CHAPTER SEVEN
ENDOCRINE SYSTEM
DEFINITIONS
Exocrine Glands: these glands have ducts. ie Salivary glands, sweat glands
Endocrine Glands: glands which secrete hormones. They do not have ducts. Ie
thyroid gland; adrenal gland.
Hormones: organic chemical messengers which are mostly protein in nature.
● Form an integrated system allowing coordination and homoeostasis
● Control functions like growth or reproduction
● They are secreted into the blood
Target Organs: organs which are stimulated by hormones
THE NEED FOR AN ENDOCRINE SYSTEM
Homeostasis: finding balance
Coordination: the linking together of all bodily activities for effective and
harmonious functioning of an organism as a whole
The two systems which are responsible for coordination in the body are the
nervous system and the endocrine system. Each system works together but each
system works differently.
NERVOUS CHEMICAL
The message is carried as an impulse The message is carried by a hormone
It's travels fast It travels slowly
It is carried along by nerves It is carried by the blood
The message acts for short period of The message acts for a long period of
time time
It targets a specific area It acts over a wide area
It causes an immediate reaction It results in a long-term reaction
which is delayed and prolonged
, GLANDS AND THEIR FUNCTIONS
HYPOTHALAMUS
● it is located on the underside of the brain
ADH
TOO LITTLE WATER
● ADH secreted in large amounts
● Increases permeability of the distal convoluted tubule and collecting
tubule walls
● More water leaves the tubules into the medulla where it is reabsorbed by
the blood capillaries
● Excessive water loss from blood is prevented
TOO MUCH WATER
● ADH secretion is decreased, the permeability of the walls decreases
● Less water leaves and the remaining water is lost with the urine
● Excess water is excreted
ENDOCRINE SYSTEM
DEFINITIONS
Exocrine Glands: these glands have ducts. ie Salivary glands, sweat glands
Endocrine Glands: glands which secrete hormones. They do not have ducts. Ie
thyroid gland; adrenal gland.
Hormones: organic chemical messengers which are mostly protein in nature.
● Form an integrated system allowing coordination and homoeostasis
● Control functions like growth or reproduction
● They are secreted into the blood
Target Organs: organs which are stimulated by hormones
THE NEED FOR AN ENDOCRINE SYSTEM
Homeostasis: finding balance
Coordination: the linking together of all bodily activities for effective and
harmonious functioning of an organism as a whole
The two systems which are responsible for coordination in the body are the
nervous system and the endocrine system. Each system works together but each
system works differently.
NERVOUS CHEMICAL
The message is carried as an impulse The message is carried by a hormone
It's travels fast It travels slowly
It is carried along by nerves It is carried by the blood
The message acts for short period of The message acts for a long period of
time time
It targets a specific area It acts over a wide area
It causes an immediate reaction It results in a long-term reaction
which is delayed and prolonged
, GLANDS AND THEIR FUNCTIONS
HYPOTHALAMUS
● it is located on the underside of the brain
ADH
TOO LITTLE WATER
● ADH secreted in large amounts
● Increases permeability of the distal convoluted tubule and collecting
tubule walls
● More water leaves the tubules into the medulla where it is reabsorbed by
the blood capillaries
● Excessive water loss from blood is prevented
TOO MUCH WATER
● ADH secretion is decreased, the permeability of the walls decreases
● Less water leaves and the remaining water is lost with the urine
● Excess water is excreted
