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biology aqa > homeostasis > Flashcards

homeostasis Flashcards

1
Q

What is homeostasis

A

The maintenance of a constant internal environment with a changing external environment

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2
Q

What is negative feedback

A

Change to a normal level that initiates a response that against the change

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3
Q

What is positive feedback

A

A change to a normal that causes an even greater deviation

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4
Q

What is a control system

A

A greater degree of control is activated by having multiple receptors and effectors

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5
Q

What is the pancreas

A

An organ with clusters of cells called islets of langerhans

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6
Q

what is the 2nd messenger model

A 
adrenaline binds to membrane receptor 
activates adenyl cyclase enzyme(AC)
AC converts ATP to cAMP 
cAMP activates protein kinase
protein kinase converts glycogen to glucose
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7
Q

what is the function of the kidney

A

osmoregulation- maintaining water potential of the blood

-producing urine

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8
Q

how does the kidney maintain water potential of the blood

A

by controlling ion and water concentration

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9
Q

what does the kidney excrete

A

ions water urea

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10
Q

what is type 1 diabetes

A

an autoimmune disease where all of the beta cells in the pancreas are destroyed so the body can not produce insulin

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11
Q

what is the treatment for type 1 diabetes

A

insulin injections

regulation of diet

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12
Q

what is type 2 diabetes

A

the cells no longer respond to insulin

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13
Q

what is the treatment for type 2 diabetes

A

regulation of diet and exercise

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14
Q

outline how insulin decreases blood glucose

A

beta cells detect rise in blood glucose
more insulin produced by beta cells
insulin binds to receptors on liver and muscle cells
which opens glucose channels in membrane
and causes more glucose channels to appear in membrane
glucose moves in by f.d and enzymes convert glucose to glycogen

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15
Q

outline how glucagon increases blood glucose

A

chad alpha cells detect fall in blood glucose
more glucagon produced by chad alpha cells
glucagon binds to receptors on liver and muscle cells
glucagon activates enzymes that convert glycogen to glucose diffuses into the blood
gluconeogenesis occurs in liver new glucose is produced from amino and fatty acids
blood glucose increases

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16
Q

what are the two types of cells in islet of langerhans

A

chad alpha cells

virgin beta cells

17
Q

how is new glucose produced

A

glucagon leads to gluconeogenesis
in the liver
glucose is produced from amino acids and fatty acids

18
Q

what is the nephron

A

the functional unit of the kidney

19
Q

outline the process of ultra filtration

A

higher hydrostatic pressure in glomerulus than in renal capsule as afferent arteriole is wider than efferent arteriole
small molecules such as glucose and urea can pass through the basement membrane
large molecules such as proteins are too large to pass through
fluid then passes through the gaps between podocytes into the lumen of the renal capsule

20
Q

where is 85% of the filtrate reabsorbed

A

in the proximal convoluted tubule

21
Q

what is reabsorbed in selective re absorption

A

all glucose reabsorbed
some water reabsorbed
some urea reabsorbed

22
Q

outline the process of how glucose is reabsorbed into the blood

A 
Na+ ions are actively transported into the blood from epithelial cell 
Na+ ions diffuse down the concentration gradient with glucose from the lumen of the proximal convoluted tubule into the epithelial cell via a co-transport protein 
this molecule(glucose) diffuses into the blood
23
Q

what is the role of the loop of henle in selective reabsorption

A

to a create a low water potential in the medulla

24
Q

what occurs in the ascending limb at the loop of henle

A

Na+ ions are actively transported from the henle

this lowers the water potential of the medulla

25
Q

what occurs in the descending limb at the loop of henle

A

water moves into medulla by osmosis

due to lower water potential is medulla

26
Q

what is the role of the distal convoluted tubule in selective reabsoprtion

A

removal of ions this means that the filtrate is more dilute

27
Q

why is homeostasis importatant for metabollic activity

A

as if pH and core temerpature are not properly maintained then enzymes will denature
which control rate of metabolic reactions

28
Q

what occurs during overhydration

A

osmoreceptor cells in hypothalamus detect higher water potential of blood
posterier pituitary secretes less ADH into blood
less activation of the enzyme of phosphorylase
collecting duct less permeable to water as less aqua pourines in cell membrane

29
Q

what occurs during dehydration

A

osmoreceptor cells in hypothalamus detect lower water potential of blood
posterier pituitary secretes more ADH into blood
more activation of the enzyme phosphorylase
collecting duct more permemable to water as more aqua pourines in cell membrane

biology aqa (31 decks)

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