5.1.4: Hormonal communication

Question 1

What is a hormone?

Answer 1

a chemical messenger secreted by a gland into the blood, which transports it to a target cell/tissue, which has specific receptors that detect it

Question 2

What is the structure of the adrenal glands?

Answer 2

• adrenal cortex (outer layer)

- medulla (inner layer)

Question 3

What is the function of the adrenal glands?

Answer 3

to secrete hormones

• cortex secretes cortisol and aldosterone
• medulla secretes adrenaline and noradrenaline

Question 4

What is the function of cortisol?

Answer 4

• regulates metabolism (controls how body converts fats, carbs, proteins, etc to energy)
• regulated blood pressure and cardiovascular function

Question 5

What is the function of aldosterone?

Answer 5

-controls blood pressure (by maintaining balance between salt and water concs in blood and body fluids) -released when triggered by kidneys

Question 6

What is the function of adrenaline?

Answer 6

-increases heart rate (to send blood quickly to brain and muscles)

Question 7

What is the function of noradrenaline?

Answer 7

• increases heart rate
• widens pupils
• widens air passages in lungs
• narrows blood vessels in non-essential organs

Question 8

What is the function of the pancreas?

Answer 8

• secretes hormones (endocrine function) eg. insulin and glucagon
• secretes enzymes (exocrine function)

Question 9

What is the microscopic structure of the pancreas?

Answer 9

-contains Islets of Langhans which have alpha and beta cells (as well as blood vessels, ribosomes, golgi body, secretory vesicles, mitochondria, etc)

Question 10

What do alpha cells do?

Answer 10

produce/secrete glucagon

Question 11

What do beta cells do?

Answer 11

produce/secrete insulin

Question 12

What is the function of glucagon?

Answer 12

to raise blood glucose conc when it is too low

Question 13

What is the function of insulin?

Answer 13

to lower blood glucose conc when it is too high

Question 14

What happens when blood glucose concentration is too low?

Answer 14

• alpha cells (in pancreas) detect change in blood glucose conc and secrete glucagon into the blood
• glucagon is detected by liver cells
• liver cells convert glycogen into glucose (glucogenesis)
• amino acids are also used to make glucose (gluconeogenesis)
• rate of facilitated diffusion of glucose into blood increases
• blood glucose concentration increases and returns to normal

Question 15

Which hormone is secreted when blood glucose concentration is too low?

Answer 15

glucagon

Question 16

What happens when blood glucose concentration is too high?

Answer 16

• beta cells (in pancreas) detect change in blood glucose conc and secrete insulin into the blood
• insulin is detected by liver cells
• rate of facilitated diffusion of glucose into liver cells increases
• liver cells convert glucose into glycogen (glycogenesis)
• excess glucose is stored as fat or lipids
• cells increase rate of respiration
• blood glucose concentration decreases and returns to normal

Question 17

Which hormone is secreted when blood glucose concentration is too high?

Answer 17

insulin

Question 18

How is insulin secretion controlled?

Answer 18

• at normal blood glucose concentrations, K+ channels in beta cells are open so K+ diffuse out of cell (inside of cell is at a potential of -70mV)
• when blood glucose concentration is high, glucose is transported into beta cells by a glucose transporter
• glucose is metabolised in mitochondria to produce ATP
• ATP binds to K+ channels, causing them to close
• K+ can no longer diffuse out of beta cells so the cell’s potential difference changes to -30mV (depolarisation)
• depolarisation causes voltage-gated Ca2+ channels to open so Ca2+ diffuse in
• Ca2+ cause secretory vesicles to move and release insulin by exocytosis

Question 19

What is diabetes mellitus?

Answer 19

when the body can no longer control blood glucose levels

Question 20

What is type 1 diabetes?

Answer 20

when beta cells don’t produce any insulin (immune system attacks/destroys beta cells)
-caused by genetics

Question 21

What is type 2 diabetes?

Answer 21

when body cells don’t respond properly to insulin or not enough insulin is produced
-caused by lifestyle (obesity, lack of exercise, etc)

Question 22

How can type 1 diabetes be treated?

Answer 22

• insulin injections

- monitoring blood glucose conc

Question 23

How can type 2 diabetes be treated?

Answer 23

-lifestyle changes (eating healthy diet, regular exercise, loosing weight, etc)

Question 24

What are the differences between type 1 and 2 diabetes?

Answer 24

• type 1 usually develops in childhood when type 2 usually develops later on
• type 1 is probs caused by genetics but type 2 is caused by lifestyle
• type 1 is treated with injections but type 2 is treated by changes to lifestyle

Question 25

Where is the insulin in insulin injections from?

Answer 25

• extracted from animal pancreases (eg. cows, pigs)

- made by genetically modified bacteria

Question 26

What is a future potential treatment of diabetes mellitus?

Answer 26

using stem cells
-stem cells could be grown into beta cells and implanted into the diabetic person’s pancreas so that they can produce insulin as normal