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Introduction to medicine (Year 1) > Microstructure and function of human muscle systems > Flashcards

Microstructure and function of human muscle systems Flashcards

- Outline the difference in function of the three main types of human muscle, and explain how their structural differences are related to these functional differences - Explain the functions of the specialised subcellular components seen, including the contractile system, the signalling membrane systems of striated and the intercalated discs of cardiac muscle

1
Q

What is the function of skeletal muscle?

A
  • Operates skeleton, links bones + tendons, also in diaphragm, upper oesophagus etc.
  • Allows movement and respiratory mechanics (diaphragm) and maintaining posture and balance
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2
Q

Is the contraction of skeletal muscle fast or slow?

A

Fast, but subject to fatigue

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3
Q

What are skeletal muscle fibres formed of?

A

Thousands of precursor cells in the embryo (myoblasts) fusing together

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4
Q

What is the function of cardiac muscle?

A
  • Producing contractility of the heart, and therefore the pumping action of the heart
  • Involuntary control
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5
Q

Is the contraction of cardiac muscle fast or slow?

A
  • Quite rapid, and resists fatigue
  • Can contract regularly for 90+ years
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6
Q

How does the structure of cardiac muscle aid its function?

A
  • Branching fibres provide extra strength, curvature (of heart) and resistance to splitting due to high-blood pressure
  • Smaller diameter fibres than skeletal muscle, allows for richer blood supply and additional connective tissue for strength
  • Numerous mitochondria and rich blood supply allows for aerobic respiration, continuous energy supply, resistance to fatigue
  • Intercalates disks- gives very strong attachments and ionic communication between fibres
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7
Q

Where is smooth muscle found?

A

Internal organs such as gut, lungs, blood vessels, uterus, bladder

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8
Q

Is the contraction of smooth muscle fast or slow?

A

Slow- but the contraction is very powerful, energy-efficient, and causes little fatigue.

It’s usually involuntary control

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9
Q

What is the epimysium and what is its function?

A
  • Thick, outermost sheath of dense connective tissue
  • Prevents friction with other muscles
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10
Q

What is the perimysium and what is its function?

A

Supporting connective tissue, carries nerves, blood vessels

Contains elastic fibres and type I collagen, which contribute to its resistance of a muscle to tensile forces

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11
Q

What is the sarcomere?

A

Contractile unit composed of actin and myosin, each sarcomere is the unit of one Z line to the next

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12
Q

What is the myofibril?

A
  • Bundle of protein filaments actin and myosin, this drives contraction and relaxation
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13
Q

What do T (transverse) tubules do?

A

Convey stimulus from plasma membrane inside fibres, pass it to SR

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14
Q

What does the SR do?

A

Spreads signal further to myofibrils, initiating contractions

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15
Q

Describe the features of cardiac muscle

A
  • Striated
  • Fusiform
  • Intercalated disks, strong end-to-end junctions between fibres
  • Actin filaments attach to disks
  • Many large mitochondria for aerobic respiration
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16
Q

What are purkinje fibres?

A

Larger, modified cardiac muscle fibres, carry stimulus rapidly to ventricles

17
Q

Describe the features of smooth muscle

A
  • No striations
  • Involuntary muscle, usually
  • Initiation of contraction varies between organ
  • No myofibrils
  • No complex membrane systems
  • Actin + myosin filaments visible
  • Junctions between fibres
  • Plasma membrane has caveolae, contains many kinds of receptors
  • Near membrane is a basic form of SR
18
Q

What are the 5 tissue types?

A
  • Epithelium
  • Connective tissue
  • Blood
  • Muscle tissues
  • Neural tissues
19
Q

What are fascicles?

A
  • Group of bundled muscle fibres that form one unit
20
Q

What is muscle surrounded by?

A

Epimysium

21
Q

What are fascicles surrounded by?

A

Perimysium

22
Q

What is muscle fibre (a muscle cell) surrounded by?

A

Endomysium and plasma membrane

23
Q

When does skeletal muscle contract?

A
  • AP spreads over fibre’s plasma membrane
  • Special intracellular membrane systems carry signal to all parts of cell, diffusion not fast enough
24
Q

What is the signalling membrane system of cardiac muscle?

A
  • Myogenic stimulus- muscle generated - AP starts from pacemaker region in RA, carries wave of contraction across heart, assisted by ion diffusion through gap junctions in intercalated disks
  • Purkinje fibres send stimulus to ventricles

Introduction to medicine (Year 1) (24 decks)

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