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nuero > Muscle microstructure and contraction > Flashcards

Muscle microstructure and contraction Flashcards

1
Q

what are Muscle types

A

Smooth
Cardiac
Skeletal

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2
Q

what is smooth muscle controlled by

A

is under involuntary control from the autonomic nervous system

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3
Q

control of cardiac

A

muscle can contract autonomously, but is under the influence of the autonomic nervous system and circulating chemicals

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4
Q

control of skeletal

A

Skeletal muscles are under voluntary control, usually attached to bones and contract to bring about movement

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5
Q

what is a fusiform

A

larger in the middle and tapered at the end

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6
Q

what are pennate muscles

A

where muscle fibres are placed at angles to the tendon

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7
Q

unipennate

A

same direction from the tendon

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8
Q

bipennate

A

2 direction from the tendons

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9
Q

multipennate

A

multiple tendons and multiple fibres

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10
Q

what is a Fascicles

A

– bundles of muscle fibres

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11
Q

what is a fascicle made up of

A

myofibre –> myofibril –> myofilament

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12
Q

how many connective tissues are muscles made up of

A

3

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13
Q

what does the epimysium made up of

A

muscle fibre

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14
Q

what are muscle fascicle bounded by

A

perimysium

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15
Q

what do endomysium sorround

A

muscle fibre

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16
Q

what is a sacrolemma

A

the plasma membrane covering myofibres

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17
Q

what is the cytoplasm in the muscle fibre

A

sacroplasm

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18
Q

what does the sacroplasm contain

A

myoglobin and mitochondria

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19
Q

sarcoplasmic reticulum

A

Network of fluid filled tubules

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20
Q

what makes up a myofibre

A

myofibrils

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21
Q

what is a sacomere

A

a repeating unit

a z disk to another

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22
Q

what gives striated (striped) appearance

A

Light and dark bands

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23
Q

what is the thin filament/light band

A

actin

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24
Q

thick filament

25
what separates sacromeres
Z-discs separate sarcomeres
26
how are dark bands represented
A band (thick - myosin)
27
and light
Light bands – I band (thin - actin)
28
what causes muscle contraction
movement of actin over myosin
29
strcuture of myosin
Two globular heads Single tail formed by two α-helices Tails of several hundred molecules form one filament
30
Structure of skeletal muscles - actin
Actin molecules twisted into helix
31
iniation of muscle contraction
1. Action potential opens voltage gated Ca2+ channels 2. Ca2+ enters pre-synaptic terminal 3. Ca2+ triggers exocytosis of vesicles 4. Acetylcholine diffuses across cleft 5. Binds to acetylcholine receptors and induces action potentials (AP) in muscle 6. Local currents flow from depolarized region and adjacent region AP spreads along surface of muscle fibre membrane 7. Acetylcholine broken down by acetylcholine esterase. Muscle fibre response to that molecule of acetylcholine ceases.
32
what happens in the muscle
1. Action potential propagates along surface membrane and into T-tubules 2. Dihydropyridine (DHP) receptor in T-tubule membrane: senses V & changes shape of the protein linked to ryanodine receptor, opens the ryanodine receptor Ca2+ channel in the sarcoplasmic reticulum (SR) Ca2+ released from SR into space around the filaments 3. Ca2+ binds to troponin & tropomyosin moves allowing.. 4. Crossbridges to attach to actin 5. Ca2+ is actively transported into the SR continuously while action potentials continue. ATP- driven pump (uptake rate < or = release rate).
33
Excitation contraction coupling
In the presence of Ca2+ movement of troponin from tropomyosin chain Movement exposes myosin binding site on surface of actin chain ‘Charged’ myosin heads bind to exposed site on actin filament This binding & discharge of ADP causes myosin head to pivot (the ‘power stroke’)  pulling actin filament towards centre of sarcomere ATP binding  releases myosin head from actin chain ATP hydrolysis  provides energy to ‘recharge’ the myosin head
34
where do upper motor nuerons have their cell bodies
motor cortex
35
The motor unit
Name given to a single motor neuron together with all the muscle fibres that it innervates. non of those muscle fibres is also innervated by another any other branches of another motor unit
36
muscles which have fine control have many or few muscles fibres innervated by a motor neurone
few
37
large muscles which are needed for large force have how many many or few muscle fibres innerveated by a single nuerone
many
38
what are the types of motor units
``` Slow (S, type I) Fast, fatigue resistant (mantain contractions for long periods of time) (FR, type IIA) Fast, fatiguable (FF, type IIB) ```
39
what are the charatistcis of slow/type 1
smallest diameter cell bodies small dendritic trees thinnest axons slowest conduction velocity
40
fast, fatigue resistant
larger diameter cell bodies larger dendritic trees thicker axons faster conduction velocity
41
fast gatiguable
larger diameter cell bodies larger dendritic trees thicker axons faster conduction velocity
42
how are muscle fibres distributed throughout the muscle.
Randomly | Muscles have different proportions of slow and fast twitch muscles
43
``` Myoglobin content Colour Aerobic capacity Anaerobic capacity of slow ```
``` Myoglobin content High Colour Red Aerobic capacity High Anaerobic capacity Low ```
44
``` Fast, fatigue resistant (FR, type IIA) Myoglobin content Colour Aerobic capacity Anaerobic capacity ```
Myoglobin content High Colour Pink Aerobic capacity Moderate Anaerobic capacity High
45
``` Fast, fatiguable (FF, type IIB) Myoglobin content Colour Aerobic capacity Anaerobic capacity ```
``` Myoglobin content Low Colour White Aerobic capacity Low Anaerobic capacity High ```
46
muscles involved in postural control have a greater proportion of slow or fast twitch fibres
greater proportion of slow twitch
47
how much force and how fast would typw 1 produce
low force | long time
48
type iia
moderate force | in moderate time
49
type iib
high force | quickly
50
what muscle fibres are high fatigue
type iib
51
fatigue resistant
iia i
52
what are the two mechanisms by which the brain regulates the force that a single muscle can produce.
Recruitment | Rate coding
53
recruitement
how many motor nuerones are being bought in or involved to fire in order to produce a contraction more morot unit recruited = more force produced
54
Motor units are not randomly recruited, there is an order.
Motor units are not randomly recruited, there is an order.
55
what is the order
Governed by the “size principle”. Smaller units are recruited first (these are generally the slow twitch units). more force is required, more units are recruited. This allows fine control (e.g. when writing), under which low force levels are required.
56
Rate coding
what frequency are action potentials are sent down the nuerone A motor unit can fire at a range of frequencies. Slow units fire at a lower frequency.
57
As the firing rate increases
the force produced by the unit increases.
58
when does summation take place
when units fire at frequency too fast to allow the muscle to relax between arriving action potentials.

nuero (36 decks)

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