Muscle Flashcards
What is myalgia?
Muscle pain
What is myasthenia?
Weakness of muscles
What is myocardium?
Muscular component of the heart
What is myopathy?
Any disease of the muscle
What is myoclonus?
Sudden spasm of the muscles
What type of muscle is striated?
Cardiac and skeletal
What type of muscle is non-striated?
Smooth
Where are the nuclei located in skeletal muscle?
Peripherals
Where are the nuclei located in cardiac muscle?
Centrally
Where are the nuclei located in smooth muscle?
Centrally
What surrounds muscle fibres/cells?
Endomysium
What does the perimysium wrap around?
A fascicle
What is perimysium?
Connective tissue carrying blood vessels and nerves
What can be found in the A band?
Actin
Where it overlaps can contain myosin
What is found in the I band?
Actin only
Where is the H zone?
The region which only contains myosin
Where is the M line?
Goes down the middle of the H zone.
What is calcium’s role in the sliding filament theory?
Calcium bind to TnC of troponin
Causes a conformational change where tropomyosin moves away from actin’s binding site.
This allows myosin heads to bind to actin and contraction begins.
What happens during contraction of skeletal muscle?
Myosin head attached to actin
This releases ADP and Pi
Myosin head pulls actin towards the M line
ATP attaches to the myosin head, releasing it from actin
ATP is hydrolysed and the myosin head moves to original position
Why does rigor mortis occur after death?
Lack of ATP to release myosin head from actin so muscles remain contacted.
Where on a sarcomere are T tubules?
At the junction between I and A bands
What leads to the contraction of skeletal muscle?
- Nerve impulse arrives at NMJ from motor neurone
- Causes release of Ach into synaptic cleft and depolarisation of sarcolemma
- Na channels are opened and Na enters the cell
- Voltage sensor proteins of T tubule membrane change their conformation
- Calcium is released from terminal cisternae into the sarcoplasm
- Calcium bind to the TnC sub unit of troponin
- Contraction cycle is initiated and calcium returns to terminal cisternae of sarcoplasmic reticulum
In cardiac muscle, where are the T tubules found?
Along the Z bands
In cardiac muscle, what are Z lines replaced by and what do they allow?
Intercalated discs
Gap junctions for electrical coupling with adjacent cells
Adherens-type junctions to anchor cells and provide anchorage for actin filaments.
What do Purkinje fibres do?
Transmit action potentials from the atrioventricular node to the ventricles.
What is the structure of the Purkinje fibres?
They are modified myocytes with abundant glycogen, sparse myofilaments and extensive gap junction sites.
Purkinje fibres conduct quicker than muscle fibres. What does this allow?
Ventricles to contact in a synchronous manner.
In which types of muscle are T tubules found in?
Cardiac and skeletal. Not present in smooth
What does smooth muscle respond to and therefore contract?
Nerve impulses, hormones, drugs, local concentrations of blood gases
How are the filaments arranged in smooth muscle?
Arranged diagonally within the cell so that it contracts in a twisting way
What happens when cardiac muscle is damaged?
Damaged tissue cannot be regenerated. Fibroblasts invade, divide and lay down scar tissue
How does skeletal muscle regenerate?
Satellite cells can divide
Can also fuse with existing muscle cells to in increase mass (hypertrophy)
Functions of skeletal muscle?
Movement
Posture
Stability of joints
Heat generation
