HUMAN ENDOCRINE SYSTEM
The nervous and endocrine systems enable animals to respond to external changes and to control
conditions inside their bodies.
CHEMICAL COORDINATION
- Described as a slow, prolonged process of communicating information throughout the body by
way of chemicals called hormones.
- A variety of hormones are secreted by special glands or tissue called endocrine glands.
- The endocrine system works together with the nervous system.
What is a Hormone?
- An organic substance, usually a protein but sometimes a steroid, secreted by an endocrine
gland and carried in the blood stream to its target organ/s where it regulates metabolic
reactions.
- Hormones do not last long in the body as they are broken down by enzymes.
What is a Target Organ?
- Although hormones are carried in the blood throughout the body, they only affect certain cells.
The specific cells that respond to a given hormone have receptor sites for that hormone.
- These cells are known as target tissue or target organs.
- They can be a single gland or scattered throughout the body.
What is an Endocrine Gland?
- A vascular, ductless gland that secretes hormones which are carried in the bloodstream to their
target organs.
- Vascular means richly supplied with blood vessels.
How do Exo- and Endocrine Glands Differ?
- The secretions of an exocrine gland are carried in ducts to where they are needed (salivary
glands, liver, pancreas).
- Endocrine glands do not have ducts and their secretions are carried in the bloodstream to their
target organs.
, ENDOCRINE GLANDS IN THE BODY
1. Hypothalamus:
Part of the brain, situated above the pituitary gland. It secretes, amongst others, the hormone
ADH (Anti-Diuretic hormone).
What is the Role of ADH?
Osmoreceptors in the blood vessels of hypothalamus detect an increase in the osmolarity (low
water levels) of the blood. The hypothalamus responds and releases ADH. ADH helps conserve
water if the body is dehydrated. It does this by causing more water to be reabsorbed back into
the blood from the collecting ducts of the kidney, so less water is lost in urine.
The nervous and endocrine systems enable animals to respond to external changes and to control
conditions inside their bodies.
CHEMICAL COORDINATION
- Described as a slow, prolonged process of communicating information throughout the body by
way of chemicals called hormones.
- A variety of hormones are secreted by special glands or tissue called endocrine glands.
- The endocrine system works together with the nervous system.
What is a Hormone?
- An organic substance, usually a protein but sometimes a steroid, secreted by an endocrine
gland and carried in the blood stream to its target organ/s where it regulates metabolic
reactions.
- Hormones do not last long in the body as they are broken down by enzymes.
What is a Target Organ?
- Although hormones are carried in the blood throughout the body, they only affect certain cells.
The specific cells that respond to a given hormone have receptor sites for that hormone.
- These cells are known as target tissue or target organs.
- They can be a single gland or scattered throughout the body.
What is an Endocrine Gland?
- A vascular, ductless gland that secretes hormones which are carried in the bloodstream to their
target organs.
- Vascular means richly supplied with blood vessels.
How do Exo- and Endocrine Glands Differ?
- The secretions of an exocrine gland are carried in ducts to where they are needed (salivary
glands, liver, pancreas).
- Endocrine glands do not have ducts and their secretions are carried in the bloodstream to their
target organs.
, ENDOCRINE GLANDS IN THE BODY
1. Hypothalamus:
Part of the brain, situated above the pituitary gland. It secretes, amongst others, the hormone
ADH (Anti-Diuretic hormone).
What is the Role of ADH?
Osmoreceptors in the blood vessels of hypothalamus detect an increase in the osmolarity (low
water levels) of the blood. The hypothalamus responds and releases ADH. ADH helps conserve
water if the body is dehydrated. It does this by causing more water to be reabsorbed back into
the blood from the collecting ducts of the kidney, so less water is lost in urine.
