Internal mechanism of control of behavior is composed of nervous system and the endocrine system. It regulates animal behavior. These systems receive information from the external environment through sensory organs. Brain and endocrine glands process these information. Brain and glands initiate responses by motor neuron. Or they show the response by changing the operations of inter I organs. The nervous system control more specific and rapid responses. But t e endocrine system monitors slower and general responses.


Nervous-system plays an important role in the control of behavior. The nervous system acts as a stimulus filter. Each organism receives stimuli from many sources continuously. The sensory organs and central nervous system block unimportant or irrelevant incoming stimuli. Thus information passes through the sens Dry filters. These information are then sorted and processed within the nerv us system for appropriate responses.

Example of blowflies

1. F eding behaviour of blow flies: The behaviour of the blow flies is cintrotled by nervous System. The blowfly has special sensory receptors on it feet. The fly moves around. It encounters different substrates. Their

r ceptors can detect the presence of certain sugars. The receptors of the feet

s nd information to nervous system. The nervous system processes these i formation. The blowfly shows response by extending their proboscis. It also mutates the oral taste receptors. Thus the fly starts feeding. Some f edback mechanism stops feeding. The foregpt of blowfly swells sufficiently after feeding. Receptors in the foregut send a message to the brain. The essage sends to the nerves that control the feeding response. It stops the further intake of the sugar solution.

2. Control of aggressive behavior in Rhesus monkey: The nervous system regulates the control of aggressive behavior in rhesus• monkeys. Some researchers identified the dominant male monkey. They were present in a group of four to six animals. They surgically implanted electrodes into the special regions of brains monkeys. This region produces or inhibits the aggressive behavior. They give mild electrical stimulation to the brain of the monkey. It produced aggressive or passive behaviors. This behavior depends on which electrode sent the message.

The researcher trained the other monkeys in the group to press a lever when the dominant monkey became aggressive. Pressing of the lever sent a message to the brain of the dominant male. It inhibits his aggression.


The endocrine system is closely interrelated with the nervous system. Many receptors located on neurons in the brain or central nervous systems. These receptors are specialized for receiving input from hormones. The brain communicates with the endocrine system through neurons. Such types of connections are between the hypothalamus and pituitary gland of vertebrates. Other endocrine glands are located throughout the body of the organism. These endocrine glands produce hormones. The hormones affect the behavior in two major ways: organizational effects and activational effects.



  1. Organizational effects of hormones

It occurs during. development of the animals. It is particularly important for sex differentiation. These effects detect the presence of hormones and critical time periods. These effects influence the developmental pathways for specific brain regions. They also influence the developing gonadal tissues. These tissues become female or male like. The major effect takes place in the middle of gestation in most male mammalian embryos (e.g., guinea pigs, monkeys). The testes produce a large amount of male hormone (testosterone). This organizes other developing tissues and certain regions of the brain. The female embryos develop in the absence of testosterone. Thus female like characteristics develop in the external anatomy and brain. These brain regions are important for sex differentiation.

Genes normally turn on the production and release of testosterone. But sometimes, the testosterone comes from an external source.

• Sometimes, cattle develop twin in the uterus. One member of the twin is male and other is female. A male fetus masculinized a female fetus. The system of male fetus turns on and releases testosterone during gestation. Some of that hormone crosses over and affect the developing female fetus. It produces a freemartin. It is a sterile heifer (offspring of cow). It shows a number of male like behavior patterns.

  • Some pregnant human females are in danger of losing their fetus. They are given, some hormone treatments. This hormone iS converted and acts like testosterone within the feinale embryo. Thus it causes masculinization of female embryos.
  1. Activational effects of hormones

An external stimulus starts a hormonally mediated response. It is called activatoonal effects of hormone.

  • Many male fishes develop territory boundary. Sometimes, their territory is threatened. Therefore, these males change color patterns. This change of colour pattern is stimulated by hormones. The color change is an .indication of • agg ressive behavior to defend the territory.
  • Many animals like domestic cats, roosters, and mice are castrated (removal of tie gonads). They lose their aggressive fighting ability. The gonads are the sauce of testosterone. It stimulates particular brain receptors to produce aggression.

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