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BRS > MSK - muscle microstructure and contraction > Flashcards

MSK - muscle microstructure and contraction Flashcards

(49 cards)

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1
Q

What muscles are under involuntary control?

and which system controls it?

A

Smooth muscles from autonomic nervous sysm

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2
Q

What is special about cardiac muscle?

A

can contract autonomously

but under influence of autonomic nervous system and chemicals

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3
Q

What muscles are under voluntary control?

What are there function?

A

skeletal muscles

attach bones to contract and bring about movement

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4
Q

Where are smooth muscles found?

A muscles eyes

B airways

C biceps

A

B

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5
Q

Which system control skeletal muscles

A

somatic nervous system

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6
Q

What are 3 connective tissue surronding each level of muscle tissue?

What do they surrond?

A

enodmysium - surrond a single muscle fibre

perimysium - surronds fascicles (multiple fibres of muscle)

epimysium - surronds entire muscle

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7
Q

Label diagram of muscle

A
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8
Q

What is muscle fibre compose of?

A

myofibrils

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9
Q

What is difference between myofibre and microfibril

A

myofibre - a muscle fibre, multinucleated muscle cell

myofibrils - Cylindrical organelles, found within muscle cells, that are the contractile unit of muscles.

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10
Q

What are 5 may components of skeletal muscle?

A

covered by plasma membrane - sarcolemma

T-tubules - tunnel into centre

sacroplasm - cytoplasm

network of fuild filled tubules - sacroplasmic reticulum

myofibrils

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11
Q

label this diagram of muscle fibre

A
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12
Q

Where are myoblobin and mitochondria found in muscle cell?

A

sacroplam

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13
Q

What is the ‘thin’ and ‘thick’ filament?

A

thin - actin

thick - myosin

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14
Q

Where are 2 types called and located on this diagram?

A

H disk and Z disk

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15
Q

do myofilaments extend along length of myofibres?

A

NO but they overlap arranged and in compartments (sarcomeres)

myfilaments are the protiens myosin and actin, they END

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16
Q

Do myofibrils extend along myofibres

A

YEs

composed of 2 main type of potiens - actin and myosin

is long line of repeating sacromeres

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17
Q

What seperates sacromeres

A

Z discs

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18
Q

What is A band

A

Where myosin is found

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19
Q

What is strucutre of myosin?

A

thickkk - golg clubs

2 globular heads

single tail formed from 2 alpha helices

tails of hundreds molecules form one filament

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20
Q

What strucutre of actin?

Study These Flashcards
A

twisted into helix

each molecule has actin binding site

contains troponin and troponmysoin

21
Q

Label this diagram of actin

22
Q

What happens to A band, I band and H zone when contraction?

Study These Flashcards
A

A same length - length of myosin

I band decreases

H zone narrows or disappears

23
Q

Steps of intiation of muscle contraction?

Study These Flashcards
A

phase 1: AP open voltage Ca2+ channels, Ca2+ enter pre-synpathic terminal, release of Acetylcholine binds to receptors + AP in muscle

Phase2:

  1. AP spread around surface membrance

Acetylcholine broken down by acetylcholine esterase, response stop

24
Q

What is mechanism of actual muscle contractions

Study These Flashcards
A

1) . action propagates into T-tubules
2) . DHP receptor in T sense chnage + change/opens ryanodine receptor in SR
3) . Ca2+ released from SR into space around filaments (actin and myosin)
4) . Binds to troponin and tropomypson moves
4) . Allows crossbridhes to attach to actin
5) . Ca2+ actively transported into continously while AP continue. uptake less than or equal to release rate

25
How exactly does myosin head couple to actin?
1) . Ca2+ causes troponin to move from tropomyosin chain 2) . exposes myosin binding sire on actin chain 3) . 'charged' myosin heads bind to exposed site on actin 4) . discharge of ADP causes 'power stroke' pulling actin towards centre of sarcromere 5) . ATP binding releases myson head from actin 6) . ATP hydrolysis energy 'recharge' myosin head
26
What nervous pathway for muscle contraction?
upper motor neurone in brain to lower motor neurone brainstem/spinal cord
27
How does the nerves innervates muscles
single neurone innervates many muscles fibres however **all in the same motor unit**
28
What is a motor unit?
A single motor neuron all muscle fibres when stimulated ALL muscle fibres in unit contract
29
Can other nerves inverve a muscle fibre that is already innverated by another nerves?
NOO only one motor innverates those fibres in that motor unit
30
What controls the fine control?
each nerves innverates - less motor units and fibres
31
What are 3 types motor units?
Slow, fast (fatigue resistant), fast fatiguable
32
What are characteristics of slow motor units?
smallest diameter cell bodies smalld endritic trees thinnest axons slowest speed
33
What are characteristics of fast, fatigue resistant motor units?
34
What are characteristics of Fast, fatiguable motor units?
larger diamter cell bodies larger dentritic rrees thicker axons faster conducitivty
35
How does each type of motor neurone appear?
36
Properties of each of motor units?
37
What are 2 mechanisms that brain regulated force a muscle can produce?
recruitment and rate coding
38
How does recruitment work?
motors not randomly recruited choosed based on size, small first (generally slow) as more force more units
39
What does recruitment allow for?
fine control - under which low force levels are required
40
What is rate coding?
motor can fire at range of frequnecies slow units at lower as firing rate rate increase, force for each unit increasees
41
What happens when rate coding too fast?
**Summation -** unit fire at frequency too fast to allow muscle relax between AP
42
What is recruitment order of the type of muscles fibres?
slow then fast resistance then fast fatigue
43
So overall what happens when as force increase when carrying item?
Increases firing rate for each muscle unit more fibred recruited
44
What are affects of neurotrophic factors?
prevent neuronal death and promote frowth after injury changes characterisitic of muscle, effect on properties
45
What does the motor unit and fibre type depend on? Or is it indepedendent if so how
**dependent on type of nerve innvating it** **if slow, muscle beocmes slow**
46
What are 3 types of muscle contraction?
isometric - no change in length of muscle concentric- muscle shorterns as force/contraction eccentric - muscle becomes longer, easily damaged, most force
47
How could injury to pathology affect muscle units?
leads to type 1 converted to 11
48
What affects microgravity have on fibres
slow to fast
49
What affects do aging have on muscle units?
loss of type 1 and 2, more 11 so more slower, type 1 fibres in ages muscles

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