Locomotor: PBL 4 Flashcards
Describe the different functions of skeletal muscle
Support soft tissues - Support organs, shield internal tissues
Guard entrances and exits - Openings of digestive/urinary tracts
Maintain body temperature - Heat released by working muscles
Store nutrient reserves - Proteins in muscles can break down
What is the name of the functional unit of skeletal muscle?
Sarcomere
Briefly describe the series of events that lead to muscle contraction starting with the action potential reaching the terminal bouton of the motor neurone
Action potential stimulates Ach release at the neuromuscular junction
ACH induces an action potential in the muscle fibre membrane
This is carried to the muscle fibre via the T-tubule system to stimulate the release of calcium from the sarcoplasmic reticulum
Calcium initiates tropomyosin displacement revealing myosin binding site
Myosin forms cross-bridges with actin and the muscle contracts
What would be the consequences on the skeleton for someone suffering from sarcopenia?
> Muscle attaches to the skeleton and moves the joints so movement and posture can be achieved leading to immobility
The loss of muscle mass and the pull of the muscle on the skeleton causes less stress on the bone and increases bone loss and osteoporosis
The loss of muscle mass also means falls are more likely as the muscle is not able to hold the body up
As there is less muscle and weaker bone falls are more likely to lead to fractures less protection of the skeleton and other internal organs
Define sarcopenia
The loss of skeletal muscle mass and strength as a result of ageing
Why does muscle power diminish quickest in ageing in comparison to strength and endurance?
The loss of fast-twitch (type II) muscle fibres exceeds the loss of slow-twitch muscle fibres in addition to a reduction in motor units.
Outline some of the proposed reasons for sarcopenia
Age-related declines in alpha motor neurones, fat gain, inadequate intake of dietary protein (due to anabolic resistance of older skeletal muscle to protein) and energy
How may accumulation of ROS contribute to sarcopenia?
Accumulation of reactive oxygen species may lead to oxidative damage of biomolecules and contribute to the loss of muscle mass and strength; elevated oxidative stress has been associated with muscle wasting in many clinical scenarios
Why may antioxidants be prescribed to those who are ageing to avoid sarcopenia?
Suggested that ROS may play a part in the process, and therefore the specific ROS should be identified, and an antioxidant given to try and alleviate and prevent some of the symptoms the individual is experiencing
How is sarcopenia diagnosed?
Low muscle mass, low muscle strength and/or low physical performance
What is activity-related sarcopenia?
Form of secondary sarcopenia resulting from bed rest, sedentary lifestyle, deconditioning or zero-gravity conditions
What is disease-related sarcopenia?
Form of secondary sarcopenia, associated with advanced organ failure, inflammatory disease, malignancy or endocrine disease
What is nutrition-related sarcopenia?
Form of secondary sarcopenia resulting from inadequate dietary intake of energy and/or protein as with malabsorption, GI disorders etc.
How is presarcopenia diagnosed?
Individual just has low muscle mass
How is sarcopenia diagnosed?
Individual has low muscle mass and low muscle strength OR low muscle performance
