Question

1. The chemical reasons for the value of the resting membrane potential for a typical
neuron (-70mV) and the electrochemical forces that act on sodium and potassium. Know the
role of the Na+/K+ pump. What is a K+ leak channel?

2. Describe the events at a synapse during neurotransmission including how a neurotransmitter
is released from the presynaptic cell (calcium triggers exocytosis), and what determines the
effect that a neurotransmitter will have on the postsynaptic cell.

3. A function of: serotonin, norepinepherine, dopamine, glutamate, and
GABA. Understand the different classes of molecules that can function as neurotransmitters
(chemicals, polypeptides, gasses, etc).

Answer 1

1. The resting membrane potential of a neuron is maintained with the help of the Na+/K+ pump. The Na+/K+ pump pumps in two potassium ions for three sodium ions that are pumped out. This generates a higher concentration of cations outside the cell than the inside, leading to the development of the resting membrane potential. The membrane also comprises of K+ and Na+ leak channels that keep fluidity in the movement of cations while the potential is maintained. As there are more K+ leak channels than Na+ leak channels in the membrane, it is more permeable to K+ ion leaks.

2. In a chemical synapse, the electrical signal in the presynaptic neuron activates the voltage-gated calcium channels with the production of an influx of calcium ions due to the action potential of the presynaptic neuron. The calcium ions then bind to synaptotagmin proteins present in the synaptic vesicle membranes, which leads to the fusion of the vesicles and the presynaptic membrane. The activity of the the voltage-gated calcium channels leads to the release of a neurotrasmitter (glutamate, dopamine, etc) which bind to the receptors present on the postsynaptic neuron.

3. Their functions are as follows -

• Serotonin: Regulates appetite, digestions, mood, sleep, muscular contractions and body temperature.
• Norepinephrine: Functions as a stress hormone.
• Dopamine: Regulates motor control, desires, motivation and reinforcement.
• Glutamate: Important for memory and learning.
• GABA: inhibition and regulation of neural activity