchondria then skeletal muscle
- Less SR and less intercellular calcium reserve
- contractions last 10 to 15 seconds longer then skeletal muscle
88
What are some characteristics of a visceral unit of smooth muscle?
- single unit
- in valls of hollow viscera, small blood vessels
- autorhythmic
- gap junctions cause fibres to contract in unison
89
What are some characteristics of multi units of smooth muscle?
- individual fibres with own motor neuron ending
| - found in large cavities, large airways, arrector pili muscles, iris, ciliary body
