Five parts of fish brain CONTENTS 1 telencephalon

Five parts of fish brain 程起超

CONTENTS 1 telencephalon 2 diencephalon 3 mesencephalon 4 metencephalon 5 myelencephalon

PART 1 telencephalon

The most anterior part is the telencephalon , or forebrain , which becomes the cerebrum of tetrapods. Its function in fishes is primarily associated with reception and passage of olfactory stimuli. The olfactory nerve ( cranial nerve 1 ) runs from the nostrils to the nerve olfactory lobe of the brain. The olfactory lobe is large in hagfishes and lampreys , huge in sharks such as the hammerheads( Sphyrnidae ) , and moderately large in teleosts such as catfishes that rely heavily on odors when foraging

PART 2 diencephalon

The diencephalon , or ' tween brain’ , lies between the forebrain and the midbrain and is also known as the saccus dorsalis. It functions as a correlation center for incoming and outgoing messages regarding homeostasis and the endocrine system. The pineal body is a hollow , invaginated well-vascularized structure dorsal to the diencephalon and connected to it by a narrow hollow stalk. It frequently underlies a more or less unpigmented area of the cranial roof and is light-sensitive in some if not all fishes. Pineal functions are diverse , including light detection , circadian and seasonal clock dynamics , and color change. The pineal contains neurosensory cells that resemble cones in the retina , Photosensitivity of the pineal has been demonstrated by behavioral tests in Rainbow Trout. Light sensitivity of the pineal may allow it to play a navigation role in the cross-ocean migrations of large tunas such as the Atlantic Bluefin , Thumnus thynnus ( Rivas 1954 ; Holmgren 1958 Murphy 1971 ). The pineal may regulate color change associated with background matching. It also produces an apocrine secretion containing glycogen. There is a possibility that the pineal may also play an endocrine role , in that it produces the hormone melatonin , implying a potentialpineal-pituitary relationship 63 ). The peripheral The optic nerve ( cranial nerve The mesencephalon , or midbrain , is important in vision.

PART 3 mesencephalon

The mesencephalon , or midbrain , is important in vision. The optic nerve brings impulses from the eyes and enters the brain here. The midbrain is also a correlation center for messages coming from other sensory receptors. Fishes have two optic lobes , which are relatively large In sightfeeding species such as trouts and minnows. A C

PART 4 metencephalon

The metencephalon , or hindbrain , functions in maintaining muscular tone and equilibrium in swimming. The cerebellum , a large singie lobe , is the largest component of the fish brain. Cranial nerve IV ( trochlear ) runs from the metencephalon to the eye muscles. The metencephalon is small in lampreys ( Petromyzontidae ) and almost in hagfishes ( Myxinidae ). In elephantfishes ( Mormyridae ) , the cerebellum is hypertrophied to form the valvula cerebelli, which extend over the dorsal surface of the telencephalon. This large cerebellum is related to reception of electrical impulses.

PART 5 myelencephalon

总结回顾 标题数字等都可以通过点击和重新输入进行更改，顶部“开始”面板中可以对字体、字号等进行修改。标题数字等都 可以通过点击和重新输入进行更改，顶部“开始”面板中可以对字体、字号等进行修改。 The myelencephalon. brainstem , or medulla oblongata is the posterior portion of the brain and the enlarged anterior part of the spinal cord. Cranial nerves V through X arise here. The myelencephalon serves as the relay station for all the sensory systems except smell ( cranial nerve ) the and sight ( cranial nerve I I). It contains centers that control certain somatic and visceral functions In bony fishes , it also contains respiratory and osmoregulatory centers 标题数字等都可以通过点击和重新输入进行更改，顶部“开始”面板中可以对字体、字号等进行修改。标题数字等都 可以通过点击和重新输入进行更改，顶部“开始”面板中可以对字体、字号等进行修改。

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