Lecture 3 Flashcards
(16 cards)
What are the types of striated muscle?
Cardiac and skeletal
Describe skeletal muscle
Type of striated muscle
around 12cm in length
20-100 micro metres in diameter
Voluntary movement
Innervated by motor neurones
Describe cardiac muscle
Type of striated muscle
Not innervated by motor neurones
Branched
10-20 micro metres in diameter
100micro metes in length
What is a sarcomere?
The distance between two Z lines
What is the A band?
Thick myosin filaments
What is the I band?
Contains only actin filaments
Why is the cardiac action potential so long?
The refractory period is long and because of this, the stimuli cannot ‘tetanise’
What happens if you bring multiple stimuli in skeletal muscle?
The contractions begin to ‘tetanise’, the final contraction produced is bigger
How is calcium released into the sarcoplasm of cardiac muscle?
Calcium induced calcium release
Action potential washes over T tubules which allows a voltage to activate calcium channels and open them
Calcium then enters the cell through the calcium channels and crosses the dyadic cleft
Calcium then binds to calcium receptors (RyR) on the sarcoplasmic reticulum
This leads to calcium entering the sarcoplasm and binding to muscle filaments to bring about contraction
How are cardiac muscles able to relax?
Calcium is taken up by SERCA which is an ATP driven pump to take calcium back into stores
Calcium from the intracellular space leaves the cell through the sodium calcium exchanger
What occurs in skeletal muscle contraction?
Voltage-induced calcium release
The L-calcium channel and the RyR are connected by smaller proteins
When an action potential washes over the T-tubules, this voltage change creates a confirmation change in the L-calcium channel which causes the plug to be broken between the L-calcium channel and the RyR
The rest that occurs happens
Taking away calcium has no difference
How does contraction occur?
Calcium binds to troponin C on actin filament
This causes troponin complex to move along with tropomyosin to reveal the myosin binding site
ATP is required for this and ATPases in the myosin head convert ATP into ADP to allow it to move forward
What is inotropy?
The strength of cardiac muscle contraction
What affects Ca sensitivity?
Temperature
pH
Pi
Drugs
How does contraction occur in smooth muscle?
Ligands can bind to receptors on smooth muscle which triggers secondary messengers to cause the release of calcium from intracellular stores
Calcium then binds to Calmodulin which activates MLCK
MLCK phosphorylates the myosin light chain, causing contraction
