What sort of receptor do skeletal muscle cells use to receive signals from somatic lower motor neurons? a. Nicotinic
b. Muscarinic
c. Adrenergic
d. Mechanoreceptive calcium channels
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Which organelles are labeled d, and what is one feature that distinguishes them from the other labeled organelles chloroplasts the only organelles that produce sugars from sunlight mosomes, only found in animal and bacterial cells centricles only found in animal cells mitochondra, the only energo-generating structures found in cells

Consider the model of the oxygen cycle on earth. the majority of earth's oxygen reservoirs are found in the a) atmosphere. b) biosphere. c) hydrosphere. d) lithosphere.

Which direction does the energy flow in this energy pyramid ?