Biology Test 227

Our eyes cannot see everything clearly when we enter a dark room from a bright light. The reason for this is that in bright light the size of pupil of our eye is small. When we enter the dark room, due to small size of pupil, very little light enters our eyes. But after some time, the pupil expands and we become able to see things as more light enter our eyes now. so there is adaptation of pupil according to light intensity

Olfactory glands, also known as Bowman's glands, are situated in the olfactory mucosa, beneath the olfactory epithelium, in the lamina propria, a connective tissue also containing fibroblasts, blood vessels, and bundles of fine axons from the olfactory neurons.

This defect in vision is called as 'myopia' - near sightedness. For correcting this defect in vision concave lend of suitable focal length is used. In this case the image of distant object is formed "Infront of the retina".

cAMP acts as a secondary messenger when epinephrine binds to protein receptors on the plasma membrane. It also acts as a secondary messenger and mediates many cell and tissue responses. Especially in the heart, it slows muscle contraction in response to acetylcholine.

The hormone human chorionic gonadotropin (better known as HCG) is produced during pregnancy. It is made by cells formed in the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall.

However, although hormones act more slowly than a nervous impulse, their effects are typically longer lasting. Additionally, the target cells can respond to minute quantities of hormones and are sensitive to subtle changes in hormone concentration.

In vertebrates, hormones are regulated by a complex feed back loop system.

The pituitary is called as the master gland because the hormones of pituitary control the secretions of other glands.

The hypothalamus secretes GnRH i.e., gonadotropin release hormone. The gonadotropin release hormone acts on pituitary and stimulates pituitary to release gonadotropins like FSH and LH.

The gonadotropins act on gonads and stimulate them to release sex hormones like testosterone in males.

The sex hormones like testosterone and estrogens are responsible for spermatogenesis and oogenesis and maintenance of secondary sexual characters in males and females.

So, if he is injected with an extract of pituitary, the condition can be improved.

Dopamine regulates the secretion of pituitary hormones: it inhibits permanently the production of prolactin and blocks the gonadotrophins and the thyroid-stimulating hormone. It stimulates inconstantly the secretion of growth hormone and it does not control corticotropin.

One of the small bodies of the medulla of the thymus having granular cells at the center surrounded by concentric layers of modified epithelial cells — called also thymic corpuscle.

Osteitis fibrosa cystica is a skeletal disorder resulting in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue, is caused by hyperparathyroidism, from over-active parathyroid glands.