Skeletal muscle function, ageing and disease Flashcards Preview

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Flashcards in Skeletal muscle function, ageing and disease Deck (27):
1

What is the most severe of all muscular dystrophies?

Duchene Muscular Dystrophy

2

some of the factors that modulate muscle mass?

hormones (GH, IGF-1, testosterone)
genetics
inflammation
protein intake
protein degradation
blood flow
exercise

3

main types of fibres?

I ---> anaerobic, slow twitching, resist exhaustion
IIa ---> middle point
IIb ---> aerobic, fast twitching, fast exhaustion

4

what do the interventions against muscle sating requires?

stopping muscle atrophy
promote muscle growth
NOT --> increasing muscle fatigue

5

example of genetic factors controlling muscle mass?

Myostatin: Negative regulator of muscle growth

6

types of muscle atrophy

Disuse Muscle Atrophy
Denervation Atrophy
Cancer Cachexia
Critical Illness Myopathy
Sarcopenia

7

why is cancer cachexia relevant?

present in 80% of cases of lung, pancreas and gastrointestinal
if muscle mass 20% of cancer deaths related to this

8

definition of Sarcopenia

age associated loss of skeletal muscle mass and function and its replacement by connective tissue and fat (also the connective tissue is more stiff)

9

Diagnosis of Sarcopenia

* gait speed < 1m/s
* appendicular lean/fat ration of <2 SD of the average of a young adult

10

people should under go a DEXA (Dual-energy X-ray absorptiometry) when

bedridden
cannot independently rise from a chair
gait speed < 1m/s

11

Definition of weakness:

inability to develop an initial force appropriate for the circumstances

12

at what age there is a severe drop in muscle strength? and what muscle are first affected?

~50
fast twitching muscles

13

What is motor unit remodelling in the context of sarcopenia?

after loss of type 2 motor units, there is an expansion of reach of the type 1 (slow) motor units

14

Sarcoplasmic reticulum dysfunction happens before any muscle loss

T

15

in terms of the spinal cord, what are 2 changes observed with ageing?

loss of Type 2b fibres
reinervation (sprouting) from type 1 fibres

16

some of the gradual changes seen in both pre and postsynaptic components

widening of the end plate
longer nerve terminals
fear side branches
loss of myelin

17

changes of again in muscle are both irreversible and inevitable T/F

T, they can be attenuated

18

Strength training in the elderly produces muscle mass recovery T/F

T, type 2 fibres specially increased

19

Duchenne Muscular Dystrophy (DMD)
Onset?
Survival?
Inheritance

early childhood
rare beyond 20s (resp failure)
X-linked recessive (33% of cases new mutation)
[most common inherited childhood lethal disorder]

20

in what medical condition is there pseudohypertrophy of the calf muscles?

Duchenne Muscular Dystrophy (DMD)

21

What is the Gowers Sign?

climbing on one self in order to stand up from all fours (pushing on the knees)

22

DMD involves a mutation on which gene?

mutation in the dystrophin gene (deficiency in expression due to a deletion of part of the gene and frameshift, cytoskeletal protein)

23

function of dystrophin

structural role stabilising the cell membrane tot he laminin of the basal lamina
might have a signalling role too (anabolic role?)

24

Explain the pathology of DMD

loss of dystrophin molecule in the cell membrane that helps anchor it to the basal lamina causes rupture of the membrane upon forceful contraction allowing for the influx of Ca+2 and increased production of ROS, necrosis and oedema

25

Becker Muscular Dystrophy (BMD)
onset?
Inheritance?

adolescence or adulthood
X-linked recessive
same thing as Duchenne but wayyyyy less severe as there is some amounts of dystrophin still present

26

reduction of force generated by muscle in relation to stretch is an indicator of....

Muscle Damage

27

main line of treatment for DMD and BMD?

corticosteroids