Question

nerve impulses
the synapse
circle the correct answer.

1. nerve impulses (do or do not) continually race along every nerve cell’s surface.
2. when a stimulus acts on a neuron, it (increases or decreases) the permeability of the stimulated point of its membrane to sodium ions.
3. an inward movement of positive ions leaves (a lack or an excess) of negative ions outside.
4. the plasma membrane of the (presynaptic or postsynaptic) neuron makes up a portion of the synapse.
5. a synaptic knob is a tiny bulge at the end of the (presynaptic or postsynaptic) neuron’s axon.
6. acetylcholine is an example of a (neurotransmitter or protein molecule receptor).
7. neurotransmitters are chemicals that allow neurons to (communicate or reproduce) with one another.
8. neurotransmitters are distributed (randomly or specifically) into groups of neurons.
9. catecholamines may play a role in (sleep or reproduction).
10. endorphins and enkephalins are neurotransmitters that inhibit conduction of (fear or pain) impulses.

if you have had difficulty with this section, review pages 174-176.

Explanation:

These questions are about nerve impulses and synapses, which are topics in Biology (a subfield of Natural Science). Let's answer each:

1. Nerve impulses do not continually race along every nerve cell’s surface (they occur when stimulated).
2. A stimulus increases the permeability of the neuron's membrane to sodium ions (to initiate action potential).
3. Inward positive ions leave an excess of negative ions outside (since positive ions move in, negative are left outside relatively).
4. The postsynaptic neuron's plasma membrane is part of the synapse (synapse has presynaptic knob, synaptic cleft, and postsynaptic membrane).
5. Synaptic knob is at the end of presynaptic neuron’s axon (releases neurotransmitters from presynaptic side).
6. Acetylcholine is a neurotransmitter (transmits signals across synapse).
7. Neurotransmitters allow neurons to communicate (not reproduce, they facilitate signal transfer).
8. Neurotransmitters are distributed specifically (target specific neuron groups).
9. Catecholamines play a role in sleep (involved in mood, sleep - wake cycles).
10. Endorphins/enkephalins inhibit pain impulses (natural painkillers, reduce pain perception).

Answer:

1. do not
2. increases
3. an excess
4. postsynaptic
5. presynaptic
6. neurotransmitter
7. communicate
8. specifically
9. sleep
10. pain