Hormonal Communication

Question 1

What is the endocrine system?

Answer 1

The glands and organs that make hormones and release them directly into the blood so they can travel to tissues and organ all over the body.

Question 2

What are hormones? What is their role in the body?

Answer 2

Hormones are chemical substances that act like messengers molecules in the body- carry information from one part of the body to another.

-Are secreted directly into the blood when a gland is stimulated (change in conc of a substance e.g blood glucose)
-Once secreted, the hormones are transported to all over the body
-diffuse out of the blood and bind to specific receptors on the membrane/ cytoplasm for that hormone
-Once bound to their receptors hormones stimulate the target cell to produce a response.

Question 3

What are the types of hormones?

Answer 3

The type of hormone determines the way it cause it’s effects on a target cell.

Steroid hormones:-
-lipid soluble
-pass through the lipid component of the cell membrane
- bind to steroid hormone receptors to form a hormone-receptor complex (receptors are in cytoplasm and nucleus)
- hormone-receptor complex formed acts as a transcription factor and inhibits the transcription of a specific gene.
E.g. Oestrogen

Non- steroid hormone:-
-hydrophilic so cannot pass through the cell membrane
-bind to specific receptors on the cell surface membrane of the target cell.
-triggers a cascade reaction mediated by chemicals called second messengers.
E.g. Adrenaline

Question 4

Hormonal vs neuronal communication? 7 each

Answer 4

Hormonal System:-

• communication by hormones
• transmitted by the blood
• travel through the whole body but target organs only respond
• response is widespread
• transmission + response is slow
• response is long lasting
• may be permanent + irreversible

Nervous system:-

• communication by nerve impulses
• transmitted by neurones
• nerve impulses travel to specific parts of the body
• response is localised
• transmission + response is rapid
• response is short lived
• effect is temporary and reversible.

Question 5

What is the structure of the adrenal gland?

Answer 5

Made of endocrine tissue:-

• adrenal cortex- the outer region of the glands, produces hormones such as cortisol and aldosterone.
• adrenal medulla- inner/ centre region of the gland, produces non essential hormones such as adrenaline.

Question 6

What hormones are produces by the adrenal cortex? What is the function of the hormone?

Answer 6

Glucocorticoids: includes-
Cortisol:-
-helps regulate metabolism by controlling the conversion of fats, proteins and carbohydrates to energy.
-helps regulate blood pressure and cardiovascular function in response to stress.
Corticosterone:-
-works with cortisol to regulate immune response and suppress inflammatory reactions.
Release of these hormones is controlled by hypothalamus.

Mineralocorticoids: includes-
Aldosterone:-
-helps control blood pressure by maintaining the balance between salt and water in the blood and body fluids.
-release is mediated by signals triggered by the kidney.

Androgens: includes-
- small amounts of male and female sex hormones are released- relatively small impact compared to testosterone and oestrogen but still important, especially for menopause in women.

Question 7

What hormones are released by the adrenal medulla?

Answer 7

Hormones from adrenal medulla are released when the sympathetic nervous system is stimulated.

• Adrenaline - increases the heart rate sending blood quickly to muscles + brain. Rapidly raises blood glucose levels, by converting glycogen to glucose in the liver.
• Noradrenaline- works with adrenaline in response to stress, produces effects such as increased heart rate, widened pupils, widening air passages in lungs, narrowing of blood vessels.

Question 8

What is the two main functions of pancreas?

Answer 8

exocrine glad:- produces enzymes and released via a duct into the duodenum.

Endocrine gland:- produces hormones and secretes them into the bloodstream.

Question 9

What is the role of the pancreas as a exocrine gland?

Answer 9

Most of the pancreas is made of exocrine tissue which produces digestive enzymes and alkaline fluid known as pancreatic juice.

Enzymes and pancreatic juice are secreted into ducts and to the pancreatic duct and then released into duodenum (top part of small intestine)

Question 10

What enzyme do the exocrine glands produce?

Answer 10

Amylases- break down starch into simple sugars. E.g. Pancreatic amylase

Proteases- break down proteins to amino acids. E.g. trypsin

Lipases- break down lipids into fatty acids and glycerol. E..g. Pancreatic lipase

Question 11

What is the role of the pancreas as an endocrine gland?

Answer 11

Pancreas produces insulin and glucagon- which control blood glucose concentration.

Within the endocrine tissues are the islets of langerhans.

Question 12

What are the islets of langerhans? what are the two types?

Answer 12

Are islands of endocrine cells scattered throughout the pancreas that produce hormones that are secreted into the bloodstream.

a- alpha cells- produce and secrete glucagon

B- beta cells- produce and secrete insulin

Question 13

Glucagon

Answer 13

Glucagon is a hormone released from a-cells in the pancreas in response to low glucose concentration in order to increase the concentration back to its optimum- it does this by activating enzymes which break down glycogen into glucose (glycogenesis), producing glucose from other molecules.

Question 14

Glycogen

Answer 14

Glycogen is a multi-branched polysaccharide of glucose that serves as a form of energy storage in animals and fungi.

Question 15

Glycogenolysis

Answer 15

Is the breakdown of glycogen to produce glucose molecules.
- glucagon triggers this process after it detects a decreased blood glucose concentration-it activates enzymes within that breakdown glycogen molecules into glucose

Question 16

Gluconeogenesis

Answer 16

Is the synthesis of glucose molecules from non-carbohydrate molecules.
-Glucagon also triggers this by activating enzymes within the liver, which convert other molecules shush as fatty acids and amino acids into glucose molecules.

