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Biology - Unit 6 > Homeostasis > Flashcards

Homeostasis Flashcards

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1
Q

Define homeostasis

A

Physiological control systems that maintain a constant internal environment

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2
Q

Summarise negative feedback system

A

Receptors detect change away from normal and mechanism activated to return body to normal

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3
Q

Summarise positive feedback system

A

A response resulting in effectors further amplifying the change away from the normal

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4
Q

Summarise how the body reacts to high blood glucose

A
  • Receptors in pancreas detect increase
  • Beta cells in islets of langerhans secrete insulin
  • Insulin binds to receptor is liver and muscle to increase glucose permeability
  • More glucose absorbed by diffusion
  • Glycogenesis occurs and respiration increased
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5
Q

Summarise how the body reacts to low blood glucose

A
  • Receptors in pancreas detect decrease
  • Alpha cells islets of langerhans secrete glucagon
  • Glucagon binds to receptors on liver cells
  • Decrease in rate of respiration
  • Gluconeogensis
  • Glycogenolysis
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6
Q

Define glycogenesis

A

Breaking down of glycogen into glucose promoted by glucagon and adrenaline

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7
Q

Define glycogenolysis

A

The making of glycogen promoted by insulin

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8
Q

Define gluconeogenesis

A

The formation of glucose from other molecules promoted by glucagon

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9
Q

Summarise glucagon in the control of blood glucose

A
  • Secreted by A cells the islets of langerhans
  • When blood glucose low
  • Attaches to liver receptors
  • Increase blood glucose
  • Decreases rate of respiration, causes glycogenesis and gluconeogensis
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10
Q

Summarise adrenaline in the control of blood glucose

A
  • Secreted by adrenal glands
  • When blood glucose low
  • Attaches to liver receptors
  • Increases blood glucose
  • Causes glycogenolysis due to secretion of glucagon and inhibits glycogenesis due to inhibitng insulin
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11
Q

Summarise insulin in the control of blood glucose

A
  • Secreted by B cells in the islets of langerhans
  • When blood glucose high
  • Attaches to liver and muscle cells
  • Decrease blood glucose levels
  • Causes glycogenesis and increase liver and muscle cell permeability to glucose
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12
Q

How does insulin increase cell permeability to glucose

A
  • Glucose carrier proteins stored in vesicles within cell
  • Insulin binds with receptors on the cell membrane
  • Causes vesicle to fuse with cell membrane
  • Carrier protein joins membrane and glucose absorbed by facilitated diffusion
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13
Q

Summarise the process of second messengers

A
  • Hormone (adrenaline or glucagon) binds to receptors on target cell
  • Enzyme on inside of the cell called adenyl cyclate activated and hydrolyses ATP into cyclic AMP
  • AMP acts as non-competitive inhibitor and activates protein kinase A by changing tertiary structure
  • Causes break down of glycogen (glycogenolysis)
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14
Q

Define diabetes

A

When blood glucose levels are not controlled fully

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15
Q

Distinguish between hyper and hypoglycaemia

A

Hyper = too much glucose and hypo = too little

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16
Q

Summarise Type I diabetes

A
  • Immune system kills B cells so lack of insulin
  • Occurs in children and young adults
  • Hyperglycaemia after eating carbs
  • Stays high and so glucose removed by kidneys in urine
  • Insulin injections/pump
  • Avoid simple carbohydrates
  • Eat regular intervals and regular exercise
17
Q

Summarise Type II diabetes

A
  • Obesity, lack of exercise and poor diet
  • Not enough insulin produced and liver and muscle cells do not respond due to lack of receptors
  • Hyperglycaemia after eating carbs
  • Stays high and so glucose removed by kidneys in urine
  • Eat healthy, lose weight, regular exercise
  • Drugs to reduce glucose, increase insulin production and sensitivity to insulin
18
Q

Summarise the structure of a nephron

A

Afferent arteriole, bowman capsule containing glomerulus, efferent arteriole, proximal convoluted tubule, descending loop of henley, ascending loop of henley, distal convoluted tubule and collecting duct

19
Q

Summarise ultrafiltration

A
  • Blood flows into bowman capsule from afferent arteriole
  • Glomerulus under high hydrostatic pressure due to wide afferent and thin efferent
  • Small molecules and liquid are forced out of glomerulus into bowman capsule forming filtrate
  • Large molecules do not fit through gaps in capillary walls, basement membrane and podocytes
  • Filtrate moves into nephron
20
Q

What does kidney filtrate contain

A 
Glucose
H2O
Amino acids
Ions
Urea
21
Q

Define selective reabsorption

A

When useful products are reabsorbed from the glomerulus filtrate by the PCT, loop of henley, distal convoluted tubule and collecting duct

22
Q

Summarise selective reabsorption

A
  • Capillaries wrap around nephron and useful substances reabsorbed
  • Microvilli increase SA for absorption
  • Urine produced once useful molecules removed
  • Glucose and amino acids absorbed by facilitated diffusion, some urea remains due to simple diffusion and water moves in by osmosis
  • Rest of glucose, amino acids and ions absorbed by active transport
23
Q

How are substances absorbed in the proximal convuluted tubule

A

 all the glucose/amino acids and some of the salts/water are sent back into blood
(from lumen of PCT, through cells lining PCT, into blood)
how:
 salts (sodium ions) are actively transported from cells lining the PCT into the blood
 this lowers sodium ion concentration in the cells, so sodium ions diffuse from the lumen of the PCT into the cells
 as sodium ions move, they pull in glucose and amino acids with them via co-transport
 glucose and amino acids build up in the cell, then diffuse into the blood
 the movement of salt/glucose/amino acids into the blood, lowers it’s water potential, so water follows into blood by osmosis

24
Q

Summarise how the function of the loop of henle

A
  • Sodium and chloride ions actively transported out of ascending limb into medulla
  • Lowers water potential of medulla
  • Ascending limb impermeable to water
  • Water moves out of descending limb by osmosis due to salty medulla and absorbed by capillaries
  • Urine hence more concentrated
25
Q

What is the effect of a long loop of henle?

A
  • More ions removed, more concentrated medulla, so more water absorbed so more concentration urine e.g desert animals
26
Q

Summarise ADH in osmoregulation

A
  • Dehydrated so lower water potential, detected by osmoreceptors in hypothalamus
  • Posterior pituitary secretes antidiuretic hormone
  • ADH carried in blood and binds to receptors
  • Increases permeability to water
  • Water moves out of collecting duct by osmosis due to medulla have lowing water potential

Biology - Unit 6 (6 decks)

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