homeostasis

Question 1

what is homeostasis?

Answer 1

the process where internal conditions are maintained within certain limits (a dynamic equilibrium)

Question 2

what are internal conditions?

Answer 2

includes temperature, pH, sugar and salt conc., water balance ect

Question 3

what system does homeostasis use?

Answer 3

negative feedback

Question 4

why do we need to control internal conditions like temperature?

Answer 4

biochemical reactions require specific conditions to work efficiently; cells may be disrupted if solute conc. changes too much

Question 5

what is the negative feedback mechanism?

Answer 5

a corrective mechanism, where any changes from the norm is detected and the body responds by returning conditions to normal levels

Question 6

what does negative feedback mechanism involve?

Answer 6

• a detector (receptor) sensing any changes
• a co-ordinator, determines what needs to be done
• an effector, brings about any required changes

Question 7

what is the output of a negative feedback mechanism?

Answer 7

reduces the original effect of the stimulus

Question 8

what is the output of positive feedback mechanisms?

Answer 8

enhances the original stimulus

Question 9

example of positive feedback?

Answer 9

during labour in childbirth, the release of oxytocin intensifies and increases contractions. The increase in contractions releases more oxytocin and the cycle goes on until the baby is born.

Question 10

what is deamination?

Answer 10

when proteins cannot be stored, so many excess amino acids must be broken down and removed from the body by the liver

Question 11

where does deamination take place?

Answer 11

in the liver

Question 12

what is the function of the kidney?

Answer 12

• osmoregulation in the body
• it removes urea from the blood
• controls solutes and pH of the blood
• forms part of the excretory system

Question 13

what is the kidney made up of?

Answer 13

hundreds and thousands of nephrons

Question 14

what are nephrons?

Answer 14

they are filtering units of the kidney

Question 15

what are the distinct parts of the nephrons?

Answer 15

• Bowsman capsule
• proximal and distal convoluted tubules
• loop of Henle
• collecting dust

Question 16

what brings in the blood to each nephron?

Answer 16

afferent arterioles

Question 17

what is enclosed in the Bowman’s capsule?

Answer 17

glomerulus (network of blood vessels)

Question 18

what causes the pressure to build up in the glomerulus?

Answer 18

the efferent arterioles leaving the network are narrower than those entering

Question 19

what happens to the molecules due to the high pressure of the glomerulus?

Answer 19

the pressure forces molecules out of tiny holes in the capillary walls and lining of the Bowman’s capsule

Question 20

what do the pedicels do in the Bowmans capsule?

Answer 20

create gaps (fenestrations)

Question 21

what are podocytes?

Answer 21

covers the glomerular capillary

Question 22

substances filtered out of blood?

Answer 22

• RBC/WBC
• hormones
• cholestrol
• water ect

Question 23

Where does selective reabsorption take place?

Answer 23

the proximal convoluted tubule to be reabsorbed by the blood

Question 24

how is water reabsorbed?

Answer 24

most of it is reabsorbed by osmosis

Question 25

how is glucose and amino acids reabsorbed?

Answer 25

all of it is reabsorbed by active transport

Question 26

how are ions reabsorbed?

Answer 26

most are reabsorbed by active transport or facilitated diffusion

Question 27

describe Na+ and glucose co-transport

Answer 27

Na+ actively pumped out of cell to create conc. gradient. Na+ diffuses into cell by a carrier protein that also binds to glucose. Glucose also brought into the cell then moves out through protein channels into the blood.

Question 28

How are the cells lining the proximal convoluted tubule specialised for absorption?

Answer 28

- many mitochondria - many microvilli - channels at the base of the cells - cells tightly bound together - capillaries run close to the cells

Question 29

why is important that proximal convoluted tubules contain microvilli?

Answer 29

more surface area means more protein carriers, therefore increased uptake of Na+ and glucose

Question 30

What is the purpose of the Loop of Henle?

Answer 30

concentrates salt in the medulla of the kidney

Question 31

how is water lost by ultrafiltration reabsorbed?

Answer 31

the collecting ducts in the loop of Henle pass through the salty medulla, allowing water to be reabsorbed

Question 32

What happens as the filtrate passes up the ascending limb?

Answer 32

Na+ and Cl- is actively pumped out into the medulla

Question 33

What is a counter-current system?

Answer 33

affects filtrate in the descending limb and water is lost as it passes into the salty medulla

Question 34

What is the effect of the counter-current system?

Answer 34

the filtrate gets more concentrated as it moves down into the medulla, whilst it becomes more dilute as it passes up the ascending limb

Question 35

What is the result of the counter-current multiplier?

Answer 35

- a very salty medulla - as the collecting duct passes through this region, water is lost by diffusion. - The water diffuses into the vasa recta and is reabsorbed into the blood

Question 36

What is osmoregulation?

Answer 36

the movement of water from collecting ducts and distal convoluted tubule can be controlled by hormones

Question 37

What is ADH?

Answer 37

Anti-diuretic hormone

Question 38

what is the function of ADH?

Answer 38

opens up protein channels in the collecting duct epithelial cells and distal convoluted tubules to be more permeable

Question 39

What effect does ADH have on the aquaporins?

Answer 39

aquaporins become incorporated in the plasma membranes, from within the cytosol

Question 40

Where does reabsorbed water from the filtrate go?

Answer 40

the surrounding hypertonic tissue fluid and then passes into blood capillaries

Question 41

where is ADH secreted?

Answer 41

the posterior pituitary gland (endocrine gland) and its release is controlled via the hypothalamus

Question 42

What detects the osmotic pressure in the blood?

Answer 42

the osmoreceptor cells in the hypothalamus

Question 43

what is the role of the hypothalamus for homeostasis?

Answer 43

hypothalamus has osmoreceptor cells which detect the fall in water potential , which results in nerve impulses passing to the posterior pituitary gland which releases ADH into the blood

Question 44

How are animals adapted with their loop of Henle's for living in different habitats?

Answer 44

animals in drier climates have longer loops of Henle

Question 45

What does the length of the loop of Henle signify?

Answer 45

the longer the loop of H, the greater the salt conc. in the medulla. This means more water can be reabsorbed from the collecting duct

Question 46

what waste products do aquatic animals produce and what issues are associated with this?

Answer 46

they produce ammonia and are highly toxic and requires huge volumes of water to dilute it