Final answer:
The adrenal medulla is the neurosecretory endocrine gland closely related to the sympathetic branch. It releases epinephrine and norepinephrine during sympathetic system activation, playing a key role in the body's stress response mechanism.
Step-by-step explanation:
The neurosecretory endocrine gland that is closely allied to the sympathetic branch is the adrenal medulla. This gland is situated above the kidneys and is part of the adrenal glands. It contains chromaffin cells, which are specialized neuroendocrine cells that release the hormones epinephrine and norepinephrine into the bloodstream. These hormones are an integral part of the sympathetic nervous system's response to stress, often referred to as the 'fight-or-flight' response.
The adrenal medulla functions as an extension of the autonomic nervous system and is activated through the sympathomedullary (SAM) pathway. The release of epinephrine and norepinephrine is induced by acetylcholine released from preganglionic sympathetic fibers that innervate it. The neural impulses that trigger this release originate from the hypothalamus.
One of the key aspects of the sympathetic nervous system is its widespread influence on the body. For instance, during a threatening situation, there would be an increase in heart rate, breathing rate, and redirection of blood flow from the digestive system to the skeletal muscles. Through the adrenal medulla, the effects of sympathetic stimulation can spread quickly across multiple organ systems.