29.3 - 29.6 Flashcards
(47 cards)
A motor unit is a ___ ___ and all of the ___ ___ innervated by it.
Motor neuron
All muscle fibres innervated by it
A motor unit is a ___ ___ and all of the ___ ___ innervated by it.
Motor neuron
All muscle fibres innervated by it
What are the 3 types of motor units/fibres?
Fast and rapidly fatigable e.g. sprint
Intermediate - fast and resistant to fatigue
Slow and resistant to fatigue e.g. endurance
There are different types of muscle fibres in people. In some fibres there is only one type of myosin i.e. ‘___’, and in others there is more than one type of myosin i.e. ‘___’.
Pure
Hybrid
Sarcopenia is an ___-associated loss of ___ muscle mass and function. It affects all people independent of lifestyle, disease states, ethnicity, etc. There is infiltration of non-contractile tissue like ___ tissue and ___, and muscle stiffening.
Age-associated loss of skeletal muscle mass and function
(Not to be confused with cachexia - wasting and weakness due to severe chronic illness)
Infiltration of connective tissue and fat
Diagnosis of sarcopenia is consistent with a gait speed of
There is loss of muscle strength with age. ___ muscles (e.g. EDL) are affected more than ___ muscles (e.g. soleus). There is age-related loss of motor ___ AND muscle ___.
Fast muscles are affected more than slow muscles - slow muscles are protected
Age-related loss of motor units AND muscle fibres
There is an overall slowing of muscle due to denervation or reinnervation of type ___ (fast) motor units. In ___, muscle fibres die. In ___, slow nerves innervate and replace fast fibres with slow fibres. Therefore, there is an increase in type ___ (slow) muscle fibres.
Type 2 (fast) motor units Denervation -> death of muscle Reinnervation -> change from fast nerve to slow nerve -> slowing of muscle Type 1 (slow) muscle fibres/motor units
In sarcopenia/ageing, there is progressive atrophy of type ___ (___ ___) fibres.
Type 2 (fast twitch)
With ageing there is a decrease in circulating levels of ___ hormones like GH, IGF-1 and testosterone. Supplementing these hormones alone is not effective at reducing sarcopenia. The best outcome is achieved by using supplements in conjunction with ___ ___.
Anabolic hormones
Strength training
Duchenne muscular dystrophy is due to a mutation in the ___ gene on ___.
Dystrophin gene
Xp21
The ___ mouse is a model of DMD as it lacks expression of ___, but it upregulates ___ leading to a normal lifespan.
Mdx mouse
Lacks expression of dystrophin
Upregulates utrophin
There are different types of muscle fibres in people. In some fibres there is only one type of myosin i.e. ‘___’, and in others there is more than one type of myosin i.e. ‘___’.
Pure
Hybrid
Sarcopenia is an ___-associated loss of ___ muscle mass and function. It affects all people independent of lifestyle, disease states, ethnicity, etc. There is infiltration of non-contractile tissue like ___ tissue and ___, and muscle stiffening.
Age-associated loss of skeletal muscle mass and function
(Not to be confused with cachexia - wasting and weakness due to severe chronic illness)
Infiltration of connective tissue and fat
The gold standard treatment for Duchenne muscular dystrophy is ___. There are many other treatments.
Corticosteroids
There is loss of muscle strength with age. ___ muscles (e.g. EDL) are affected more than ___ muscles (e.g. soleus). There is age-related loss of motor ___ AND muscle ___.
Fast muscles are affected more than slow muscles - slow muscles are protected
Age-related loss of motor units AND muscle fibres
There is an overall slowing of muscle due to denervation or reinnervation of type ___ (fast) motor units. In ___, muscle fibres die. In ___, slow nerves innervate and replace fast fibres with slow fibres. Therefore, there is an increase in type ___ (slow) muscle fibres.
Type 2 (fast) motor units Denervation -> death of muscle Reinnervation -> change from fast nerve to slow nerve -> slowing of muscle Type 1 (slow) muscle fibres/motor units
In sarcopenia/ageing, there is progressive atrophy of type ___ (___ ___) fibres.
Type 2 (fast twitch)
The ___ nephron reabsorbs calcium by a series of transporters e.g. ECaC, Na+-Ca2+ antiport, Ca2+ ATPase.
Distal
With ageing there is a decrease in circulating levels of ___ hormones like GH, IGF-1 and testosterone. Supplementing these hormones alone is not effective at reducing sarcopenia. The best outcome is achieved by using supplements in conjunction with ___ ___.
Anabolic hormones
Strength training
PTH hyposecretion (e.g. hypoparathyroidism) is usually due to ___ attack of the gland and results in ___calcaemia and ___phosphataemia.
Autoimmune attack
Hypocalcaemia
Hyperphosphataemia
The ___ mouse is a model of DMD as it lacks expression of ___, but it upregulates ___ leading to a normal lifespan.
Mdx mouse
Lacks expression of dystrophin
Upregulates utrophin
What is the sequence of tissue phases after skeletal muscle injury? What phase is important for recruitment of stem cells?
Degeneration > inflammation > regeneration > fibrosis
Inflammation is important for recruitment of stem cells
In normal muscle repair, inflammation allows activation of ___ cells i.e. muscle stem cells. But in DMD, the inflammatory signature is different resulting in ___ - the replacement of contractile muscle fibres with extracellular connective tissue.
Satellite cells i.e. muscle stem cells
Fibrosis
