2. Glands and Hormones
• Gland is an organ that releases a chemical
substance which travels somewhere else in
the body to carry out function
• Two type of glands;
– Exocrine glands – Secrete their products
through a duct
Ex: Salivary glands, tear glands
– Endocrine glands (Ductless glands) –
Secrete products straight away to the
blood stream
Ex: Pituitary gland, Thyroid gland
• The hormones travel all around the body but
affect only recptoers of the targeted organ
Ex: Insulin affects cells of the liver which have insulin receptors
6. The thyroid and control of metabolic
rate
• Thyroid gland is the only gland that stores large amounts of hormone ( 100
day supply of thyroxin)
• Thyroxin contains element iodine
• Lack of iodine causes goiter (enlarged thyroid gland)
• Rate of Oxygen consumption is called as the Basal Metabolic Rate (BMR)
• Thyroxin
– increases BMR, stimulating cells to respire aerobically to produce more
ATP
– Increases protein synthesis which encourages growth and
development in children
7. BMR becomes back to normal
TSH act on Thyroid gland to produce thyroxin
hormone
TRH act on pituitary gland to produce TSH
(Thyroid Releasing Hormone)
Hypothalamus responds by releasing TRH (
Thyrotrophic Releasing Hormone)
Hypothalamus detects slightest drop in BMR
8. Negative Feedback
• When a change in conditions
in the body is detected,
starting a process that works to
return conditions to normal
– Metabolic Rate
– Temperature
– Water level
• Normal value in the feedback
system is called as the set
point
9. Adrenaline – The fight or flight
hormone
• Adrenaline is secreted from adrenal glands situated on the top of kidney
• Secreted in stressful events
• fight or flight response;
– Increase breathing rate and depth of a breath to receive more oxygen to body
– Increase heart rate to supply more O2 and glucose to muscles
– Blood is diverted away from the intestine to muscles
– Glycogen in the liver are metabolized in to glucose to absorb in to the muscles
– Pupils dilate, increasing visual sensitivity to movement
– Mental awareness is increased
Watch this link: https://www.youtube.com/watch?v=GilWRuk81tk
10.
11. Controlling blood glucose
• Adrenaline raises blood glucose in an emergency
• Other than adrenaline, two other hormones made by the pancreas are responsible in controlling glucose
levels by a negative feed back system
– Glucagon
• Raises the glucose concentration in the blood when it is too low
• Stimulates the liver cells to break down glycogen in to glucose
– Insulin
• Lowers the glucose concentration in the blood when it is too high
• Stimulates removal of glucose from the blood stream in to cells
• Stimulates liver cells to convert glucose in to glycogen
• This keeps blood glucose constant at a little less than 1g of glucose in every dm3 of blood
• Sugars from digested carbohydrate pass in to blood and are carried to the liver through hepatic portal vein
• In liver, glucose is converted in to glycogen and bold in the hepatic vein will have a low glucose
concentration
12. Diabetes
• A disease in which the body’s ability to produce or respond to the hormone insulin is impaired,
resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood
• Symptoms;
– Glucose in urine detected by test strips (healthy people don’t have glucose in urine)
– Frequent thirst – high blood glucose concentrated in blood is detected by hypothalamus and
stimulate thirst centers
– Frequent urination
– Loss of body weight
• In severe cases, it can lead to diabetic coma and death
• Management;
– Dietary control – limiting carbohydrate amount
– Anti diabetic medication
• Insulin injections
– Regular checkups in blood glucose level
13. Insulin
• Islets of the pancreas have two types of
specific cells
– Large alpha cells - produce glucagon
– Small beta cells – produce insulin
• Insulin is a protein
• It cannot be taken from mouth as it would be
broken down in the gut, so it is injected
• It was originally extracted from pancreases of
animals (pigs and cows) in the past
• Now, human insulin is commercially
produced from genetically modified bacteria
