Chapter 13 - Synapses

Question 1

A specialized site of contact of one neuron with another neuron (or effector) is known as a

A. neuron.

B. receptor–neurotransmitter complex.

C. membrane.

D. synapse.

Answer 1

D. synapse.

Question 2

Which of the following transmits information the fastest?

A. Ionotropic EPSP

B. Metabotropic IPSP

C. Electrical synapse

D. Fast EPSP

Answer 2

C. Electrical synapse

Question 3

In an electrical synapse, the main structure responsible for transmission of an impulse from one cell to the next is ___________.

Answer 3

the gap junction

Question 4

Ultimately, it is the _______ that determines whether the postsynaptic membrane produces an inhibitory postsynaptic potential (IPSP) or an excitatory postsynaptic potential (EPSP).

A. frequency of action potentials

B. movement of ions

C. neurotransmitter

D. receptor’s affinity for the neurotransmitter

Answer 4

B. movement of ions

Question 5

Two sets of axons carry stimuli near the axonal hillock. One set produces an IPSP and the other set produces an EPSP. If both sets produce action potentials at the same time, what is the likely effect at the axonal hillock?

A. There will be a hyperpolarization.

B. There will be a depolarization.

C. An action potential will be produced.

D. The potentials created will cancel each other out.

Answer 5

D. The potentials created will cancel each other out.

Question 6

The _______ is the flow of ions through all the channels that open in response to release of a neurotransmitter.

A. postsynaptic potential

B. synaptic current

C. action potential

D. voltage

Answer 6

B. synaptic current

Question 7

Once acetylcholine is released into the synapse it

A. is actively pumped back into the presynaptic neuron.

B. crosses the postsynaptic membrane and then is broken down inside that cell.

C. is inactivated by calcium.

D. is broken down by acetylcholinesterase.

Answer 7

D. is broken down by acetylcholinesterase.

Question 8

Which neurotransmitter elicits responses of both ionotropic and metabotropic receptors?

A. Acetylcholine

B. Dopamine

C. Glutamate

D. Both acetylcholine and glutamate

Answer 8

D. Both acetylcholine and glutamate

Question 9

What are the steps in an action potential?

Answer 9

1. Resting Membrane Potential
   The membrane is most permeable to K+ at rest, there are leakage channels present and always open.
2. Rising Phase
   The voltage-gated Na+ channels open, and high permeability to Na+ ions dominates, driving the membrane potential to E(Na).
3. Falling Phase
   The Na+ channels inactivated shortly after they open, the voltage-gated K+ channels open, driving the Vm to E(K).
4. Recovery
   The K+ channels remain open for a short time after the action potential, Na+ channels recover from their inactivation and open when depolarization occurs.

Question 10

TRUE or FALSE? Synaptic transmission can be fast and inhibitory and exciatory.

Answer 10

TRUE

Question 11

What are the two kinds of synapses?

Answer 11

1. Electrical
   Low resistance pathways that allow currents to flow DIRECTLY between neurons, changing the membrane potential.
2. Chemical
   Currents escape between neurons and do not enter postsynaptic cell, a neurotransmitter carries signal across the synaptic cleft.

Question 12

What is the difference between Iontropic receptor and Metabotropic receptor?

Answer 12

Iontropic: Fast excitation, inhibitory. Directly alters the permeability to ions

Metabotropic: Slow excitation, inhibitory. Triggers signaling cascade to secondary messengers.

Question 13

What are advantages to chemical synapses?

Answer 13

1. Amplify current flow
2. Either be excitatory or inhibitory
3. One-way, presynaptic neuron excites or inhibits the postsynaptic cell
4. More modifiable, plasticity is important for development in the nervous system.

Question 14

Differences between action potential and synaptic potential.

Answer 14

Action potential

• all or nothing
• same amplitude and duration as it travels through the axon
• travels long distances

Synaptic potential

• considerably smaller
• hyperpolarize with IPSP or depolarize with EPSP
• travels short distances

Question 15

How do you measure quanta release?

Answer 15

Quanta
-neurotransmitters are released in multimolecular vesicles, about 5000 in each quantum

Measure through vesicle exocytosis.