5.4 hormonal communication

Question 1

define endocrine system

Answer 1

a communication system using hormones as signalling molecules released into the bloodstream

Question 2

define hormones

Answer 2

molecules that are released by endocrine glands directly into the blood that at as messengers carrying a signal from the endocrine gland to a specific target organ or tissue

Question 3

define target cells

Answer 3

cells that posses a specific receptor on their plasma membrane and the shape of the receptor is complementary to the hormone molecules

Question 4

what are the 2 different types of hormones

Answer 4

protein
steroid

Question 5

Describe the difference between steroid and protein hormones

Answer 5

Proteins are not soluble in the phospholipid bilayer and do not enter the cell so they need to bind to the plasma membrane and release a second messenger inside the cell

steroid hormones however, can pass through the plasma membrane and enter the cell and nucleus and have a direct effect on the DNA

Question 6

what are endocrine glands

Answer 6

ductless glands that consist of groups of cells that manufacture and release hormones directly into the blood capillaries running through the gland

Question 7

define exocrine glands

Answer 7

consist of groups of cells surrounding a small duct which they secrete their product into which the leads to the site for example the salivary glands

Question 8

what are non-steroid hormones also known as

Answer 8

first messengers

Question 9

Describe the action of non-steroid hormones and the activation of the second messenger

Answer 9

Non-steroid hormones(except insulin) have this pathway

The hormone binds to the receptor on the plasma membrane, causing the activation of a G protein which in turn activates the effector - adenyl cyclase- which converts ATP into cAMP which is the second messenger and acts directly on another protein such as an ion channel

Question 10

what is the adrenal cortex

Answer 10

the outer layer of the adrenal gland

Question 11

what is the adrenal gland

Answer 11

one of a pair of gland lying above the kidneys which release adrenaline and a number of other hormones known as corticoids

Question 12

What is the adrenal medulla

Answer 12

the inner layer of the adrenal gland

Question 13

What is the name of the outermost layer of the adrenal cortex

Answer 13

zona glomerulosa

Question 14

what is the name of the middle layer of the adrenal cortex

Answer 14

zona fasciculata

Question 15

what is the name of the inner most layer of the adrenal cortex

Answer 15

zona reticularis

Question 16

what are the names of the layers in the adrenal cortex from out in

Answer 16

zona glomerulosa
zona fasciculata
zona glomerulosa

Question 17

What is the function of the zona glomerulosa

Answer 17

secretes mineralocoricoids such as aldosterone which acts on absorption of sodium and decreasing absorption of potassium ions, therefore increasing water retention and blood pressure

Question 18

What is the function of the zona fasciculata

Answer 18

secretes glucocorticoids such as cortisol which control metabolism of carbohydrates, fats and proteins in the liver and is also released in response to stress

Question 19

what is the role of the zona reticularis

Answer 19

also secretes precursor molecules and cortisol however if the correct enzymes are not present for the release of cortisol they release precursor androgens into the blood which are taken up by the testes and ovaries and converted into sex hormones

Question 20

what kind of hormones does the adrenal cortex and medulla release

Answer 20

the medulla releases protein hormones such as adrenaline and noradrenaline whereas the adrenal cortex releases steroid hormones

Question 21

Describe the action of steroid hormones

Answer 21

The steroid hormone passes through the plasma membrane of the cell and binds with a specific receptor in the cytoplasm

the receptor-steroid hormone complex enters the nucleus of the target cell and binds to another specific receptor on the chromosomal material

the binding stimulates the production of messenger RNA molecules which code for the production of proteins

Question 22

what hormones does the adrenal medulla release

Answer 22

adrenaline and noradrenaline

Question 23

what are the effects of adrenaline on the body

Answer 23

causing body hair to stand erect
increasing heart rate
dilating the pupils
increasing mental awareness
inhibiting the action of the gut

Question 24

describe the pancreas

Answer 24

they are a small organ below the stomach with both endocrine and exocrine functions

Question 25

what are the two main secretions of the pancreas

Answer 25

pancreatic juice containing enzymes which are secreted into the small intestine hormones which are secreted from the islets of Langerhan into the blood

Question 26

where are the exocrine cells found in the pancreas

Answer 26

they are in small groups surrounding tiny tubules and each group is called an acinus or acini plural

