Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Musculoskeletal and Rheumatology > Lecture 2: Muscle Contraction > Flashcards

Lecture 2: Muscle Contraction Flashcards

1
Q

What are the 3 muscle types?

A
  • smooth muscle (involuntary control, autonomic nervous system)
  • cardiac muscle (autonomic nervous system + circulating chemicals)
  • skeletal muscle (voluntary control)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Skeletal muscles are…?

A
  • under voluntary control from somatic nervous system
  • usually attached to bones
  • contract to bring about movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Outline macroscopic structure of skeletal muscles.

A

bone –> tendon –> muscle surrounded by epimysium –> fascicles bounded by perimysium –> muscle fibre (myofibre) surrounded by endomysium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Outline microscopic structure of skeletal muscles

A

muscle fibre –> covered by plasma membrane called sarcolemma –> t-tubules tunnel into centre –> cytoplasm called sarcoplasm contains myoglobin + mitochondria –> network of fluid filled tubules = sarcoplasmic reticulum –> composed of myofibrils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Facts about myofibrils?

A
  • 1 to 2 micrometres in diameter
  • extend along entire length of myofibres
  • composed of 2 main types of protein: ACTIN and MYOSIN
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What gives skeletal muscle it’s striated (striped) appearance?

A

Myofilaments of light and dark bands
Don’t extend along length of myofibre
Overlap and are arranged in compartments called sarcomeres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the dense protein areas that separate sarcomeres called?

A

Z-discs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the dark bands called and what are they made of?

A

A bands (thick - made of myosin, also some overlapping actin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the light bands called and what are they made of?

A

I band (thin - made of actin)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do the myosin and actin filaments do?

A

They overlap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Structure of myosin?

A
  • 2 globular heads
  • single tail formed by 2 alpha helices
  • tails of several hundred molecules form 1 filament
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Structure of actin?

A
  • actin molecules twisted into helix
  • each molecule has myosin binding site
  • filaments also contain troponin and tropomyosin
  • troponin complex covers the binding site for myosin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the sliding filament theory of muscle contraction?

A
  • during contraction I band became shorter (thin, actin band)
  • A-band remained the same length (thick, myosin)
  • H-zone narrowed or disappeared
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the H-zone?

A

The middle of the A band where there is only myosin (thick filaments)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How is muscle contraction initiated (steps)?

A

1) AP opens VGCaCs
2) Ca2+ enters pre-synaptic terminal
3) Ca2+ triggers exocytosis of vesicles
4) ACh diffuses across cleft
5) Binds to ACh receptors, induces APs in muscle
6) local currents flow from depolarized region + adjacent region, AP spread along surface of muscle fibre membrane
7) ACh broken down by acetylcholine esterase - muscle fibre response to that molecules of ACh ceases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How is muscle contraction activated after the muscle has received an AP?

A

1) AP propagates along surface membrane into T-tubules
2) Dihydropyridine (DHP) receptor in T-tubule membrane: senses change in voltage and changes shape of protein linked to ryanodine receptor
3) opens ryanodine receptor Ca2+ channel in the sarcoplasmic reticulum (SR)
4) Ca released from SR into space around filaments
5) Ca binds to troponin and tropomyosin moves
6) allows crossbridges to attach to actin
7) Ca is actively transported into SR continuously while APs continue. ATP driven pump

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Outline steps in excitation contraction coupling.

A

1) in presence of Ca –> movement of troponin from tropomyosin chain
2) exposes myosin binding site on surface of actin chain
3) ‘charged’ myosin heads bind to exposed site on actin filament
4) binding and discharge of ADP causes myosin head to pivot (POWER STROKE) –> pulls actin filament towards centre of sarcomere
5) ATP binding –> releases myosin head from actin chain
6) ATP hydrolysis –> provides energy to recharge myosin head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Which protein filament does the pulling during muscle contraction?

A

myosin

19
Q

Which neurons control muscle contraction?

