Skeletal Muscle Flashcards
What is endomysium?
Connective tissue surrounding each individual muscle fibre
What is perimysium?
Connective tissue bundling muscle fibres into fascicles
What is epimysium?
Connective tissue between fascia and muscle body
Give an example of a fusiform muscle
Biceps brachii (larger amplitude, smaller force)
Give an example of a unipennate muscle
Extensor hallucis longus muscle (smaller amplitude, larger force)
Give an example of a bipennate muscle
Rectus femoris muscle (very small amplitude, maximal force)
What does fascicle arrangement determine?
Contraction amplitude and force of contraction
In skeletal muscle, what is the ratio of muscle fibre: synapse?
1:1, there is one synapse per muscle fibre
How are action potentials generated in skeletal muscle?
. 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.
What is the function and innervation of muscle spindles?
. Give information about length changes of muscle
. Innervated by γ motor neurones
What is the function of Golgi tendon organs?
. Give information about strength of muscle contraction
Why are muscle spindles and Golgi tendon organs important?
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)
How many myosin isoforms are there in human muscle fibres? Name these isoforms.
. There are three myosin isoforms in human muscle tissue
. I, IIa, IIx
How can oxidative capacity be measured?
By measuring NADH activity
Compare the oxidative capacity of Type 1 (slow twitch) to Type 2 (fast twitch) muscle fibres.
Type 1 has greater oxidative capacity because relies mainly on aerobic respiration, so has more mitochondria than Type 2
What does alpha glycerolphosphate dehydrogenase activity show?
Glycolytic capacity
Compare the glycolytic capacity of different muscle fibres.
. Type 2 (fast twitch) has greater glycolytic capacity than Type 1 (slow twitch)
. Type IIx has greater glycolytic capacity than IIa
What is glycolytic capacity?
Ability to produce lactate
What is the Size Principle?
. 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
Compare the sizes of Type 1 and Type 2 muscle fibres.
Type 1 (slow twitch) fibres are smaller than Type 2
Describe nervous conduction relating to contraction in the heart
. Purkinje fibres conduct the AP
. Cardiomyocytes get activated by their neighbours via gap junctions
How do endurance training and resistant training affect skeletal muscle?
. Endurance training increases mitochondrial content
. Resistance training increases fibre size
