physiological organisation + control of behaviour I

Question 1

what are Paramecium caudatum and how do they move

Answer 1

they are single celled protozoa who move backwards and turn with anterior stimulation and swim forward more quickly with posterior stimulation

Question 2

what causes reversal in P. caudatum

Answer 2

Ca2+ influx which depolarises the cell. reversal stops when Ca2+ is pumped out enough to return to normal levels

Question 3

what causes forward propulsion in P. caudatum

Answer 3

K+ efflux which causes hyperpolarisation of the cell, along with minor Ca2+ influx which is necessary for movement of cilia to propel the cell

Question 4

what are the levels of Ca2+ and K+ intracellularly in P. caudatum

Answer 4

K+ concentration is higher intracellularly than in pond water, Ca2+ is lower

Question 5

what is the topological distribution of ion channels

Answer 5

there are more K+ channels at the posterior and Ca2+ at the anterior

Question 6

what happens in salt- rich environments with P. caudatum

Answer 6

Na+ selective channels open and cause depolarisation, causing reversal into areas with less salinity at which point the cell is repolarised and reversal stops

Question 7

why is Ca2+ so essential in all movement of P. caudata

Answer 7

it is needed for the movement of cilia which propels the cell- both forwards and backwards

Question 8

what is Balanus balanus

Answer 8

an acorn barnacle whose behaviour is controlled by electrical activity

Question 9

what is the shadow reflex

Answer 9

B. balanus is open and feeding in sunlight but when in the shadow of a predator it will retract cirri and close plates to prevent being eaten

Question 10

describe the mechanism of B. balanus in light

Answer 10

the photoreceptor is depolarised and the ganglia are hyperpolarised, using histamine as an inhibitory neuroreceptor to prevent action potentials and keep adductor muscles relaxed

Question 11

describe the mechanism of B. balanus in shadow

Answer 11

the photoreceptor is hyperpolarised and the ganglia are depolarised. histamine is no longer used as an inhibitory neuroreceptor and action potentials propagate, contracting adductor muscles

Question 12

how are B. balanus adapted

Answer 12

they recycle histamine, as well as ensuring they are reactive to shadows irrespective of the level of ambient light

Question 13

what are the types of vertebrate reflex

Answer 13

polysynaptic eg bee sting and monosynaptic eg knee jerk. changes in reactivity can be indicators of damage and disease clinically