Answers

Questions

1. Identify the parts of the human respiratory system represented by this model.
   (Straw = windpipe; balloon = lung; balloon skin = diaphragm, cup = rib cage of lung cavity)
2. How is this model fundamentally different from the human system?
   (Humans have two lungs that are operated by the action of the diaphragm, rather than the one lung modeled here.)
3. What happens to the balloon inside the cup when the rubber skin wrapped around the base of the cup is pulled down? Why
   (The balloon inflates. The volume of the artificial lung is increased, so the pressure of the air inside is decreased. Outside air pressure pushes air into the cup to equalize the pressure, inflating the balloon.)
   
4. What happens when the rubber skin is pushed upwards? Why?
   (The balloon deflates. The volume of the artificial lung is decreased, so the pressure on the air inside is increased. Air is released from the cup to equalize the pressure, deflating the balloon.)
5. Based upon this model, where would you insert the FES electrodes on a person who was unable to breathe on his own? Why?
   (The electrodes should be inserted into the diaphragm since this is the muscular wall that creates changes in the size of the chest cavity, just as the rubber skin changed the size of the "cup cavity.")
   

EXTENSIONS

Critical Thinking Extension
Suppose you were in charge of programming the electronics that would trigger an FES signal to the diaphragm. How often would you send this signal to a person who normally experiences 7 inhalations and 7 exhalations in a one-minute period? Explain.
(You'd send about 7 signals per minute. Since only the inhalation needs to be "triggered", you need to send an FES signal to initiate these actions. The exhalations are passive and will automatically occur when the inhalation contraction ends.)

Workout Connection
Have you ever seen advertisements for electrical pad muscle toners, used most often to tone the appearance of abdominal muscles? These pads cause muscles to contract as a response to surface electric stimulation. Think about it. How are the mechanics of this device similar to FES?
(Both devices rely upon electrical signals to stimulate muscle contractions)
How are the different?
(One is for cosmetic use, the other for more necessary life functions).

Reflex Actions
A reflex action is an automatic and involuntary response during which a motor signal is sent, not from the brain, but from a lower level of the spinal column. Think about it. What type of disorders or injuries would interfere with the knee-jerk reflex? Would a person who has a spinal injury maintain this reflex response? Why or why not?
(A reflex action takes place at a certain slice of the spinal column. No message needs to travel up the spinal cord to the brain. Therefore, if the spinal cord is damaged above this reflex arc, the intact nerves will still produce a reflex response even though the individual may not have awareness of the movement. If, however, the spinal damage also compromises the activity of nerves below the injury point, then the reflex may be lost.)