PSY290 Lecture 4: Microanatomy & Neural Transmission

What are the 3 Principal Types that neurons are classified into?

Multipolar neurons

• The most abundant neuron in the CNS

• Have one central axon extending from the cell body. On the top many dendrites extending from the cell body itself

• Multipolar because it has many extensions extending from the cell body

• When look at the brain, majority of the neurons (75-85%) are multipolar in nature

Bipolar Neurons

• There are 2 opposite ends: has one extension from either end of the neuron

• One dendrite at top & other axon at bottom

Unipolar

• Only have one extension from a cell body

• One core branch that extends off that extension, forming dendrites on one side & axons on other side

What are Golgi-Stained Pyramidal & Stellate Neurons?

Pyramidal

• Triangular shaped body. Soma looks like a pyramid.

• Have a few distinct branches extending from it

• Has one large trunk. Other branches on the side

• These cortical pyramidal cells are the most abundant kind of cell in mammalian cortical structures

• Important role in advanced cognitive function in neural processing

• Main source of excitatory activity in the brain (generated AP)

Stellate neurons

• See one thicker branch & a number of thinner

• Thicker branch is the axon & thinner is the dendrites

• Less abundant than pyramidal in CNS

• Inhibitory activity in brain (sculpt AP)

Bipolar Neurons

• Multipolar neurons are most abundant neuron in the brain, they are found everywhere in the CNS. Bipolar & unipolar neurons are more focused or isolated to where we see them

• Bipolar neurons often found in sensory system relays to take the transduction of electrical signal from the sensory neuron like a rod or a cone and conduct that activity & transmit it to the brain

• Olfactory neurons are classified as bipolar projecting dendrites which project to the mucus & axons to the olfactory bulb

  • Bipolar neuron where its dendrites project right through the mucus of our nose, forming dendritic nobes where olfactor cilia exists (the fingers or extensions that detect odour molecules to detect something we smell)

Unipolar Neurons

• The dorsal root ganglion (sensory neuron entering into the spinal cord) is an example of a unipolar neuron

• Unipolar neurons have one cell body with a single extension from it and then two branches off of that extension

  • One has to be axon and a dendrite, sending information to and from different areas