15.1B: Comparing the Nervous and Endocrine Systems
The nervous system and endocrine system both use chemical messengers to signal cells, but each has a different transmission speed.
- Distinguish between the nervous system and the endocrine system
Key Points
- The nervous system can respond quickly to stimuli, through the use of action potentials and neurotransmitters.
- Responses to nervous system stimulation are typically quick but short lived.
- The endocrine system responds to stimulation by secreting hormones into the circulatory system that travel to the target tissue.
- Responses to endocrine system stimulation are typically slow but long lasting.
Key Terms
- hormone : A molecule released by a cell or a gland in one part of the body that sends out messages affecting cells in other parts of the organism.
- neurotransmitters : Endogenous chemicals that transmit signals from a neuron to a target cell across a synapse.
The body must maintain a constant internal environment, through a process termed homeostasis, while also being able to respond and adapt to external events. The nervous and endocrine systems both work to bring about this adaptation, but their response patterns are different. The nervous system and the endocrine system use chemical messengers to signal cells, but the speed at which these messages are transmitted and the length of their effects differs.
Nervous System
The nervous system responds rapidly to stimuli by sending electrical action potentials along neurons, which in turn transmit these action potentials to their target cells using neurotransmitters, the chemical messenger of the nervous system. The response to stimuli by the nervous system is near instantaneous, although the effects are often short lived. An example is the recoil mechanism of an arm when touching something hot.
Endocrine System
The endocrine system relies on hormones to elicit responses from target cells. These hormones are synthesized in specialized glands at a distance from their target, and travel through the bloodstream or inter-cellular fluid. Upon reaching their target, hormones can induce cellular responses at a protein or genetic level.
This process takes significantly longer than that of the nervous system, as endocrine hormones must first be synthesized, transported to their target cell, and enter or signal the cell. However, although hormones act more slowly than a nervous impulse, their effects are typically longer lasting.
Additionally, the target cells can respond to minute quantities of hormones and are sensitive to subtle changes in hormone concentration. For example, the growth hormones secreted by the pituitary gland are responsible for sustained growth during childhood.
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