Synaptic Transmission and Excitation Contraction Coupling Flashcards
site where electrical signal from one excitable cell is communicated to another
synapse
What is the neurotransmitter involved in the neuromuscular junction?
ACh
In the neuromuscular junction, a presynaptic axon can innervate what?
as few as 1 or many muscle cells
In the neuromuscular junction, a postsynaptic cell (muscle) receives signal from?
ONLY ONE presynaptic axon
ACh diffuses across the synaptic cleft to the post-synaptic membrane. This specialized region of the muscle fiber is known as what?
motor end plate
Once the action potential spreads over the muscle surface and into T-tubules, the action potential in skeletal muscle affects DHPR how?
DHPR will physically alter the state of underlying ryanodine receptors (RYRs)
what happens when the ryranodine receptors are altered by DHPR?
the Ca2+ channels will open
perception of fatigue or loss of motivation possibly brought on by increasing levels of byproducts of contraction
central fatigue
contraction requires the availability of ATP
peripheral fatigue
How many different fiber types are found in skeletal muscles?
3
Which fiber type has white fibers?
fast twitch glycolytic fibers
Why are slow twitch oxidative fibers red?
Because of their large amount of myoglobin and mitochondria
Which muscle fiber has a larger diameter?
fast twitch glycolytic
Which muscle fiber uses phosphocreatine and glucose?
fast twitch glycolytic
Which muscle fiber is fatigue resistant?
slow twitch
Which muscle fiber is between slow twitch oxidative and fast twitch glycolytic?
Fast twitch oxidative
What two things determine the force of a contraction?
the starting length of the sarcomere and how rapidly the fiber is stimulated by the nerve
If the sarcomere is very short…
myosin cannot pull the actin very far before hitting the z-line
if the sarcomere is very long…
there is a bigger H zone
if second twitch is initiated before complete relaxation…
the second twitch reaches a greater force
the greater the frequency of stimulation…
the greater the potential force
overlap of twitches such that complete relaxation is not achieved between them
tetanus
a neuron that innervates more motor units will generate?
a greater force than one which innervates fewer
