✵ chapter 11.7-11.9 : anatomy ✵

✵ Which of the following statements is true of both membrane potential responses shown in the graphs?

Both responses are examples of graded potentials. - Both responses are short-lived, relatively small changes in the membrane potential.

✵ Which of the following is false or incorrect?

A nerve impulse occurs if the excitatory and inhibitory effects are equal.

✵ Which of the following will occur when an excitatory postsynaptic potential (EPSP) is being generated on the dendritic membrane?

A single type of channel will open, permitting simultaneous flow of sodium and potassium.

✵ Subthreshold stimulus

An insufficient stimulus to reach an action potential.

✵ Threshold stimulus

Any stimulus at or above this level will result in action potential.

✵ The effect of acetylcholine can be stimulating or inhibiting. Which of the following gives the best explanation for why this is so?

Different post synaptic cells will have different receptors.

✵ Which description of synapses is NOT correct?

Direct signaling involves the activation of G Proteins. - Indirect signaling involves G Proteins. Direct signaling involves opening ion channels that affect the polarization of the membrane.

✵ T/F : Opening K+ or Cl- channels in a postsynaptic membrane would produce an inhibitory postsynaptic potential (IPSP).

True - Opening K+ or Cl- channels in a postsynaptic membrane, resulting in K+ efflux or Cl- influx, respectively, would induce hyperpolarization. As the membrane potential increases and is driven farther from the axon's threshold, the postsynaptic neuron becomes less and less likely to "fire," and larger depolarizing currents are required to induce an action potential (AP). Hyperpolarizing changes in potential are called inhibitory postsynaptic potentials (IPSPs).

✵ If a post synaptic cell is stimulated to threshold by temporal summation this implies that ________.

a presynaptic neuron is initiating frequent EPSP

✵ What ion is entering the axon terminal at A, and what effect does it have?

Ca2+, which then causes release of neurotransmitter from the axon terminal - Calcium ion channels open when the membrane is depolarized, and the inflow of Ca2+ leads to the release of neurotransmitters from synaptic vesicles.

✵ When a neurotransmitter like acetylcholine is acting in an excitatory manner which of the following is likely a result of the acetylcholine acting on the post synaptic cell?

Chemically gated sodium channels will open.

✵ Which of the following is an excitatory neurotransmitter secreted by motor neurons innervating skeletal muscle?

acetylcholine

✵ How would the receptors at C best be classified?

chemically gated - The receptors at C are affected by the binding of a chemical neurotransmitter.

✵ Which of the following neurotransmitters inhibits pain and is mimicked by morphine, heroin, and methadone?

endorphin

✵ By which method does the structure at B release neurotransmitter?

exocytosis - The influx of Ca2+ triggers the release of neurotransmitters stored in synaptic vesicles (B) by exocytosis.

✵ An inhibitory postsynaptic potential (IPSP) is associated with ________.

hyperpolarization

✵ When a neurotransmitter like GABA is acting in an inhibitory manner which of the following is likely a result of the GABA acting on the post synaptic cell?

hyperpolarization of the postsynaptic cell membrane

✵ Loss of function in the enzyme acetylcholinesterase would result in which of the following?

inability to destroy and remove acetylcholine from the synaptic cleft

✵ Which of the following is not a chemical class of neurotransmitters?

nucleic acid

✵ Which of the following stimuli caused the reaction in the graph on the left?

opening of gated Na+ channels - Opening of gated Na+ channels allows Na+ to diffuse into the neuron, causing an increase in the local membrane potential.

✵ Which of the following is expected to occur first if the membrane potential decrease shown in the graph on the left were to reach the threshold value indicated at ~ -55 mV?

opening of voltage-gated Na+ channels - The threshold value is the point at which voltage-sensitive Na+ channels open. This leads to the characteristic rapid depolarization phase of the action potential.

✵ The box labeled D illustrates three mechanisms by which the effects of a neurotransmitter may be terminated. Which of the following mechanisms is NOT included in the figure?

reuptake of the neurotransmitter by transport into the postsynaptic cell - Neurotransmitters are generally not transported into the postsynaptic cell upon which they exert their effects.

✵ Which of the following describes the excitatory postsynaptic potential?

short distance depolarization

If a postsynaptic neuron is stimulated to threshold by spatial summation this implies that ________.

the postsynaptic cells has many synapses with many presynaptic neurons

✵ Select the correct statement regarding chemical synapses.

the synaptic cleft uses the action potential to release a chemical signal to the post synaptic cell

✵ Temporal summation

Numerous nerve impulses arriving at a synapse at closely timed intervals exert a cumulative effect.

✵ Which of the following does NOT describe the process of summation?

One EPSP fails to bring the cell to threshold. - This statement is true, but summation considers the action of multiple synaptic potentials working on a cell simultaneously.

✵ Spatial summation

Stimulation of a postsynaptic neuron by many terminals at the same time.

✵ Which of the following statements most accurately describes the effects caused by binding of the neurotransmitter (green dots) to the structure labeled C?

The membrane potential of the postsynaptic membrane changes. - of the neurotransmitter to the receptor at C causes the opening of receptor-associated ion channels. Depending on the particular types of channels that open, diffusion of certain ions (typically Na+, K+, or Clâˆ') will cause a depolarizing or hyperpolarizing effect on the postsynaptic membrane.

✵ Suppose that both stimuli seen in these graphs happened equally at the same time on a postsynaptic membrane as a result of two different synapses. Which of the following best describes the result?

There would be little or no graded potential. - In order for a graded potential to occur, there must be an overall change in membrane potential. Due to spatial summation, these stimuli would cancel each other.

✵ T/F : A stimulus traveling toward a synapse appears to open calcium ion channels at the presynaptic end, which in turn promotes fusion of synaptic vesicles to the axonal membrane.

True