Adrenergic receptors Select one: a. can be activated by the release of epinephrine. b. have two structural forms - muscarinic and nicotinic. c. when activated stimulate skeletal muscles to contract. d. can be found in both the sympathetic and parasympathetic divisions. e. are activated by the release of acetylcholine.

The correct answer is  a. can be activated by the release of epinephrine.

Explanation:

Epinephrine is a hormone and neurotransmitter naturally secreted by the body through the adrenal glands, synthesized and stored in the adrenal medulla and released into the systemic circulation. Epinephrine is a non-selective adrenergic agonist, stimulating alpha1-, alpha2, beta1, and beta2-adrenergic receptors. The systemic actions of catecholamines are mediated by the binding of these compounds to plasma membrane receptors, of the GPCR type widely distributed throughout the body and known as adrenergic receptors, which are activated by the catecholamines adrenaline (epinephrine) and noradrenaline . These receptors cause different effects depending on the G protein subtypes to which they are associated and the signal transduction mechanism linked to the specific G protein.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.