5.4 Hormonal communication

Question 1

define exocrine gland

Answer 1

do not release hormones and consist of groups of cells surrounding a small duct( their products are secreted into ducts)

Question 2

define endocrine gland

Answer 2

release hormones directly into the blood stream

Question 3

define hormone

Answer 3

proteins or steroids that are released by endocrine glands directly into the blood. They act as messengers, carrying a signal from the endocrine gland to a specific target organ or tissue

Question 4

define target cells

Answer 4

for non-steroid hormones, cells that possess a specific receptor on their plasma membrane. The shape of the receptor is complementary to the shape of the hormone molecule.

Question 5

what are the 2 types of hormone

Answer 5

protein hormones
steroid hormones

Question 6

describe protein hormones and give examples

Answer 6

not lipid soluble so bind to cell surface membrane and release second messenger inside the cell (adrenaline, insulin and glucagon)

Question 7

describe steroid hormones and give examples

Answer 7

lipid soluble, have direct effect on DNA (oestrogen and testosterone)

Question 8

why are non steroid (protein) hormones known as first messengers

Answer 8

they are signalling molecules outside the cell that bind to the cell surface membrane and initiate an effect inside the cell which causes the release of another signalling molecule in the cell which stimulates a change in the activity of the cell

Question 9

how does a protein hormone (apart from insulin) cause effect on a cell

Answer 9

-The hormone binds to a specific receptor on the cell surface membrane
-This activates the G protein which activates adenyl cyclase ( a enzyme that converts an inactive molecule into the second messenger)
-this converts ATP to cAMP (this is the second messenger)
-cAMP may act directly on another protein or initiate a cascade of enzyme controlled reactions that alter the activity of the cell

Question 10

how does a steroid hormone cause an effect on a cell

Answer 10

-steroid hormone passes through the plasma membrane of the target cell
-it 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 DNA
-binding stimulates the production of mRNA which codes for the production of new proteins

Question 11

what are the parts of the adrenal glands in the kidney

Answer 11

adrenal medulla (makes protein hormones)
adrenal cortex (makes steroid hormones)

Question 12

what does the adrenal medulla produce

Answer 12

adrenaline and noradrenaline

Question 13

what happens when the adrenal medulla produces adrenaline

Answer 13

it travels through the blood stream to its target area where it binds with a specific receptor: this activates the G protein which activates the effector molecule adenal cyclase. This turns ATP into cAMP and this will either act directly on another protein or may initiate a cascade of enzyme controlled reactions.

Question 14

what are the effects that adrenaline has on the body

Answer 14

-relaxes smooth muscle in the bronchioles
-increases stroke volume of the heart
-increases heart rate
-stimulates conversion of glycogen to glucose
-dilates the pupils
-increases mental awareness
-causes body hair to stand erect

Question 15

what are the 3 layers of the adrenal cortex

Answer 15

-zona glomerulosa (outermost layer)
-zona fasciculata (middle layer)
-zona reticularis (inner layer)

Question 16

what does the zona glumerulosa do

Answer 16

secretes mineralocorticoids such as aldosterone. The mineral corticoids help control concentrations of sodium and potassium in the blood which contributes to maintaining blood pressure.
Aldosterone acts on the cells of the distal tubules and collecting ducts in the kidney which increases absorption of sodium ions, decreases absorption of potassium ions and increases water retention so increases blood pressure

Question 17

what does the zona fasciculata do

Answer 17

secretes glucocorticoids such as cortisol.
glucocorticoids help control the metabolism of carbohydrates, fats and proteins in the liver. Cortisol is released in response to stress or low blood glucose concentration. It stimulates the production of glucose from stored compounds in the liver.

Question 18

what does the zona reticularis do

Answer 18

secretes precursor molecules that are used to make sex hormones. Cortisol may also be released. If correct enzymes are not present for the release of cortisol, then the zona reticularis release precursor androgens into the blood. These are taken up by the ovaries/testes and converted to sex hormones.

Question 19

why is the pancreas unusual

Answer 19

it has endocrine and exocrine functions

Question 20

what does the pancreas have that acts as exocrine

Answer 20

cells that secrete enzymes
a tubule in the centre of group of enzyme secreting cells
acinus of exocrine tissue (the tubule and cells altogether)

Question 21

what does the pancreas have that acts as endocrine

Answer 21

islet of langerhans
alpha cells
beta cells

Question 22

what do the tubules of the acini join to form

Answer 22

intralobular ducts then they combine to from the pancreatic duct which carries fluid containing enzymes into the first part of the small intestine (duodenum)

Question 23

EXOCRINE FUNCTION: what does the fluid from the pancreatic duct contain

Answer 23

-pancreatic amylose- a carbohydrase which digests amylose to maltose
-trypsinogen-inactive protease which will be converted to active form trypsin when it enters the duodenum
-lipase- digests lipid molecules
-sodium hydrogen carbonate- makes it alkaline, helps neutralise the contents of the digestive system that have just left the acid environment of the stomach

Question 24

n what is the endocrine function of the pancreas

Answer 24

alpha cells- glucagon
beta cells- insulin

Question 25

describe how insulin is secreted

Answer 25

-cell membrane has potassium and calcium ion channels
-potassium ion channels are normally open so they diffuse out making the inside of the cell more neg
-when blood glucose conc is high, glucose moves into the cell
-glucose is metabolised with glucokinase to produce ATP
-extra ATP closes potassium ion channels
-potential difference across membrane is altered and the cell become less neg
-change in potential difference opens the calcium ion voltage gated channels
-calcium ions enter the cell and cause the secretion of insulin by moving the vesicles containing insulin to the plasma membrane and initiating exocytosis

Question 26

what happens if blood glucose rises too high

Answer 26

-person eats meal containing glucose
-blood glucose levels rise which is detected by the islet of langerhan which causes the beta cells to begin secreting insulin and the alpha cells stop secreting glucagon
-insulin binds with a specific membrane bound receptor on the target cells (liver, muscle cells and brain)
-this activates the enzyme tyrosine kinase which causes phosphorylation which causes inactive enzymes to become active
-vesicles containing glucose transporter proteins fuse with the plasma membrane enabling extra glucose to enter the cell

Question 27

what effects does insulin have on a cell

Answer 27

-more transporter proteins specific to glucose are placed into the cell surface membrane=more glucose leaves the blood and enters the cell
-glucose in the cell is converted to glycogen for storage
-more glucose is converted to fats
-more glucose is used in respiration

Question 28

what happens if blood glucose levels drop too low

Answer 28

-a person does a lot of exercise
-lowers the blood glucose levels which is detected by the islet of langerhan: beta cells stop secreting insulin and alpha cells begin secreting glucagon into the blood
-glucagon binds to specific receptors for glucagon on its target cells
-this stimulates the G protein inside the membrane which activates adenyl cyclase
-this converts ATP to cAMP which activates a series of enzyme controlled reactions in the cell
- this raises blood glucose levels

Question 29

what are the effects of glucagon

Answer 29

-glycogenolysis
-more fatty acids are used in respiration
-gluconeogensis

Question 30

why is the control of blood glucose levels an example of negative feedback

Answer 30

insulin and glucagon have opposite effects on blood glucose concentration

Question 31

why does the concentration of glucose in the blood not remain constant

Answer 31

it fluctuates around the required conc, when glucose conc rises too high, the release of insulin will bring it down, if the conc falls too low, the release of glucagon will bring it up

Question 32

why is it important that a persons blood glucose levels do not get too low for a long period of time.

Answer 32

hypoglycaemia: inadequate delivery of glucose to the body tissues and brain
causes tiredness and irritability. In serious cases, impairment of brain function and confusion, seizures, unconsciousness and death

Question 33

why is it important that a persons blood glucose levels do not get too high for a long period of time.

Answer 33

hyperglycaemia:leads to significant organ damage and can be used as diagnosis for diabetes

Question 34

define glycogenolysis

Answer 34

glycogen broken down to glucose

Question 35

define glucagon

Answer 35

hormone released from alpha cells

Question 36

define glycogen

Answer 36

an energy storage molecule

Question 37

define glycogenesis

Answer 37

glucose converted to glycogen

Question 38

define glyconeogenesis

Answer 38

amino acids and fats converted into glucose

Question 39

define glucose

Answer 39

used in respiration to generate ATP

Question 40

what does type 1 diabetes result from

Answer 40

-starts in childhood
-autoimmune response (immune system attacks and destroys beta cells, receptors on B/T cells are complementary to the antigens on beta cells)
-viral attack

Question 41

what does type 1 diabetes mean for someone

Answer 41

they are unable to synthesise sufficient insulin and cannot store excess glucose as glycogen so:
-glucose in blood is not removed quickly-prolonged period of high conc.
-when blood glucose falls, no store of glycogen to release glucose, period of low conc.

Question 42

how can you treat type 1 diabetes

Answer 42

-insulin injections
-insulin pump therapy(small device constantly pumps insulin into bloodstream through needle that is permanently inserted under the skin
-islet cell transportation
-complete pancreas transplant
-in future, looking to use stem cells to grow new islets of langerhans

Question 43

what does type 2 diabetes result from

Answer 43

-starts in later life
-can produce insulin but not enough
-responsiveness to insulin declines as specific receptors on target cells become less responsive

Question 44

what factors can bring on type 2 diabetes

Answer 44

-obesity
-lack of regular exercise
-diet high in sugars
-family history

Question 45

how can you treat type 2 diabetes

Answer 45

-changes in lifestyle: losing weight, exercising regularly, monitoring diet
-medication that reduces amount of glucose the liver releases to the bloodstream and boosts amount of insulin released from the pancreas
-severe cases, insulin injections

Question 46

what are the advantages of using insulin from genetically modified bacteria other than pigs

Answer 46

-exact copy of human insulin (fast acting and effective)
-less chance of developing tolerance to the insulin
-less chance of rejection due to an immune response
-lower risk of infection
-cheaper to manufacture than extract from animals
-process is more adaptable to demand
-less moral objections