The internal mechanisms that control animal behavior are the nervous system and endocrine system. The nervous system acts as a stimulus filter, processing sensory information and initiating motor or organ responses. The endocrine system works more slowly through hormonal effects that influence development and activation of behaviors. Both systems receive external stimuli and work together to regulate behaviors like feeding, aggression, and territorial defense.

1. CONTROL OF BEHAVIOR
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 this 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
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 sense Dry filters. This information is then sorted and processed
within the nervous system for appropriate responses.
Example of blowflies
1. Feeding behavior of blow flies: The behavior of the blow flies is controlled by nervous
System. The blowfly has special sensory receptors on it feet. The fly moves around. It
encounters different substrates. Their receptors can detect the presence of certain sugars. The
receptors of the feet
send 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 feedback mechanism stops feeding. The foregut of blowfly
swells sufficiently after feeding. Receptors in the foregut send a message to the brain. The
message 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.
ENDOCRINE SYSTEM
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 activation 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

2. 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 males 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 embryo. Thus, it causes masculinization of female embryos.
2. Activation effects of hormones
An external stimulus starts a hormonally mediated response. It is called activation effects of
hormone.
 Many male fishes develop territory boundary. Sometimes, their territory is
threatened. Therefore, these males change color patterns. This change of color
pattern is stimulated by hormones. The color change is an indication of aggressive
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.