✨Module 5: Hormonal communication

Question 1

What is the endocrine system?
Give some examples of endocrine glands.

Answer 1

Endocrine glands secretes hormone directly into the bloodstream.
Pancreas, adrenal glands, pituitary gland.

Question 2

Function of the pituitary gland?

Answer 2

RELEASES ADH which increases water absorption in kidneys.

Question 3

Function of the thyroid gland?

Answer 3

Produces thyroxine which controls rate of metabolism and rate that glucose is used up in respiration.

Question 4

Function of adrenal glands?

Answer 4

Produces adrenaline which increases heart and breathing rate and raise blood sugar level.

Question 5

Function of thymus?

Answer 5

Produces thymosin which produces white blood cells.

Question 6

Function of ovary?

Answer 6

Produces oestrogen which controls ovulation and secondary sexual characteristics.
Progesterone which prepares the uterus lining for receiving an embryo.

Question 7

Function of testes?

Answer 7

Produces testosterone which controls sperm production and secondary sexual characteristics.

Question 8

What is an exocrine gland?

Answer 8

Secrete chemicals through ducts into organs/to surface of body.

Question 9

Explain what steroid hormones are.

Answer 9

Lipid soluble so they diffuse through phospholipid bilayer and bind to steroid hormone receptors.
The hormone receptor complex formed acts as a transcription factor which facilitates or inhibits the transcription of a specific gene. E.g oestrogen.

Question 10

What are non-steroid hormones?

Answer 10

Hydrophilic/water soluble so they can’t directly diffuse through phospholipid bilayer as they won’t fit through channel proteins as they’re too big. They bind to specific receptors on plasma membrane of the target cell.
This triggers a cascade of reactions controlled by secondary messengers. Acetylcholine can act as a hormone in this way.

Question 11

Comparisons between hormonal and nervous system?

Answer 11

Nervous - by nerve impulses by neurones, very quickly, response is localised and short lived.

Hormonal - hormones travel in bloodstream, longer lasting and widespread effect as hormones are not broken down as quickly as neurotransmitters, slower transmission than nervous as hormones aren’t directly released onto target cells.

Question 12

Describe the 2 distinct parts (surrounded by a capsule) that make up the adrenal gland.

Answer 12

Adrenal cortex - outer region that produces cortisol and aldosterone.
Medulla - inner region that produces peptide hormones such as adrenaline. Peptide based hormones cannot cross cell surface membrane so they bind to complementary receptors. Steroids can cross cell surface membrane so has a direct effect.

Question 13

The adrenal cortex produces what 3 main types of hormone?

Answer 13

Glucocorticoids, mineralocorticoids, androgens.

Question 14

Type of glucocorticoid hormone.

Answer 14

Cortisol regulates blood pressure, metabolism and increase blood glucose in response to STRESS. Gluconeogenesis, glycolysis. It can decrease the sensitivity of tissues to insulin and also cause gluconeogenesis.

Question 15

Type of mineralocorticoid.

Answer 15

Aldosterone regulates blood pressure and water balance in the blood by controlling Na+ and K+ levels in the body. Aldosterone signals the kidneys to increase the amount of sodium and water reabsorbed from the urine and back into the bloodstream. This increase in sodium and water in the blood contributes to an increase in blood volume, which in turn can raise blood pressure.

Question 16

Androgens

Answer 16

Sex hormones for male and female that coordinate ovary function and fertility.

Question 17

When does the adrenal medulla release hormones?

Answer 17

When the sympathetic nervous system is stimulated. This occurs when body is stressed.

Question 18

What are 2 hormones released by adrenal medulla and describe their function.

Answer 18

1. Adrenaline - increases hr by sending blood quickly to muscles and brain. Also rapidly raises blood glucose by converted glycogen to glucose in liver.
2. Noradrenaline - works with adrenaline in response to stress by increasing alertness. Widens pupils, increases hr, narrowing blood vessels in non-essential organs.

Question 19

Fight or flight physiological responses.

Answer 19

=> Heart rate increases to pump more oxygenated blood around the body.
=> Pupils dilate to allow more light in for better vision.
=> Arterioles in skin constrict so more blood towards muscles, brain, heart.
=> Blood glucose level rises to increase respiration for muscle contraction.
=> Smooth muscle of airways relaxes too allow more oxygen into lungs.

Question 20

Describe the mechanism for the fight or flight response.

Answer 20

1. Sensory neurones detect environmental stimuli associated with danger and send impulses to the brain.
2. The amygdala in the cerebrum sends impulses to other parts of brain, including the hypothalamus.
3. Hypothalamus sends impulses via the sympathetic nerves to the adrenal glands, so the adrenal medulla secretes adrenaline.
4. At the same time, the hypothalamus also releases a peptide hormone that stimulates the anterior pituitary gland to release ACTH.
5. ATCH is transported to the adrenal glands via the bloodstream, causing the adrenal cortex to secrete the hormone cortisol. Cortisol stimulates target organs and tissues to increase blood pressure, blood glucose ensuring the tissues have sufficient glucose and oxygen needed for rapid response. Cortisol also suppresses the immune system.

