Responding to Changes

Question 1

what is the exposed axon called?

Answer 1

Nodes of ranvier

Question 2

What do myelin sheaths assist in

Answer 2

Saltatory conduction (potentials leap between nodes of ranvier therefore are faster)

Question 3

What is the difference between rod cells and cone cells

Answer 3

Cone cells are for colour, includes green, red, blue sensitive pigment
Neurone per cone cell therefore dedicated/specialised requires large amount of action potential/stimuli to respond to change in colour therefore higher resolution, works best in high light intensity
- photosensitive pigment (idhopsin and rhodopsin)
Rods are for black and white
multiple neurones per rod (temporal or summative) therefore lower resolution but more photosensitive only black and white (distinguishes between light and dark)

Question 4

Ratchet mechanism????

Answer 4

• Ca2+ actively pumped into sarcoplasmic reticulum
• tropomyosin binds to Ca2+ shifts in 3’ structure moves to reveal actin binding site
• myosin head goes from high energy level to induce fit on complementary actin binding site.
• ATP used, cross bridge formed.
• cross bridge allows ATP to bind on
• therefore myosin head repositions to high energy level

Question 5

What is I-band?

Answer 5

only actin

Question 6

What is H-band?

Answer 6

only myosin (thicker filament)

Question 7

Where is IAA located?

Answer 7

root tip, shoot tips