Bioastronautics: Space Exploration and its Effects on the Human Body Course Sampler


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This three-day course is intended for technical and managerial personnel who wish to be introduced to the effects of the space environment on humans. This course introduces bioastronautics from a fundamental perspective, assuming no prior knowledge of biology, physiology, or chemistry. The objective of the course is to provide the student with basic knowledge that will allow him or her to contribute more effectively to the human space exploration program. The human body, that through evolution is uniquely designed to function on the Earth, adapts to the space environment characterized by weightlessness and enhanced radiation. These alterations can impact the health and performance of astronauts, especially on return to the Earth.

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Bioastronautics: Space Exploration and its Effects on the Human Body Course Sampler

  1. 1. Bioastronautics: Space Exploration and its Effects on the Human Body Instructors: L. E. Wehren, MD V. L. Pisacane, PhDSchedule:
  2. 2. www.ATIcourses.comBoost Your Skills 349 Berkshire Drive Riva, Maryland 21140with On-Site Courses Telephone 1-888-501-2100 / (410) 965-8805Tailored to Your Needs Fax (410) 956-5785 Email: ATI@ATIcourses.comThe Applied Technology Institute specializes in training programs for technical professionals. Our courses keep youcurrent in the state-of-the-art technology that is essential to keep your company on the cutting edge in today’s highlycompetitive marketplace. Since 1984, ATI has earned the trust of training departments nationwide, and has presentedon-site training at the major Navy, Air Force and NASA centers, and for a large number of contractors. Our trainingincreases effectiveness and productivity. Learn from the proven best.For a Free On-Site Quote Visit Us At: Our Current Public Course Schedule Go To:
  3. 3. HUMAN SPACEFLIGHT Effects of Spaceflight on the Human Body Neurovestibular Adaptation by L. E. Wehren, MD V. L. Pisacane, PhD©VL Pisaane, 2012 Neurovestibular - 1
  4. 4. NEUROVESTIBULAR ADAPTATION Topics  Introduction  Control Mechanisms  Vestibular Apparatus  Neurovestibular System  Spatial Disorientation During Aircraft Flight  Neurological Disorientation from Spaceflight  Definitions©VL Pisaane, 2012 Neurovestibular - 2
  5. 5. INTRODUCTION Background  First human space flights showed no significant sensory system problems in space  Many astronauts reported motion sickness of varying severity  First space neurovestibular studies focused on causes and consequences of space motion sickness  Since Apollo missions, studies of neurovestibular system have increased in complexity  Weightless environment shown to provide different stimulus to otolith organs of inner ear; therefore signals from otolith organs no longer correspond with visual and other sensory signals sent to brain  After a few days in space, astronaut begins to adapt to new neural input  On return to Earth gravity, astronaut confronted with undoing changes in neurovestibular responses developed in space©VL Pisaane, 2012 Neurovestibular - 3
  6. 6. INTRODUCTION Problem  Space environment – Weightlessness alters function of some sensory organs – Visual scene distorted in that objects float, no up or down, cabinets and drawers on all four sides  Effects – Uncertain spatial orientation and illusion of motion of themselves or objects – Space adaptation syndrome (SAS) leading to potential nausea and vomiting – Disturbed hand-eye coordination – Increased nystagmus and changes in its properties  On return to gravity – Problems with balance, orientation, and walking resolve in few days©VL Pisaane, 2012 Neurovestibular - 4
  7. 7. CONTROL MECHANISMS Introduction  Feedback regulation can occur at different levels Effectors – Anatomical – Physiological – Biochemical  Response to change occurs to correct deviation by either enhancing it with positive feedback or depressing it with Effectors negative feedback©VL Pisaane, 2012 Neurovestibular - 5
