Nervous systems have two unique types of cells: neurons and glia. There are many types of neurons, but they can all generate and conduct electric signals, and most generate APs. A neuron has four regions: cell body, dendrites, axon, and axon terminals. Neurons communicate with target cells at synapses, which can be chemical or electrical. Although glia do not generate APs, they have a variety of functions, including contributing to the blood–
learning outcomes
You should be able to:
Describe the parts of a neuron and explain their functions.
Explain how the functions of axons and dendrites make it possible to communicate information across the synapse.
Describe the different functions of glial cells.
Draw two neurons, including a synapse between them, and label all of the parts. At a chemical synapse, how does a signal from one neuron cross the synaptic space to another neuron?
Explain how a neuron integrates information received from several other neurons.
A neuron can receive both excitatory and inhibitory input at multiple synapses located throughout its dendrites and on the cell body. Summation of inputs determines whether the postsynaptic neuron becomes sufficiently depolarized to initiate an action potential.
Explain how astrocytes modulate synaptic activity.
Astrocytes can take up neurotransmitters that have been released into the synapse and thereby control the postsynaptic response. Astrocytes can also directly release neurotransmitters that bind to receptors to affect the excitability of a neuron.
The one feature common to neurons is that they process information in the form of changes in the electric potential across their cell membranes. In the next section we will focus on how electric signals are generated and transmitted by neurons.