Response To Stimuli - Revision Checklist

Question 1

What effect does IAA have on the shoots of plants

Answer 1

Controls cell elongation of plant growth

Question 2

How does IAA affect roots differently to shoots

Answer 2

IAA causes cell elongation to shoots whereas IAA inhibits cell elongation to roots

Question 3

Be able to explain that taxes are directional responses, and how tropisms are growth based responses, not movement responses

Answer 3

Taxes are directional responses because it is an organisms response that involves movement in a specific direction. Tropisms are growth based responses because it is a response specific for plant growth and not movement

Question 4

Write a null hypothesis for the ff. experiments:

A) an experiment to test the effect of sunlight intensity on the size of strawberries in a crop.

B) an experiment to test the effect of the installation of speed cameras on the number of car accidents on Columbia Road.

C) an experiment to test the effect of caffeine on the mood of 6th form students at the Bourne Academy.

Answer 4

A) sunlight intensity has no effect on the size of strawberries in a crop

B) the installation of speed cameras has no effect on the number of car accidents on Columbia Road

C) caffeine has no effect on the more of 6th form students at the Bourne Academy

Question 5

Explain what the ff. p values would mean for the experiments listed above:

A) p = 0.17
B) p = 0.01
C) p = 0.43

Answer 5

A) there is a 17% chance that the experiment is null.
B) there is a 1% chance that the experiment is null.
C) there is a 43% chance that the experiment is null.

Question 6

Explain how the arrangement of one cone cell to one neurone (bipolar cell) results in high visual acuity in the fovea.

Answer 6

The brain receives separate impulses from each cone cell so good resolution

Question 7

Explain why rod cells have a high sensitivity to light by referring to the arrangement of multiple rod cells to one neurone/bipolar cell.

Answer 7

Rod cells have a high sensitivity to light due to more rod cells connected to one bipolar cell which makes it easier to reach the threshold for an action potential to occur.

Question 8

Recall the pigments in the rod and cone cells and which one is broken down more easily

Answer 8

Rod: rhodopsin
Cone: iodopsin

Rhodopsin breaks down more easily as it requires lower light intensity than iodopsin

Question 9

Describe what the radial and circular muscles of the iris do when the pupil constricts and dilates (widens)

Answer 9

Pupil constricts: radial muscles relaxes and circular muscles contracts

Pupil dilates: radial muscles contracts and circular muscles relaxes

Question 10

Describe what allows cone cells to distinguish different colours in terms of the wavelengths of light

Answer 10

Cone cells are able to distinguish different colours due to having 3 types of cone cells each responding to a different wavelength of light

Question 11

Thinking about the heart, state the location and function of the:

A) sino-atrial node (SAN)
B) atrio-ventricular node (AVN)
C) atrioventricular valves
D) semi-lunar valves
E) bundle of His
F) right atrium
G) left ventricle

Answer 11

A) upper part of the right atrium; pacemaker
B) junction of the right and left ventricle; transmits impulses from atria to ventricles by a delay response
C) between atria and ventricles ; allow passage of blood into the ventricle and closes to prevent backflow of blood
D) between the pulmonary artery and ventricle; allows blood to flow into arteries and prevents backflow of blood
E) deep within the connective tissue; transmits electrical impulses from AVN to Purkinje fibres
F) upper left of the heart; receives deoxygenated blood from the body and pumps it to the right ventricle
G) lower right of the heart ; pumps oxygenated blood to the body

Question 12

Explain how the heart beats and why the order of the contractions is:

A) atrial systole
B) ventricular systole
C) diastole

Answer 12

The heart beats due electrical impulses sent by the medulla oblongata via the sympathetic nerve to SAN. SAN then starts the pace of how the heart beats. The order of contractions is actual systole - ventricular systole - diastole because deoxygenated blood from the body will go to the atria first then blood becomes oxygenated in the ventricle which will be delivered to the arteries in its resting state

Question 13

Explain how changing pressure causes blood to flow through the heart; explain the valves open and close at specific times. You are talking about the left side of the heart:

“blood flows into the left atrium from the pulmonary vein…”

Answer 13

Blood flows into the left atrium from the pulmonary vein causing the atrio-ventricular valve to close. Once there is a high pressure in the left atrium, the atrio-ventricular valve opens and blood flows into the left ventricle as the semi-lunar valve closes. Then the atrio-ventricular valve closes once all blood has flown to the left ventricle to prevent backflow of blood. The semi-lunar valve opens once there is a high pressure in the ventricle to deliver blood into the arteries.

Question 14

How does a Pacinian Corpuscle produce a generator potential? You need to use the correct term for the sodium ion channels in your answer.

Answer 14

When pressure is applied, the stretch-mediated sodium channel opens causing sodium ions to diffuse into the neurone reaching a threshold to send electric impulses to the brain creating a generator potential

Question 15

Explain the roles of the parasympathetic and sympathetic nervous systems on heart rate; explain how these two systems control the rate of the heartbeat by referring to the pathway of control starting with the chemoreceptors in the carotid arteries.

Answer 15

Parasympathetic NS: slows down heart rate
Sympathetic NS: speeds up heart rate

Increase in carbon dioxide causes chemoreceptors to transmit more nervous impulses to he centre in the medulla oblongator that increases heart rate. Centre sends impulses via the sympathetic NS to the SAN leading to an increase in heart rate. When carbon dioxide deceases signals are sent through the parasympathetic NS to the SAN leading to a decrease in heart rate

Question 16

Describe the meaning of:

A) gravitropism
B) hydrotropism
C) phototropism

Answer 16

A) shoots of the plant grows towards gravity

B) plant roots grow towards water in order to absorb it for use in photosynthesis and other metabolic processes as well as for support

C) stems grow towards light as light is needed for photosynthesis

Question 17

Explain the difference between the central and peripheral nervous system.

Answer 17

CNS is made up of the brain and spinal cord whereas PNS is made up of nerves that originate from litter the brain or the spinal cord

Question 18

Describe the pathway of the reflex arc starting with the receptors in the hand detecting extreme heat (a hot object).

Answer 18

Sensory neurone carries nervous impulses from receptor to the spinal cord. Intermediate neurone in the spinal cord sends nervous impulses from the sensory neurone to the motor neurone. Motor neurone then carries nervous impulses from the spinal cord to a muscle or gland initiating a response

Question 19

Explain the difference between the voluntary and autonomic nervous system.

Answer 19

Voluntary nervous system carries nerve impulses to body muscles under voluntary control. Autonomic nervous system carries nerve impulses to glands, smooth muscle and cardiac muscle involuntarily

Question 20

Explain which side of the autonomic nervous system would respond to high blood pressure, and how it would respond, using the heart rate nerve pathways.

Answer 20

If blood pressure is high, pressure receptors transmit more nervous impluses to the centre in the medulla oblongata to decrease heart rate. Centre sends impulses via parasympathetic NS to the SAN which leads to a decrease in heart rate