Physiological Psychology Chapter 2

1.              How did Sherrington discover that neurons communicated with each other via a synapse?

Sherrington discovered a delay in reflexes that could not be accounted by the time it took for an action potential signal to travel along an axon. He concluded that there had to be something impeding the speed: a synapse.

2.              Define an EPSP and IPSP.  How do each of these affect the cell’s ability to produce an action potential?

EPSP: excitatory postsynaptic potential is when sodium ions flow into the neuron from a presynaptic neuron exciting a possible action potential depolarizing the cell. If the sodium ions are enough, then the cell’s action potential will exceed the threshold necessary for action, then a signal will be sent to the next neuron.

IPSP: inhibitory postsynaptic potential is when synaptic input selectively opens the gates for potassium ions to leave the cell or for chloride ions to enter the cell. When this happens, the cell becomes hyperpolarized to be negative which decreases the probability of action potential.

3.              Define/describe both spatial summation and temporal summation.

Temporal summation: the build-up of separate stimuli attacking one neuron to produce a response.

Spatial summation: the build-up of separate stimuli from multiple neurons to produce a response.

4.              List the major events, in sequence, which occur at a synapse.

1.     The neuoron synthesizes chemicals that serve neurotransmitters, and neuropeptides in the cell body.

2.     Action potentials travel down the axon, and that action potential then enables calcium to enter the cell which releases neurotransmitters into the synaptic cleft.

3.     The released molecules then attach to receptors and alter the activity of the postsynaptic neuron.

4.     Neurotransmitter molecules separate from their receptors.

5.     Neurotransmitter molecules may go through a process of reuptake where they are recycled or they may diffuse away.

6.     Postsynaptic cells send reverse messages to control the further release of neurotransmitter by presynaptic cells.

5.              Contrast ionotropic and metabotropic synaptic mechanisms.  Give an example of a behavior that would rely on each mechanism.

Ionotropic synaptic mechanisms compared to metabotropic synaptic mechanisms are much faster, and the process itself is less complex because it requires a neurotransmitter to attach to the channel itself whereas the metabotropic mechanism relies on a series of metabolic events to open the channels. The metabotropic mechanism lasts much longer and the synapse uses many different neurotransmitter whereas the ionotropic effects are shorter and primarily uses either glutamate or GABA. The metabotropic effects affects much of the cell whereas the ionotropic effect is limited to a specific membrane of the cell.

Smelling relies metabotropic synaptic mechanisms as the instant up to date information is less important. Vision generally relies upon ionotropic synapses.

6.              What is a G-protein?  What is the “first messenger”?  What is one common second messenger?

A G-protein is often known as the “second messenger” that sends messages throughout the inside of the cell by way of an metabotropic effect. The “first messenger” is the neurotransmitter that brings messages from outside the cell. A common second messenger is  cyclic adenosine monophosphate (cyclic AMP).

7.              List 3 differences between a neuropeptide (neuromodulator) and a neurotransmitter.

1.     Neuropeptides do not only release from the axon terminal, but from the dendrites, the cell body, and the sides of the axon.

2.     Require repeated stimulation and not just one action potential.

3.     Affect more than the adjacent cell but spread widely throughout their region of the brain.

8.              Discuss how drugs such as DOPA, cocaine, antidepressants, and antipsychotic drugs affect the dopamine synapse.

Some drugs (cocaine and antidepressants) affect the reuptake process by blocking reuptake. This temporarily prolongs the effects of the neurotransmitters, but it also means that afterwards, COMT breaks down the neurotransmitter in the synapse faster than it can be replaced, leaving the person in withdrawal. DOPA and antipsychotic drugs often work to replenish dopamine stores.

9.              How do hormones differ from neurotransmitters?

Hormones can send messages to the whole body. It is conveyed by the blood cell to anyone tuned into that hormones station. In contrast to neurotransmitter sending message from cell to cell.