6 topics with concise breakdowns: definitions, key facts, and class questions.
The nervous system communicates in the language of electrical impulses and chemical signals. In this section, we examine how information travels through the body: from the propagation of an action potential to its transmission to the next cell.
You will study the laws of excitation conduction along nerve fibers and their classification (including types A, B, and C). You will examine in detail the structure of the synapse, key neurotransmitters, and the mechanism of synaptic transmission itself. Special attention is paid to inhibition in the CNS—an active process without which the adequate functioning of the nervous system would be impossible.
In seminars and exams, instructors most often ask you to draw a diagram of a chemical synapse, explain the principle of saltatory conduction in myelinated fibers, and compare the mechanisms of presynaptic and postsynaptic inhibition. Focus on these nuances—they will become a solid foundation for future pharmacology and neurology.
No, this is an exclusively active biological process that purposefully prevents the development or continuation of excitation.
Why is saltatory conduction faster than continuous conduction?
In myelinated fibers, local currents do not pass through every micrometer of the membrane sequentially. They "leap" over the myelin-insulated segments, closing only at the nodes of Ranvier and spanning 3–5 nodes at once, which enormously saves time.
Why does the compound action potential of a nerve change its shape far from the stimulation site?
A nerve consists of various fiber groups. Because they differ in thickness and degree of myelination, excitation is conducted at varying speeds and arrives at a distant point asynchronously, making the potential waveform complex.
Can a single neuron synthesize multiple different neurotransmitters?
No, according to the classical Dale's principle, each nerve cell synthesizes only one primary neurotransmitter. However, additional substances—cotransmitters—may be released along with it.
Why is excitation in a synapse transmitted in only one direction?
Unidirectional conduction is due to structural features: the neurotransmitter is released only from the presynaptic terminal, and receptors capable of responding to it are located exclusively on the postsynaptic membrane.
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