Muscle Flashcards
What causes the striations in skeletal muscle?
Sarcomeres
Where are calcium ions in the muscle released from?
The Sarcoplasmic reticulum
What do the calcium ions bind to in the muscle?
troponin
What happens when calcium ions bind to troponin?
They remove the tropomyosin blocking protein
What happens once the tropomyosin has been removed?
The actin filaments are exposed
What happens when the actin filaments are exposed?
They interact with the myosin filaments to form cross bridges which cause contraction
What happens once the muscle has contracted?
The calcium ions return to the sarcoplasmic reticulum through the use of ATP
What happens once the calcium ions have returned to the sarcoplasmic reticulum?
The tropomyosin returns to its orginial position and the contraction ends
What does increasing overlap mean?
There is increased tension in the muscle
What is an isotonic twitch?
A contraction with a shortening length (running)
What is an isometric twitch?
A contraction with constant length (weightlifting)
When are more motor units recruited?
As the load on the muscle increases, more motor units are needed to compensate
What is tetanus?
A state of extended contraction via the summation of action potentials.
What causes tetanus?
Tropomyosin is held in the non-blocking state as there is no respite in which the calcium can return to the sarcoplasmic reticulum.
What is fatigue?
A state caused by repeated muscle stimulation.
What are Oxidative muscle fibres?
More mitochondria, red, more vascular for oxygen delivery
What do fast oxidative muscle fibres do?
They have an intermediate resistance to fatigue
What do slow oxidative muscle fibres do?
They resist fatigue
What are Glycolytic muscle fibres?
few mitochondria, higher concentration of glycolytic enzymes and glycogen. White.
What do fast glycolytic muscle fibres do?
Fatigue very quickly.
Where does smooth muscle exist?
In hollow organs, e.g. GI tract and the bladder.
What nerves supply smooth muscle?
The autonomic nervous system
How does contraction and relaxation differ in smooth muscle than to skeletal muscle?
In smooth muscle, calcium binds to calmodulin which binds to myosin light chain kinase. This phosphorylates the myosin with ATP and forms the cross bridges. Mysoin light chain phosphatase relaxes the muscle.
