Chemical messengers
for homeostasis
(Chapter 3)
Endocrine glands do not have particular ducts
to carry hormones to various tissues. Hence they are known as ductless
glands. Hormones are transported through blood.
Only those cells having specific receptors can
receive a specific hormone. Each hormone molecule binds with the receptor to
form a hormone-receptor complex. Following this, enzymes are activated within
the cell and certain changes occur in cellular activities.
Pancreas
Pancreas is the gland that is connected to the
duodenum, the continuation of the stomach. The beta cells in the cell cluster
of this gland called Islets of Langerhans
Alpha cells glucagon
Beta cells insulin
How does the deficiency of insulin or the inability
of cells to use insulin affect the body?
ü Decreased
production of insulin due to the destruction of beta cells or the inability of
cell to utilize the insulin produced, raises the level of glucose in blood.
Excess glucose in the blood is expelled through urine.
·
Normally, there is no glucose in urine. Diabetes is clinically
referred to as a condition when the level of glucose before breakfast is above 126mg/100ml
of blood.
· Increased
appetite and thirst and frequent urination are the major symptoms
of diabetes.
Thyroid
gland
The anabolic and catabolic processes taking
place in the body are commonly referred a metabolism.
The thyroid gland secretes two hormones – thyroxine and calcitonin.
FUNCTIONS
OF THYROXINE
- Increases
energy production
- Raises the
rate of metabolism.
- Accelerates
the growth and development of the brain in the foetal stage and infancy.
- Regulates
growth in children.
Hypothyroidism
This is a condition in which the production of
thyroxine Decreases.
Cretinism: The decrease
in production of thyroxine during the foetal stage or infancy, hinders proper
physical and mental development.
Myxoedema: Prolonged
deficiency of thyroxine in adults
Symptoms
Low metabolic
rate- Sluggishness
- Increase in
body weight
- Hypertension
- inflammation
in body tissues
Hyperthyroidism
This is a condition in which all life
activities controlled by thyroxine accelerate due to the continuous and
excessive production of thyroxine.
Symptoms
- High metabolic
rate
- Rise in body
temperature
- Excessive
sweating
- Increased
heart beat
- Weight loss
- Emotional
imbalance
Goitre
Iodine is essential for the production of
thyroxine. The production of thyroxine is blocked in the absence of iodine. In
an attempt to produce more thyroxine, the thyroid gland enlarges.
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