Taneil Thompson
Human Endocrine System
PLEASE NOTE THAT I HAVE SIFTED THROUGH THE IEB FINAL PAPERS
FROM 2011 TO 2018 AND ADDED SOME INFORMATION THAT KEPT
COMING UP. THIS INFORMATION IS IN PINK. I HAVE ALSO CHECKED
THROUGH THE SAGS DOCUMENT TO MAKE SURE THAT ALL THE
RELEVANT INFORMATION IS HERE. J
-enable animals to respond to external changes and to control condition
inside their bodies
Chemical Co-ordination
-slow, prolonged process of communication through the body using
hormones
-hormones secreted by endocrine glands
What is hormone?
-organic chemical substance, usually protein, sometimes steroid
-secreted by endocrine glands, carried in blood to target organ to regulate
metabolic reactions
-broken down by enzymes, don’t last long in body
What is a target organ?
-cells that respond to a hormone have receptor sites for that hormone
What is an endocrine gland?
-vascular (richly supplied with blood vessels), ductless gland that secretes
hormones
How do exo- and endocrine glands differ?
-EXO= secretions carried in ducts to where they are needed
-ENDO= no ducts, secretes going through bloodstream
Endocrine glands in the body
1. Hypothalamus:
-part of brain, above pituitary gland
-secretes ADH (anti-diuretic hormone)
SAHETI School, 2019
, Taneil Thompson
Role of ADH:
-osmorecpetors in blood vessels of hypothalamus detect increase in
osmolarity (less water) of blood, ADH released
-conserves water, more water gets reabsorbed into blood from
collecting ducts and distal convoluted tubules in kidney
2. Pituitary Gland (Hypophysis):
-acts a chemical co-ordinator of other endocrine glands, “master gland”.
-attached to hypothalamus at bad of brain by short stalk
Hormones secreted by pituitary:
1. Thyroid stimulating 2. Follicle stimulating hormone (FSH):
hormone (TSH): stimulates oogenesis in ovary (formation of
stimulates thyroid gland ova) in females. Stimulates
to secrete thyroxin spermatogenesis in testes (sperm
formation)
3. Luteinizing
hormone (LH); 4. Prolactin: stimulates production of milk in
stimulates ovulation female mammary glands after birth and
(release of ovum) in responsible for maternal instinct
ovary and formation
of corpus luteum 5. Oxytocin: stimulates contraction of
(structure that womb (uterus) during childbirth and
develops in ovary lactation
after ovum is
discharged but
degenerates unless
pregnancy has begun)
6. Growth hormone (GH) or Somatotropic hormone (STH): promotes
skeletal and muscular growth by stimulating protein synthesis
-increases during puberty for a growth spurt
-levels can be tracked in blood because hormone goes through
blood to target organs
SAHETI School, 2019
Human Endocrine System
PLEASE NOTE THAT I HAVE SIFTED THROUGH THE IEB FINAL PAPERS
FROM 2011 TO 2018 AND ADDED SOME INFORMATION THAT KEPT
COMING UP. THIS INFORMATION IS IN PINK. I HAVE ALSO CHECKED
THROUGH THE SAGS DOCUMENT TO MAKE SURE THAT ALL THE
RELEVANT INFORMATION IS HERE. J
-enable animals to respond to external changes and to control condition
inside their bodies
Chemical Co-ordination
-slow, prolonged process of communication through the body using
hormones
-hormones secreted by endocrine glands
What is hormone?
-organic chemical substance, usually protein, sometimes steroid
-secreted by endocrine glands, carried in blood to target organ to regulate
metabolic reactions
-broken down by enzymes, don’t last long in body
What is a target organ?
-cells that respond to a hormone have receptor sites for that hormone
What is an endocrine gland?
-vascular (richly supplied with blood vessels), ductless gland that secretes
hormones
How do exo- and endocrine glands differ?
-EXO= secretions carried in ducts to where they are needed
-ENDO= no ducts, secretes going through bloodstream
Endocrine glands in the body
1. Hypothalamus:
-part of brain, above pituitary gland
-secretes ADH (anti-diuretic hormone)
SAHETI School, 2019
, Taneil Thompson
Role of ADH:
-osmorecpetors in blood vessels of hypothalamus detect increase in
osmolarity (less water) of blood, ADH released
-conserves water, more water gets reabsorbed into blood from
collecting ducts and distal convoluted tubules in kidney
2. Pituitary Gland (Hypophysis):
-acts a chemical co-ordinator of other endocrine glands, “master gland”.
-attached to hypothalamus at bad of brain by short stalk
Hormones secreted by pituitary:
1. Thyroid stimulating 2. Follicle stimulating hormone (FSH):
hormone (TSH): stimulates oogenesis in ovary (formation of
stimulates thyroid gland ova) in females. Stimulates
to secrete thyroxin spermatogenesis in testes (sperm
formation)
3. Luteinizing
hormone (LH); 4. Prolactin: stimulates production of milk in
stimulates ovulation female mammary glands after birth and
(release of ovum) in responsible for maternal instinct
ovary and formation
of corpus luteum 5. Oxytocin: stimulates contraction of
(structure that womb (uterus) during childbirth and
develops in ovary lactation
after ovum is
discharged but
degenerates unless
pregnancy has begun)
6. Growth hormone (GH) or Somatotropic hormone (STH): promotes
skeletal and muscular growth by stimulating protein synthesis
-increases during puberty for a growth spurt
-levels can be tracked in blood because hormone goes through
blood to target organs
SAHETI School, 2019
