In this lab we will explore the anatomy & physiology used for interpreting the environment both within and outside our bodies. The essential component is neurons, the major functional cells in nervous tissue. In many sensory organs, additional cells and tissues will contribute to the process of signal transduction.
Signal transduction is the process of a receptor detecting specific forms of matter or energy, and activating chemical and electrical changes in neurons. The neurons can then communicate with other neurons in the nervous system via synapses and networks to coordinate responses.
Receptor is a term used for the part of a sensory organ that detects the signal. ‘Receptor’ can refer to specific protein molecules which first interact with the matter or energy, or it can refer to the cell(s) that contains those proteins, or an assembly of cells in the larger organ.
Sensory Organs The major sensory organs can be grouped based on various characteristics, i.e. what type of matter or energy they detect, and subsequently ‘transduce’ to produce our perceptions (e.g. vision, taste). Eventually there are electrical and chemical signals within our brains. Specific organs include:
|Sensory Organ (major receptor)||Matter/Energy detected by receptor||General anatomy & physiology||Perceived sensation|
|Eye (retina)||Visible light (electromagnetic radiation)||Multilayered nervous sheet within the eye, with muscles and lenses for focusing||Vision|
|Physical force (sound)||Flexible ‘hair’ cells that release signal molecules based on waves in fluid started by motion of the eardrum.||Hearing|
|Physical force||Flexible ‘hair’ cells that release signal molecules based on waves in fluid started by motion of the head.||Movement|
|Nose(olfactory epithelium)||Chemicals ('odorants')||A layer of neurons at the top of the nasal cavity||Smell ('olfaction')|
|Tongue (taste buds)||Chemicals||Clusters of epithelial cells that release signals to neurons if specific chemicals are present (e.g. sodium ions)||Taste ('gustation')|
|Physical force||Various neurons that respond to physical movements||Touch|
|Heat transfer||Specific neurons that respond to increases in temperature||Hot|
|Heat transfer||Specific neurons that respond to decreases in temperature||Cold|
|Muscles & Tendons||Physical force||Neurons respond to stretch and contraction of muscles & tendons||Body position (proprioception)|
|Most of the body||Various signals||Neurons respond to physical force, temperature & specific chemicals to warn of (potential) damage.||Pain ('nociception')|
In order to investigate and understand sensory processes, we will investigate their anatomical structures (at macro- and microscopic levels) and physiological functions. An important distinction to consider is how humans can functionally separate Sensation (activation of the different receptors) as compared to Perception (the conscious awareness of the sensation). This distinction reveals how sensory deficits can result from damage in brain regions, even though the sensory organ is intact. Also, we may have perceptions that are only present in the brain, even though the sensory organs are silent.