Question 27

Describe the exocrine function of the pancreas

Answer 27

the cells of the acini secrete the enzymes they produce into the tubule at the centre of the group the tubules then join to form intralobular ducts that eventually combine to form the pancreatic duct that carries the pancreatic fluid into the first part of the small intestine

Question 28

Describe the contents of the pancreatic fluid

Answer 28

pancreatic amylase lipase trypsinogen

Question 29

Explain why trypsinogen is in pancreatic fluid and not trypsin

Answer 29

because trypsinogen is an inactive form of trypsin and it is so that the pancreatic duct is not broken down by the protease enzyme

Question 30

describe the structure and function of the endocrine system of the pancreas

Answer 30

dispersed in small patches along the acini are the islets of Langerhan The islets of Langerhan contain alpha cells which secrete glucagon and beta cells which secrete insulin

Question 31

describe the release of insulin from the beta cells

Answer 31

the plasma membrane of the beta cells contain both calcium and potassium ion channels The potassium ion channels are open normally and the calcium ion channels are normally closed allowing the potassium ions to diffuse out and the potential difference inside the cell is at around-70mV When glucose concentration is high the glucose moves into the cell and is quickly used to produce ATP using the enzyme glucokinase The extra ATP causes the potassium ion channels to close so they no longer diffuse out and so the potential difference inside the cell becomes more negative This causes calcium ion voltage gated channels to open and calcium ions diffuse in and cause vesicles with insulin to fuse with the plasma membrane and diffuse out releasing insulin by exocytosis

Question 32

What is the name of the enzyme used in metabolism of glucose to make ATP

Answer 32

glucokinase

Question 33

what is the normal blood concentration of glucose

Answer 33

4-6 mmol/dm3

Question 34

define hypoglycaemia

Answer 34

when the blood glucose is too low for a long period of time

Question 35

Define hypergylcaemia

Answer 35

When blood glucose remains too high for a long period of time

Question 36

What happens if blood glucose concentration changes

Answer 36

A high blood glucose concentration is detected by the beta cells in the islets of Langerhan and insulin is released and a low blood glucose concentration is detected by the alpha cells and glucagon is released

Question 37

Describe the effects of insulin on the cell

Answer 37

more glucose enters the cell glucose is converted into glycogen for storage - glycogenesis more glucose is converted into fats more glucose is used in respiration

Question 38

What are the effects of glucagon on a cell

Answer 38

glycogen is converted into glucose glycogenolysis more fatty acids are used in respiration amino acids and fats are converted into additional glucose by gluconeogenesis

Question 39

Describe how insulin acts on a cell as a first messenger

Answer 39

when insulin binds to the insulin receptor on the plasma membrane it activates the enzyme tyrosine kinase which associated with the receptor on the inside of the plasma membrane Tyrosine kinase causes phosphorylation of inactive enzymes in the cell leading to vesicles containing glucose transporter proteins fusing and imbedding them in the plasma membrane then extra glucose enters the cell and can be converted to glycogen and fats etc.

Question 40

define diabetes mellitus

Answer 40

a condition in which blood glucose concentration cannot be controlled effectively

Question 41

define stem cells

Answer 41

unspecialised cells that have the potential to develop into any type of cell

Question 42

describe type 1 diabetes

Answer 42

insulin-dependant diabetes and usually starts in childhood thought to be as a result of autoimmune attack where the beta cells are destroyed no longer able to synthesise sufficient insulin and cannot store excess glucose as glycogen

Question 43

describe type 2 diabetes

Answer 43

non-insulin dependant as they can produce insulin but not enough and responsiveness to insulin declines caused by lack of exercise obesity a high sugar diet

Question 44

What are the treatments for type 1 diabetes

Answer 44

insulin injections insulin pump therapy islet transplantation pancreas transplant using stem cells to grow new islets of langerhan

Question 45

How would you treat type 2 diabetes

Answer 45

changes in lifestyle

Question 46

what is the source of insulin for treating diabetes

Answer 46

used to be extracted from the pancreas of animals such as pigs however more recently it is from bacteria that have undergone genetic modification

Question 47

What are the advantages of using GM bacteria as a source of insulin and not animal insulin

Answer 47

exact copy of human insulin so it is faster acting less chance of developing tolerance less chance of rejection lower risk of infection cheaper to manufacture less moral objections