Brainscape's Knowledge GenomeTM

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


See full index

BRS Term 2 > Muscle microstructure and contraction (21) > Flashcards

Muscle microstructure and contraction (21) Flashcards

1
Q

What are the 3 main types of muscle?

A
  • smooth muscle: involuntary from autonomic nervous system
  • cardiac muscle: involuntary/autonomic
  • skeletal muscle: under voluntary control- usually attached to bones- contract to bring about movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where is smooth muscle found?

A

in the walls of the airways

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

What are the general features of skeletal muscle?

A
  • under voluntary control from the 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
4
Q

What are the different arrangements of muscle fibres? (not really year 1)

A
  • parallel
  • fusiform
  • triangular
  • multipennate
  • bipennate
  • unipennate
  • pennate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are fascicles?

A

bundles of muscle fibres (myofibres)

multiple fascicles make up a muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the structure of skeletal muscle from macroscopic to microscopic?

A
  • muscle
  • fascicles
  • myofibres (muscle fibres)
  • myofibrils
  • myofilaments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the name of the connective tissue that surrounds muscle fascicles?

A

perimysium

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

What is the name of the connective tissue that surrounds muscle fibres?

A

endomysium

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

What cells give rise to skeletal muscles?

A

myoblasts- fused such that muscle fibres have many nuclei

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

What plasma membrane covers myofibres?

A

sarcolemma

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

Why is there such a big blood supply to muscle fibres?

A

muscles require lots of energy to function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the function of T-tubes?

A

conduct impulses from the sarcolemma down into the centre–> to the sarcoplasmic reticulum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What 2 main types of protein do myofibrils contain?

A

actin and myosin- overlap- arranged all the way along myofibres in sarcomeres–> dark and light bands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What dense protein areas separate sarcomeres?

A

Z-discs

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

What is an M line?

A

halfway mark between adjacent Z-discs

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

What protein causes the dark A bands?

A

thick filaments- myosin

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

What protein causes the light I bands?

A

thin filaments- actin

18
Q

What is the structure of a myosin filament?

A
  • 2 globular heads
  • single tail formed by 2 alpha helices
  • tails of several hundred molecules form 1 filament
19
Q

What is the structure of actin filament?

A
  • actin molecules twisted into helix
  • troponin complex cover myosin binding sites
  • troponin complexes are on tropomyosin
20
Q

What evidence is there for the sliding filament theory?

A
  • during contraction I band became shorter (actin being pulled)
  • A band remained same length
  • H zone narrowed
21
Q

What is the mechanism of initiation of muscle contraction (N.B. AP)?

A
  1. AP opens voltage gated calcium channels
  2. calcium enters pre-synaptic terminal
  3. triggers exocytosis of vesicles
  4. ACh diffuses across the cleft
  5. binds to ACh receptors and induces AP in muscle
  6. local currents flow- AP spreads along surface of muscle fibre membrane
  7. ACh broken down- contraction stops
22
Q

What is the mechanism of muscle contraction occur INSIDE the muscle?

A
  1. AP propagates along surface membrane into T-tubule
  2. DHP receptor in T-tubule membrane senses change in voltage
  3. leads to opening of ryanodine receptor calcium channel in SR (sarcoplasmic reticulum)
  4. calcium released from SR into space around filaments
  5. calcium binds to troponin on tropomyosin (filament wound around actin)
  6. cross bridges attach myosin to actin
  7. calcium actively transported into SR continuously whilst APs continue
23
Q

What is the process of excitation contraction coupling? https://www.youtube.com/watch?v=ousflrOzQHc amazing video

A
  • calcium ions bind to troponin on actin molecules
  • troponin initiates contraction process by moving tropomyosin molecules off of the myosin binding sites on actin
  • allowing myosin heads to attach to actin filaments
    N.B. contraction begins when a bound ATP is hydrolysed to ADP and Pi–> causes myosin head to extend and attach to binding site on actin–> forming cross-bridge
    …an action- ‘power stroke’ is triggered- allowing myosin to pull actin filament towards M-line- shortening sarcomere
    … ADP and Pi are released during ‘power stroke’…myosin remains attached to actin until new ATP binds
24
Q

Where are the upper and lower motor neurons that control voluntary muscle contraction?

A
  • upper motor neurons in primary motor cortex of brain

- lower motor neurons in brainstem or spinal cord

25
Q

What is the arrangement of neurons: muscle fibres?

A
  • 1 neuron can innervate many muscle fibres (all will contract)
  • no muscle fibre can be innervated by more than 1 neuron
26
Q

What is a motor unit?

A

a single motor neuron and the muscle fibres it innervates

27
Q

What are the different types of motor units?

A
  • slow (S, type 1)
  • fast, fatigue resistant (FR, type 2A)
  • fast, fatiguable (FF, type 2B)
28
Q

What are the characteristics of neurons in slow motor units?

A
  • smallest cell body diameter
  • small dendritic trees
  • thinnest axons
  • slowest conduction velocity
29
Q

What are the characteristics of neurons in fast motor units?

A
  • large diameter cell bodies
  • large dendritic trees
  • thick axons
  • fast conduction velocity
30
Q

What are the characteristics of slow muscle fibres?

A
  • high myoglobin content
  • red
  • high aerobic capacity
  • low anaerobic capacity
31
Q

What are the characteristics of fast, fatigue resistant muscle fibres?

A
  • high myoglobin content
  • pink
  • moderate aerobic capacity
  • high anaerobic capacity
32
Q

What are the characteristics of fast, fatiguable muscle fibres?

A
  • low myoglobin content
  • white
  • low aerobic capacity
  • high anaerobic capacity
33
Q

What 3 features help us classify the motor unit types?

A
  • amount of tension generated
  • speed of contraction
  • fatiguability
34
Q

What 2 mechanisms does the brain use to regulate muscle force?

A

recruitment and rate coding

35
Q

What is the principle behind motor unit recruitment?

A

varying the number of activated motor units

- as more force is required, more units are recruited

36
Q

What is the principle behind motor unit rate coding?

A

varying the rate at which each active motor unit generates action potentials
- as firing rate inc., the force produced by the unit inc.

37
Q

What are neurotrophic factors?

A

type of growth factor–> prevent neuronal death and promote growth of neurons after injury

38
Q

What evidence shows that motor unit and fibre characteristics are dependent on the nerve that innervates them?

A

if a fast and slow twitch muscle are cross innervated, the slow one becomes fast and vice versa

39
Q

What are the 3 types of muscle contraction?

A
  • concentric: muscle gets shorter
  • eccentric: muscle gets longer
  • isometric: muscle stays same length, but force is generated
40
Q

Can we change the properties of muscle fibres?

A

type 2B–>2A most common following training

N.B. type 1–>2 possible in severe reconditioning or spinal cord injury (or microgravity)

41
Q

What muscle fibre changes occur during ageing?

A

loss of slow and fast, but preferentially fast

–> results in larger proportion of type 1 fibres in aged muscle + slower contract times

BRS Term 2 (36 decks)

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