Name: Anonymous 2017-06-26 18:06
Insect brains consist of 105 to 106 neurons and brain neurons outnumber those composing the ventral nerve cord . A house fly brain includes about 350,000 neurons, that of a honeybee (worker) about 850,000. On the other hand each thoracic ganglion in any insect consists of 3000 to 5000 neurons and each abdominal ganglion of only 400 to 850 neurons .
The insect brain can be divided into three large regions, protocerebrum deutocerebrum, and tritocerebrum. As mentioned above each of them is associated with one of the three anteriormost ancestral body segments .
The deutocerebrum is a bilaterally symmetrical brain region that consists of the antennal lobe and the dorsal lobe. The antennal lobe receives the axons of olfactory receptor neurons from the antenna . In at least some insects such as flies and moths, the antennal lobe also receives olfactory receptor axons from the labium. The dorsal lobe receives mechanosensory and gustatory receptor neurons from the antenna and also contains the motor neurons controlling the antennal muscles. The dorsal lobe is called antennal mechanosensory and motor center (AMMC) in some insects. For flies, this name may be retained because they differ from almost all other insects in not having an antennal gustatory system. The anntennal nerve is carrying all sensory axons from the antenna to the deutocerebrum and also contains efferent neurons, in particular the motor neurons of the pedicellus muscles. Generally, a second nerve emanates from beneath the antennal lobe that contains the axons of the motor neurons of the scapus muscles, which are located in the head capsule
The thoracic ganglia possess motor centers that control important behaviors, such as flight, walking, and vocalization.
The abdominal ganglia possess motor centers related to posture control, rhythmic behavior, such as respiration, and circulation and the control of copulation and egg laying.
The higher order neuropils in protocerebrum, such as mushroom body, central complex, and lateral protocerebrum, receive sensory information from optic lobe, deutocerebrum, tritocerebrum, suboesophageal ganglion, and ventral nerve cord through several layers of filters in a preprocessed form. The higher neuropils integrate information from various modalities and relay outputs that can eventually results in activating output neurons such as motor neurons of the brain or descending interneurons transmitting command information to the ventral nerve cord, which is important in controlling a wide range of behaviors. Thus, overall control mechanisms such as for triggering particular behaviors are localized in the brain and are separated from local control mechanisms that are responsible for aspects like the maintenance of motor patters for wing flapping or walking are localized in the thoracic ganglia. This is not to say that the ventral nerve cord is a fully hardwired system: In seminal experiments, Horridge could demonstate that cockroaches and locusts are capable of leg position learning, which is even improved by removal of the head. Thus, plasticity is possible at short time scales even in thoracic circuits controlling very basic behaviors.
The insect brain can be divided into three large regions, protocerebrum deutocerebrum, and tritocerebrum. As mentioned above each of them is associated with one of the three anteriormost ancestral body segments .
The deutocerebrum is a bilaterally symmetrical brain region that consists of the antennal lobe and the dorsal lobe. The antennal lobe receives the axons of olfactory receptor neurons from the antenna . In at least some insects such as flies and moths, the antennal lobe also receives olfactory receptor axons from the labium. The dorsal lobe receives mechanosensory and gustatory receptor neurons from the antenna and also contains the motor neurons controlling the antennal muscles. The dorsal lobe is called antennal mechanosensory and motor center (AMMC) in some insects. For flies, this name may be retained because they differ from almost all other insects in not having an antennal gustatory system. The anntennal nerve is carrying all sensory axons from the antenna to the deutocerebrum and also contains efferent neurons, in particular the motor neurons of the pedicellus muscles. Generally, a second nerve emanates from beneath the antennal lobe that contains the axons of the motor neurons of the scapus muscles, which are located in the head capsule
The thoracic ganglia possess motor centers that control important behaviors, such as flight, walking, and vocalization.
The abdominal ganglia possess motor centers related to posture control, rhythmic behavior, such as respiration, and circulation and the control of copulation and egg laying.
The higher order neuropils in protocerebrum, such as mushroom body, central complex, and lateral protocerebrum, receive sensory information from optic lobe, deutocerebrum, tritocerebrum, suboesophageal ganglion, and ventral nerve cord through several layers of filters in a preprocessed form. The higher neuropils integrate information from various modalities and relay outputs that can eventually results in activating output neurons such as motor neurons of the brain or descending interneurons transmitting command information to the ventral nerve cord, which is important in controlling a wide range of behaviors. Thus, overall control mechanisms such as for triggering particular behaviors are localized in the brain and are separated from local control mechanisms that are responsible for aspects like the maintenance of motor patters for wing flapping or walking are localized in the thoracic ganglia. This is not to say that the ventral nerve cord is a fully hardwired system: In seminal experiments, Horridge could demonstate that cockroaches and locusts are capable of leg position learning, which is even improved by removal of the head. Thus, plasticity is possible at short time scales even in thoracic circuits controlling very basic behaviors.