5.1.4: Hormonal communication

Question 1

Exocrine glands

Answer 1

Secrete molecules into a duct which transports them to their site of action
• Don’t secrete hormones
• e.g. salivary glands

Question 2

Endocrine glands

Answer 2

Secrete hormones directly into the bloodstream, have no ducts.

Question 3

How does a hormone know where to act?

Answer 3

• Target cells have specific receptors that are complementary to the shape of the hormone.
• Cells only respond to the hormones for which they have receptors.
• Target cells are usually grouped together to form target tissues.

Question 4

Types of hormones

Answer 4

• Protein, peptide, amino acid derivatives
⟶ e.g. adrenaline, insulin
⟶ Act on cell surface receptors triggering a cascade reaction mediated by second messengers
• Steroid hormones = lipid based

Question 5

Adrenal glands are exocrine/endocrine glands?

Answer 5

Endocrine glands

Question 6

Adrenal cortex

Answer 6

Outer region of adrenal gland

Question 7

The adrenal cortex secretes

Answer 7

Hormones vital to life
• Glucocorticoids
• Mineralocorticoids
• Androgens

Question 8

Adrenal medulla

Answer 8

Inner region of adrenal gland

Question 9

The adrenal medulla secretes

Answer 9

Non-essential (for the day-to-day) hormones that help the body respond to stress
• Adrenaline
• Noradrenaline

Question 10

Mineralocorticoids

Answer 10

• controls blood pressure by maintaining salt and water concentrations of blood and bodily fluids
• mediated by signals from kidney
• e.g. aldosterone

Question 11

Glucocorticoids

Answer 11

• regulate metabolism by controlling how body converts fats, proteins, etc. to energy
• regulate immune response
• associated with responses to stress

Question 12

Androgens

Answer 12

• small amounts of male and female hormones

* effect is minor by important

Question 13

Adrenaline

Answer 13

• increases heart rate

* stimulates glycogenolysis in the liver

Question 14

Noradrenaline

Answer 14

• dilates bronchi

* stimulates narrowing of blood vessels to non-essential organs which raises blood pressure

Question 15

Pancreas contains

Answer 15

both exocrine and endocrine tissues
• Exocrine tissue secretes digestive enzymes (pancreatic amylase) into pancreatic duct to duodenum
• Endocrine tissue secretes insulin, glucagon into blood

Question 16

Islets of Langerhans

Answer 16

• Endocrine tissue: produce and secrete hormones
• Large spherical clusters made up of 𝜶 and 𝛽 cells
• Lightly staining

Question 17

Pancreatic acini

Answer 17

• Exocrine tissue: produce and secrete digestive enzymes
• Small, berry-like clusters
• Darkly staining
• 1 acinar cell –cluster of–> an acinus
many clusters = acini

Question 18

Normal blood glucose level

Answer 18

90mg per 100cm³ of blood

Question 19

Hyperglycaemia

Answer 19

Abnormally high blood glucose

⟶ Can impact osmotic balance leading to water being excreted

Question 20

Hypoglycaemia

Answer 20

Abnormally low blood glucose

⟶ Can mean insufficient glucose for respiration, leading to coma and death

Question 21

Insulin is produced by

Answer 21

𝛽 cells in the Islets of Langerhans in the pancreas

Question 22

Glucagon is produced by

Answer 22

𝜶 cells in the Islets of Langerhans in the pancreas

Question 23

Insulin (effect on body)

Answer 23

• Inhibit the release of glucagon from 𝜶 cells
• Increase respiratory rate of body
• Stimulates glycogenesis in liver and muscle cells
• Activates enzymes which convert glucose into fat

Question 24

Glucagon (effect on body)

Answer 24

• Stimulates glycogenolysis in liver cells
• Liver cells absorb less glucose from blood
• Liver cells convert amino acids and glycerol into glucose (gluconeogenesis)
• Fatty acids are used in respiration rather than glucose

Question 25

Which hormone responds to low blood glucose?

Answer 25

Glucagon

Question 26

Which hormone responds to high blood glucose?

Answer 26

Insulin

Question 27

Control of blood sugar (and homeostatic control generally) is an example of

Answer 27

negative feedback

Question 28

Negative feedback

Answer 28

feedback causes the corrective measures to be switched off when the system returns to 'set point'

Question 29

Control of insulin secretion (resting state)

Answer 29

* K+ channels in the plasma membrane of 𝛽 cells are open * K+ ions diffuse out of the cell * The potential difference across the membrane is -70mV

Question 30

Control of insulin secretion (increase in blood glucose)

Answer 30

• Glucose enters cell via glucose transporter • Glucose is used in respiration --> mitochondria synthesise ATP • ATP binds to ATP-sensitive K+ channels, causing them to close • K+ ions can no longer diffuse out of the cell The potential difference across the membrane reduces to -30mV as the membrane becomes depolarised • Voltage gated Ca2+ ion channels open • Ca2+ ions diffuse into the cell • This causes secretory vesicles containing insulin to fuse with the plasma membrane and release insulin by exocytosis

Question 31

Cause of Type 1 diabetes

Answer 31

𝛽 cells in the Islets of Langerhans do not produce insulin

Question 32

Cause of Type 2 diabetes

Answer 32

𝛽 cells do not produce enough insulin or person's body cells do not respond to insulin

Question 33

Original cause of Type 1 diabetes

Answer 33

Not known; maybe an autoimmune attack on 𝛽 cells

Question 34

Original cause of Type 2 diabetes

Answer 34

* (generally) excess body weight, physical inactivity, overeating of refined carbohydrates * genetic components in some cases

Question 35

Typically age of onset Type 1 diabetes

Answer 35

Childhood (usually)

Question 36

Typically age of onset Type 2 diabetes

Answer 36

Traditionally 40+

Question 37

Treatment for Type 1 diabetes

Answer 37

Regular insulin injections

Question 38

Treatment for Type 2 diabetes

Answer 38

* Regulation of carbohydrate intake * Increased exercise * Drugs to stimulate insulin production

Question 39

Current treatments for diabetes

Answer 39

Pancreas transplant | Insulin produced by genetically engineered bacteria

Question 40

Future treatments for diabetes

Answer 40

Potential use of stem cells to create person's 𝛽 cells