Communication, Homeostasis and Energy

Question 1

14.1
What is the endocrine system?

Answer 1

It is a communication and control system in the body.
- It involves hormones instead of electrical impulses like the nervous system

Question 2

14.1
What is the endocrine system made up of?

Answer 2

The endocrine system is made up of endocrine glands that synthesise and secrete hormones directly into blood vessels flowing through the glands

Question 3

14.1
What are hormones?

Answer 3

Hormones are chemical messengers that are secreted into the blood, transported in the bloodstream, and detected by target cells and tissues

Question 4

14.1
What are the different glands?

Answer 4

Pituitary gland, parathyroid glands (behind thyroid), thyroid gland, thymus, adrenal glands, pancreas, ovaries, testes

Question 5

14.1
What are the adrenal glands?
- what does it have

Answer 5

The adrenal glands are endocrine glands. They are located just above the kidneys
- An adrenal gland has a central medulla surrounded by a cortex

Question 6

14.1
What is the adrenal medulla?
- what does it produce and secrete

Answer 6

The medulla produces and secretes adrenaline in response to stress, pain and shock

Question 7

14.1
What does the adrenal cortex produce?
- what is mineralocorticoids and glucocorticoids

Answer 7

The cortex produces steroid hormones from cholesterol. For example:
- mineralocorticoids - help control potassium and sodium ion concentration in blood
- glucocorticoids - help control metabolism of proteins and carbohydrates in the liver

Question 8

14.2
What is the structure of the pancreas?

Answer 8

The pancreas is another example of an endocrine organ. It is a small organ found just below the stomach.

Question 9

14.2
What is the function of the pancreas?

Answer 9

The hormone-secreting cells are arranged in the islets of Langerhans. These produce insulin and glucagon, hormones that control blood glucose concentration

Question 10

14.2
Under a microscope, what would islets of Langerhans look like?
- what’s its tissue type and function

Answer 10

• lightly stained
• large, spherical clusters
• endocrine pancreas tissue type
• produce and secrete hormones

Question 11

14.2
Under a microscope, what would pancreatic acini look like?
- what’s its tissue type and function

Answer 11

• darker stained
• small, berry-like clusters
• exocrine pancreas
• produce and secrete digestive enzymes

Question 12

14.3
What is negative feedback?

Answer 12

Many homeostatic processes in the body are controlled by negative feedback. Negative feedback occurs when a change in conditions is detected and restored back to its normal level through a series of corrective measures

Question 13

14.3
How is the control of glucose an example of negative feedback?

Answer 13

Insulin and glucagon are both involved in regulating blood glucose concentration through negative feedback mechanisms, tp keep it at its normal level of 90 mg per 100 cm3 blood

Question 14

14.3
What is the body’s response when there is a decrease in blood glucose?

Answer 14

• A fall in blood glucose conc. below normal is detected by alpha cells in islets of Langerhans
• Alpha cells secrete glucagon
• Glucagon acts on liver cells to increase blood glucose concentration
• Blood glucose concentration returns to normal

Question 15

14.3
What is the body’s response when there is an increase in blood glucose?

Answer 15

• A rise in blood glucose conc. above the normal is detected by beta cells in the islets of Langerhans
• Beta cells secrete insulin
• Insulin acts on target cells, particularly muscle and liver cells, to reduce blood glucose concentration
• Blood glucose concentration returns to normal

Question 16

14.3
What is the role of insulin?

Answer 16

Insulin binds to receptors on the cell membrane of target cells, particularly muscle and liver cells. It reduces blood glucose concentration by:
1) causing more glucose channels to be inserted into the cell surface membrane, so increasing the uptake of glucose, especially by muscle cells
2) increasing the rate of respiration, so more glucose is used
3) activating enzymes involved in the conversion of glucose to glycogen - glycogenolysis - in muscle and liver cells
4) causing excess glucose to be converted into fat

Question 17

14.3
What is the role of glucagon?

Answer 17

Glucagon works in the opposite way to insulin. Only liver cells have receptors for glucagon. Glucagon binds to receptors on the cell surface membranes of liver cells and raises blood glucose concentration by:
1) converting glycogen to glucose - glycogenolysis
2) converting glycerol and amino acids into glucose - gluconeogenesis
3) causing the body to use more fatty acids in respiration

Question 18

14.3
What type of cells secrete insulin?

Answer 18

The secretion of insulin by beta cells has to be carefully controlled in response to changing concentrations of blood glucose

Question 19

14.3
How is the control of insulin levels achieved?
- What are the first 3 stages

Answer 19

1) Beta cell surface membranes contain calcium ion channels, which are closed
2) there’re also potassium ion channels in beta cell-surface membranes, which are open. These allow potassium ions to diffuse out of cell. Cell’s inside becomes more negative, + sets up potential difference (p.d.) of -70mV across membrane
3) Under high blood glucose concentrations, glucose molecules diffuse into the cell + are quickly respired to release ATP

