Neuronal Anatomy-exam 1

What is the Input Zone? (1)

Dendrites & soma receive neurotransmitters from other neurons and convert them into graded local electrical signals. (EPSPs/IPSPs)

What is the Integration Zone? (2)

Axon hillock integrates excitatory (EPSP) and inhibitory (IPSP) signals. If threshold is reached, an action potential starts.

What is the Conduction Zone? (3)

The axon conducts action potentials away from the cell body toward their destination.

What is the Output Zone?

Axon terminals/synaptic boutons release neurotransmitters into the synaptic cleft to signal the next cell.

What defines a Multipolar Neuron?

One axon + many dendrites. Most common CNS type; examples: motor neurons and cerebral cortex neurons.

What defines a Bipolar Neuron?

One axon + one dendrite from opposite sides of the cell body. Found in specialized sensory systems, such as the retina and auditory system.

What defines a Unipolar (Pseudounipolar) Neuron?

One process exits the cell body and splits into sensory-receptor and spinal-cord branches. Typical of touch/pain neurons, such as dorsal root ganglion cells.

What is the Myelin Sheath?

A fatty insulating layer around the axon that speeds nerve transmission and prevents electrical signal loss.

What are the Nodes of Ranvier?

Uninsulated gaps in myelin with concentrated voltage-gated channels. They let action potentials jump node-to-node via saltatory conduction.

What do Oligodendrocytes do?

Form myelin in the CNS. One oligodendrocyte can myelinate segments of multiple axons.

What do Schwann Cells do?

Form myelin in the PNS. Each Schwann cell wraps around only one axon segment.

How are neurons structurally classified?

By the number of projections/processes extending from the cell body: multipolar, bipolar, or unipolar.

What is the difference between the CNS and PNS?

CNS: Brain + spinal cord; processes information; myelin = oligodendrocytes.
PNS: Cranial + spinal nerves outside CNS; carries signals to/from CNS; myelin = Schwann cells.