Muscles Flashcards
(98 cards)
1
Q
What is the cytoplasm called in muscle fibres?
A
Sarcoplasm
2
Q
What is it called that muscle fibres have many nuclei?
A
Multinucleated
3
Q
What is the cell membrane called in muscle fibres?
A
Sarcolemma
4
Q
What surrounds myofibrils?
A
Sarcoplasm
5
Q
Why do you nuclei need to be dotted all over sarcoplasm?
A
Transcription
All muscle cells controlled
6
Q
What organelle will be in large number in sarcoplasm?
A
Mitochondria
RER
SER
7
Q
Why is there lots of mitochondria in sarcoplasm?
A
ATP for contraction + protein synthesis
8
Q
Why is there lots of RER in the sarcoplasm?
A
Protein synthesis
9
Q
Why is there lots of SER in the sarcoplasm?
A
Storage of Ca2+ for contraction
10
Q
Describe the structure of striated muscles
A
Individual filaments called myofibrils
Fuse together to form muscle fibres
When individual cells fuse together + microfibrils lay parallel
Each fibre shares sarcoplasm surrounding myofibrils
And sarcolemma
A single muscle cell = multinucleated
11
Q
What do myofibrils consist of?
A
Actin
Myosin
12
Q
Describe actin
A
Thinner
Made up of 2 strands coiled around each other
13
Q
Describe myosin
A
Thicker
Consists of rod-shaped fibres with “bulbed heads”
Bulbed heads project outwards
14
Q
What do myofibrils also contain?
A
Multiple sarcomeres
Banding pattern
15
Q
What does the banding pattern of myofibrils cause?
A
Them to appear striped
16
Q
What are the two main components of the sarcomere?
A
Dark bands
Light bands
17
Q
What type of bands are dark bands?
A
Anisotropic bands
A - bands
18
Q
What are the dark bands?
A
Actin + myosin overlap
19
Q
What do the dark bands depend on?
A
Myosin length
20
Q
What are the light bands?
A
No overlap
21
Q
What type of bands are the light bands?
A
Isotropic bands
I - bands
22
Q
What is the area called where there is only myosin filaments?
A
H - zone
23
Q
What is the structure of an I - band?
A
Thin actin filaments only
24
Q
What is the structure of the H - zone?
A
Thick myosin filaments only
25
What is the structure of an A - band?
Thick + thin filaments
26
How would you calculate the mean length of one sarcomere?
Measure the length from one z - line to another
| Repeat + calculate
27
When a muscle contract what happens to the sarcomere?
It shortens
| Patterns of light + dark bands change
28
Why do the patterns of the bands change when a muscle contracts?
Actin + myosin slide over each other
29
Why do the sarcomere shorten when the muscle contracts?
Sarcomere slides inwards = shortens
30
What are the 3 connective tissues?
Tendon
Ligament
Cartilage
31
What does the tendon connect?
Bone to muscle
32
What does the ligament connect?
Bone to bone
33
What does the cartilage connect?
Found between bones - "shock absorber"
34
What are muscles?
Bundle of fibres
Different structures
Different jobs
35
What are the three types of muscle?
Cardiac
Skeletal
Smooth
36
What is a cardiac muscle?
Present in the heart + acts involuntary (myogenic)
37
What is a skeletal muscle?
Attached to bones, vast majority of muscle, discontinuous contraction + controlled voluntarily
38
What is a smooth muscle?
Involuntary muscle, found in the gut, blood vessel walls + iris
Slow weak contraction
39
How do muscles act by?
Receiving nerve impulse
Work antagonistic pairs (do opposite jobs)
Pulling bones
40
What is antagonistic?
One muscle (prime mover) contracts + the other (antagonist) relaxes
41
What are myofibrils individually?
Very weak
42
What are the two types of fibres?
Slow twitch
| Fat twitch
43
What is the speed of contraction for a fast twitch fibre?
Fast
44
What is the speed of contraction for a slow twitch fibre?
Slow
45
What is the power of contraction for a fast twitch fibre?
High intensity
46
What is the power of contraction for a slow twitch fibre?
Low intensity
| BUT can contract for a prolonged amount of time
47
What is the type of activity of a fast twitch fibre?
High level of activity
| eg. sprinting
48
What is the type of activity of a slow twitch fibre?
Low level of activity (endurance)
| eg. walking + long distance run
49
What type of respiration for a fast twitch fibre?
Anaerobic
50
What type of respiration for a slow twitch fibre?
Aerobic
51
What is an example of a muscle containing fast twitch fibres?
Biceps
52
What is an example of a muscle containing slow twitch fibres?
Calf muscles
53
What are the adaptions of a slow twitch muscle fibre?
```
Large amount of myoglobin
Good supply of glycogen
Good blood vessel network
Many mitochondria
Small diameter
Darker in colour
```
54
Why does a slow twitch muscle have a large amount if myoglobin?
Steady supply of O2 for respiration (aerobic)
55
Why does a slow twitch muscle have a good supply of glycogen?
