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Biology > M6 - Hormones and Glands > Flashcards

M6 - Hormones and Glands Flashcards

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1
Q

What are endocrine vs exocrine glands?

A

Endocrine glands secrete hormones directly into to blood in capillaries inside the gland (ductless).

Exocrine glands secrete substances (not hormones) into a duct that carries substance to its site of action.

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2
Q

What are hormones? What do they do? What are they also known as?

A

Chemical messengers - they bind to specific receptors in target cells that have a complementary shape.

They are also known as First messengers.

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3
Q

What are the two types of hormone?

A

Polypeptide/protein hormones - receptors located in plasma membrane e.g. insulin.

Steroid hormones - receptors located in cytoplasm inside the cell.
(because lipid soluble)

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4
Q

What are the possible cell responses to hormones binding to receptors?

A

Change in gene expression, change in enzyme activity or opening of ion channels.

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5
Q

What cells do the Islets of Langerhans contain and secrete?

A

Contain alpha cells that secrete glucagon.

Contain Beta cells that secrete insulin.

Both hormones are protein hormones secreted directly into blood capillaries (endocrine gland action).

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6
Q

What are factors that increase and decrease blood glucose conc?

A

Increase: After eating

Decrease: exercise, fasting, increased rate of respiration, mental exertion

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7
Q

Why regulate blood glucose?

A
  • Required by cells for respiration. Some cells (brain and red blood cells) only use glucose.
  • Maintain a constant water potential - effects tissue fluid and blood pressure.

(Stored as glycogen granules - especially in liver and muscle.
Animals transport carbohydrate as glucose in the blood.)

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8
Q

What is glycogenesis?

A

Making glycogen from glucose.

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9
Q

What is glycogenolysis?

A

Splitting glycogen, forming glucose.

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10
Q

What is gluconeogenesis?

A

Making new glucose from other molecules e.g. fats, amino acids etc

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11
Q

What happen when blood glucose concentration increases?

A

Alpha cells in Islets of Langerhans stop secretion of glucagon and Beta cells secrete insulin.

Liver and muscle cells increase uptake of glucose from blood. Glycogenesis.
Increased use of glucose in respiration.

Blood glucose conc falls.

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12
Q

What happen when blood glucose concentration decreases?

A

Alpha cells in Islets of Langerhans secrete of glucagon and Beta cells stop secreting insulin.

Liver releases glucose into blood. Glycogenolysis.
Gluconeogenesis.
Use of fatty acids in respiration.

Blood glucose conc rises.

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13
Q

How is insulin secreted?

A
  • K+ channels in Beta cells are normally open.
  • Glucose levels rise and glucose diffuses into cell and is phosphorylated (by glucokinase).
    It enters glycolysis to produce ATP in respiration.
  • Rise in ATP closes K+ channels. K+ cannot diffuse out so membrane potential changes.
  • This opens Ca2+ channels so Ca2+ enters cell down conc gradient.
  • Ca2+ cause vesicles to move to cell surface membrane and insulin secreted by exocytosis.
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14
Q

Describe molecular level of insulin action. (3 ways)

A

Insulin binds to receptors on Target cells and…..

  • Target Cells increase uptake of glucose by increasing number of glucose channel proteins on the surface of cell - changing tertiary structure to open them.
  • Insulin activates enzymes in target cells that convert glucose to glycogen (glycogenesis).
  • Insulin causes an increase in the rate of respiration in target cells.
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15
Q

Describe the action of glucagon at a molecular level.

A

Glucagon binds to receptors on target cells and…

  • activates enzymes that break glycogen down into glucose (glycogenolysis).
  • activates the production of glucose from glycerol and amino acids (Gluconeogenesis)
  • decreases rate of respiration in target cells
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16
Q

Where and when is adrenaline produced? What does it do?

A

Adrenaline = protein hormone
Produced in the Adrenal medulla when blood glucose levels are low, when you are stressed and when you are exercising.

Activates glycogenolysis.
Inhibits glycogenesis.
Activates glucagon secretion and inhibits insulin secretion.

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17
Q

How do glucagon and adrenaline act via second messengers?

A

Second messenger = cyclic AMP (cAMP)

Hormone binding to receptor changes its shape. This leads to activation of the enzyme adenylate cyclase that synthesises cAMP from ATP.

cAMP activates Protein kinase A which activates a series of reactions leading to the breakdown of glycogen.

18
Q

What is Type 1 daibetes?

A

When beta cells in the pancreas are destroyed by the autoimmune reaction so no insulin is produced.

Requires regular injections of insulin and a carefully controlled diet.

19
Q

What is Type 2 diabetes?

A

Insulin is produced but liver/muscle cells fail to respond (e.g. due to fewer receptors).

Controlled by diet and exercise. Associated with obesity.

20
Q

What are the 2 things diabetes can lead to?

A

Hyperglycaemia and Hypoglycaemia

21
Q

How does Hyperglycaemia occur?

A

After a meal, blood glucose conc rises:

  • Slow uptake of glucose by liver/muscle so no glucose stored as glycogen.
  • Kidneys cannot reabsorb all glucose so some present in urine (glucosuria).
  • Large amounts of dilute urine produced (leads to dehydration).
  • Increased use of lipids/proteins for respiration.
  • May lead to build-up of excess keto acids in blood that lowers blood pH (ketoacidosis)
22
Q

How does Hypoglycaemia occur?

