5. What effect would the gravity-free environment of space have on an astronaut’

Question

5. What effect would the gravity-free environment of space have on an astronaut’s bones?

6. The Huaorani Indians of South America use blowguns to shoot darts poisoned with curare to hunt monkeys. Curare is a plant toxin that binds to and inactivates nicotinic ACh receptors. What happens to a monkey if it has been hit with Curare?

5. What effect would the gravity-free environment of space have on an astronaut's bones? [4 points] 6. The Huaorani Indians of South America use blowguns to shoot darts poisoned with curare to hunt monkeys. Curare is a plant toxin that binds to and inactivates nicotinic ACh receptors. What happens to a monkey if it has been hit with Curare? [9 points]

Explanation / Answer

5)Some of the processes and functions of bones after the astronaut has lived in microgravity for several days.in space,the amount of weight that bones support in reduced to almost zero.At the same time many bones that aid in movement are no longer subjected to the same stress that they are subjected to on earth.overtime, calcium normally stored in the bones is broken down and released into the blood stream.The high amount of calcium found in astronauts blood during spaceflight reflects the decrease in bone density.This drop in density known as disuse osteoporosis,leaves bone weak and less able to support the body weight and movement upon return to earth, putting the astronaut at a higher risk of fracture.

6)If the monkey has been hit with curare,Action potentials in skeletal muscle cells are due to mechanisms in which voltage dependent change in Na+ permiability followed by a delayed increase in K+ permiability.

Curare blocks the endplate potential because it is competitive inhibitor of acetylcholine,the transmitter released at the pre synaptic terminal.curare does not block the voltage dependent Na+ conductance or the voltage dependent K+ conductance that underlies the muscle action potential.Curare affects the stimulus which normally leads to initiation of the muscle action potential.An animal that is poisoned with curare will asphyxiate because the process of neurotransmission at respiratory muscles is blocked.

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