Coordination And Control

Question 1

What occurs in a long day short night in plants

Answer 1

P730 accumulates during the long day, and is not sufficiently removed during the short night so is mostly P730, so long day plants flower

Question 2

What occurs in a short day long night in plants

Answer 2

P730 is removed during the long night and is not produced sufficiently during the short day, little P730, short day plants flower

Question 3

What occurs in a short day long night, interrupted by a short light in plants

Answer 3

During the night, the short light period converts P660 to P730, enabling sufficient P730 to accumulate so Long day plants flower

Question 4

What’s the difference between red light and far red light

Answer 4

Red light is rapid conversion of P730
Far red light is rapid conversion of P660

Question 5

What are the 3 growth hormones in plants

Answer 5

Auxins
Cytokinins
Gibberellins

Question 6

Where are Auxins produced and what is their effect

Answer 6

Produced in the growing tip of the stem, and stimulate elongation of cells

Question 7

Where are Cytokinins produced and what is their effect

Answer 7

Produced in actively dividing tissues and promote cell division

Question 8

Where are Gibberellins produced and what is their effect

Answer 8

Produced in the apical buds and leaves, and stimulate elongation of intermodal regions

Question 9

What is the process of auxin action

Answer 9

Produced in the apical meristem
They diffuse down the shoot
They then bind to specific receptors sites, which causes the membrane pumps to move H ions out

Question 10

What is the structure of a neuron

Answer 10

A centron which contains the nucleus and other organelles
Dendrons which transmit impulses to the cell body
Axons which transmits impulses away from the cell body

Question 11

What are the axons and dendrons myelinated in, and what is there function

Answer 11

A myelin sheath of Schwann cells, which insulated the axon, preventing ion movement

Question 12

What are the gaps in the myelin sheath called

Answer 12

Nodes of Ranvier

Question 13

What is the resting potential

Answer 13

When the large potential difference in the neurone occurs at rest

Question 14

What is the action potential of a neurone

Answer 14

The reserve of the potential difference

Question 15

Why does an action potential occur

Answer 15

When a neurone is stimulated, the cell-surface membrane allows sodium ions to diffuse in, changing the potential difference

Question 16

What is the threshold value

Answer 16

When a critical potential difference is reached, then ions surge in and the neurone becomes depolarised

Question 17

What is the refractory period

Answer 17

The recovery period after an action potential occurs

Question 18

What occurs on both sides of axons or dendrons during local circuits

Answer 18

On one side, the membrane is still recovering its resting potential, and on the other excitable side, the local circuits triggers depolarisation and the formation of an action potential. This process is repeated at each section of the membrane along the neurone

Question 19

Why can local circuits not occur in a myelinated neurone

Answer 19

It cannot be set up in the parts of the myelin sheath

Question 20

How does a myelinated neurone have local circuits

Answer 20

The action potential ‘jumps’ from one Node of Ranvier to the next, called Saltatory Conduction

Question 21

What is the first step of Synaptic transmission

Answer 21

The impulse arrives at the synaptic bulb, and the membrane becomes permeable to calcium ions which diffuse into the bulb

Question 22

What is the last step of synaptic transmission

Answer 22

The breakdown products diffuse across the cleft and are reabsorbed into the synaptic bulb where they are resynthesised into the neurotransmitter using energy in the form of ATP

Question 23

What is the role of calcium ions in synaptic transmission

Answer 23

They stimulate movement of synaptic vesicles towards the pre-synaptic neurone

Question 24

What is the function of synaptic vesicles in synaptic transmission

Answer 24

They fuse with the pre-synaptic membrane and release the neurotransmitter molecules by Exocytosis into the synaptic cleft

Question 25

What is the function of neurotransmitter molecules in synaptic transmission

Answer 25

They diffuse to the post-synaptic membrane, where they attach to specific receptors causing ion channels to open so that the potential difference in the post-synaptic membrane is altered

Question 26

What occurs when a neurotransmitter molecule attaches to a receptor site

Answer 26

A sodium ion channel opens and the post-synaptic membrane becomes depolarised

Question 27

Why is the breakdown of the neurotransmitter important in synaptic transmission

Answer 27

It allows the resting potential to be established, where they diffuse across the synaptic cleft and are reabsorbed into the synaptic bulb