Brainscape's Knowledge GenomeTM

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


See full index

BIOM30002 - M2M > Lecture 31 - Muscular Dystrophies - Muscle Structure, Function and Neuromuscular Transmission > Flashcards

Lecture 31 - Muscular Dystrophies - Muscle Structure, Function and Neuromuscular Transmission Flashcards

1
Q

What are muscle disorders?

A

Affect one or more of the different muscle tissue type (smooth, cardiac, skeletal)

Muscles needed to move joints, thus these diseases result in motion disorder

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

Differentiate between myopathies and muscular dystrophies

A

Myopathies:
• Genetic and acquired disorders of the muscle contractile apparatus (thick, thin filaments etc)
• Generally static pathology

Muscular dystrophies:
• Genetic disorders of the supporting structures (DAPC)
• Progressive degeneration
e.g.
• Sacrolemmal proteins
• Proteins which anchor the contractile apparatus in place

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

Outline these features of skeletal muscle:
• Location
• Function
• Structure

Talk about the variation seen in these features

A

• Attached to bone

Function
• Voluntary control
• Different contraction velocities depending on ability
• Variable metabolic processes used to generate energy

Structure:
• Made up of muscle fibres (the cells)
• Striated
• Variable colour depending on myoglobin content

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

What are striations?

A

Muscle fibres (cells) containing alternating light and dark bands

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

What is myoglobin?

A

Oxygen storage protein for mitochondria

Has a higher affinity for oxygen that haemoglobin → oxygen movement into muscle cells from blood favoured

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

Discuss the differences in skeletal and smooth muscle

A

Skeletal muscle:
• Myofibres: parallel muscle fibres grouped into bundles
• Sacromeres

Smooth:
• Involuntary
• Not striated

NB both are:
• Multinucleated
• Contractile

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

Describe muscle fibres in detail

A

Hierarchy:
Muscle belly - Epimysium - Perimysium - Fasciculus - Endomysium - Muscle fibres (cells) - Myofibrils within cells

Fasciculi: bundles of muscle fibres

Muscle fibres: the cells
Consists of:
 • Sarcolemma (membrane)
 • Myofibrils: contractile component
 • Sarcoplasm
 • Multinucleated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the sarcolemma?

A

The membrane of muscle fibres

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

Compare the location of the following:
• Epimysium
• Perimysium
• Endomysium

A

These are all cocnective tissues surrounding various structures

Epimysium:
• Ensheaths entire muscle

Perimysium:
• Ensheaths fasciculi

Endomysium:
• Ensheaths individual muscle fibres

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

What is a sarcomere?

Describe its structure in detail

A

Organised subunit repeated along the length of muscle fibres

Smallest contractile portion of a muscle

Structure:
• Thick (myosin) filaments, w/ globular heads: ‘Cross-bridges’
• Thin (actin) filaments
• M line: central anchor of sarcomere
• A band: length of myosin filaments, + actin (Dark band)
• H zone: centre of sarcomere, myosin filaments
• Z disc: attaches actin filaments in adjacent sarcomeres
• I band: isotropic, aligned actin filaments (Light band)
• Troponin
• Tropomyosin: weaved around the actin filaments

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

Describe the sliding filament model of muscle contraction

A

At rest:
• Tropomyosin covers myosin binding sites on actin

Muscle contraction:

  1. Ca2+ influx into cytoplasm and binds to troponin
  2. Tropomyosin moves, revealing myosin binding sites on actin
  3. Myosin heads bind to actin forming cross bridges
  4. Release of ADP and Pi
  5. Conformational change of myosin head: powerstroke
  6. Actin pulled into the centre of the sarcomere: Z discs pulled into centre
  7. ATP binds myosin head, cross-bridge breaks, myosin returns to unattached position
  8. ATP hydrolysis brings about cocking of myosin head
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the sarcoplasm contain?

A

Glycogen
Fat particles
Enzymes
Mitochondria

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

What are ‘cross-bridges’?

A

The globular myosin heads protruding from myosin filaments

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

When do the following events occur:
• Cocking of myosin head
• Breakage of cross-bridges
• Powerstroke

A

Cocking of myosin head: ATP hydrolysis

Breakage of cross bridges: new ATP binding to myosin head

Powerstroke: ADP and Pi release from myosin head

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

Describe the events that lead to muscle contraction

A
  1. Motor neuron ACh release onto motor end plate
  2. ACh binds to nAChR
  3. Change in nAChR conformation → influx of Na+ ions into muscle fibres
  4. Initiation of post-synaptic action potential in muscle
  5. AP travels along T (transverse) tubules until it reaches sarcoplasmic reticulum
  6. AP changes permeability of SR → Ca2+ ions flow into sarcomere
  7. Ca2+ binds troponin → tropomyosin pulled away to reveal myosin binding site on actin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

List some of the supporting proteins for the myofibrils

A
  • Dystrophin-associate glycoprotein complex
  • Sarcoglycans
  • Dystrophin
  • Emerin, lamin A (proteins of the nuclear envelope)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe muscle metabolism

A

ATP as energy

Sources of ATP:
1. Within fibre
• Enough for muscle contraction for a few seconds

  1. Creatine phosphate
    • High energy molecule stored in muscle cells
    • Transfers its high energy phosphate group to ADP to form ATP
    • Enough ATP generated to maintain contraction for 15 seconds
  2. Glycogen stored within cells
    • Glycogenolysis → glucose
    • ATP then generated from glucose
  3. Glucose and fatty acids form blood stream
    • Liver glycogen broken down into glucose
    • Fatty acids from adipose cells and liver
    • ATP generated from these by cellular respiration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is CrPo4?