A

Blood glucose falls.
- No glycogen to breakdown to maintain blood glucose concentration.
- Glucose can be produced by gluconeogenesis.
- Increased use of lipids/proteins for respiration.
- May lead to coma due to lack of glucose for respiration in the brain.

23
Q

What are the advantages of Genetically Engineered Insulin?

A

1) Human insulin gene - so more effective
2) Less chance of developing tolerance to insulin.
3) Less chance of rejection due to immune response.
4) More rapid response.
5) Cheaper to produce.
6) Supply can be adjusted to meet demand.
7) More ethically acceptable

24
Q

How did we use to get insulin for treatment? Issues?

A

From pancreas of pigs/cattle.

But expensive, can cause side effects and less ethical.

25
Q

What are the current investigations of using Stem cells for insulin treatment?

A

Precursor cells have been identified in the pancreas of mice that are capable of differentiating into a varierty of cell types.

Attempts being made to find similar cells in humans that could be used to produce new Beta cells for transplant into type 1 diabetes patients.

(however would likely be destroyed again as autoimmune disorder).

26
Q

What additional problems can Type 2 diabetes lead to?

A

Visual impairment and kidney problems.

27
Q

How is the government trying to reduce diabetes?

A

Educating people on healthier life choices.
Challenging the food industry to reduce advertising of junk food.
Food companies reducing sugar. Sugar tax.

However conflict of interest because unhealthy products are popular and generate a lot of profit.

28
Q

What are the 2 functions of the kidney?

A

To filter the blood and remove nitrogenous waste (urea)

Osmoregulation

29
Q

Label the Nephron

A

1 - afferent arteriole (wider)
2 - efferent arteriole
3 - glomerular capillary
4 - Bowman’s capsule
5 - Proximal convoluted tube
6 - Distil convoluted tube
7 - Collecting duct
8 - blood capillaries
9 - loop of Henle (ascending and descending limb)

30
Q

What are the 3 main processes of the Nephron?

A
  1. Ultrafiltration
  2. Selective Reabsorbtion
  3. Secretion
31
Q

Describe Ultrafiltration

A

Small soluble molecules are filtered from the blood under pressure in the glomerulus. Filtrate produced is similar to blood plasma but containing no cells or proteins.

Filtrate enters the Bowman’s Capsule.

32
Q

What are the adaptations for formation of the glomerular filtrate?

A

Afferent arteriole is WIDER than efferent arteriole - increasing hydrosatic pressure within glomerulus.

Endophelium of glomerular capillaries has PORES to allow filtrate to pass through.

Podocyte cells have SPACES BETWEEN them to allow filtrate to pass though.

Basement membrane between glomerular capillaries and podocytes act as a MOLECULAR SEIVE - proteins and cells too large to fit through.

(Pressue - ways through - molecular seive)

33
Q

Describe Selective Reabsorbtion

A

SR ensures useful products (glucose, amino acids, ions etc) are reabsorbed back into the blood as filtrate moves through tubule.

Approx 85% of filtrate is reabsorbed in the proximal conviluted tube (including all glucose and most water and salt).

Co-transport of Glucose with Na+ ions into bloodstream in capillary.

34
Q

What are the adaptations of cells of the proximal convoluted tubule?

A

Microvili and highly folded plasma membrane - increases SA
mitochondria - ATP for active transport of Na+ (co-transport)

35
Q

How does selective reaborbtion take place in the loop of Henle?

A
  1. In ascending limb Na+ (and Cl-) is actively transported out of the loop resulting in high conc of ions in the tissue fluid of the medulla / low water potential.
  2. Thick ascending limb is impermeable to water so water potential of filtrate inside increases as it ascends.
  3. In descending limb only a small number of Na+ ions diffuse in as it is relatively impermeable to ions but is permeable to water which leaves by osmosis, so water potential of filtrate decreases.
  4. The longer the loop (the deeper into the medulla), the lower the water potential in the tissue fluid of the medulla.
  5. (This is an example of counter-current multiplier)
36
Q

How is urine excreted from the kidneys?

A

Urine produced by nephrons is collected in the collecting ducts, travels through the pelvis of the kidney to the ureter, is stored in the bladder and then finally leaves the body via the urethra.

37
Q

What is osmoregulation?

A

The control of water content and solute composition of body fluids.

38
Q

What is the receptor, coordinator and effector in osmoregulation?

A

Receptor - hypothalamus
Coordinator - Posterior Lobe of Pituitary Gland
Effector - walls of Collecting Ducts (and DCT) of kidney

39
Q

How is the water potential of the blood measured?

A

By osmoreceptors in the hypothalamus.

When w.p. decreases, water moves out of osmoreceptor cells by osmosis causing decrease in cell volume. This sends a signal to other cells of hypothalamus that send nerve impulses to the posterior pituitary gland which releases ADH into the blood.

40
Q

What is ADH and what does it do?

A

Anti-diuretic hormone (anti-wee-hormone):
- Makes walls of the collecting ducts more permeable to water.
- causes aquaporins to be inserted into the membranes of cells of the DCT and collecting duct - increasing rate at which water leaves the tubule.

so… more water absorbed into the blood (leaves by osmosis) and conc of filtrate increase.

41
Q

How is there always a water potential gradient in the kidneys?

A

…

Biology (17 decks)

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