Adaptive Eating: Sensory Deficits

Blog:  Blog: Adaptive Eating Ability: Sensory Deficits

This will be a two part topic.  In this blog I will provide an overview of how the sensory system works and in part two I will look at how sensation contributes to the activity of self feeding.  Sensation encompasses the special senses ie vision, taste, smell and hearing and somatosensation which is touch, pressure, pain, temperature, joint position and muscle length and tension.  We will be focusing on somatosensation although vision is also critical. The functional unit of all sensation is the nerve cell ie. Neuron.

The parts of the neuron are the dendrites, the cell body and the axon. Dendrites receive impulse from other neurons and axons transmit impulses to other nerves.  This is typically  a one way street from the periphery … ie the hand up to the spinal cord and then up to the brain.  For sensation to work the street has to be open and clear.  For sensation to be perceived consciously the impulse must reach the sensory cortex in the brain.

Nerve conduction is not the same as electricity but it can be thought of in the same way.  So let’s follow what happens in a typical sensory event to understand better how sensory deficits and self feeding are related. In this example a person will be grasping a spoon in preparation for performing an eating activity. The spoon contact with the finger will stimulate a nerve that is receptive to touch/pressure.  Pressure is a mechanical entity so it must be changed to a neural transmission impulse.  A nerve that first picks up the sensation of touching the spoon is termed a transducer.  It changes the mechanical energy into a neural signal.  That nerve will travel all the way to the spinal cord and the neural signal will then make it’s way up to the brain and the person will be aware of touching the spoon.  Let’s imagine what would happen if you didn’t have that wonderful nerve/nerves.  Your vision would tell you that you are holding a spoon but you would have no feeling of holding the spoon! It is clear that when evaluating Adaptive Eating Ability that sensory deficits should be considered.

This has obvious implications for the ability to manipulate the spoon. In addition to touch/pressure there are also pain, joint position and muscle length and tension to consider.  Being able to sense pain is very important for protection of body structures.  For example, skin may be damaged if something hot or sharp is held without awareness and a protective response. If you are a therapist working with someone with diminished sensation you know that one of the first things you should do is warn them about the dangers of tissue damage and provide strategies to prevent this. What about joint position and muscle length and tension? 

Having these inputs is also very important for efficient muscle movement and function.  Joint position works in a similar way to touch and pressure.  There are nerve endings located in our joints that are transducers for joint movement. This information is also conducted to the spinal cord and then to the cortex.  So we are somewhat consciously aware of our joint positions.  But there is another structure that is much smarter than the cortex in terms of knowledge about joint position and muscle length and tension. Please check back for Part 2 where we will discuss the Cerebellum and talk about utensil manipulation and plate to mouth movement in self feeding. Thanks for visiting and you are invited to contact us at anytime.