Response To Stimuli

Question 1

What is a taxis?

Answer 1

A simple directional response determined by the direction of the stimulus. Movement towards a positive stimulus or away from a negative one.

Question 2

What is kineses?

Answer 2

A change in the speed or rate at which the organism changes direction. If an organism moves into an unfavourable environment it will turn rapidly to increase its chances of re-entering the favourable environment.

Question 3

What is a tropism?

Answer 3

The growth of a plant in response to a directional stimulus using plant growth factors/auxins.

Question 4

What is IAA?

Answer 4

Indoleacetic acid

Question 5

What happens to IAA in phototropism in the shoots and what is the effect of this?

Answer 5

IAA is initially distributed evenly down the shoot by the cells in the tip, then moves to the shaded side. Causes elongation of cells so plant bends towards light.

Question 6

What happens to IAA in phototropism in the roots and what is the effect?

Answer 6

Moves to darker side and inhibits cell growth so roots bend down.

Question 7

What is the effect of IAA on gravitropism in the roots?

Answer 7

Gravity influences movement if IAA so builds up on lower side. Inhibits cell growth.

Question 8

What is the effect of gravitropism in the shoots?

Answer 8

Greater concentration on lower side causes cell elongation so shoot grows up against gravity.

Question 9

How does IAA increase cell plasticity?

Answer 9

Acid growth hypothesis involving active transport on H+ from cytoplasm into spaces in cell wall causing cell to become more plastic and allowing cell to elongate.

Question 10

What is peripheral nervous system divided into?

Answer 10

Sensory neurones and motor neurones.

Question 11

What are the motor neurones divided into?

Answer 11

Semantic and autonomic nervous system

Question 12

What is the name given to something that can create a change in a form of energy.

Answer 12

Transducer

Question 13

What is a generator potential?

Answer 13

The potential created when receptors convert energy of stimulus into a nervous impulse.

Question 14

What happens when pressure is applied to a pacinian corpuscle.

Answer 14

It becomes deformed and widens the stretch mediated Na+ channels, allowing influx of Na+ depolarising the membrane creating a generator potential

Question 15

Why do Rod cells have low visual acuity?

Answer 15

Because many rod cells are connected to a single bipolar cell.

Question 16

What is the pigment in rod cells?

Answer 16

Rhodopsin

Question 17

What is the pigment in cone cells?

Answer 17

Iodopsin

Question 18

What is temporal summation?

Answer 18

When you have many impulses going into one cell.

Question 19

What is the action of the sympathetic nervous system?

Answer 19

Speeds up activities in the body: fight or flight

Question 20

What is the action of the parasympathetic nervous system?

Answer 20

Slows down activities in the body: rest and digest.

Question 21

What is the layer of non-conduction tissue called that separated the atria from the ventricles?

Answer 21

Atrioventricular septum

Question 22

What does the AV node transmit its wave of excitation down?

Answer 22

Purkyne tissue (bundle of his)

Question 23

What are changes in heart rate coordinated by?

Answer 23

The medulla oblongata

Question 24

What does the cardioacceleratory centre communicate with the sino-atrial node by?

Answer 24

The sympathetic nervous system.

Question 25

What does the cardioinhibitory centre communicate with the AV node by?

Answer 25

The parasympathetic nervous system.

Question 26

Where are chemoreceptors found?

Answer 26

In the carotid arteries

Question 27

Where are baroreceptors found?

Answer 27

In the carotid arteries and aorta.