Question 20

14.3
How is the control of insulin levels achieved?
- What are the last 3 stages

Answer 20

4) increase in ATP causes potassium ion channels to close. Potassium ions can’t move out of cell + p.d. Across membrane becomes less negative
5) change in p.d. Opens voltage-gated calcium ion channels to allow calcium ions to diffuse into the cell down their concentration gradient
6) calcium ions cause insulin-containing vesicles to move into, + fuse with, the cell surface membrane, releasing insulin by exocytosis

Question 21

14.3
What is the role of the liver in controlling blood glucose concentration?

Answer 21

The liver is the site of 3 important processes in the control of blood glucose levels: glycogenesis, glycogenolysis and gluconeogenesis
- liver cells (hepatocytes) are target cells for the hormones insulin and glucagon

Question 22

14.3
What is glycogenesis?

Answer 22

The conversion of glucose to glycogen under the influence of insulin

Question 23

14.3
What is glycogenolysis?

Answer 23

The conversion of glycogen to glucose under the influence of glucagon

Question 24

14.3
What is gluconeogenesis?

Answer 24

The conversion of non-carbohydrates to glucose under the influence of glucagon

Question 25

14.4
What is diabetes mellitus?

Answer 25

Diabetes mellitus is a medical condition where a person is unable to control their blood glucose concentration.
- These are two types of diabetes mellitus: type 1 (insulin dependent) and type 2 (insulin independent)

Question 26

14.4
What is the cause of type 1 diabetes?

Answer 26

• the pancreas stops producing insulin, usually in childhood

Question 27

14.4
What is the treatment of type 1 diabetes?

Answer 27

• injections of insulin, 2-3 times a day
• immunosuppressants

Question 28

14.4
What is the cause of type 2 diabetes?

Answer 28

• glycoprotein receptors on cell membranes are lost or lose sensitivity
• there may be a reduction in insulin production

Question 29

14.4
What is the treatment of type 2 diabetes?

Answer 29

• regulate dietary carbohydrates, especially refined sugars
• may require insulin or drugs to stimulate insulin production

Question 30

14.4
What are the potential treatments for diabetes mellitus?

Answer 30

• Diabetes used to treated with insulin from the pancreas tissue of animal (e.g. pigs)
• However, insulin is now produced by genetically modified bacteria and this has many benefits

Question 31

14.4
What are the benefits of genetically modified bacteria being used to make insulin?

Answer 31

• less chance of diabetic developing tolerance (so it’s no longer effective) and lower risk of infection
• cheaper to manufacture
• fewer ethical objections
• exact copy of human insulin, so more effective

Question 32

14.4
How could stem cells potentially be used to treat type 1 diabetes?

Answer 32

• Stem cells may provide a future treatment for Type 1 diabetes. Scientists have found precursor cells in pancreatic tissue of adult mice
• If similar cells could be found in human pancreatic tissue, they could be used to produce new beta cells

Question 33

14.5
What is adrenaline?
- what does it do

Answer 33

Adrenaline prepares the body for the ‘fight and flight’ response with numerous physiological changes

Question 34

14.5
What are the physiological changes adrenaline causes?
- fight and flight

Answer 34

The adrenaline physiological changes include:
- an increased heart rate
- pupil dilation
- increased blood glucose concentration and metabolic rate
- increased sweat production
- increased rate and depth of breathing

Question 35

14.6
What is the human heart beat at rest?
- Why must it increase at times

Answer 35

• At rest, the human heart rate beats at approximately 70 bpm.
• But when exercising or in times of danger, it is essential that heart rate increases to provide extra oxygen requires for increased respiration

Question 36

14.6
What part of the brain controls heart rate?

Answer 36

• Heart rate is involuntary and controlled by the autonomic nervous system.
• The medulla oblongata in the brain is responsible for controlling heart rate and making any necessary changes

Question 37

14.6
What are the 2 centres of the medulla oblongata?
- what do they do

Answer 37

There are 2 centres within the medulla oblongata, linked to the sinoatrial node (SAN) node in the heart by motor neurons:
- one centre raises HR by sending impulses through sympathetic nervous system, these impulses are transmitted by accelerator nerve
- one centre lowers HR by sending impulses through parasympathetic nervous system, these impulses are transmitted by the vagus nerve

Question 38

14.6
What are the 2 types of receptors, in blood vessels, which provide information that affects heart rate?

Answer 38

• baroreceptors
• chemoreceptors

Question 39

14.6
What are baroreceptors?

Answer 39

These are pressure receptors which detect changes in blood pressure
- for example. If a person’s blood pressure is low, the heart rate needs to increase to prevent fainting
- baroreceptors are present in the aorta, vena cava, and carotid arteries

Question 40

14.6
What are chemoreceptors?

Answer 40

• these are chemical receptors that detect changes in the level of particular chemicals in the blood
• for example, a chemical such as carbon dioxide
• chemoreceptors are located in the aorta, the carotid artery (a major artery in neck that supplies brain with blood), and the medulla

Question 41

14.6
What else can heart rate be influenced by?

Answer 41

Heart rate is also influenced by the presence of hormones

Question 42

14.6
Give an example of how HR can be affected by hormones?

Answer 42

• For example, in times of stress adrenaline and noradrenaline are released
• These hormones affect the pacemaker region of the heart itself (wall of upper right atrium) - they speed up your heart rate by increasing the frequency of impulses produced by the SAN