Chemical coordination and integration 3 Flashcards
testes structure
A pair of testis is present in the scrotal sac (outside abdomen) of male
individuals (Figure 22.1). Testis performs dual functions as a primary
sex organ as well as an endocrine gland. Testis is composed of
seminiferous tubules and stromal or interstitial tissue. The Leydig
cells or interstitial cells, which are present in the intertubular
spaces produce a group of hormones called androgens mainly
testosterone.
what are the functions of the andorgens
Androgens regulate the development, maturation and functions of
the male accessory sex organs like epididymis, vas deferens, seminal
vesicles, prostate gland, urethra etc. These hormones stimulate muscular
growth, growth of facial and axillary hair, aggressiveness, low pitch of
voice etc. Androgens play a major stimulatory role in the process of
spermatogenesis (formation of spermatozoa). Androgens act on the central
neural system and influence the male sexual behaviour (libido). These
hormones produce anabolic (synthetic) effects on protein and carbohydrate
metabolism
give the structure of ovayr
Females have a pair of ovaries located in the abdomen (Figure 22.1). Ovary
is the primary female sex organ which produces one ovum during each
menstrual cycle. In addition, ovary also produces two groups of steroid
hormones called estrogen and progesterone. Ovary is composed of
ovarian follicles and stromal tissues. The estrogen is synthesised and
secreted mainly by the growing ovarian follicles. After ovulation, the
ruptured follicle is converted to a structure called corpus luteum, which
secretes mainly progesterone.
what is the function of oestrogen and progesterone
Estrogens produce wide ranging actions such as stimulation of growth
and activities of female secondary sex organs, development of growing ovarian follicles, appearance of female secondary sex characters (e.g., high
pitch of voice, etc.), mammary gland development. Estrogens also regulate
female sexual behaviour.
Progesterone supports pregnancy. Progesterone also acts on the
mammary glands and stimulates the formation of alveoli (sac-like
structures which store milk) and milk secretion.
what are hormones of heart?
the atrial wall of our heart secretes
a very important peptide hormone called atrial natriuretic factor (ANF),
which decreases blood pressure. When blood pressure is increased, ANF
is secreted which causes dilation of the blood vessels. This reduces the
blood pressure.
what hormones are secreted by kidney
The juxtaglomerular cells of kidney produce a peptide hormone called
erythropoietin which stimulates erythropoiesis (formation of RBC).
explaint he different hormones secreted by gastro-intestinal trct
Endocrine cells present in different parts of the gastro-intestinal tract
secrete four major peptide hormones, namely gastrin, secretin,
cholecystokinin (CCK) and gastric inhibitory peptide (GIP).
-Gastrin
acts on the gastric glands and stimulates the secretion of hydrochloric
acid and pepsinogen.
-Secretin acts on the exocrine pancreas and
stimulates secretion of water and bicarbonate ions.
-CCK acts on both
pancreas and gall bladder and stimulates the secretion of pancreatic
enzymes and bile juice, respectively.
-GIP inhibits gastric secretion and
motility.
what do non endocrine tisssue secrete
Several other non-endocrine tissues secrete hormones called
growth factors. These factors are essential for the normal growth of tissues
and their repairing/regeneration.
how do hormones act
Hormones produce their effects on target tissues by binding to specific
proteins called hormone receptors located in the target tissues only.
Hormone receptors present on the cell membrane of the target cells are
called membrane-bound receptors and the receptors present inside the
target cell are called intracellular receptors, mostly nuclear receptors
(present in the nucleus).
what happens after binding
Binding of a hormone to its receptor leads to the
formation of a hormone-receptor complex (Figure 22.5 a, b). Each
receptor is specific to one hormone only and hence receptors are specific.
Hormone-Receptor complex formation leads to certain biochemical
changes in the target tissue. Target tissue metabolism and hencephysiological functions are regulated by hormones.
types of hormones based on chemical nature
(i) peptide, polypeptide, protein hormones (e.g., insulin, glucagon,
pituitary hormones, hypothalamic hormones, etc.)
(ii) steroids (e.g., cortisol, testosterone, estradiol and progesterone)
(iii) iodothyronines (thyroid hormones)
(iv) amino-acid derivatives (e.g., epinephrine).
Hormones which interact with membrane-bound receptors normally
do not enter the target cell, but generate second messengers (e.g., cyclic
AMP, IP3
, Ca++ etc) which in turn regulate cellular metabolism (Figure
22.5a). Hormones which interact with intracellular receptors (e.g., steroid
hormones, iodothyronines, etc.) mostly regulate gene expression or
chromosome function by the interaction of hormone-receptor complex
with the genome. Cumulative biochemical actions result in physiological
and developmental effects
