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Autonomic Nervous System Team

A question to consider as you read . . .

Vocabulary that will help you understand this section

• autonomic nervous system
• cardiovascular
• messenger
• neurotransmitter
• orthostatic intolerance
• receptor
• synapse

Upon return to Earth, crewmembers typically experience dizziness when moving from sitting to standing upright. Referred to as orthostatic intolerance, the phenomenon is caused by the shift in body fluids brought on as the body begins readaptation to a gravitational environment. It is understood that inadequate flow of blood to the brain is a key parameter associated with this body fluid shift. Orthostatic intolerance is also a problem for a multitude of Earth-bound individuals who experience similar consequences when blood flow to the brain is impeded.

On Neurolab, the Autonomic Nervous System Team will explore the autonomic nervous system, which governs involuntary actions of cardiovascular regulation and thus regulates the blood flow to the brain. The team was formed to integrate the proposed research of four individual investigators, Drs. Baisch, Blomqvist, Eckberg and Robertson. The result is a tightly integrated research effort to achieve three main goals: First, to understand the way the autonomic nervous system changes during exposure to microgravity for a period of approximately two weeks; second to identify the response made by the autonomic nervous system due to changes that occur during space flight; and third, to examine the results of a changed autonomic nervous system immediately after space flight.

Changes to the autonomic nervous system are determined by measuring the level of neurotransmitters and their metabolic by-products in plasma and urine samples; by observing the excess release of neurotransmitters and the release process; and by recording muscle nerve activity in the leg. Measurements will be obtained before, during, and after space flight with each blood sample supporting all four experiments. Investigators will share measurement and analysis activities, as well as the data obtained.

Dr. Robertson's Study

Dr. Robertson will analyze urine samples and the excess neurotransmitters in the synapses between the receptor and the messenger. Recordings gathered from leg nerve activity will support the experiments proposed by Drs. Blomqvist, Eckberg, and Robertson.

Responses to the autonomic nervous system are determined by measuring blood flow to the brain and relating the measurement to the characteristics of blood flow in the rest of the body. The blood flow of astronauts will be measured before, during and after space flight, and the data will be analyzed by Dr. Blomquist. In addition, the astronauts' cardiac output, which is also an indicator of changes in the autonomic nervous system, will be measured before and after flight and collected in support of Drs. Baisch and Blomquist.

By examining the adapted autonomic nervous system as it is presented immediately after space flight, investigators expect to better understand the role of respiration, stroke volume, cardiac period, arterial pressure, muscle nerve activity, and subsequent blood flow to the brain. These studies will not only offer greater insight into the body's adaption to microgravity and readaptation to gravity, but will also increase basic understanding of orthostatic intolerance.