  8. 8. CONTROL MECHANISMS Negative Feedback  Negative feedback causes system to respond to reverse direction of change tending to move away from homeostasis  Example: concentration of CO2 in body Effectors – As CO2 increases, lungs signaled to increase their activity to expel more CO2 and ingest more air by deeper breaths and increased rate of respiration  Example: thermoregulation – When body temperature rises (or falls), Effectors receptors in skin and hypothalamus sense change and cause brain to trigger commands to decrease or (increase) body temperature by several means, including shunting blood to or from surface of body©VL Pisaane, 2012 Neurovestibular - 6
  9. 9. CONTROL MECHANISMS Positive Feedback  Positive feedback is response that amplifies change in variable that can often result in destabilizing effect, further departure from Effectors homeostasis  Positive feedback generally less common in organic systems than negative feedback  Example: in nerves, threshold electric potential triggers the generation of much larger action Effectors potential  Example: blood clotting – Injured tissue releases signal chemicals that activate platelets in blood that in turn release chemicals to activate more platelets, causing rapid cascade and formation of blood clot©VL Pisaane, 2012 Neurovestibular - 7
  10. 10. CONTROL MECHANISMS Antagonistic Mechanisms  Body uses strategy of antagonistic mechanisms to solve problem of maintenance of body equilibrium or homeostasis  Antagonistic mechanisms maintain equilibrium by means of alternating compensatory mechanisms – Some mechanisms • Lower pH and others increase it • Increase body temperature and others to lower it • Some hormones reduce level of glucose in blood and others increase it©VL Pisaane, 2012 Neurovestibular - 8
  11. 11. CONTROL MECHANISMS Feedback and Feedforward Control 1/2  Illustrated control loop controls dynamic behavior of plant to maintain Set Point by both negative feedback and feedforward responses to changing conditions  In feedback control sensed states subtracted from Set Point to form Error Signal that, with delay, affects plant  Feedforward control is open loop strategy that compensates for disturbances before they affect controlled variable  Feedforward control measures disturbance variable, predicts its effect on plant, and applies corrective action  In feedforward control disturbances are measured without reference to actual system condition and results in much faster response than feedback control system©VL Pisaane, 2012 Neurovestibular - 9
  12. 12. CONTROL MECHANISMS Feedback and Feedforward Control 2/2  Feedforward control depends on set of stored rules known to be successful in given situational context  As example, human upright posture is inherently unstable – To counter mechanical effect of large- scale perturbation such as a slip, central nervous system can make adaptive adjustments in advance to improve stability of body’s center-of-mass – Such feedforward control relies on accurate internal representation of stability limits, which must be function of anatomical, physiological, and environmental constraints  If one or more anatomical, physiological, or environmental constraints should change, feedforward control is disrupted©VL Pisaane, 2012 Neurovestibular - 10
  13. 13. CONTROL MECHANISMS Examples of Feedforward Control  Feedforward control can be described as learned anticipatory responses to known cues  Example: when one tries to maintain constant speed while driving there is tendency to depress gas pedal as one begins to climb hill even before car slows A  Figure A contrasts feedback and feedforward control to maintain hot water at constant temperature  Figure B illustrates feedforward control based on input to plant together with feedback control based on plant’s response to changed input B©VL Pisaane, 2012 Neurovestibular - 11
  14. 14. CONTROL MECHANISMS Virtual Cliff Experiment  When brain and central nervous system involved, feedforward response often plays important role  Experiment by Gibson and Walk in 1960 illustrated that some of nominal rule-based feedforward response may be inherited  They set up “virtual cliff experiment” for babies, as illustrated  Young babies have no problem crawling over the elevated region  Reluctant to crawl over “cliff” even when their mothers encourage them to do so  See internet video at: – http://cognitivepsychologyisfun.blogspot.c om/2009/10/virtual-cliff-experiment.html©VL Pisaane, 2012 Neurovestibular - 12
