K12 - Communication

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Biological communication occurs at many levels, from one cell communication with its neighbour in a tissue (paracrine), to signals released into the blood from one cell to signal to another cell or tissue (endocrine or hormone signaling). The signalling that occurs in the brain, spinal cord and other nervous tissues involves electrical (action potentials) signaling.

This page will introduce development of signaling in our special sensory nervous systems: the eyes for vision and the ears for hearing. Both systems convert signals in one medium (light or sound) into an electrical signal that our brain can understand.

K12 Links: Start Here | Week 1 | Week 2 | Week 3 | Week 4 | Week 5 to 8 | Arms and Legs | Heart | Fetus | Brain Growth | Eyes and Ears | Animal Development Times | Humans and Animal Embryology | Comparative Embryology | Thalidomide

Sound - Hearing

Hearing cartoon.jpg

This cartoon shows the adult "ear" with the 3 main divisions (outer, middle, inner).

Outer Ear
  • directs sound waves into the ear canal.
Middle Ear
  • converts sound waves in to mechanical movements or vibrations.
Inner Ear
  • converts mechanical movements into electrical signals.

Hearing Before Birth

Can a baby "hear" like we do before it is born?

External Ear Growth before Birth

What's so important about the outer ear?

Month 3 - Fetus Month 4 - Fetus Month 5 - Fetus
Streeter1922-plate04.jpg Streeter1922-plate05.jpg Streeter1922-plate06.jpg

Testing a Baby's Hearing

Newborn hearing test

If a baby cannot hear you talk they cannot easily learn to speak!

Much of your first learning comes from being able to copy sounds that you hear. The parents or doctors would only know that a baby could not hear if they were not developing speech correctly or meeting other developmental milestones.

  • In the past - the tests were very simple, like turning their head to a bell or sound. They could also not be easily carried out on newborn infants.
  • Today - the tests are computer-based, requiring no infant response and can be easily carried out on newborn infants.

Light - Vision

Eye and retina cartoon.jpg

This cartoon[1] shows the eyeball (left), a cartoon of the retinal cell organisation (middle) and an actual slice of the human retina.

The Eye
  • This is a cut through the eyeball showing the eye anatomy.
  • The retina forms the inner lining of the most of the back part of the eye.
  • The retina is the structure that converts light into electrical signals.
Retinal Cell Organization

These are the names of the cells and neurones required to convert light into electrical signals. (detect, process and carry)

  • Carry the signal to the brain - retinal ganglion cells (G, GCL) take the signals from the eye to the brain in the optic nerve.
  • Process the signals from the light detectors - Müller cell M, amacrine cell A, bipolar cell B, horizontal cell H process the signals from rods and cones.
  • Detect light - rod cells R and cone cells C, detect light and convert light into an electrical signal (action potential).

Notice that light has to pass through all the other cell layers to the detection cell layer.

Glossary Links

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Cite this page: Hill, M.A. (2020, September 23) Embryology K12 - Communication. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_-_Communication

What Links Here?
© Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
  1. <pubmed>20855501</pubmed>| PMC3101587 | JCB