Hormones Flashcards
Define hormone
It is a chemical substance, produced by a glad, carried by the blood, which alters the activity of one or more specific target organs and is destroyed by the liver
What controls the endocrine system in the brain?
The hypothalamus acts as a central monitoring and control station in many of the body’s activities like thermoregulation and osmoregulation, and controls the endocrine system through its control of the pituitary gland
What are endocrine glands?
The glands that produce and secrete hormones.
They are ductless (no duct to carry away its secretions) and the hormones are secreted directly into the bloodstream and distributed around the body
What is the anti-diuretic hormone (ADH)?
It is produced by the hypothalamus, stored and released by the pituitary gland (both in the brain)
Function: osmoregulation
Target organ: walls of the collecting duct (of the kidney nephron)
What is insulin?
Secreted by the pancreas’ islets of Langerhans when blood glucose concentration is too high
Targets liver and muscle cells
- increases permeability of cell membranes to glucose, intake and removal from blood
- activates an enzyme that catalyses conversion of glucose to glycogen
What is adrenaline?
It is secreted by the adrenal glands
Functions: produced under situations of fear, stress, anger, anxiety
Target organs: heart, lungs, pupils, skin
Liver and muscle: increased conversion of stored glycogen into glucose for more respiration
Heart: increased heart rate, more glucose and oxygen supply for muscle respiration
Lungs: increased breathing rate, more oxygen absorption for respiration
Brain: increased blood flow, think more clearly
Muscle: increased blood flow, blood with oxygen and glucose can reach for more aerobic respiration
Eyes: pupil dilation, more light enters for enhanced vision
Digestive system, kidneys, skin: reduced blood flow, for more blood to brain and muscles
What is testosterone?
It is secreted by the testes
Functions as the male sex hormone
What are oestrogen and progesterone?
They are secreted by the ovaries
Function as the female sex hormone
Target organ: the uterine lining of the uterus
What is the pancreas’ function in homeostasis?
It functions as both an endocrine and exocrine gland
Endocrine (islets of Langerhans)
Cells produce hormones insulin and glucagon, secreting it directly into the bloodstream
Exocrine
Digestive enzymes and bicarbonate ions produced by pancreas are secreted into the pancreatic duct which leads to the duodenum
How does blood glucose regulation occur?
Islets of Langerhans of pancreas are stimulated
High blood glucose: insulin is secreted by beta cells, stimulating liver and muscles to convert excess glucose to glycogen for storage, reducing amount of blood glucose
Low blood glucose: glucagon is secreted by alpha cells, stored glycogen (only in liver) is converted back to glucose and enters the bloodstream, increasing the amount of blood glucose
What is diabetes mellitus?
Where the Islets of Langerhans of the pancreas does not produce sufficient insulin
The body is thus unable to control its blood glucose concentration
High blood glucose: remain high, exceeds kidney’s ability to completely reabsorb all the glucose, glucose excreted in urine
Low blood glucose: oxidase fats instead of glucose to release energy, producing ketones that are excreted in unrine
Glucose cannot be stored or effectively utilised, no glycogen stores, weak and loss of weight, potential death
Why are hormones usually produced in the form of small molecules?
Hormones are more soluble in blood plasma to be released from endocrine glands easily
Diffusion of the hormones in blood plasma is faster and it is able to reach cells of the target organs faster
Why should blood glucose be regulated?
Blood glucose levels should not get too high than norm level because blood water potential would become much more negative than norm level. Hence, causing water molecules to be drawn out of the body cells by osmosis. Hence, would increase the volume of blood, and thus put a strain on the heart due to higher blood pressure.
Blood glucose levels should not get too low than norm level because glucose is needed as a respiratory substrate (i.e. energy source for cells). Otherwise, the patient may result in unconsciousness or coma.
What is glucagon?
Released by Islets of Langerhans of pancreas when blood glucose concentration is too low
Targets muscle cells only
- activates enzyme that catalyses conversion of glycogen to glucose
