Bio 201
Question 1
Match each description with the term that is described.
The neurotransmitter at the neuromuscular junction.
The enzyme that remains within the synaptic cleft
A chemically-gated channel AChR
This ensures that one stimulus in the motor neuron produces only a short contraction.
Found only on the endplate membrane.
All Answer Choices
A. ACh
B. AChR
C. AChE
Question 2
Match the SR transporter with the descriptions.
calcium leaves the SR through these
this is a type of active transport
this is for facilitated diffusion
calcium enters the SR through these
the action of these helps to stop a contraction
the action of these helps to lead to a contraction
This is completely passive
these are voltage-gated
All Answer Choices
A. calcium channels
B. calcium pumps
Question 3
The calcium channel in the SR is considered to be gated. That calcium channel is specifically voltage-gated. That means that it opens when the action potential runs along the [3]. The gating of the channel [4] ATP to occur.
Meanwhile, on the postsynaptic membrane of the neuromuscular junction there are also gated channels. These are also called [5] receptors. These channels are considered to be [6]-gated. In order to open, it [7] ATP. When these gated channels are open they allow [8] to pass through them.
All Answer Choices
requires
does not require
ACh
calcium
chemically
closes
mechanically
opens
sodium and potassium
SR membrane
t-tubules
voltage
Question 4
Please keep in mind that an answer can be used more than once.
In a sarcomere there are both actin and myosin filaments. The myosin filament has tropomyosin associated with it. When a muscle fiber is resting, the tropomyosin blocks the [2] on each actin protein. After calcium is available, tropomyosin is tugged out of the way by [3]. This enables each myosin [4] group to attach to the thin filament with its [5]. When the powerstroke occurs, the myosin protein bends at the [6] on its neck. The powerstroke pulls on the entire [7] so that the Z-lines are pulled inward. In order to do this again, another adenosine triphosphate molecule has to bind to the [8] on the [9] region of the myosin molecule so that the cross-bridge can disconnect. To become re-energized, the head group has to break down the ATP molecule using its [10] function. Throughout this entire time, the [11] region of the myosin molecules are not doing anything but remaining stuck within the [12] to hold all the myosin molecules together.
All Answer Choices
actin filament
myosin filament
actin-binding site
myosin-binding site
ATP-binding site
ATPase
troponin
head
tail
hinge
Response Feedback:
I think that the hardest part of this question might be about the binding sites. Remember, if I shake your hand, you also shake my hand. So, my hand is like a binding site for your hand, and your hand is like a binding site for my hand.
Question 5
Put the items below about the neuromuscular junction into the right order.
an action potential reaches the motor axon terminal.
calcium ions enter the axon terminal
acetylcholine diffuses across the synaptic cleft
synaptic vesicles fuse with the axon terminal membrane
the sarcolemma generates an action potential adjacent to the endplate
an action potential runs along the entire sarcolemma including the t-tubules
the muscle fiber becomes more positively charged near the endplate
voltage-gated calcium channels open
acetylcholine binds to acetylcholine receptors
Sodium ions enter the muscle fiber across the endplate membrane
Question 6
Examine the steps below and put them in the correct order.
An action potential is generated in the muscle fiber
ACh levels rise in the neuromuscular junction
Na+ enters into the muscle fiber through ACh receptor channels.
Calcium ions are pumped by active transport into sarcoplasmic reticulum
Action potential travels along sarcolemma and t-tubules causing the DHP receptor to change shape
DHP receptor changing shape causes calcium ion to be released from the sarcoplasmic reticulum into the cytosol.
Calcium ions bind to troponin allowing formation of cross bridges
Calcium unbinds from the troponin
Power stroke carried out by myosin heads
Myosin heads release and elastic filaments pull filaments back to relaxed position.
