Q49.1-3CC - Campbell Biology

Question

Most tissues regulated by the autonomic nervous system receive both sympathetic and para sympathetic input from postganglionic neurons. Responses are typically local. In contrast, the adrenal medulla receives input only from the sympathetic division and only from preganglionic neurons, yet responses are observed throughout the body. Explain why (see Figure 45.19).

Step-by-Step Solution

Answer

The response received by the adrenal medulla from the sympathetic division and preganglionic neurons produces hormones such as epinephrine and norepinephrine. These hormones travel throughout the body and take part in different reactions; thus, adrenal responses are observed.

Step 1: Sympathetic and parasympathetic responses from the post-ganglionic neurons

The short axons of the post-ganglionic neurons send signals to the cells of effector tissues. The terminal ganglia of the parasympathetic nervous system are located within the innervated tissue; thus, they have less divergence than the sympathetic system.

Step 2: Adrenal medulla

The inner part of the adrenal gland, the small organs on the top of the kidneys, is the adrenal medulla. The main function of the adrenal medulla is to control the hormones that initiate the fight or flight response.

The cells of the adrenal medulla are controlled by the preganglionic fibers of the sympathetic nervous system.

Step 3: Adrenal responses observed throughout the body

The adrenal gland produces epinephrine and norepinephrine hormones that play a crucial role in fight and flight responses. When a person undergoes stress, these two hormones come into action, but they also play an essential function in day-to-day body activities.

These hormones are also further released in the body for maintaining homeostasis in blood pressure, heart rate, and blood sugar levels. 

Thus, these hormones are present throughout the body, so the adrenal responses are observed throughout the body instead of the autonomic nervous responses.