Muscle and Tendon Flashcards
(88 cards)
1
Q
Describe the gross anatomy of skeletal muscle
A
muscle is comprised of a primary muscle belly, consisting of sub-units called fascicles, which are a bunch of muscle fibres
2
Q
State the primary unit of muscle
A
muscle fibre = muscle cell
3
Q
What is aponeurosis?
A
a connective tissue that continues on the surface of (and surrounds) the muscle belly
4
Q
State the function of aponeurosis
A
“acts as a bridge b/n:
- muscle & bone
- muslce & tendon”
5
Q
State two ways by which the primary muscle belly can attach to bone
A
”- tendon
- aponeurosis”
6
Q
State the role of skeletal muscle in the body (4)
A
”- joint movement
- joint stabilisation (prevention of joint movement)
- postural control
- generation of heat”
7
Q
State the role of smooth muscle in the body (8)
A
”- continence
- mastication
- swallowing
- digestion
- birthing
- vasodilation/vasoconstriction
- bronchodilation/bronchoconstriction
- pupil dilation/constriction”
8
Q
State the role of cardiac muscle in the body
A
maintaining a cardiac rhythm
9
Q
Describe the design of cardiac muscle (4)
A
”- striated
- single nucleus (which is centrally located)
- involuntary
- irregular arrangement w/ intercalated disks”
10
Q
Describe the design of smooth muscle (4)
A
”- no striation
- single nucleus
- involuntary
- longer contractions”
11
Q
Define ‘muscle architecture’
A
the arrangement of muscle fibres (relative to the direction in which that muscle is pulling)
12
Q
State the two types of muscle arrangements
A
”- pennate
- parallel”
13
Q
Describe pennate muscle (5)
A
”- large no. of muscle fibres per unit
- very strong
- the muscle tires easily
- arranged in a diagonal direction onto the tendon
- ↑ Physiological Cross-Sectional Area (PCSA) = ↑ muscle force”
14
Q
Describe parallel muscle (4)
A
”- fibres run parallel to the line of pull of the muscle
- long muscle
- not very strong
- high endurance”
15
Q
Where is muscle positioned in the limb?
A
proximal
16
Q
Where is tendon positioned in the limb?
A
distal
17
Q
State the function of tendon (5)
A
”- Minimizes distal limb mass
- Joins muscle to bone (transmits muscle force to skeleton)
- Elastic energy storage
- Energy conservation
- Power amplification of muscles”
18
Q
Describe the structure of tendons
A
Each tendon > Fascicles > Sub-fascicles (primary fibre bundle)
19
Q
State the two main components of sub-fascicles
A
”- collagen fibres
- collagen fibrils”
20
Q
State the observable pattern of a tendon under a microscope
A
crimping structure
21
Q
Which element is important in directly triggering contraction?
A
calcium ions
22
Q
In relaxed muscle, what is the myosin-binding site on actin blocked by?
A
tropomyosin
23
Q
During muscle contraction, when does the cross-bridge detach?
A
the myosin head binds to an ATP molecule
24
Q
What causes muscle relaxation to occur?
A
calcium ions are actively transported into the sarcoplasmic reticulum
25
How would muscle contractions be affected if ATP was completely depleted in a muscle fibre?
if ATP was completely depleted, no ATP could bind to myosin and therefore myosin heads could not detach from actin. This would mean that muscle remained in a contracted state.
26
Explain the mechanisms involved in muscle contraction
"1. The muscle receives an impulse from a nerve cell in the form of an action potential
2. The impulse penetrates to the centre of the muscle fibre via transverse tubules, deep infoldings of the sarcolemma
3. This causes calcium ion channels in the sarcoplasmic reticulum membranes to open
4. Calcium ions diffuse out rapidly into the myofibrils to bind to the troponin molecules
5. The troponin molecules change shape, causing the tropomyosin to move to a different position on the actin filaments
6. The myosin-binding site on the actin is now free and the extended myosin heads bind to actin
7. The bound ADP and phosphate are released causing the myosin heads to change back to their relaxed shape, so pulling the actin filaments towards the centre of the sarcomere
8. The binding of an ATP to each myosin head causes them to let go of the actin
9. Each myosin head acts as an ATPase. The breakdown of ATP to ADP and phosphate in the myosin heads releases energy which extends the head once again
10. If calcium is still present and there is still a supply of ATP, this process will continue again and again.
11. After the action potential has passes, the calcium ion channels close and the calcium ions are pumped back into the sarcoplasmic reticulum. This allows the troponin to return to its previous state and causes the muscle to relax"
27
What occurs to actin and myosin filaments when muscles contract?
