Tag Archives: Action potential

ACTION POTENTIAL & NERVES-TUTORIAL

Image via Wikipedia

Nerves Have Axons, Dendrites and Cell Bodies

Nerve cells are designed to respond to stimuli and transmit information over long distances
Nerve cell has 3 parts:
- Cell body:
  - Has single nucleus
  - Has most of nerve cell metabolism, especially protein synthesis
  - Proteins made in cell body must be delivered to other parts of nerve
- Axon:
  - Long cylinder, designed to transmit an electrical impulse
  - Can be several meters long in vertebrates (giraffe axons go from head to tip of spine)
  - Has axonal transport system for delivering proteins to ends of cell

Chemical Transmitters Carry the Signal Across Synapses & Neuromuscular Junctions

A contact between 2 nerves is called a synapse
At the synapse there is a break in electrical transmission (the action potential cannot cross)- instead chemicals are released that carry the signal to the next nerve
- The release of chemical transmitters at nerve endings was first shown by Otto Loewi in the frog heart
A neuromuscular junction (NMJ) is a contact between a nerve and a muscle- it is like a synapse, the action potential stops and the signal is carried by a chemical

This is a preview of SYNAPSES AND NEUROMUSCULAR JUNCTIONS OF NEURONS-TUTORIAL. Read the full post (1266 words, 3 images, estimated 5:04 mins reading time)

Muscles Are Organized Into Motor Units

When a single nerve enters a muscle it splits and makes neuromuscular junctions (NMJs) with several muscle cells
A nerve and the muscle cells it makes NMJs with is called a motor unit
When the nerve fires the whole motor unit is stimulated and the muscle cells contract together
Muscles with large motor units have coarse movements
Muscles with small motor units give fine, graded movements
This is a small motor unit with only 3 muscle fibersTwo Basic Types of Contraction Are Isotonic and Isometric