A

Creatine phosphate 4

High energy molecule

Transfers its high energy phosphate group to ADP to form ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Compare the various pathways of cellular respiration

A
  1. Anaerobic (glycolysis)
    • No O2 present, i.e. does not require oxygen
    • Glucose → pyruvic acid → lactic acid
    • Only 2 ATP generated
    • Lactic acid diffuses into blood, and then to the liver, where it is converted back to pyruvic acid
    (in the presence of O2 this can be oxidised into mitochondria)
    • Occurs in cytosol
2. Aerobic (oxidative)
 • Pyruvate & fatty acids → CO2 and H20
 • Requires oxygen
 • Occurs in mitochondria
 • Produces 36 ATP
 • Slower than anaerobic respiration
20
Q

What happens when ATP from creatine phosphate is depleted?

A

Anaerobic respiration forced to begin

21
Q

How long can anaerobic respiration provide ATP?

A

30 secs

22
Q

Describe the timeline of cellular respiration in muscle

A
  1. ATP/Cr system
  2. Anaerobic respiration - 30 secs
  3. Aerobic respiration

– oxygen depleted –

  1. Anaerobic respiration may still support further muscle contraction
  2. Accumulation of lactic acid and depletion of ATP, O2 and glycogen lead to muscle fatigue → halted muscle contraction
23
Q

What is the first thing to be depleted in the muscle?

A

ATP/Cr System

24
Q

What energy production system takes the longest to kick in?

A

Aerobic respiration

25
Q

Compare fibre types in skeletal muscle

A 
Type I: red fibres
 • Slow oxidative
 • Slow twitch
 • Fatigue resistant
 • Large amount of myoglobin
 • Many mitochondria
 • Many blood capillaries (i.e. good blood supply)
 • Slow rate of ATP splitting
 • Aerobic respiration
 • Slow contraction velocity
 • Found in postural muscles
Type IIA: 'red' fibres
 • Fast twitch 'A'
 • Fatigue resistant (but not as much as Type I)
 • Large amounts of myoglobin
 • Many mitochondria
 • Many capillaries
 • High ATP generation capacity by oxidation
 • Great rate of ATP splitting
 • High contraction velocity
Type IIB: 'white' fibres
 • Fast twitch B
 • Fatigue-able
 • Low myoglobin content
 • Few mitochondria
 • Few capillaries
 • Large amount of glycogen
 • Great rate of ATP splitting
 • Anaerobic glycolysis
 • Fatigue
26
Q

Which types of muscle fibres contain large amounts of myoglobin?

A

Type I

Type IIA

27
Q

Which are the fast twitch, fatigue resistant muscle fibres?

A

Type IIA

28
Q

Compare the types of physical activity enabled by the various types of muscle fibres

A

Type I: endurance running

Type IIA: middle distance running, swimming

Type IIB: sprinting

29
Q

Describe different muscle fibre composition of different muscles

What can change the proportions?

A

Individual muscles are a mixture of all 3 types of muscle fibre

Proportions vary depending on action of that muscle

Exercise can induce changes:
• Endurance athletes have more type I fibres
• Sprinters have more type IIB fibres

30
Q

Describe the sex and age dependence of muscle fibre distribution

A

No sex or age differences

i.e. N° of mucles fibres constant throughout life

31
Q

Describe muscle fibre participation in various movements

A

Weak contraction: only type I motor units activate

Stronger contraction: type IIA + type I

Maximal contractions: type IIB/X fibres

32
Q

Heat production?

A

Muscle tissue also is a major organs giving rise to heat in the body

33
Q

What does multinucleate cells indicate?

A

Multiple cells have fused to form the muscle fibres

These precursors are called myofibroblasts

34
Q

What are the boundaries of the sarcomere?

A

From on Z disc to another

35
Q

What are I bands?

A

Region containing only actin filaments
Spans ends of two sarcomeres

Decreases in length in muscle contraction

36
Q

What are the A bands?

A

Length of the myosin filaments

Doesn’t change size in muscle contraction

37
Q

What is the H zone?

A

Only myosin

Disappears in muscle contraction

38
Q 
What are the:
 • Lines
 • Zones
 • Bands
 • Discs?
A

Zones: H

Bands: I and A

Discs: Z

Lines: M

39
Q

Which filaments are attached to the Z discs?

A

Actin filaments

40
Q

Which filament has a globular protein head?

A

Myosin

41
Q

Characterise the formation and breaking of the myosin heads to actin

A

Occur independently

If it happened synchronously, the actin fibres would slip out

42
Q

What are T-tubules?

A

Pores that extend from the muscle fibre surface into the sarcoplasm and SR

43
Q

Which fibre types are low in mitochondria, myoglobin and capillaries?

A

‘White’ fibres

Type IIB

44
Q

Which fibre types are important in postural muscles?

A

Type I fibres

45
Q

Which fibre types are fatigue-resistant?

A

Type I

Type IIA

46
Q

What is the only thing that changes muscle fibre type distribution?

A

Exercise

Age and sex do not affect composition

47
Q

What is a sarcoplasm?

A

Similar to cytoplasm in regular cells

BIOM30002 - M2M (36 decks)

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