Homeostasis

Question 1

define homeostasis

Answer 1

the maintenance of a stable internal environment

Question 2

what factors affect enzyme activity

Answer 2

increase in temp
increase in pH
decrease in temp
decrease in pH

Question 3

control mechanisms process

Answer 3

receptors detect changes around the body
effectors carry out corrective measures in response to the change
the brain acts as a control centre

feedback loop informs the receptor of the changes to the system brought about the effector

Question 4

negative feedback definition

Answer 4

when there is an increase/decrease from the set point
the opposite effect is instigated
produces a response that returns the value to the norm

Question 5

positive feedback definition

Answer 5

a deviation from an optimum causes changes that result in an even greater deviation from the normal

Question 6

what happens to the body if body temp is too low

Answer 6

enzyme-controlled reactions take place too slowly
due to lack of kinetic energy

Question 7

what happens to the body if the body temp is too high

Answer 7

enzymes could be denatured
due to breaking of Hydrogen & Ionic bonds that hold the specific 3D tertiary structure

Question 8

what happens if pH deviates

Answer 8

enzymes and other proteins will be denatured

Question 9

important info about hormones

Answer 9

each hormone is chemically, structurally different
complementary to receptors

Question 10

which hormone does an alpha cell produce

Answer 10

glucagon

Question 11

which hormone does a beta cell produce

Answer 11

insulin

Question 12

influence of insulin

Answer 12

high levels of blood glucose conc are detected by B cells
B cells release insulin to lower it
insulin binds to complementary receptors on target cells
increases no. glucose carrier proteins
activates enzymes to stimulate glycogenesis

Question 13

influence of glucagon

Answer 13

low levels of blood glucose conc are detected by Alpha cells
Alpha cells release glucagon to increase it
glucagon binds to receptors on target cells
activates enzymes involved in the hydrolysis of glycogen to glucose
activates enzymes involved in gluconeogenesis

Question 14

second messenger model

Answer 14

adrenaline and glucose bind to receptor
hormone receptor complex formed
activates adenylate cyclase
results in conversion of ATP to cAMP
cAMP activates protein kinases to allow for
glycogenolysis

Question 15

what is diabetes caused by

Answer 15

failure of glucose homeostasis

Question 16

type 1 diabetes

Answer 16

severe insulin deficiency due to autoimmune killing of β cells

Question 17

type 2 diabetes

Answer 17

Insulin is produced
but the insulin receptors in the target cells are unresponsive

a lack of sensitivity to insulin

Question 18

symptoms of diabetes

Answer 18

1. High thirst due to osmosis of water from cells to the blood, which has a low water potential
2. Large volumes of urine production due to excess water in blood
3. Poor vision due to osmotic loss of water from the eye lens

Question 19

structure of the kidney

Answer 19

medulla
cortex
fibrous capsule
renal pelvis
ureter
renal artery

Question 20

process of osmoregulation

Answer 20

osmoreceptor cells in the hypothalamus detect fall in water potential
ADH is secreted into capillaries by posterior pituitary gland
ADH travels to kidneys in blood and increases permeability of cells of DCT and collecting duct

Question 21

formation of glomerular filtrate

Answer 21

blood enters through renal artery
enters bowman’s capsule
afferent arteriole is wider than efferent arteriole
high hydrostatic pressure
pushes glucose,water,urea and mineral ions out the fenestrations
forms glomerular filtrate

Question 22

How is urea removed from the blood?

Answer 22

Hydrostatic pressure
Causes ultrafiltration
Through basement membrane
Enabled by small size of urea molecule

Question 23

Describe how ultrafiltration produces glomerular filtrate

Answer 23

High hydrostatic pressure
forces glucose, water, urea out
Pass through basement membrane
Protein too large to go through
Presence of fenestrations in capillary endothelium
Presence of podocytes

Question 24

Explain how urea is concentrated in the filtrate

Answer 24

1. Reabsorption of water by osmosis;
2. At the PCT and descending LoH;
3. At the DCT and CD;
4. Active transport of ions

Question 25

process of re-absorbance of water

Answer 25

Na+ are actively transported out of the ascending limb using ATP
Na+ ions re-enter the descending limb
lowering water potential
drawing water out of the permeable descending limb by osmosis
The water from the descending limb then enters capillaries returning to the blood

Question 26

Distal convoluted tubule

Answer 26

make final adjustments to the water and salts that are reabsorbed
To achieve this, the permeability of its walls becomes altered under the influence of various hormones = osmoregulation

Question 27

collecting duct

Answer 27

collecting duct is permeable to water and so water continues to move out by osmosis as the countercurrent multiplier
ensures there is always a water potential gradient along the entire collecting duct