Appendix C
Glossary
adrenergic agents:
Compounds with actions similar to those of the adrenal hormones epinephrine (adrenaline) and norepinephrine that stimulate the sympathetic nervous system.
arrhythmia:
Alteration in the rhythm of the heartbeat either in time or in force.
autonomic regulation:
Regulation of the portion of the nervous system that modulates blood pressure, heart rate, and other involuntary functions.
baroreceptor:
Receptor that responds to changes in blood pressure.
Bion:
Russian space capsule that can support animals (e.g., monkeys, rats) and insects in orbit up to three weeks.
bone mineral density:
Bone mineral content corrected for bone size (bone mineral content/cross-sectional area).
bone remodeling:
Continuous process of breakdown and renewal of bone that occurs throughout life.
chromosome translocation:
Transfer of a segment of one chromosome to another nonhomologous chromosome.
colony-stimulating factor:
Protein that causes division and maturation of immature bone marrow cells into mature white blood cells.
corpus striatum:
Neuroanatomical term for cerebral gray matter in three basal ganglia, including the caudate nucleus, putamen, and globus pallidus; involved in the control of movement.
countermeasure:
Any step taken to prevent or alleviate decrements in the physiological or psychological status of astronauts that may result from spaceflight. Measures may include in-flight protocols such as medication and exercise, as well as the screening of astronaut candidates using medical selection criteria.
cytokine:
Class of proteins that mediates immune (and other) responses.
dosimetry:
Experimental procedure used to determine dose (joules per kilogram) of ionizing radiation.
functional magnetic resonance imaging (fMRI):
Noninvasive scanning technology used to produce images of localized neural activity in the human brain. It is based on the fact that there are changes in local blood flow and blood oxygenation in response to neural activity.
hindlimb unloading:
Simulation of some aspects of microgravity effects on rodents by unloading of muscles and head-down tilt by employing various harnessing strategies to elevate the animal and prevent its hindlimbs from weight bearing on the floor.
histomorphometric:
Referring to structural changes in tissues observed and quantitated on biopsy specimens.
hypothalamus-pituitary-adrenal (HPA) axis:
Neuroendocrine axis that interacts with the immune response; mediates response to stress and other factors that could have a profound effect on immune response and resistance.
leukocyte:
White blood cell.
leukocyte distribution:
Distribution of subtypes of white blood cells (e.g., CD4+ and CD8+ lymphocyte distribution); indication of host potential for normal immune function.
leukocyte proliferation:
Response of lymphocytes and macrophages (white blood cells) to stimulation in which lymphocytes divide after receiving signals from macrophages; evidence of intact immune function.
locomotor:
Affecting or involving the organs that mediate active movements.
natural killer cells:
Immune cells found in the body under normal conditions that can destroy target virus-infected and tumor cells by an as-yet-unknown recognition mechanism.
neuroendocrine:
Referring to the complex integration of the central nervous system with pituitary hormone secretion.
Neurolab:
Shuttle mission (1998) dedicated to studies in neurosciences.
neuroplasticity:
Ability of differentiated neurons to alter structure or function in response to altered physiological demands.
neurovestibular:
Pertaining to the sensory system concerned with maintenance of posture and balance by perceiving gravity (linear acceleration) and rotary movements of the head.
oculomotor:
Related to the control of eye movement.
orthostatic hypotension:
Drop in blood pressure when going from a lying or sitting position to a standing position.
orthostatic intolerance:
Inability to stand erect without a drop in blood pressure that induces weakness or fainting.
osteoblast:
Bone-forming cell.
osteoclast:
Multinucleated, bone-resorbing cell related to macrophages.
otoconia:
Biogenerated calcium carbonate crystals embedded in a gelatinous membrane accelerated during body movements and stimulating receptor hair cells of the inner ear.
otolith:
Otoconial matrix mass suspended on hair cells of the inner ear sensitive to linear acceleration.
proprioceptive:
Conscious awareness of positions of various parts of the body in space provided by joint and muscle sensory inputs; also, sensory stimulation arising from receptors within muscles.
sensorimotor:
Combined sensory and neural aspects of neural-dependent body activity.
skin test reaction:
Reaction due to cell-mediated immune processes on skin when individuals are exposed to substances to which they have been exposed previously (e.g., tubercle bacillus).
space map:
Organization of groups of neurons into specific arrangements in the central nervous system that reflect the structure and/or function of the spatial environment representing the sensory or motor areas of the brain.
space motion sickness:
Condition similar to terrestrial motion sickness, often encountered by astronauts on entry into orbit; typical symptoms include pallor, increased body warmth, cold sweating, dizziness, nausea, and vomiting.
teleoperation:
Remote control by a human operator of a robot or machine such as an extraterrestrial exploration vehicle.
telepresence:
State of a human operator feeling physically present at a remote site because of the degree of realism of the information transmitted about the machine being controlled remotely.
thermoregulation:
Process by which mammals control body temperature.
translocation yields:
Fraction of cells containing chromosome translocations, usually per 1,000 cells observed.
vestibular:
Pertaining to the sensory system concerned with maintenance of posture and balance by perceiving gravity (linear acceleration) and rotary movements of the head.
vestibulo-collic:
Neuronal connections formed by axons of vestibular nuclei neurons with motor neurons in cervical spinal cord, which activate neck muscles to support the head during head movements.
vestibulo-ocular (or vestibular ocular) reflex:
Passive eye movements elicited by activation of receptors in the vestibular apparatus.
