Response To Change

Question 1

Which have a higher sensitivity rods or cones

Answer 1

Rods as satiation of generator potential come from more than 1 receptor so can see in low light whereas cones have low sensitivity as high intensity light is needed to the bleach the cones

Question 2

Which has a higher aquity rods or cones

Answer 2

Cones as 1:1 ratio with bipolar neurone so location of stimulating light is clear. Rods can connect to 1 bipolar neurone so location of the stimulating light is unclear

Question 3

What do rods and cones do

Answer 3

Transduce light energy into electrical impulses

Question 4

Where are rods and cones found

Answer 4

Deep in the retina

Question 5

Adaptation of alveolar epithelium

Answer 5

-flattened cells to reduce DD
- permeable allowing diffusion of oxygen

Question 6

Practical method to test for memory cells

Answer 6

-inject vaccine
-memory cells more rapid production
-add enzymes attached to 2nd antibody against memory cells
-colour change shows memory cell is present

Question 7

Explain how a rise in blood pressure results in a decrease in the rate
of heartbeat.
(6 marks)

Answer 7

•high blood pressure detected by baroreceptors in aorta
• send impulses to cardiovascular centre
• which sends impulses along parasympathetic nerves
• decrease heart rate by sending impulses via SAN in the heart

Question 8

Describe how a heartbeat is initiated and coordinated

Answer 8

-SAN sends wave of electrical activity impulse across atria causing contraction
-Non-conducting tissue prevents immediate contraction of ventricles
-AVN delays nerve impulse allowing blood to leave atria and ventricles to fill
-AVN sends impulses down Bundle of His
-causing ventricles to contract from base up

Question 9

Explain the role and action of insulin on liver and muscle cells.

Answer 9

-High blood glucose detected
-b cells in islets of langherhan in pancreas releases insulin
-travels in blood to liver and muscle cells
-insulin binds to receptors on CSM
-causes glucose carrier proteins to open
-glucose moved into cells by FD
-causes liver enzymes to convert glucose into glycogen

Question 10

Explain how inhibiting adenylate cyclase may help to lower the blood glucose concentration.

Answer 10

Less/no ATP is converted to cyclic AMP/cAMP;
2. Less/no kinase is activated;
3. Less/no glycogen is converted to glucose

Question 11

Adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase

Answer 11

.
(a) 1. Adenylate cyclase activated / cAMP produced / second messenger produced;
2. Activates enzyme(s) (in cell so) glycogenolysis / gluconeogenesis occurs / glycogenesis inhibited;

Question 12

Describe the role of glucagon in gluconeogenesis.

Answer 12

1. (Attaches to receptors on target cells and) activates/stimulates
2. Glycerol/amino acids/fatty acids into glucose;

Question 13

When blood glucose levels are high

Answer 13

Insulin secreted

Question 14

When blood glucose levels are low

Answer 14

Glucagon secreted

Question 15

When blood glucose levels are low and need fast supply of glucose

Answer 15

Adrenaline

Question 16

Explain role and action of glucagon and adrenaline on liver and muscle cells

Answer 16

Glucagon released from alpha cells in loL of pancreas
Adrenaline released from adrenal glands in kidney
Glucagon/adrenaline bind to complementary receptor on liver CSM
adenylate Cyclase catalyses
Many ATP-> cAMP
protein kinase is activated
Glycogen is converted to glucose glycogenolysis
Released into the blood

Question 18

Describe the process of ultrafiltration
Model Answer

Answer 18

High hydrostatic pressure causes ultrafiltration;
Forces small molecules e.g. Glucose and Urea out of the pore in the capillary endothelium.
Larger proteins remain in the capillary.
Molecules then pass through the basement membrane.
They are then absorbed via the epithelium of the Bowman’s Capsule (podocytes).

Question 19

Antigen

Answer 19

Molecule that stimulates an immune response

Question 20

Phagocytosis

Answer 20

Phagocytes move towards pathogen by chemotaxis
Phagocyte CSM molds around and engulfs pathogen phagocytosis into a phagosome
Lysosomes fuse with phagosome to form phagolysosome
Lysozymes hydrolyse the pathogen
Destroyed pathogen remains and leaves by exocytosis antigens kept and displayed on CSM

Question 21

How presentation of a antigen leads to secretion of an antibody against this antigen

Answer 21

T cells bind to the antigen on antigen presenting cell and becomes activated
T cells divide by osmosis and differentiates into helper T cells
These stimulate a B cell
B cells divide by mitosis into plasma cells which secrete AB

Question 22

How B lymphocytes would respond to an antigen injection

Answer 22

B cell binds to specific antigen
B cells divide by mitosis
Differentiates into plasma cell
They secrete antibodies
Plasma cells can developed into memory cells

Question 24

How receptors work

Answer 24

-stimulus energy causes sodium ions channels to open
-sodium ions move into the receptor by FD
-that builds a generator potential that breaches threshold level
-sodium ion channel opens so more sodium ions move into receptor by FD
-action potential is made transmitted and carried by sensory neurone as a nerve impulse

Question 25

How the Pacinian corpuscle produced a generator potential

Answer 25

-Stretch mediated sodium channels in sensory neuron -deform due to increased pressure and changes the lamella so changes sodium ion channels -and open to increase permeability of membrane to Na+ -Na+ diffuse in by FD -if threshold reached -depolarisation

Question 26

Explain the role of ADH in the production of concentrated urine.

Answer 26

-When water potential of the blood too low; -Detected by receptors in the hypothalamus; -Pituitary secretes / releases (more) ADH; -ADH increases the permeability / recruitment of aquaporins / opens channels for water in the DCT / collecting duct; -More water is reabsorbed / leaves the nephron moves into the blood; -By osmosis down the water potential gradient;

Question 27

Stimulation of osmoreceptors can lead to secretion of the hormone ADH. Describe and explain how the secretion of ADH affects urine produced by the kidneys.

Answer 27

Permeability of membrane / cells (to water) is increased; More water absorbed from / leaves distal tubule / collecting duct; Smaller volume of urine; Urine becomes more concentrated.

Question 28

Explain how a resting potential is maintained across the axon membrane in a neurone.

Answer 28

Na ions are AT out and k+ are transported in Due to the higher conc of Na ions outside the neurone and K+ inside of the neurone The membrane is more permeable to K+ ions (leaving) Or less permeable to Na+ (entering)