Glucose store
56
Why does a slow twitch muscle have a good blood vessel network?
High O2 conc
57
Why does a slow twitch muscle have many mitochondria?
More respiration
58
Why does a slow twitch muscle have a small diameter?
Smaller diffusion pathway
59
Why does a slow twitch muscle tend to be darker in colour?
Good blood supply for O2
60
What are the adaptations of a fast twitch muscle fibre?
Thicker + more myosin filaments
High conc of enzymes
Store phosphocreatine
61
Why does a fast twitch muscle have a high conc of enzymes?
For anaerobic respiration
62
Why does a fast twitch muscle have a store of phosphocreatine?
Provide energy to restore ATP
63
Why do fast twitch muscle fibres tire quickly?
Fewer blood vessels
Run out of O2 much quicker
Thicker larger diffusion distance
64
What colour are fast twitch muscle fibres?
Light
65
What colour are slow twitch muscle fibres?
Dark
66
Why do you need two different types of muscle fibres?
So we can carry out two different levels of activity
67
Why are fast twitch muscle fibres light?
Fewer blood vessels
As only needs a short burst of energy
So respires anaerobically
So doesn't need steady supply of O2
68
Why are slow twitch muscles dark?
Good blood vessel supply
As respires aerobically
So needs readily available O2 supply
69
What is a neuromuscular junction?
Where a motor neuron meets skeletal muscle fibre
70
What do multiple junctions allow in neuromuscular junctions?
Multiple fibres stimulated
Speeds up response
Contraction quicker + more powerful
Threshold met
71
The strength by which a nerve or muscle fibre responds to a stimulus is independent of what?
Strength of the stimulus
72
What happens if the stimulus does not have enough energy?
Threshold value not met
73
What happens at a neuromuscular junction?
Cholinergic synapse
74
What is the neurotransmitter at neuromuscular junction?
Acetylcholine
75
What is the enzyme that hydrolyses neurotransmitters?
Acetylcholinesterase
76
Explain how synaptic transmission takes place at neuromuscular junction
```
Depolarisation of presynaptic neurone
Ca channels open
Influx of Ca2+ into presynaptic knob
Vesicle fuse with membrane
Neurotransmitter diffuse across synaptic cleft
Bind to Na channels
Na channels open
Influx of NA+ into muscle fibre
New A.P if threshold exceeded
```
77
How do muscles contract?
A.P travels deep into muscle fibre through:
T tubules
Branch through sarcoplasm
Cause Ca2+ released
78
What type of neurone is a neuromuscular junction?
Motor neurone
79
What is the neuromuscular junction?
Only excitatory
80
Where does the neuromuscular junction happen?
Neurone to muscles
81
What does the neurotransmitter bind to in a neuromuscular junction?
Acetylcholine binds to receptor on membrane of muscle fibre
82
What is the cholinergic synapse?
Excitatory or inhibitory
83
Where does cholinergic synapse happen?
Neurone to neurone or effectors
84
What neurones are involved in cholinergic synapse?
All 3
85
What does the neurotransmitter bind to in cholinergic synapse?
Acetylcholine binds to receptors on post synaptic membrane
86
What is tropomyosin?
Long + thin fibrous strands
| Wrap around actin filament
87
What is troponin?
Globular protein involved in muscle contraction
88
What doe Ca do in the sliding filament model?
Activates ATPase
| Causes tropomyosin to change shape + free binding site
89
What does ATP do in the sliding filament model?
Hydrolysis of ATP = energy for head to detach
90
Describe the sliding filament model
Ca2+ channels open in plasm membrane + SR
Ca2+ released from SR + binds to troponin
Causes tropomyosin change shape + free binding site
ADP attaches to myosin head
Binds to actin binding site + flexes
ATP attaches to head = detaches
Hydrolysis of AT = energy for myosin to "cock" head + return to normal
Myosin with ADP attaches then reattaches further along actin
91
What happens when the nervous stimulation stops what will happen?
```
Ca2+ actively transported back into SR
Troponin reverts to original shape
Tropomyosin blocks binding site
Myosin head cannot bind
Muscle relaxes
```
92
What does muscle contraction rely on energy to do?
Move myosin head
| Reabsorb Ca+ into ER
93
Where does the energy come from?
Oxidative phosphorylation in mitochondria
| Anaerobically = phosphorylation using phosphocreatine
94
What is phosphocreatine?
Buffer supply of phosphate stored in the muscle, used to restore ATP
95
How is this energy released from phosphocreatine?
```
Reverse supply of phosphate
Broken down when energy is needed
Combines with ADP to reform ATP
Immediately available
Replenished using phosphate from ATP when muscle relaxed
```
96
What happens to the A-band in the sarcomere when a muscle contracts?
Stays the same
97
What happens to the I-band in the sarcomere when a muscle contracts?
Gets shorter
98
What happens to the H-zone in the sarcomere when a muscle contracts?
Gets shorter