Question 21

effect of adrenaline/

Answer 21

=> Increases diameter of bronchioles by relaxing smooth muscle. Increases airflow to alveoli.
=> Less blood flow to skin and gut via vasoconstriction. This leads to higher blood pressure.
=> More blood flow to brain and muscles by vasodilation.
=> Glycogen broken down into glucose in liver cells.
heart rate increases to pump more oxygeneted blood around body.
pupils dilate to take in much light for better vision.
Arterioles in skin constrict so more blood to major muscle groups (vasodilation) like brain, heart, muscles.
blood glucose increases

The secondary messenger model and adrenaline.
Blood glucose concentration increases when adrenaline is secreted. Adrenaline binds to receptors on the cell surface membrane of liver cells. Change in shape of receptor. Activates a G protein. G protein activates adenyl cyclase enzyme. This enzymes catalyses the formation of the secondary messenger cyclic AMP from ATP. cAMP binds to protein kinase A enzymes, activating them. Active protein kinase A enzymes activate phosphorylase kinase enzymes by adding phosphate groups to them. Active phosphorylase kinase enzymes activate glycogen phosphorylase enzymes. Glycogen phosphorylase enzymes catalyse the breakdown of glycogen to glucose => glycogenolysis.

What is the primary and secondary messenger for adrenaline?
1st - adrenaline that transmits a signal around the body.
2nd - cAMP transmits signal inside the cell.

Question 22

Why do people feel cold in times of stress?

Answer 22

2 Less blood in the skin to keep it warm, hence the skin feels cold (1); as the blood has been
redirected to muscles to aid movement/ability to run

Question 23

Explain how nervous and endocrine system work together to enable the body to respond to danger.

Answer 23

Danger detected by the autonomic nervous system (1); hypothalamus triggers
sympathetic nervous system (1); nervous impulse triggers release of hormones from adrenal medulla
(1); adrenaline causes glycogenolysis in liver cells (1); credit detail of second messenger model (1);
increased blood glucose used for respiration/create energy for muscle contraction (1); other
appropriate hormone and response (1); pituitary gland stimulates the adrenal-cortical system (1);
hormones release from adrenal cortex (

Question 24

Explain the EXOCRINE function of the pancreas.

What 3 digestive enzymes does the pancreas produce?

Answer 24

Produces pancreatic juice (containing digestive enzymes) to be delivered to the small intestine where it helps in the digestion of food.

Amylase - break down starch into simple sugars.
Lipase - break down lipids into fatty acids and glycerol.
Protease - break down proteins into amino acids.

Question 25

Describe briefly how the pancreas is also an endocrine gland.

Answer 25

Islets of Langerhans produces and secretes the hormones insulin and glucagon into the bloodstream.

Question 26

Within the Islets of Langerhans there are 2 types of cell called ...

Answer 26

Alpha cells - produce and secrete glucagon. Beta cells - produce and secrete insulin. Alpha cells are larger and more numerous than beta cells. Insulin and glucagon bind to their specific receptors on liver cells to have their function.

Question 27

Does diet increase glucose concentration in blood?

Answer 27

Yes, carbohydrate rich foods such as pasta and cakes are broken down to glucose in the digestive system. The glucose is reabsorbed into bloodstream, so concentration rises.

Question 28

Explain the two processes that happen when blood glucose concentration is low.

Answer 28

Glycogenolysis - glycogen stored in liver and muscle cells are broken down into glucose, triggered by glucagon. Gluconeogenesis - production of glucose from non-carbohydrate sources. E.g liver can make glucose from lipids and amino acids.

Question 29

Explain two processes that happen when blood glucose concentration is high.

Answer 29

Glycogenesis - produces glycogen in liver. Respiration - some glucose in blood is used by cells to release energy.

Question 30

How does insulin released by beta cells lower blood glucose?

Answer 30

1. Increasing the absorption of glucose into cells - when insulin binds to its glycoprotein receptor, it causes a change in tertiary structure of glucose transport channels. This causes channels to open to allow more glucose into the cell. 2. Increasing rate of glycogenesis. 3. Inhibiting the release of glucagon from alpha cells. 4. Increasing rate of respiration in cells so higher uptake of glucose from blood.

Question 31

Decreased blood glucose concentration.

Answer 31

=> Decrease in blood glucose concentration is detected by α and β cells in the pancreas. => α cells respond by secreting glucagon. => β cells respond by stopping insulin secretion. => Glucagon binds to receptors in the cell surface membranes of liver cells. => This binding causes a conformational change in the receptor protein that activates a G protein. => This activated G protein activates the enzyme adenylyl cyclase. => Active adenylyl cyclase catalyses the conversion of ATP to the second messenger, cyclic AMP (cAMP) => cAMP binds to protein kinase A enzymes, activating them. => Active protein kinase A enzymes activate phosphorylase kinase enzymes by adding phosphate groups to them. => Active phosphorylase kinase enzymes activate glycogen phosphorylase enzymes that break down glycogen to glucose. This is glycogenolysis. The hormone adrenaline also increases the concentration of blood glucose. It does this by binding to different receptors on the surface of liver cells that activate the same enzyme cascade and lead to the same end result – the breakdown of glycogen by glycogen phosphorylase. Adrenaline also stimulates the breakdown of glycogen stores in muscle during exercise. The glucose produced remains in the muscle cells where it is needed for respiration.

