Skeletal Muscle

Question 1

What is endomysium?

Answer 1

Connective tissue surrounding each individual muscle fibre

Question 2

What is perimysium?

Answer 2

Connective tissue bundling muscle fibres into fascicles

Question 3

What is epimysium?

Answer 3

Connective tissue between fascia and muscle body

Question 4

Give an example of a fusiform muscle

Answer 4

Biceps brachii (larger amplitude, smaller force)

Question 5

Give an example of a unipennate muscle

Answer 5

Extensor hallucis longus muscle (smaller amplitude, larger force)

Question 6

Give an example of a bipennate muscle

Answer 6

Rectus femoris muscle (very small amplitude, maximal force)

Question 7

What does fascicle arrangement determine?

Answer 7

Contraction amplitude and force of contraction

Question 8

In skeletal muscle, what is the ratio of muscle fibre: synapse?

Answer 8

1:1, there is one synapse per muscle fibre

Question 9

How are action potentials generated in skeletal muscle?

Answer 9

. Motor end plates generate action potentials- there are no gap junctions
. Very quick feedback is given via proprioception, which includes signals from muscle spindles and Golgi tendon organs.

Question 10

What is the function and innervation of muscle spindles?

Answer 10

. Give information about length changes of muscle

. Innervated by γ motor neurones

Question 11

What is the function of Golgi tendon organs?

Answer 11

. Give information about strength of muscle contraction

Question 12

Why are muscle spindles and Golgi tendon organs important?

Answer 12

They allow very precise control of movement via proprioception because they give information about length changes in muscles (muscle spindles) and strength of contraction of muscles (Golgi tendon organs)

Question 13

How many myosin isoforms are there in human muscle fibres? Name these isoforms.

Answer 13

. There are three myosin isoforms in human muscle tissue

. I, IIa, IIx

Question 14

How can oxidative capacity be measured?

Answer 14

By measuring NADH activity

Question 15

Compare the oxidative capacity of Type 1 (slow twitch) to Type 2 (fast twitch) muscle fibres.

Answer 15

Type 1 has greater oxidative capacity because relies mainly on aerobic respiration, so has more mitochondria than Type 2

Question 16

What does alpha glycerolphosphate dehydrogenase activity show?

Answer 16

Glycolytic capacity

Question 17

Compare the glycolytic capacity of different muscle fibres.

Answer 17

. Type 2 (fast twitch) has greater glycolytic capacity than Type 1 (slow twitch)
. Type IIx has greater glycolytic capacity than IIa

Question 18

What is glycolytic capacity?

Answer 18

Ability to produce lactate

Question 19

What is the Size Principle?

Answer 19

. During muscle contraction, the type I motor units (small) are always recruited first (even during fast movement)
. If more force of contraction is needed, Type II motor units (large) are then recruited (IIa followed by IIx, which is recruited at maximum force)
. It’s called the Size Principle because Type II motor units have more fibres and are thus larger and recruited when a greater force of contraction is required

Question 20

Compare the sizes of Type 1 and Type 2 muscle fibres.

Answer 20

Type 1 (slow twitch) fibres are smaller than Type 2

Question 21

Describe nervous conduction relating to contraction in the heart

Answer 21

. Purkinje fibres conduct the AP

. Cardiomyocytes get activated by their neighbours via gap junctions

Question 22

How do endurance training and resistant training affect skeletal muscle?

Answer 22

. Endurance training increases mitochondrial content

. Resistance training increases fibre size