K12 - Communication
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.
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Sound - Hearing
This cartoon shows the adult "ear" with the 3 main divisions (outer, middle, inner).
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|
The position and shape of the external ear can tell you about how the head grows before birth!
Testing a Baby's Hearing
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.
|About Newborn Hearing Tests|
Whats an Automated Auditory Brainstem Response?
(AABR) uses a stimulus which is delivered through earphones and detected by scalp electrodes. The test takes between 8 to 20 minutes and has a sensitivity 96-99%. The basis of a neonatal hearing test that uses a trigger stimulus delivered through earphones and subsequent brain electrical activity then detected by scalp electrodes. Then by computer analysis, averaging all the electrical activity following the trigger, peaks emerge reflecting signal passage activity through brain stem nuclei in the hearing central neural pathway. The infant test takes between 8 to 20 minutes, has a sensitivity 96-99%, and unlike other childhood auditory testing does not require a subject response. An alternative and simple test (pass/refer) used at a later stage is otoacoustic emission testing.
Light - Vision
This cartoon shows the eyeball (left), a cartoon of the retinal cell organisation (middle) and an actual slice of the human retina.
||Retinal Cell Organization
These are the names of the cells and neurones required to convert light into electrical signals. (detect, process and carry)
Notice that light has to pass through all the other cell layers to the detection cell layer.
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Cite this page: Hill, M.A. (2020, September 26) Embryology K12 - Communication. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/K12_-_Communication
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G