Question 32

Increased blood glucose concentration.

Answer 32

=> Detected by β cells in the pancreas. => Glucose molecules enter the β cells by facilitated diffusion. => The cells respire this glucose and produce ATP. => High concentrations of ATP causes the potassium channels in the β cells to close, producing a change in the membrane potential. => This change in the membrane potential causes the voltage-gated calcium channels to open, so influx of Ca2+ ions into the β cell. => This causes the β cells to secrete insulin. => Insulin-containing vesicles move towards the cell-surface membrane where they release insulin into the capillaries. => It stimulates the uptake of glucose by muscles cells, fat cells and the liver.

Question 33

What is the role of insulin?

Answer 33

Muscle cells and liver cells have glucose transporter proteins in their surface membranes. These are insulin sensitive. => Insulin binds to specific receptors on the membranes of target cells. => This stimulates them to activate/add more glucose transporter proteins to their cell surface membrane which increases the permeability of the cells to glucose. So more facilitated diffusion of glucose into cells and in the liver by glycogenesis. => Once glucose has entered a liver cell an enzyme rapidly converts it to glucose phosphate. => Different enzymes then convert glucose phosphate into glycogen. => α and β cells in the pancreas act as the receptors => They release the hormones glucagon (secreted by α cells) and insulin (secreted by β cells) => Liver cells act as the effectors in response to glucagon and liver, muscle and fat cells act as the effectors in response to insulin.

Question 34

Diabetes.

Answer 34

The kidneys are unable to filter out this excess glucose in the blood and so it often appears in the urine. The increased glucose concentration also causes the kidneys to produce large quantities of urine, making the individual feel thirsty due to dehydration. Type 1: pancreas can't produce insulin due to an autoimmune response that attacks the beta cells of the islets of Langerhan. Fatigue, organ damage. Regular blood tests to work out the dose of insulin to inject. Type 2: pancreas produces insulin but receptors don't respond to it. Or insufficient insulin produced by pancreas. The lack of response to insulin means there is a reduced glucose uptake which leads to an uncontrolled high blood glucose concentration. This can cause the β cells to produce larger amounts of insulin which ultimately damages them. Maintain a low carbohydrate diet and regular exercise to reduce need for insulin.

Question 35

producing insulin using GM bacteria.

Answer 35

DNA that has been altered by introducing nucleotides from another source is called recombinant DNA (rDNA) If the organism contains nucleotides from a different species it is called a transgenic organism Any organism that has introduced genetic material is a genetically modified organism (GMO) Recombinant DNA has been used to produce recombinant proteins (RP), thus recombinant proteins are manipulated forms of the original protein Recombinant proteins are generated using microorganisms such as bacteria, yeast, or animal cells in culture. They are used for research purposes and for treatments (eg. diabetes, cancer, infectious diseases, haemophilia) Most recombinant human proteins are produced using eukaryotic cells (eg. yeast, or animal cells in culture) rather than using prokaryotic cells, as these cells will carry out the post-translational modification (due to the presence of Golgi Apparatus and/or enzymes) that is required to produce a suitable human protein In 1982, insulin was the first recombinant human protein to be approved for use in diabetes treatment Bacteria plasmids are modified to include the human insulin gene Restriction endonucleases are used to cut open plasmids and DNA ligase is used to splice the plasmid and human DNA together These recombinant plasmids are then inserted into Escherichia coli by transformation (bath of calcium ions and then heat or electric shock) Once the transgenic bacteria are identified (by markers), they are isolated, purified and placed into fermenters that provide optimal conditions The transgenic bacteria multiply by binary fission and express the human protein - insulin, which is eventually extracted and purified The advantages for scientists to use recombinant insulin are: It is identical to human insulin unless modified to have different properties (eg. act faster, which is useful for taking immediately after a meal or to act more slowly) There is a reliable supply available to meet demand (no need to depend on the availability of meat stock) Fewer ethical, moral or religious concerns (proteins are not extracted from cows or pigs) Fewer rejection problems or side effects or allergic reactions Cheaper to produce in large volumes It is useful for people who have animal insulin tolerance

Question 36

Producing insulin using stem cells.

Answer 36

Stem cells can be treated so that they differentiate into pancreatic β cells These newly developed β cells can then be transplanted into the pancreas of a diabetic individual, replacing the damaged cells and allowing them to produce insulin.

Question 37

Explain why the protein insulin must be administered intravenously rather than orally.

Answer 37

Insulin is a protein, if it was taken orally it would be digested by the enzyme protease found in the gut before entering the bloodstream.