Large regions such as forests, deserts, and grasslands, with distinct climates and species, are called .

hormones in blood stream

image: dtc.ucsf.edu

endocrine glands secrete hormones into the blood stream near them; the hormones then travel in our bloodstream until it reaches its destination, called a target cell, in distance parts of the body. in the target tissue, hormones lock onto the target’s plasma membrane, called the receptor site.

synapse nervous system

gag reflex, poor dentition, gum retraction

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