Lecture 1: Muscle and Exercise Physiology Keynote Flashcards
What mechanisms dictate how much muscle mass changes in the body?
Muscle mass is a balance between protein synthesis and protein degradation.
What happens if cytoskeletal proteins of muscles are damaged?
It can lead to devastating diseases (eg muscular dystrophy)
What happens if the length-tension relationship is dysrupted?
Dysruption of the length tension relationship can cause damage to the overall muscle architecture.
What kinds of muscle fibers are there?
Muscle fibers exist as either “pure” or as hybrids
What do “pure” muscle fibers consist of?
One type of MyHC
What do hybrids contain?
Multiple forms of MyHC
How do muscle fibers work in the “big picture” of muscles?
Muscles are typically composed of several different fiber types but can be predominantly a certain muscle type based on requirements.
How can muscle fiber composition be changed in a certain muscle?
Drug therapies
Physical Exercise
What are the goals of interventions to attenuate muscle wasting?
To attenuate muscle atrophy
To promote muscle strength
To do both these functions while not increasing muscle fatigue
What are the causes of disuse atrophy of muscles?
Prolonged bed rest
immobilisation
Plaster casting
Hindlimb unweighting
Spaceflight
What happens during spinomuscular atrophy?
Nerve contact to muscle is lost and electrical contact with muscle is required to prevent atrophy.
What happens during cancer cachexia?
Muscle wasting and fat loss resulting in a reduced quality of life.
Impaired chemotherapy and radiotherapy results as well.
Which cancer patients typically get cachexia?
Up to 80% of Lung, pancreatic, and gastrointestinal cancer patients early in disease.
What percentage of cancer patients die of cachexia?
more than 20%
What typically causes muscle wasting in the ICU?
Significant inflammatory response typically is the cause
What are some methods being tested for efficacy in treating ICU muscle wasting?
Electrical stimulation of muscles
What are some other causes of muscle wasting?
Burn injuries
HIV
CKD
Heart failure
COPD
What muscles are affected by Duchenne’s and Becker’s muscular dystrophy?
Limbs and trunk muscles as well as other muscles nearby typically experience weakness and wasting.
Calves are often enlarged at the early stages but as the disease progresses these fibers break down along with the rest of the body.
When does duchenne’s muscular dystrophy typically first appear?
Early childhood at about 2 to 6 years of age.
What is the typical life expectancy of a child with Duchenne’s Muscular Dystrophy?
Beyond the late twenties is becoming more and more common.
How is Duchenne’s Muscular Dystrophy Inherited?
It is X-linked recessive
Why isn’t genetic counseling enough to prevent DMD?
1 in 3 cases of duchenne’s muscular dystrophy are the result of a new mutation.
What are the characteristic manifestations of duchenne’s muscular dystrophy?
Proximal lower girdle weakness, calf hypertrophy, and elevated creatine kinase levels.
Wheelchair dependent at the age of 7-13.
Cardiac and smooth muscle are also affected.
At the age of 20 there is a dependence on cardiorespiratory failure.
What are some early signs of duchenne’s muscular dystrophy?
Developmental delay
Falling more frequently
Short stature
Difficulty running
Lordotic gait between 3 and 6 years of age.
Gower sign appears
Enlargement of calves, gluteal muscles, lateral vastus, deltoids, and infraspinatus muscles.
What is the gower sign?
To get up from a lying down position the stand is “walked into”
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