(Don't use this quizlet.. use other one) Anatomy Test part 2 - Muscle Contraction (Test: 12/15/21)
(c) What happens at the end of the axon (presynaptic terminal)?
the AP causes Ca2+ channels to open
What are Ca2+ ions are no longer released from?
the S.R.
When myosin heads attach to active sites, what kind of connection is this called?
the cross bridge
What happens when ATP binds to myosin heads?
the cross bridge b/t actin and myosin breaks
What is existing ACh is broken down by?
the enzyme acetylcholinesterase (AChE)
What does the energy from the ATP power?
the myosin heads
Previously released ACh is still interacting with what?
the postsynaptic membrane
What is it called when the myosin's bend forward?
the power stroke
(i) Where does T-tubules transmit the AP to?
the sarcoplasmic reticulum
(e) What does ACh travels across?
the synaptic cleft
What happens when there are no cross bridges?
there is nothing holding the sarcomeres in place. they will be stretched out by gravity or the action of another muscle
(b) Action potential (electrical signal) travels down the axon of a motor neuron
.
What will the S.R. will transport
Ca2+ ions back inside itself
With ACh broken down, what will no longer exist?
a muscle AP
What do myosin heads attach to?
active sites
What releases when ATP is broken down into ADP + P
energy
(g) Where is new AP is created?
in the sarcolemma
What does the tropomyosin's rotation do?
it opens active sites on actin
(h) Where does the muscle AP travel along
the sarcolemma and down the T-tubules
(j) Why does the AP trigger the SR?
to release Ca2+ ions into the sarcoplasm
What does Ca2+ binds to
troponin
What does no Ca2+ mean?
troponin turns & rehides the active sites. now no cross bridge can form between actin & myosin
What is ATP broken down into?
ADP + P
What happens to ADP?
It is ejected
What happens to phosphate (broken off ATP)?
It is ejected
What does tropomyosin do?
It rotates
(Starting the contraction step 1)
Muscles are controlled by nerve cells (specifically motor neurons)
What happens when the nervous system stops sending APs?
The ACh is no longer released.
What happens when myosin's bend forward?
actin pulls toward the center of the sarcomere
Which way do myosin heads bend?
forward
What does ATP bind to?
myosin heads
(d) What is Acetylcholine?
neurotransmitter (chemical communicator)
(f) Where does ACh bind to receptors?
on the postsynaptic membrane of the muscle
When myosin heads spring back loaded with energy ready to start the process again. What is this process called?
return stroke
(d) What does Ca2+ cause synaptic vesicles to do?
secrete acetylcholine (ACh) into the synaptic cleft
When myosin heads spring back loaded with energy, what are they ready to do?
start the process again
