Tissues 7 - Muscle Flashcards
Draw the structure of a sarcomere
See diagram.
Where is skeletal muscle found?
Attached to bone, produces movement of the body relative to the external environment.
What are antagonist muscle pairs (+example)?
A flexor muscle (bicep) and a extensor muscle (tricep)
What are the types of isotonic contractions?
In isotonic contractions, the muscle changed length and tension stays the same - concentric is shortening, eccentric is lengthening.
What is an isometric contraction of the smooth muscle?
This is where tension develops but the muscle does not change length - if you’re carrying something, the load force is equal to the muscle tension. So myosin heads will reattach to the same point on the actin chain. Requires ATP (energy expenditure).
Describe the arrangement of muscle cells in the skeletal muscle.
Arranged in a bundle of myofibres. These are cylindrical and multinucleated.
What is the structure of myofibres?
They are round, cylindrical, multinucleate, and packed with myofibrils.
How does excitation contraction coupling in the skeletal muscle work?
- The action potential propagates along the myofibre membrane (T tubules).
- Depolarisation opens the dihydropyridine receptors (DHPR) and this causes the ryanodine receptors (RyR) to open.
- Ca2+ opens and calcium ions flood in.
Summarise the sliding filament theory
- In the presence of Ca2+ troponin is moved from tropomyosin which exposes the actin myosin binding site.
- Charged myosin heads bind to the exposed site and ADP is discharged as the myosin head pivots, pulling the actin to the centre of the sarcomere.
- ATP binds (releasing the myosin head from the actin chain) and is hydrolysed to ADP to provide energy for the myosin head to recharge.
What cell types are present in the heart?
Cardiomyocytes, pacemaker cells (SA and AV node) and conducting fibres (eg. Purkinje fibres).
Describe the structure of cardiac muscle.
Walls of the heart are primarily cardiac muscle. Striated muscle connected by intercalated discs with many gap junctions. Contains sarcomeres.
What are the differences between cardiac muscle excitation contraction complying and skeletal muscle E-C coupling?
- Depolarisation of the membrane opens voltage gated Ca2+ ion channels rather than dihydropyradine receptors.
- Ca2+ influx causes ryanodine receptors to open, releasing Ca2+, by binding to the receptors on the ER.
Describe the structure of smooth muscle
Smooth muscle is present in the walls of hollow organs - it is non-striated, without a regular arrangement of actin and myosin. Spindle shaped cells.
Describe the process of excitation contraction coupling in the smooth muscle.
- Depolarisation opens voltage gated calcium channels.
- Ca2+/Calmodulin complex activates myosin light chain kinase
- Myosin light chain kinase phosphorylates myosin light chains
- Forms cross bridges with actin filaments, resulting in contraction.
What is CICR in cardiac muscle contraction?
Ca2+ induced Ca2+ release
