Axon vs Dendrite: Neuroscience Knockout

Can’t get enough Versus competitions? Can’t get enough neuroscience? Don’t worry, we’re here with a head-to-head battle that will satisfy your cravings for both!

Let’s take a closer look at a couple important structures that help neurons do their jobs!

Axon

The axon is a long projection from a neuron’s body, and is typically quite thin – thus making it also particularly hard to trace! Axons are messengers, transmitting information to neurons, muscles, and glands. Bundles of axons are called nerves, and are the primary transmission lines of the nervous system.

Distinguishing features of axons:

  • Generally consistent in shape and radius throughout (may be thicker near the cell body)
  • Can be very long – (The longest axons in the human body run from the base of the spinal cord to the big toe of each foot!)
  • Transmits a signal
  • 1 per customer (but a single axon can have many branches)

Most axons carry action potentials – electrochemical impulses that begin at the cell body and travel along the axon, terminating at points where the axon makes a synaptic connection with its target cell. Action potentials are “all-or-nothing” signals, meaning they travel from one end of the axon to the other without any reduction in size.

There is an exception to this rule however – some types of neurons with short axons carry graded electrochemical signals with variable amplitude.

The synaptic process follows these steps (often in less than a 1000th of a second!):

  1. Calcium ion channels in the axon’s membrane open
  2. Calcium ions flow across the membrane
  3. The increasing calcium concentration signals synaptic vesicles to fuse with the axon’s membrane and empty neurotransmitter chemicals
  4. The neurotransmitter is released from the presynaptic neuron
  5. The neurotransmitter binds to receptors activated by the neurotransmitter chemical
  6. Depending on the activated receptors, the target cell can be excited, inhibited, or have an altered metabolism

One final thing you may know about the axon is that it sometimes is blanketed in a myelin sheath, a fatty substance that protects the axon and increases the speed of signal transmission.  If you were lucky you may have come across myelin sheath in our datasets, and have had the conundrum over whether to include it in your trace or not (we’ve collectively decided not to trace it for consistency).

Dendrite

The word “dendrite” is derived from the Greek for “tree” and it’s no wonder why! The branches of a neuron do often have an uncanny resemblance to the branches of a tree! Lots of dendrite related phrases also relate back to the tree – “dendritic branching,” “dendritic arbor.”

Dendrites form synapses with the axons of other cells. At these junctions they receive electrochemical signals, which they send down to their cell’s soma. If these electrical impulses are large enough, they will generate an action potential, which will be transmitted down the axon.

Distinguishing features of dendrites:

  • Inconsistent shape/radius
  • Restricted to a smaller area surrounding the cell body
  • Receive signals
  • The more the merrier

There are three main types of neurons, which are at least partially defined by their dendritic structures. Multipolar neurons have one axon and many dendritic trees. Bipolar neurons have one axon and one dendritic tree at opposing ends of the soma. Unipolar neurons have a stalk that protrudes from the cell body and separates into two branches – one for the dendrites and one for the axon terminals.

Dendrites appear to be capable of plasticity during all stages of life in animals, including adulthood. During adulthood, extrinsic signals (external stimuli rather than intrinsic programming from the cell’s genome) become highly influential and cause significant changes to the dendritic structure.

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So whether you’re an Axonal Enthusiast or a Dendritic Defender, it’s your time to shine! Pick your team and let a very close to home VS commence! The neuron battle begins at 11:00 AM ET on 8/9 and goes for 48 hours.

Bonuses:

  • Starting Lineup – top 3 players on each team, who earn 75% of their score in bonus points
  • All Other Players – earn 50% of their score in bonus points
  • Winning Team – 20,000 additional points
  • Each Team’s MVP – 5,000 additional points

The winning team is determined by average points per player, with 2x weight given to Starting Lineup players. To qualify for any of the above bonuses or affect the team score, players must earn a minimum baseline of 2,000 points.

Art by Elena Daly