Nervous System

classes of neurons

*sensory neurons* (afferent neurons) - *motor neurons* (efferent neurons) *interneurons* (association neurons) - local interneurons: short axons and form circuits with nearby neurons to analyze small pieces of information - relay interneurons: long axons and connect circuits of neurons in one region of the brain with those in other regions.

neural cell

- Neurons (nerve cells) - process and transmit information - Glial Cells (neuroglia or glia) - support neurons Most neural cells share some structural features 1. the soma (or the cell body) contains the nucleus and most of the organelles 2. processes (long, thin extensions) coming out of the soma. Vary in number, length, thickness, degree of branching, and terminal structures.

structural types of neurons

- Unipolar neurons: feature a single primary projection that functions as both axon and dendrites. the most common invertebrate neuron. - Bipolar neurons have one axon and one dendrite extending from the soma. usually inhabit sensory organs like the eye and nose. - Multipolar neurons contain one axon and many dendrites, the most common neuron in the vertebrate nervous system. - Pseudounipolar neurons: a single axon emerges from the cell body and heads in two opposite directions, one end heading for the skin, joints and muscle and the other end traveling to the spinal cord. Responsible for the sense of touch, pain and pressure.

basic functions of a neuron

1. Receive signals (or information). 2. Integrate incoming signals (to determine whether or not the information should be passed along). 3. Communicate signals to target cells (other neurons or muscles or glands).

axon

A long, slender projection of a neuron, that typically conducts electrical impulses away from the neuron's cell body. The function of the axon is to transmit information to different neurons, muscles and glands. Axons make contact with other cells—usually other neurons but sometimes muscle or gland cells—at junctions called synapses.

neurite

A neurite refers to any projection from the cell body of a neuron. This projection can be either an axon or a dendrite. The term is frequently used when speaking of immature or developing neurons, especially of cells in culture, because it can be difficult to tell axons from dendrites before differentiation is complete.

synapses

Neuron-to-neuron connections that are made onto the dendrites and cell bodies of other neurons. The synaptic connections between neurons and skeletal muscle cells are generally called neuromuscular junctions, and the connections between neurons and smooth muscle cells or glands are known as neuroeffector junctions.

dendrite

branched projections of a neuron that conduct the impulses received from other neural cells to the cell body.