Question 17

Glycogenesis

Answer 17

Is the production of glycogen, when the blood glucose concentration is too high excess glucose taken from the diet is converted into glycogen which is stored in the liver and muscle cells.

Question 18

Outline the process of the secretion of insulin at high blood glucose concentration?

Answer 18

When a tide of blood glucose level is detected by the B-cells in the islets of langerhans- insulin is released.

1.At normal blood glucose levels, potassium channels in the plasma membrane of B-cells are open and potassium ions diffuse out of the cell.

2. As blood glucose concentration rises- glucose enters the cell by a glucose transporter.
3. The glucose is metabolised inside the mitochondria, resulting in the production of ATP.
4. The ATP binds to potassium channels-causing them to close (known as ATP-sensitive potassium channels)
5. As potassium ions can no longer diffuse out of the cell- depolarisation of the ions in the membrane o occurs
6. Depolarisation causes the voltage-gated calcium channels to open- calcium ions enter the cell

7.calcium ions cause secretory vesicles to
release the insulin contain by exocytosis.

Question 19

What are the two types of diabetes and describe their differences?

Answer 19

Type 1 diabetes:-
-unable to produce insulin (B-cells in islets of langerhans do not produce insulin)
-the cause is not known and the disease cannot be prevented or cured- possible to treat symptoms
-condition can arise due to result of an autoimmune response.
- normally begins in childhood- symptoms are developed quickly.

Type 2 diabetes:-
-the body cannot effectively use insulin to control blood sugar levels.
- B-cells do not produce enough insulin
-the body cells do not respond properly to insulin- glycoprotein insulin receptors on the cell membrane do not work properly.
-can be the result of excess body weight, physical inactivity and habitual excessive overeating of carbohydrates.
-begins at a later age- develops slowly.

Question 20

What is the treatment for Type 1 diabetes?

Answer 20

Is insulin-dependent
- controlled by regular injections of insulin
The insulin injected increases the amount of glucose absorbed by cells and causes glycogenesis resulting in a reduction of blood glucose concentration.

Blood sugar levels are regularly tested with a machine.

Question 21

What can happen is someone with type 1 diabetes injects themselves with too much or too less insulin?

Answer 21

If a person injects themselves with too much insulin-may experience
Hypoglycaemia (low blood glucose concentration) can result in unconsciousness.

If a person injects with too less insulin- may experience
Hyperglycaemia (high blood glucose concentration) can result in unconsciousness and death if left untreated.

Question 22

What is the treatment for type 2 diabetes?

Answer 22

The first line of control is to regulate a persons carbohydrate intake through their diet and exercise.
Loosing weight for overweight people

Also used:-
-Drugs that stimulate insulin production
-Drugs that slow down the rate at which the -body absorbs glucose from the intestines.
Insulin injections

Question 23

How is medically produced insulin produced?

Answer 23

Insulin was originally obtained from the pancreas of cows and pigs- difficult and expensive process.
Could cause allergic reactions as it’s different from human insulin.

Is now made by genetically modified bacteria
The advantages of this is:
- less likely to cause allergic reactions
- can be produced in much higher quantities
- cheaper production
- overcomes ethical and religious issues.

Question 24

How can blood glucose levels be increased?

Answer 24

• Diet- eating carbohydrate-rich foods, carbohydrates are broken down in the digestive system to release glucose and the glucose is absorbed in the bloodstream.
• Glycogenolysis
• Gluconeogensis
• Reduces amount of glucose absorbed by liver cells

Question 25

How can blood glucose levels be decreased?

Answer 25

• Respiration- glucose is used by cells to respite
• Glycogenesis-

Question 26

What is the role of insulin?

Answer 26

insulin is produced by B cells in the islets of langerhans in the pancreas- if blood glucose levels are too high B cells detect this and respond by secreting insulin into the bloodstream.
All body cells have insulin receptors on their cells surface membrane.
When insulin binds to the glycoprotein receptors it causes the tertiary structure of the glucose transport protein channels to change in shape- opening them up more and allowing glucose to enter the cell .

Question 27

How does insulin lower blood glucose concentration?

Answer 27

• increasing the rate of absorption of glucose by cells.
• increasing the respiratory rate of cells
• increasing rate of glycogenesis
• increasing the rate of Glucose to fat conversion
• decreasing the release of glucagon from a cells in the islets of langerhans in the pancreas.

Question 28

How is insulin broken down?

Answer 28

Is broken down by enzymes in the cells in liver

Insulin is constantly secreted to maintain its effect

But as blood glucose concentration returns to normal, this is detected by B cells and Insulin secretion is reduced.

Question 29

How does glucagon increase blood glucose levels?

Answer 29

Glucagon is produced by A-Cells in the islets of langerhans in the pancreas.

The decrease in blood glucose levels is detected by the a-cells and glucagon is secreted into the bloodstream.

Only liver cells and fat cells have glucagon receptors therefore they respond to glucagon.

Question 30

How does glucagon raise blood glucose concentration?

Answer 30

• Glycogenolysis
• reducing the amount of glucose absorbed by liver cells.
• increasing gluconeogenesis