GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Action Potentials and Synapses
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
Example Questions
Example Question #271 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
Which of the following choices corresponds to what is happening in a cell when an action potential reaches its peak?
Voltage-gated sodium channels open
The sodium-potassium pump stops
Sodium channels are inactivated
Potassium channels close
Sodium channels are inactivated
The peak of an action potential signals the inactivation of sodium channels. This effectively prevents more sodium from entering the cell and halts the depolarization that was previously occurring, resulting in a maximum depolarization value. Potassium channels remain open, and are the cause for the membrane potential to start dropping (positive charge is leaving the cell). The sodium-potassium pump does not stop during this process. In fact, its continued function is essential for eventually restoring the resting membrane potential.
Example Question #1 : Cellular Signals And Communication
An action potential occurs in an axon that synapses at a muscle; this specific type of synapse is called a neuromuscular junction. During the action potential, the membrane potential of the axon sharply depolarizes as the signal moves towards the terminal. Upon reaching the synaptic terminal, neurotransmitters are released and interact with receptors on the muscle. Which of the following best summarizes the changes that occur in the post-synaptic muscle after a neurotransmission event?
Activation of receptors causes opening of ion channels on the muscle, and the muscle hyperpolarizes.
Activation of receptors causes opening of ion channels on the muscle, and the muscle depolarizes.
Activation of receptors depletes the muscle of intracellular calcium stores and the muscle depolarizes.
Activation of receptors causes closing of ion channels on the muscle, and the muscle hyperpolarizes.
Activation of receptors opens ion channels, but the membrane potential is unchanged.
Activation of receptors causes opening of ion channels on the muscle, and the muscle depolarizes.
Neurotransmitters will bind their respective receptors on the post-synaptic membrane, which is a muscle in this case. This binding causes changes to other proteins on that membrane, which results in an opening of ion channels. The muscle then depolarizes due to the influx of positively charged ions, and this can be measured as a positive change in the muscle membrane potential.
Example Question #272 : Gre Subject Test: Biochemistry, Cell, And Molecular Biology
What protein is responsible for maintaining the resting potential across a neuronal plasma membrane?
Ligand-gated sodium channels
Sodium-chlorine pump
Potassium-ATP transporter
Proton pump
Sodium-potassium pump
Sodium-potassium pump
The sodium-potassium pump maintains the resting membrane potential by utilizing 1 ATP to transport 2 potassium ions into the cell, and pumping 3 sodium ions out, which makes the inside of the cell negative relative to the outside of the cell.
Example Question #1 : Cellular Signals And Communication
Which phase of the action potential begins when there is a rapid and massive influx of sodium ions into the neuron?
Depolarization
Undershoot
Repolarization
Overshoot
Hyperpolarization
Depolarization
Depolarization, also known as the rising phase, occurs when the membrane potential goes from being negative to positive very quickly. This is instigated by the influx of ions through the open voltage gated channels, and the positive ions make the cell more positive relative to the resting potential.
All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources
