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Biology > Chapter 14 - Hormonal Coordination > Flashcards

Chapter 14 - Hormonal Coordination Flashcards

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1
Q

What does endocrine system use and for what?

A
  • uses the blood circulatory systems to transport hormones as signalling molecules for communication
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2
Q

What are hormones?

A
  • molecules (proteins/steroids) that are released by endocrine glands directly into the blood
  • act as messengers, carrying a signal from the endocrine gland to a specific target organ/tissue
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3
Q

What are the 2 types of hormones?

A
  • steroid hormones (eg. oestrogen and testosterone)
  • non steroid hormones - protein and peptide hormones, and derivatives of amino acids (eg. adrenaline, insulin and glucagon)
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4
Q

What is the difference between the 2 types of hormones?

A
  • steroid hormones can pass through the membrane + enter the cell and the nucleus, to have a direct effect on the DNA in the nucleus
  • non steroid hormones - proteins are not soluble in (lipids) the phospholipid membrane + do not enter the cell. Non steroid hormones bind to the cell surface membrane that triggers a cascade of responses with cell (release a second messenger inside the cell)
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5
Q

What are endocrine glands?

A
  • ductless glands which have groups of cells that make + release hormone directly into blood in capillaries running through the gland
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6
Q

What are target cells?

A
  • cells receiving an endocrine signal
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7
Q

What must non- steroid hormones target cells possess?

A
  • they must have a complementary shaped receptor on cell surface membrane of target cell
  • hormone binds to this receptor + initiates changes in the cell
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8
Q

What are first messengers?

A
  • non-steroid hormones
  • signalling molecules outside the cell that bind to the cell surface membrane + initiate an effect inside the cell
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9
Q

Second messengers

A
  • first messengers cause the release of another signalling molecule in the cell
  • it stimulates a change in the activity of the cell
  • cAMP is the second messenger
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10
Q

What is the adrenal gland?

A
  • endocrine glands
  • humans have 2 (above each kidney)
  • made up of adrenal cortex and adrenal medulla surrounded by a capsule
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11
Q

What is the adrenal cortex?

A
  • outer layer of the adrenal gland
  • controlled by hormones secreted by pituitary gland
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12
Q

What is adrenal medulla?

A
  • inner layer of adrenal gland
  • controlled by the nervous system
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13
Q

What does the Adrenal cortex secrete?

A
  • Glucocorticoids
  • Mineralocorticoids
  • Androgens
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14
Q

What does the Adrenal medulla secrete?

A
  • Adrenaline - increases heart rate and raises blood glucose conc (for energy if u need to fight or flight)
  • Noradrenaline - increases heart rate, causes pupils to dilate and widens airways in the lungs and narrows blood vessels in non essential organs to create a higher blood pressure
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15
Q

What is adrenaline?

A
  • hormone released from the adrenal glands, which stimulates the body to prepare for fight/flight
  • a polar molecule derived from tyrosine
  • means it can’t enter cells through the plasma membrane like a steroid hormone
  • must be detected by specialised receptors on the plasma membrane of the target cells
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16
Q

What are the 3 layers within the adrenal cortex?

A
  • zona glomerulosa - outermost
    (secretes mineralocorticoids such as aldosterone)
  • zona fasciculata - middle
    (secretes glucocorticoids such as cortisol)
  • zona reticularis - innermost
    (secrete precursor molecules that are used to make sex hormones)
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17
Q

What does the adrenal cortex use cholesterol for?

A
  • produce a range of hormones:
  • steroid based + able to enter cells directly by dissolving into the cell surface membrane
  • steroid hormones enter nucleus + have direct effect on the DNA to cause protein synthesis
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18
Q

What do steroid hormones do? (4)

A
  • pass through the cell membrane of the target cell
  • binds with a specific receptor with a complementary shape in the cytoplasm
  • receptor-steroid hormone complex enters nucleus of target cell + binds to another specific receptor on the chromosomal material
  • binding stimulates the production of mRNA molecules, which code for the production of proteins
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19
Q

What does mineralocorticoids from the zona glomerulosa do?

A
  • help control the conc of Na and K in the blood
  • therefore they contribute to maintaining blood pressure
  • aldosterone acts on the cells of the DT + collecting ducts in the kidney
  • increases absportion of Na+, decreases absorption of K+ and increases water retention = increases blood pressure
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20
Q

What does glucocorticoids from the zona fasciculata do?

A
  • control the metabolism of carbs, fats and proteins in the liver
  • cortisol is released in response to stress/ result of a low blood glucose concentration
  • stimulates the production of glucose from stored compounds
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21
Q

What is released by the zona reticularis when incorrect enzymes present to release cortisol ?

A
  • precursor androgens into the blood
  • taken up by the ovaries/testes + converted to sex hormones
  • sex hormones help development of the secondary sexual characteristics + regulate the production of gametes
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22
Q

Where is adrenaline released from and to? and How?

A
  • adrenal medulla into the blood + transported around the body
  • it attaches to receptors on surface of target cells and causes protein G to be activated
  • therefore ATP converted into cAMP
  • cAMP activates enzyme to hydrolyse glycogen into glucose (PROCESS OF GLYCOGENOLYSIS)
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23
Q

What effects does adrenaline have on the body?

A
  • relax smooth muscle in bronchioles
  • ↟stroke volume of the heart
  • ↟ heart rate
  • causing general vasoconstriction to ↟ blood pressure
  • stimulates conversion of glycogen -> glucose via hydrolysis in liver
  • dilating the pupils
  • increasing mental awarenes
  • inhibiting the action of the gut
  • causing body hair to stand erect
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24
Q

The pancreas and what is it?

A
  • gland located behind the stomach
  • releases hormones to control blood glucose levels (functioning as an ENDOcrine gland)
  • also release enzymes for digestion (functioning as an EXOcrine gland)
  • mostly made up of exocrine tissue (secreting amylase, proteases and lipases)
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25
Q

What are the 2 main secretions of the pancreas?

A
  • exo = Most of the cells of the pancreas secrete digestive enzymes found in pancreatic juices secreted into small intestine
  • endo = hormones which are secreted from the islets of Langerhans into the blood (insulin and glucagon)
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26
Q

What do exocrine glands do ?

A
  • secrete substances into a duct
27
Q

What is the exocrine function of the pancreas?

A
  • cells in the pancreas synthesise + release digestive enzymes
  • to produce pancreatic juice (containing digestive enzymes) to be delivered to the small intestine
28
Q

acini and that

A

group of cells = acinus
- acini grouped together into small lobules separated by connective tissue
- exocrine part of pancreas
- secretes digestive enzymes into duct
- tubules from the acini join = intralobular ducts that combine = pancreatic duct

29
Q

What enzymes are within the fluid from the pancreatic duct?

A
  • pancreatic amylase = carbohydrase which digests amylose to maltose
  • trypsinogen = inactive protease which’ll be converted to the active form trypsin when it enters the duodenum
  • lipase = which digests lipid molecules
30
Q

What does the fluid from pancreatic duct contain?

A
  • sodium hydrogen carbonate which makes it alkaline
  • helps neutralise contents of the digestive system
31
Q

Where are the islets of Langerhans?

A
  • dispersed in small patches among the lobules of acini
  • they are an endocrine tissue
32
Q

What do the islets of Langerhans contain?

A
  • alpha + beta cells that make up the endocrine tissue in the pancreas
    alpha cells secrete glucagon
    beta cells secrete insulin
33
Q

What happens when insulin is secreted from the beta cells in the islets of Langerhans?

A
  • effects that reduce blood glucose concentration
  • BGC is too ↟, insulin is released from the beta cells
  • liver cells become more permeable to glucose and enzymes are activated to convert glucose to glycogen
  • BGC is too ↡, insulin secretion stops
  • glucose is stored as glycogen in cells
34
Q

What happens when glucagon is secreted from the alpha cells in the islets of Langerhans?

A
  • effects that increase blood glucose concentration
  • BGC is too low, glucagon is released from the alpha cells
  • adrenal gland also releases adrenaline
  • second messenger model occurs to activate enzymes to hydrolyse glycogen
  • BGC is too high, glucagon release stops
35
Q

How is insulin released from the beta cells when glucose is too high?

A
  • high glucose is detected by the β cells in the pancreas
  • the conc. of glucose is high = glucose molecules enter the β cells by facilitated diffusion (via glucose transporter)
  • cells respire this glucose and produce ATP which bind to potassium ion channels
  • K+ channels are normally opened and Ca+ channels are normally closed.
  • high conc. of ATP causes the K+ channels in the β cells to close (at rest the potential difference across the cell membrane is about -70mV) producing a change in the membrane potential as K can no longer diffuse out and this means it becomes less -ve
  • depolarisation occurs as K+ can’t diffuse out
  • change in the membrane potential causes the voltage-gated Ca channels to open
  • response to influx of calcium ions, the β cells secrete insulin
  • secretory vesicles carry insulin and move towards the cell-surface membrane and fuse with it where they release insulin into the capillaries via exocytosis
  • once in the bloodstream, insulin circulates around the body + stimulates the uptake of glucose by muscles cells, fat cells and the liver
36
Q

What are the effects insulin has on the cell?

A
  • attaching to receptors on surface of target cells changes tertiary structure of channel proteins so more glucose is absorbed via faciliated diffusion
  • more protein carriers are incorporated into cell membranes so more glucose absorbed into cell
  • more active enzymes involved in conversion of glucose to glycogen for storage - results in glycogenesis in liver
  • more glucose is converted to fats
  • more glucose used in respiration
37
Q

What is hypoglycaemia?

A
  • BGC drops below 4mmoldm-^3 + remains too low for long periods
38
Q

What is the main problem caused by hypoglycaemia?

A
  • inadequate delivery of glucose to the body tissues, and in particular, to the brain
  • cause tiredness + irritability to impairment of brain function + confusion -> lead to seizures, unconsciousness + death
39
Q

What is hyperglycaemia?

A

When BGC rises too ↟ for long periods of time
- permanently high -> significant organ damage

40
Q

What is used as the diagnosis for diabetes mellitus?

A
  • BGC consistently ↟ than 7mmol dm^-3
41
Q

How is low blood glucose dealt with?

glycogenolysis

A
  • glucagon attaches to the complimentary receptors on the surface of target cells (liver cells (hepatocytes)) when blood passes these cells
  • activates a G protein that activates the enzyme adenylyl cyclase (this is cuz the shape of enzyme adenylyl cyclase changes so its activated)
  • which catalyses the conversion of ATP to the second messenger, cyclic AMP (cAMP)
  • cAMP binds to protein kinase A enzymes to activate them
  • Active protein kinase A enzymes activate phosphorylase kinase enzymes by adding phosphate groups to them
  • Active phosphorylase kinase enzymes activate glycogen phosphorylase enzymes
  • they then catalyse breakdown of glycogen to glucose
42
Q

What are the effects of glucagon?

A
  • more fatty acids are used in respiration
  • amino acids + fats are converted into additional glucose, by gluconeogenesis
43
Q

Glycogenesis

A
  • converting glucose into glycogen
  • occurs in liver and catalysed by enzymes there
44
Q

Glycogenolysis

A
  • hydrolysis of glycogen to glucose
  • occurs in liver due to second messenger model
45
Q

Gluconeogenesis

A
  • creating glucose from other molecules
  • eg aminoacids/glycerol from liver
46
Q

What is the conc of blood glucose controlled by?

A
  • negative feedback mechanism incl. both insulin and glucagon
47
Q

What are glucagon and insulin referred to as?

A
  • antagonistic - they have opp effects on BGC
  • inhibit the effect of the opposing hormone
48
Q

What is diabetes mellitus?

A
  • type 2
  • a condition in which body is no longer able to produce sufficient insulin to control its BGC
49
Q

What can diabetes mellitus lead to ?

A
  • prolonged ↟ conc of glucose (hyperglycaemia) after a meal rich in sugars + carbohydrates
  • can also lead to conc dropping too low (hypoglycaemia) after exercise or fasting
50
Q

What are the other 2 names Type 1 diabetes is referred to as?

A
  • insulin-dependent diabetes
  • juvenile-onset diabetes (starts in childhood)
51
Q

What is Type 1 Diabetes thought to be the result of?

A
  • autoimmune response in which the body’s immune system attacks + destroys the beta cells
  • may also result from a viral attack
52
Q

What is a person with Type 1 no longer able to do ?

A
  • synthesise sufficient insulin + cannot store excess glucose as glycogen
  • excess glucose in the blood isn’t removed quickly, leaving high conc
  • when blood glucose falls, there is no store of glycogen so it falls even lower
53
Q

What is Type 2 diabetes known as?

A
  • non-insulin-dependent diabetes
54
Q

What is Type 2 diabetes?

hereditary

A
  • person can produce insulin but not enough to control their glucose levels
  • BGC is almost permanently raised, which can damage major organs
55
Q

Why do people’s responsiveness to insulin decline as they age?

A
  • specific receptors on the surface of the liver and muscle cells become less responsive + cells lose ability to respond to insulin in the blood
56
Q

Which 5 factors bring an earlier onset of Type 2 diabetes?

A
  • obesity
  • lack of regular exercise
  • diet high in sugars, particularly refined sugar
  • Asian/Afro-Caribbean origin
  • family history
57
Q

How is Type 1 diabetes treated?

A
  • insulin injection
  • diet - lots of fruit and veg
  • BGC must be monitored+correct dose of insulin administered to keep GC stable
58
Q

What are 3 alternatives to insulin injections?

A
  • insulin pump therapy - small device constantly pumps insulin into bloodstream through permanently inserted needle under skin
  • islet cell transplantation - healthy beta cells from the pancreas of a deceased donor implanted into the pancreas
  • complete pancreas transplant
59
Q

What does recent research show that might be possible to treat Type 1 diabetes?

A

using stem cells to grow new islets of Langerhans in the pancreas
- stem cells are not differentiated yet + can be induced to develop into variety of cell types

60
Q

What have scientists found in pancreas of adult mice?

A
  • precursor cells
  • capable of developing into variety of cell types + may be true stem cells
  • if similar can be found in human pancreas, it could be used to produce new beta cell
61
Q

How can Type 2 diabetes be treated?

A
  • changes in lifestyle
  • lose weight, exercise regularly + monitor diet
  • medication reduces glucose the liver releases to blood/ amount of insulin released from the pancreas
62
Q

What are the 7 advantages of using insulin from genetically modified bacteria?

A
  • exact copy of human insulin - faster acting + more effective
  • less chance of developing tolerance to insulin
  • less chance of rejection due to immune response
  • lower risk of infection
  • cheaper to manufacture the insulin than extract from animals
  • manufacturing process is more adaptable to demand
  • people are less likely to have moral objections to using insulin produced from bacteria than to use those extracted from animals
63
Q

COMMON EXAM QUESTION !!!

Explain why the protein insulin must be administered intravenously rather than orally.

A

Insulin is a protein, if it was taken orally it would be digested by the enzyme protease found in the gut before entering the bloodstream.

Biology (25 decks)

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