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Saturday, 4 August 2018

Endocrine systems of vertebrates and their hormones.




Endocrine systems of vertebrates


Endocrine system of vertebrates are more complex than invertebrates animals.
Following three aspects are known that are related of vertebrates animals
1.      Hormones (or neuropeptides) with the same function in different species may not be chemically identical.
2. Special hormones are species-specific according to their function that conversely in some hormones produced in one species may be completely functional in another species.
3. A hormone from one species may
responses a different functions in the same target cell or tissue of a different species.

Endocrine system in fishes

 The brain and spinal cord of fishes are produced more complex hormones, with other glands being rudimentary (see figure ).

 Three major regions in jawed fishes secrete neuropeptides. The two are present in the brain that are the
pineal gland of the epithalamus and the preoptic nuclei of the hypothalamus. The neuropeptides hormone  that produced by the pineal gland  influence the certain tissue pigment and inhibit reproductive development, both of which are stimulated by light.
Pineal glands also produces,the
melatonin hormone, has major effects on body metabolism perform activity patterns at the same time with light intensity and day length.
 The preoptic nuclei produce  different other type neuropeptides that control different functions in fishes for example, growth, sleep, locomotion. The third major region of fishes that has neuropeptide function is the urophysis.
The
urophysis is a distinct structure that are present in the tail of spinal cord. The urophysis produces  hormone neuropeptides that help blood pressure, control water, ion balance, , and smooth muscle contractions.
In many fishes, , hormones (e.g., melatonin) from the pineal gland control variations in skin color. When this hormone produced by one species is injected into another species, it can induce immediately color changes (see figure).
 Hormone prolactin that  also produced by the pituitary gland. Prolactin stimulates reproductive migrations in many animals (e.g., the movement of salamanders to water). Prolactin causes brooding behavior in some fishes. That control water and salt balances, and is essential for certain saltwater fishes to enter freshwater during spawning runs.
Some aquatic animals have several small ultimobranchial glands that form in ventral to the esophagus (see figure). These glands produce the hormone calcitonin that helps
controle the concentration of blood calcium.
Specialized endocrine cells (chromaffin tissue) or glands (adrenal glands)  that lie near the kidneys   and ready thesome vertebrates for stressful emergency situations. These tissues and glands produce two hormones epinephrine or adrenaline, and norepinephrine or noradrenaline that cause vasoconstriction increased blood pressure, changes in the heart rate, and increased blood glucose levels. These hormones are involved in the “fightor-flight” reactions.

Endocrine system in birds


In some birds such as pigeons and doves, the pituitary gland secretes the hormone prolactin. Prolactin stimulates the production of “pigeon’s milk” by sloughing off cells in the pigeon’s crop. Prolactin perform some function in birds such as they stimulates and regulates broodiness and certain other kinds of parental behavior, and along with estrogen, stimulates full development of the brood (incubation) patch (see figure)
. The brood patch helps keep the eggs at a temperature between 33 and 37° C.
The endocrine glands of birds contain the following part of hormone of the pituitary, thyroid, pancreas, parathyroids, pineal, hypothalamus, ovary, testes, adrenals,  thymus, ultimobranchial, and bursa of Fabricius.

The bird’s thyroid gland produces the hormone thyroxine. Thyroxine regulates  molt cycle, normal development of feathers and plays a role in the early stage of migratory behavior. In male birds, the testes produce the hormone testosterone. Testosterone controls the 2nd sexual characteristics of the male, such as, spurs, bright plumage color, comb
and —all of which strongly influence sexual behavior.
Dorsal of the cloaca have is a sac like structure of bursa of Fabricius that just lies it. . During the bird’s embryological development, it start to begins to shrink and than after hatching. Its tissues produce secretions that are responsible for the maturation of white blood cells (B lymphocytes), which play an important role in immunological reactions.
The ultimobranchial glands are small, paired structures in the neck just below the parathyroid glands. They secrete the hormone calcitonin, that perform the function to regulate blood calcium concentrations.


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