A

Voluntary neural control from upper motor neurons in brain and lower motor neurons in brainstem

20
Q

What is a motor unit?

A

name given to single motor neuron together with all the muscle fibres that it innervates
SMALLEST FUNCTIONAL UNIT OF MUSCLE CONTRACTION

21
Q

What does stimulation of 1 motor unit cause?

A

contraction of all muscle fibres in that unit

22
Q

What are the 3 types of motor unit?

A
  • slow (S, type I)
  • fast, fatigue resistant (FR, type IIA)
  • fast, fatiguable (FF, type IIB)
23
Q

Key features of slow motor units?

A
  • smallest diameter cell bodies
  • small dendritic trees
  • thinnest axons
  • slowest conduction velocity
24
Q

Key features of FR type IIA motor units?

A
  • larger diameter cell bodies
  • larger dendritic trees
  • thicker axons
  • faster conduction velocity
25
Q

Key features of FF type IIB motor units?

A
  • larger diameter cell bodies
  • larger dendritic trees
  • thicker axons
  • faster conduction velocity
26
Q

How are muscle fibre types distributed throughout muscle?

A

randomly distributed - muscles have diff proportions of slow + fast twitch muscles

27
Q

What muscle fibre characteristic is associated with high amounts of S (type 1 motor units), high FR type IIA and low FF, type IIB?

A

myoglobin content

28
Q

What colour is associated with each type of motor unit?

A

Slow - red
FR, type IIA - pink
FF, type IIB - white

29
Q

What aerobic capacities are associated with each type of motor unit?

A

Slow - high
FR, type IIA - moderate
FR, type IIB - low

30
Q

What anaerobic capacities are associated with each type of motor unit?

A

Slow - low
FR, type IIA - high
FR, type IIB - high

31
Q

How are motor unit types classified?

A

By amount of tension generated, speed of contraction and fatiguability of motor neuron

32
Q

Properties of Type I motor units?

A
  • slow twitch
  • low force
  • fatigue resistant
33
Q

Properties of Type IIA motor units?

A
  • fast twitch
  • moderate force
  • fatigue resistant
34
Q

Properties of Type IIB motor units?

A
  • fast twitch
  • high force
  • high fatigue
35
Q

Which 2 mechanisms does the brain use to regulate the force that a muscle can produce?

A

recruitment and rate coding

36
Q

What is recruitment?

A
  • motor units are not randomly recruited, there is an order
  • governed by ‘size principle’ smaller units are recruited first - generally slow twitch units
  • as more force is required, more units are recruited - allows fine control under which low force levels are required
37
Q

What is rate coding?

A
  • motor unit can fire at range of frequencies - slow units fire at a lower frequency
  • as firing rate increases, force produced by unit increases
  • summation occurs when units fire at frequency too fast to allow muscle to relax between arriving APs
38
Q

How is muscle force regulated?

A

by the number of motor units recruited

39
Q

What are the effects of neurotrophic factors?

A
  • type of growth factor
  • prevent neuronal death
  • promote growth of neurons after injury
  • motor unit + fibre characteristics dependent on nerve which innervates them
  • if fast + slow twitch muscle are cross innervated, slow one becomes fast and vice versa
  • motor neuron has some effects on properties of muscle fibres it innervates
40
Q

What are the 3 main types of muscle contraction?

A
  • concentric (muscle gets shorter)
  • eccentric (muscle gets longer)
  • isometric (muscle stays the same length)
41
Q

What may cause muscle fibres to change from type IIB to IIA?

A

most common following training

42
Q

What may cause type I to change to type II muscle fibres

A

possible in cases of severe deconditioning or spinal cord injury - microgravity during spaceflight results in shift from slow to fast muscle fibre types

43
Q

What effect does ageing have on muscle fibre types?

A
  • loss of type I and II fibres but also preferential loss of type II fibres
  • results in larger proportion of type I fibres in aged muscle

Musculoskeletal and Rheumatology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions