Lecture 11 Flashcards
What is the sarcolemma?
The skeletal cell membrane
What is the sarcoplasmic reticulum?
When the Ca2+ is stored
How does the depolarisation of a skeletal muscle cell get from the membrane (sarcolemma) into the cell?
Through the T-tubules (transverse tubules).
What is the function of dihydropyridine (DHPR) receptor?
It is a voltage sensor. It senses the change in membrane potential, which can lead to the opening of Ca channels.
What are ryanodine receptors (RyR)?
They are Ca2+ channels which are connected to the DHPR. They sit on the sarcoplasmic reticulum membrane.
What is the function of the SERCA pump?
It pump Ca2+ back into the SR, and uses ATP to terminate cross-bridge cycling.
How is heat produced in muscle?
As a by product of the breakdown of ATP to ADP + Pi. It is needed to maintain body temperature
What is Hyperthermia?
It is when body temperature rises above normal.
it can lead to nausea, vomiting, headaches, confusion and even death
What is Malignant Hyperthermia?
It is an autosomal dominant, life-threatning disease. It occurs due to mutations in RyR or DHPR, and is trigger by volatile anaesthetics. it can lead to muscle rigidity, a hyper metabolic state and increased CO2 production. these lead to spontaneous muscle contraction and extra Ca2+ release which means overactivity of SERCA pumps. As this process requires the breakdown of ATP, heat is generated very quickly, leading to death.
What is a twitch?
The generation of force (by an AP) for a short period of time.
What is the role of tropomyosin?
It blocks the myosin binding sites on actin.
What is the role of troponin?
It has a calcium binding it. It senses when Ca2+ enters the cell and causes a conformational change to allow the binding of Ca2+
What is the actin-myosin interaction?
Actin has sites that myosin can bind. in low [Ca2+], these are covered by tropomyosin. When Ca2+ enters the cell and binding to troponin, tropomyosin moves off the binding site and myosin head can engage. A cross bridge is formed.
What is the cross-bridge cycle?
- ATP attached to the myosin head, and it detaches from the actin filaments.
- ATP is hydrolysed to ADP+Pi: the myosin head is energised.
- If [Ca2+] is low, the myosin binding sites are covered, and the reaction stops there.
- if [Ca2+] are high (due to action potential releasing Ca2+ from SR), then tropomyosin moved off the myosin binding sites and myosin head bind the acting filaments.
- ADP+Pi are released, the myosin head flexes - force is generated!
What is rigor mortis?
This happens when the ATP head stays attached, and the muscle stays stiff. this happens at death.