during muscle contraction, actin and myosin filaments do not shorten but they slide past each other
28
State and describe the 3 types of muscle contractions
"- isometric = contraction occurs, overall length of muscle does not change; muscle resists motion
- concentric = produces movement, muscle shortens in length
- eccentric = produces movement, muscle is being stretched; muscle tries to control, slow, or prevent movement at the joint"
29
State what occurs after muscle contraction
Ca2+ ions in the myoplasm are pumped back into the SR
30
State the name of the pump responsible for actively transporting calcium ions back into the SR
Ca2+ ATPase
31
What is the cell membrane of a muscle fibre called?
sarcolemma
32
The correct order for the smallest to the largest unit of organisation in muscle tissue is:
myofilament, myofibril, muscle fibre, fascicle
33
State what the stripy appearance of the muscle fibres is caused by
the regular arrangement of the myofilaments w/i the myofibrils
34
State the function of the M-line
provides an attachment point for myosin filaments
35
State the function of the Z-line
provides an attachment point for actin filaments
36
State the appearance and function of the A-band
"- the darker band of the myofibril
| - contains the myosin filaments"
37
State the appearance and function of the H-band
"- the lighter section in the middle of the A-band
| - only myosin is present"
38
State the appearance and function of the I-band
"- the lighter band of the myofibril
| - contains only actin filaments"
39
State the main difference between a muscle cell and any other typical cell in the body
muscle cells contain contractile proteins
40
Describe the 3 functions of ATP in skeletal muscle contraction
"- re-energization of the myosin head (provides energy for cross-bridge movement and force generation)
41
Explain 3 sources of ATP for skeletal muscle contraction
"- phosphorylation of ADP by creatine phosphate
- oxidative phosphorylation of ADP in the mitochondria (Aerobic respiration)
- phosphorylation of ADP in the cytosol (glycolytic/anaerobic respiration)"
42
phosphorylation of ADP via creatine phosphate Production speed
very rapid
43
phosphorylation of ADP via creatine phosphate Requirements
creatine phosphate in cell
44
phosphorylation of ADP via creatine phosphate Type of physical activity
onset of muscle contraction
45
onset of muscle contraction Production speed
slow
46
onset of muscle contraction Type of respiration
aerobic
47
onset of muscle contraction Requirements
"- blood borne fuels (glucose, oxygen, fatty acids)
| - muscle glycogen"
48
onset of muscle contraction Type of physical activity
moderate levels of activity
49
phosphorylation of ADP in cytosol via glycolysis Type of respiration
anaerobic
50
phosphorylation of ADP in cytosol via glycolysis Requirements
muscle glycogen and/or blood borne glucose
51
phosphorylation of ADP in cytosol via glycolysis Type of physical activity
intense exercise
52
State the 3 muscle fibre types
"- slow oxidative (type I)
- fast oxidative glycolytic (type IIa)
- fast glycolytic (type IIb)"
53
slow oxidative (type I) Myosin ATPase activity
low
54
slow oxidative (type I) Oxidative and/or Glycolytic capacity (type of metabolism)
high oxidative capacity
55
slow oxidative (type I) Diameter
smaller (weaker)
56
slow oxidative (type I) Relation to fatigue
fatigue resistant
57
fast oxidative glycolytic (type IIa) Myosin ATPase activity
high
58
fast oxidative glycolytic (type IIa) Oxidative and/or Glycolytic capacity (type of metabolism)
high oxidative + glycolytic capacity
59
fast glycolytic (type IIb) Myosin ATPase activity
high
60
fast glycolytic (type IIb) Oxidative and/or Glycolytic capacity (type of metabolism)
high glycolytic capacity
61
fast glycolytic (type IIb) Diameter
larger (stronger)
62
fast glycolytic (type IIb) Relation to fatigue
fatigue easily
63
Fibre type adaptation: what can fibre types be influenced by? (5)
"- genetics (species/breed)