  15. 15. VESTIBULAR APPARATUS Introduction  Aircraft and spacecraft maintain positions based on information from sensors as part of control systems  Similarly, neurovestibular system responsible for sensing body’s movements and interfacing with brain to – Sense orientation – Maintain balance – Coordinate body motions  Relevant sensors – Brain – Eyes – Vestibular organ or apparatus • Otolith detects linear acceleration and gravity • Semicircular canals detect rotational acceleration – Proprioceptors • Sensory nerve terminals that give information concerning movements and position of body • Located primarily in muscles and tendons©VL Pisaane, 2012 Neurovestibular - 13
  16. 16. VESTIBULAR APPARATUS Constituents  Six Semicircular Canals  Otoliths in two Saccules  Otoliths in two Utricles From: NASA,©VL Pisaane, 2012 Neurovestibular - 14
  17. 17. VESTIBULAR APPARATUS Semicircular Canals False sense of rotation From:NASA, /vestibularbrief.htm©VL Pisaane, 2012 Neurovestibular - 15
  18. 18. VESTIBULAR APPARATUS Sensing Linear Acceleration and Gravity  Otoliths have greater specific gravity than surrounding tissue and, thus, provide inertia saccule  Gravity or linear acceleration forces otolith to bend, utricle producing a force on hair cell  Utricle essentially horizontal and primarily registers accelerations in horizontal plane of head  Saccule essentially vertical and mostly registers accelerations in vertical plane of head Otolith Organ (saccule or utricle); senses linear acceleration From:NASA,©VL Pisaane, 2012 Neurovestibular - 16
  19. 19. NEUROVESTIBULAR SYSTEM Neurovestibular Control System©VL Pisaane, 2012 Neurovestibular - 17
  20. 20. NEUROVESTIBULAR SYSTEM Example: Posture Control  Posture control example of function of neurovestibular system  If one shuts his eyes, has greater tendency to sway than when eyes are open  Posture control is learned capability; babies must learn to stand; sway increases among elderly  For example, if knocked out, we fall but keep breathing, which is innate capability©VL Pisaane, 2012 Neurovestibular - 18
  21. 21. NEUROVESTIBULAR SYSTEM Posture Control with Eyes Shut  Figures show influence of stance and eyes on sway in 20 young adults  Note increase in sway with eyes closed – L-L = lateral –lateral, A-P (anterior-posterior) – Score = 0 -10 rating by subject – Sway area measured in mm2 From: M Schieppatia, E. Tacchini, A Nardone, J Tarantoola, S Corna, Subjective perception of body sway, J Neurol Neurosurg Psychiatry,1999;66:313-322©VL Pisaane, 2012 Neurovestibular - 19
  22. 22. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT Introduction  Spatial disorientation defined as failure of pilot to correctly sense attitude or motion of aircraft or of him or herself, resulting from inadequate or erroneous sensory information  Aeronautical Information Manual ranks spatial disorientation among most frequently cited contributing factors to fatal aircraft accidents  During period of 1994-2003, 184 of 202 spatial disorientation accidents (91%) were fatal  Spatial disorientation makes only modest contribution to overall accident rate, but is responsible for high percentage of its fatalities  VFR flight into IMC is number one cause of spatial disorientation accidents Figures from: – VFR rated 69 or 83% Air Safety – IMC rated 14 or 17% Foundation, Safety Advisor,  Weather Conditions Physiology No. – IMC = Instrument Meteorological Conditions 1, 2004 – VMC = Visual Meteorological Conditions  Flight Ratings – VFR = Visual Flight Rules – IFR = Instrument Flight Rules©VL Pisaane, 2012 Neurovestibular - 20
  23. 23. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT False Sense of Tilt  Figure A shows upright head with nominal resting frequency stimulated by position of hair cells A  Figure B shows tilted head, that alters resting frequency  Figure C shows forward linear acceleration, which cannot be B distinguished from head tilt  When adequate visual reference is not available, aircrew members may experience illusion of backward tilt during increase in acceleration and forward tilt during decrease in acceleration C Figures from: Department of the Army FM 3-04.301 Aeromedical Training for Flight Personnel©VL Pisaane, 2012 Neurovestibular - 21
