Muscle Types

Question 1

What are the features of a skeletal muscle?

Answer 1

Muscles attach to origins and insertions by connective tissue:
Fleshy attachments - connective tissue fibres are short
Indirect attachments - connective tissue forms a tendon or aponeurosis
Bone markings present where tendons meet bones’ tubercles, trochanters and crests

Question 2

What is the structure of skeletal muscle?

Answer 2

Composed of muscle cells (fibres), connective tissue, blood vessels, nerves
Fibres are long, cylindrical and multinucleate
Tend to be a smaller diameter in small muscles and larger in large muscles
1mm-4cm in length
Develop from myoblasts; numbers remain constant
Striated appearance
Nuclei are peripherally located

Question 3

What are the two individual fibre types?

Answer 3

Fast fibres - type II fibres

Slow fibres - type I fibres

Question 4

What fibre types do power athletes possess?

Answer 4

Sprinters possess high percentage of fast fibres

Question 5

What fibre types do endurance athletes possess?

Answer 5

Distance runners have high percentage of slow fibres

Question 6

What fibre types do ‘others’ possess?

Answer 6

Weight lifters and non-athletes have about 50% slow and 50% fast fibres

Question 7

What is the structure of smooth muscle?

Answer 7

It is innervated by autonomic nervous system
Visceral or unitary smooth muscle
Only a few fibres innervated in each group
Impulse spreads through gap junctions
Whole sheet contracts as a unit
Often auto-rhythmic

Question 8

What is the structure of cardiac muscle?

Answer 8

Found only in heart where it forms a thick layer (myocardium)
Striated fibres that branch
Each cell usually has one centrally-located nucleus
Fibres joined by intercalated disks
Allow excitation in one fibre to spread quickly to adjoining fibres
Under control of ANS and endocrine system
Some cells auto-rhythmic
Fibres spontaneously contract (aka pacemaker cells)