Adrenergic receptors are the integral proteins present in the postsynaptic plasma membranes. These receptors are activated when the neurotransmitter norepinephrine and the hormones norepinephrine and epinephrine bind to them. The alpha 1 adrenergic receptors are found in the smooth muscle fibers of blood vessels that serve the salivary glands, skin, and kidneys. These receptors are also found in the radial muscle of iris of the eye as well as in the sphincter muscles of the stomach and urinary bladder.
They exert excitatory effect and lead to contraction of smooth muscles of the blood vessels, dilation of pupil, and closure of sphincters of the bladder.
Using its web as a gill, the diving-bell spider can live underwater with only occasional visits to the surface. The arachnid (Argyroneta aquatica) breathes air from a bubble that it grabs from the surface of water using fine hairs on its abdomen.
DNA is the genetic information used to make proteins, and it contains the hereditary traits of organisms. There are two types of DNA: mitochondrial DNA, which you can only get from your mother, and nuclear DNA, which is a combination of both your ancestors' DNA.
