Chemical Coordination and integration — BIOLOGY STD 11 Science — Question

1. The hypothalamus and pituitary function as an integrated and coordinated system because both of them are connected at the base of the brain.

They interact to each other in two ways:

1. By the hypophyseal portal system, which is a system of blood vessels that connects part of hypothalamus to the anterior lobe of pituitary gland. Hypothalamus secretes hormones into this portal system and the hormones act on the anterior pituitary, triggering the synthesis/ secretion of pituitary hormone.
2. The other is that they have direct anatomical connection between the hypothalamus and the posterior lobe of pituitary (posterior pituitary is actually are extension of hypothalamus). Thus, it is said that hormones released through posterior pituitary are actually released from the hypothalamus.

2. Puberty is the phenomenon of physical changes by which child's body matures into an adult male, capable of sexual reproduction to enable fertilisation. It is initiated by the hormonal signals from the brain to the gonads, i.e., testes in a male. In response to the signals, gonads produce hormones that in turn stimulates libido and the growth, function and transformation of the brain, muscles, blood, hair, sexual organs, etc. An androgen called as testosterone in males, functions as principal sex hormone, producing all changes in male and related to growth and development at puberty.