- training
- age
- lifestyle
- diet"
64
State what the pattern of muscle contraction is determined by
the pattern of activity in motor neurons
65
Define 'motor unit'
one motor neuron and all the muscle fibre that it innervates
66
"Compare the ratio of nerve to muscle fibres for:
- strength
- control"
"strength:
- one nerve
- many fibres
control:
- one nerve
- few fibres"
67
State which part of a nerve cell is involved in the neuromuscular junction (NMJ)
axon terminal
68
"State which parts of a nerve cell is involved with the:
- central nervous system (CNS)
- peripheral nervous system (PNS)"
"CNS:
- dendrites
PNS:
- axon
- axon terminal"
69
State 4 specialised features of the NMJ
"- acetylcholine (ACh) neurotransmitter is contained in synaptic vesicles
- sarcolemma is folded to increase surface area
- receptors reside in the ""mouth"" of the sarcolemma folds
- the enzyme acetylcholinesterase acts on ACh to cease activity at the NMJ"
70
Explain the events that occur at the NMJ
"1. Action potential propagated down axon.
2. Depolarised pre-synaptic membrane causes opening of voltage-gated Ca2+ channels —> Ca2+ ions diffuse into presynaptic nerve cytoplasm.
3. Presence of Ca2+ ions causes synaptic vesicles to move and fuse to presynaptic membrane. Acetylcholine is released into synaptic cleft.
4. Acetylcholine diffuses across cleft and binds with receptors on postsynaptic membrane.
5. Binding of Acetylcholine causes ligand-gated ion channels to open. Na+ ions move into the muscle cell causing depolarisation of the motor end plate (END PLATE POTENTIAL).
6. End Plate Potential causes opening of further voltage-gated ion channels along the muscle fibre - an action potential is propagated.
7. Acetylcholinesterase breaks down Acetylcholine to acetyl and choline molecules."
71
State the 2 events that the 'excitation - contraction coupling' link together
"- events that happen at a NMJ
| - muscle contraction events"
72
State the function of the sarcoplasmic reticulum (SR)
"- stores calcium ions
| - flows around each individual myofibril and connects them"
73
State the function of the T-tubules
"- link the SR to the cell membrane
| - provides a means for the action potential to be conveyed deeper into the w/i the muscle fibre"
74
Explain how the depolarization of the post-synaptic membrane results in muscle contraction
"1. Muscle action potential is propagated
2. Depolarization of the T-tubule causes Ca2+ channels to open b/n the myoplasm and SR
3. Calcium is released into the SR - ""calcium transient""
4. Calcium binds to troponin C"
75
Muscle contractions will not occur w/o the presence of __________
calcium ions
76
State the functions of the dihydropyridine receptor (DHPR) and the ryanodine receptor (RyR)
"- opens when an action potential travels down the sarcolemma, releasing calcium ions into the cytosol of the cell
- calcium ions diffuse through the cytoplasm towards the actin filaments and binds to troponin to initiate muscle contraction"
77
State where the DHPR and the RyR are located
they are embedded in the sarcolemma
78
What is epimysium
epimysium is a thin layer of connective tissue
79
What is a fascicle
a bundle of independent sub unit known as muscle fibres
80
Each fascicle is bounded by ____
perimysium
81
Muscle fibres are surrounded by another connective tissue called...
endomysium
82
What are myofibrils
a contractile protein
83
State the function of myofibrils
They bring about muscle contraction
84
What is Force
the push or pull on an object with mass that causes it to change velocity
85
What is work
force x total distance
86
What is power
rate of performing work ( total work/total time)
87
What is the purpose of the general pattern of muscle and tendon
allows limb to swing easily and with minimal energy
88
What are tenocytes?
- the primary cell types of tendon are the spindle shaped tenocytes
- they are mature tendon cells that are found throughout the tendon structure, anchored to collagen fibres
