Endocrine (Hormonal System), like the nervous system → serves as a means of co-ordination within the body. In both cases → a stimulus causes the transmission of a message to a target organ (effector) → which carries out the response.
Example: decrease in water potential of the blood (stimulus) causes more antidiuretic hormone (ADH) to be produced by the pituitary gland and transported to the kidneys. ADH → increases the permeability of the walls of the collecting duct to water → so that the kidneys respond by reabsorbing more water (effect) Refer to: Regulating Blood Water Potential
However → nervous control differs from the endocrine control in several ways For example:
- nervous control may affect only a particular part of the body, i.e. it is localised.
- since hormones are usually transported around the body by the blood → several target organs may be affected by the same hormone
- An example of this is the effects of the hormone adrenaline on heart, arteries, and metabolic rate.
Differences between Endocrine Control and Nervous Control
| Endocrine Control | Nervous Control |
|---|---|
| Involves hormones (chemical substances) as signals | Involves nerve impulses as signals |
| Hormones are transported by blood | Nerve impulses are transmitted by neurones |
| Usually slow responses | Usually quick responses |
| Responses may be short lived (eg: adrenaline) or long lived (eg: growth hormone) | Responses are short lived |
| Always involuntary | May be voluntary or Involuntary |
| May affect more than 1 target organ | Usually localised |
Definition
target organ: has receptors for a specific hormone which when attached causes specific chemical reactions to take place #BiologyDefinitions