Response To Stimuli

Question 1

What is the basic sequence of response

Answer 1

Stimulus
Receptor
Coordinator
Effector
Response

Question 2

Define stimulus

Answer 2

Detectable change to environment

Question 3

Define Effector

Answer 3

Cells that produce response

Question 4

Define receptors

Answer 4

Cells that detect stimulus

Question 5

What are the types of response in motile organisms

Answer 5

Taxis

Kineses

Question 6

Describe taxis

Answer 6

Directional movement
In relation to stimulus
+ve is towards
-ve is away

Question 7

Examples of taxis

Answer 7

+ve phototaxis of algae

+ve chemotaxis of bacteria to glucose

Question 8

Describe kinesis

Answer 8

Changes to speed
Changes to rate of turns
Random and non-directional movement

Question 9

Explain how kinesis works

Answer 9

Once in unfavourable conditions = many turns

Much time in unfavourable conditions= less turns and faster movement

Question 10

Types of movement in Non-motile organisms

Answer 10

Tropism

Question 11

Examples of tropism

Answer 11

Geotropism
Gravitropism
Phototropism

Question 12

Use of tropism in shoots

Answer 12

+ve phototropism = more light for Photosynthesis

-ve geotropism= grows up towards light

Question 13

Use of tropism in roots

Answer 13

+ve geotropism= grows down for support

+ve hydrotropism= water for Photosynthesis

-ve phototropism = grows down towards light

Question 14

What chemicals are involved in tropism

Answer 14

Plant growth factors

Question 15

What is the difference between plant growth factors and hormones

Answer 15

Made by cells throughout plant

May have effect on nearby cells

Question 16

What does IAA stand for

Answer 16

Índoleacetic acid

Question 17

Give examples of plant growth factors

Answer 17

Auxins

IAA

Question 18

How does IAA work

Answer 18

Controls cell elongation in flowering plants

Question 19

Describe how phototropism occurs in shoots

Answer 19

IAA produced in shot tip
Travels down both sides evenly at first
IAA accumulates on shaded side
Increase IAA conc causes cells to elongate faster than on light side
Shoot grows towards light

Question 20

What theory explains how IAA works

Answer 20

Acid growth hypothesis

Question 21

Describe the acid growth hypothesis

Answer 21

IAA attaches to cell membrane
More H+ are Transported in cell wall
Decreased PH causes microfibrils to be stretched

More plasiticity= elongated

Question 22

What is the response to touch called

Answer 22

Thigmotropism

Question 23

Describe the effect of IAA on roots

Answer 23

Produced in tip
Diffuse down sides evenly
Accumulate on lower side due to gravity
IAA inhibits elongation

Upperside grows quicker than lowerside

Grows down

Question 24

What is the spinal cord made up of

Answer 24

Pairs of motor and sensory neurons entering and leaving

Intermediate neurons within

Question 25

What is the coordinator in a reflex arc

Answer 25

Intermediate neuron

Question 26

Why are reflex arcs important

Answer 26

Prevent tissue damage Allow brain to carry out more complex responses Very quick Don't have to be learnt

Question 27

Why are reflexes so quick

Answer 27

Very few neurons involved

Question 28

What are the features of receptors

Answer 28

Specific to one stimulus Transducers (convert energy from one form to another)

Question 29

What must occur for an action potential to be generated

Answer 29

Generator potential must exceed threshold

Question 30

What do pacinian corpuscles respond to

Answer 30

Mechanical pressure

Question 31

What is a graded response

Answer 31

Where increase in stimulus causes increase in generator potential frequency of action potentials

Question 32

Describe the structure of the pacinian corpuscles

Answer 32

Neuron end with ending surrounded by layers of connective tissue with viscous gel between layers

Question 33

Describe what occurs what pressure is applied to a pacinian corpuscles

Answer 33

Layers of tissue deform Neuron membrane is stretched causing strech mediated sodium ion channel to open Na+ Diffuse in Membrane is de polarised Generator potential created If exceeds threshold then action potentials produced

Question 34

What is an action potential

Answer 34

Nervous impulse

Question 35

Describe why pacinian corpuscles have a graded response

Answer 35

Larger pressure= Larger deformity of membrane = Larger polarisation = Larger generator potential= increase frequency of action potentials

Question 36

What receptors are present in the eye

Answer 36

Rods and cones

Question 37

Where are Rod cells found

Answer 37

At periphery only

Question 38

Describe and explain the visual acuity of rod cells

Answer 38

Low visual acuity due to retinal convergence (multiple rod cells conected to same bipolar neuron and ganglion cell)

Question 39

Describe and explain the sensitivity to low light intensity of rod cells

Answer 39

Very sensitive due to summation Generator potentials added up due to retinal convergence so more likely to surpass threshold

Question 40

Describe and explain visual acuity of cone cells

Answer 40

High because each cone cell is attached to one neuron

Question 41

Describe and explain the sensitivity to low intensities of light in cone cells

Answer 41

Poor No retinal convergenc so larger stimulus need to surpass threshold

Question 42

Are Rod or cone cells more abundant

Answer 42

Rod

Question 43

How many types of rod cells are there

Answer 43

One

Question 44

How many types of cone cells are there

Answer 44

``` 3 Red Blue Green Light detection ```

Question 45

Where are cone cells found

Answer 45

Mainly at fovea some at periphery

Question 46

What parts of the nervous system control heart rate

Answer 46

Periphery nervous system Autonomic Sympathetic and parasympathetic

Question 47

Define myogenic

Answer 47

Initiated within the muscle

Question 48

Describe how a heart beat is started

Answer 48

Wave of electrical excitement starts from SAN Move across atria walls causing contraction AVseptum prevents waves entering ventricles After delay wave eminates from AVN down bundle of his and purkinji fibres Ventricles contract from apex up

Question 49

What does SAN stand for

Answer 49

Sino atrial node

Question 50

Where is the SAN

Answer 50

Right atrium wall

Question 51

What does AVN stand for

Answer 51

Atrioventricular node

Question 52

What is the AV septum

Answer 52

Non conductive tissue seperating atrium and ventricles

Question 53

Where is the AVN found

Answer 53

Right atrium walls

Question 54

Where are chemo receptors found

Answer 54

Carotid artery walls

Question 55

What do chemo receptors respond to

Answer 55

Changes in PH

Question 56

Describe how chemo receptors respond to decreased PH

Answer 56

Chemo receptors increase frequency of nervous impulses to accelatory centre in medulla oblognata Increase in waves down Sympathetic nerves More electrical waves emitted from SAN Increased heart rate and blood flow Carbon dioxide concentration decreases PH increases

Question 57

What is the alternative name for pressure receptors

Answer 57

Baro receptors

Question 58

Where are pressure receptors found

Answer 58

Carotid artery walls | And aorta

Question 59

What are carotid arteries

Answer 59

Arteries leading to brain

Question 60

How do pressure receptors respond to increased blood pressure

Answer 60

More impulses to inhibitory centre in medulla oblognata More pulses via parasympathetic nerves Less waves from SAN Reduced heart rate

Question 61

How do barorecptors respond to decreased blood Pa

Answer 61

More impulses to accelatory centre in medulla oblognata More pulses via sympathetic nerves More waves from SAN Increased heart rate