  24. 24. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT False Sense of Flying Level  A problem arises when an aircraft accelerates about its roll axis below pilots vestibular sensory threshold  If pilots attention is diverted during this time, when he shifts his attention back to attitude indicator, he will find display portraying unexpected attitude  That will result in conflict between his vestibular sensations, which tell him he is flying straight and level, and his visual sensations, which tell him he is in banked attitude  Should he initiate a sharp control movement to correct undesired attitude shown on display, he will feel as though he is rotating from wings-level attitude into bank, when just the opposite is the case  In other words, his eyes will tell him positively that he is correcting an undesirable situation, while his inner ear (vestibular sensations) will tell him positively that he is moving into one©VL Pisaane, 2012 Neurovestibular - 22
  25. 25. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT Coriolis Illusion of Rotation  Coriolis illusion is most dangerous of all vestibular illusions for aircraft  Can cause overwhelming disorientation  Occurs whenever prolonged turn is initiated and the pilot makes head motion in different geometrical plane; illustrated in first figure  For example, if pilot initiates head movement in a geometrical plane other than that of turn, fluid Figure From: T R Czarnik, Artificial gravity: current concerns and design considerations, March 1999 stabilizing in original canal and simultaneously moves in new canals stimulating two other cupulas  Combined effect of deflection in all three cupulas creates perception of motion in three different planes of rotation: yaw, pitch, and roll  Result is that pilot experiences overwhelming head-over-heels tumbling sensation Figures from: Department of the Army FM 3-04.301 Aeromedical Training for Flight Personnel©VL Pisaane, 2012 Neurovestibular - 23
  26. 26. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT Graveyard Spin  Illusion that leads to graveyard spin usually occurs in fixed-wing aircraft  For example, pilot enters spin and remains in it for several seconds  Pilot’s semicircular canals reach equilibrium; no motion is perceived  Upon recovering from spin, pilot From: Instrument Flying Handbook By Federal Aviation Administration undergoes deceleration, sensed by semicircular canals  Pilot has sensation of being in spin in opposite direction even if flight instruments contradict that perception  If deprived of external visual references, pilot may disregard instrumentation and make control corrections against falsely perceived spin  If so, aircraft will then re-enter spin in original direction Figures from: Department of the Army FM 3-04.301 Aeromedical Training for Flight Personnel©VL Pisaane, 2012 Neurovestibular - 24
  27. 27. SPATIAL DISORIENTATION DURING AIRCRAFT FLIGHT Proprioceptive Illusions  Proprioceptive system responsible for illusions including – False perception of true vertical – Drunken walk of sailor who feels ship as steady and dry land as heaving – Person viewing wide field of objects or stripes moving at constant speed will eventually see display as fixed and person as moving Courtesy of NASA – Rotary motion can evoke illusions of body tilt  Properly executed turn vectors gravity and centrifugal force through vertical axis of aircraft such that pilot may falsely interpret it as climbing in altitude  Recovering from turns lightens pressure on seat and creates illusion of descending – This may cause the pilot to pull back on Figures from: Department of the Army FM 3-04.301 stick, which would reduce airspeed Aeromedical Training for Flight Personnel©VL Pisaane, 2012 Neurovestibular - 25
  28. 28. NEUROLOGICAL DISORIENTATION FROM SPACEFLIGHT Introduction  Astronauts frequently experience momentary disorientation when entering or returning from space  Many astronauts report some symptoms of space adaptation syndrome (SAS) (motion sickness) during first days in orbit  Nystagmus (jerky eye movements) observed in some astronauts early in flight  Adaptation to weightlessness often leads, upon return to Earth, to – Disorientation – Postural instability – Motion sickness – Modifications in body segment motion – Increased response latencies to external perturbations  These effects would impede astronaut’s response if emergency occurred  Longer the time in weightlessness, more pronounced symptoms upon return©VL Pisaane, 2012 Neurovestibular - 26
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