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14.3: Comparing Endocrine and Nervous Systems

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    Since the overall job and main functions of the endocrine system are very similar to several functions performed by the nervous system, why does the body have both systems? A comparison reveals that these systems complement rather than duplicate each other.

    The nervous system can cause adaptive responses such as the blink of an eye with pinpoint accuracy and within a fraction of a second because it uses nerve impulses and highly specialized and localized connections. It is also able to provide remembering and thinking. However, the nervous system can directly control only neurons, muscle contractions, and secretions from a few glands (e.g., sweat glands, salivary glands). Furthermore, this system has difficulty sustaining long-term control of activities because neurotransmitters become depleted.

    While minutes or hours may be required for an endocrine structure to secrete enough hormone to cause an adaptive response, the hormone may remain in the blood and cause the adaptive response to continue for many hours. Additional hormone can be secreted gradually to continue long-term responses for days, weeks, or months (e.g., growth, maturation). Furthermore, hormones can directly control many body cells and functions that are not influenced by neurotransmitters, including epidermis, bone, cartilage, and blood cells. Representative functions include growth and gene activity. In fact, every type of body cell has at least some of its functions regulated by hormones.

    Though the nervous and endocrine systems have exclusive control of certain body activities, they share responsibility for regulating others, such as GI tract functioning and blood pressure.

    Coordinated Operation

    Coordination of the nervous and endocrine systems is provided by three communication links. The hypothalamus and infundibulum at the base of the brain provide one main link by which the brain can influence hormone secretion by the pituitary gland ((Figure 14.1, Figure 14.2).

    The hypothalamus uses neurons to send hormones through the infundibulum and into the blood in the posterior pituitary gland. In contrast, the hypothalamus uses blood vessels in the infundibulum to send hormones to the anterior pituitary gland. These hormones regulate the production of other hormones by the anterior pituitary gland. Since the pituitary secretes many hormones, some of which regulate the secretion of other hormones, influencing the pituitary gland produces widespread effects on the endocrine system.

    Production of most hormones by the hypothalamus is controlled by negative feedback mechanisms. In addition, the production of hormones destined for the anterior pituitary gland can be influenced by brain activities involved in psychological states and emotional reactions.

    The nervous system also uses certain sympathetic nerves to stimulate epinephrine and norepinephrine secretion by the adrenal medulla (inner part of the adrenal glands). Epinephrine and norepinephrine have similar effects. Recall that many sympathetic nerves in other parts of the body release norepinephrine as a neurotransmitter.

    The third link between these systems is the circulatory system, which delivers hormones to the brain. Some hormones significantly alter brain function. Of course, altered brain function in turn can result in modified hormone secretion.

    This page titled 14.3: Comparing Endocrine and Nervous Systems is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Augustine G. DiGiovanna via source content that was edited to the style and standards of the LibreTexts platform.

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