Stimuli and Response

Question 1

What is a tactic response (taxis)?

Answer 1

-Directional movement in response to a stimulus, the direction of the stimulus affects the response

Question 2

What is kinetic response (kinesis)?

Answer 2

-Non-directional (random) movement in response to a stimulus, the intensity of the stimulus affects the response

Question 3

What is a sensory neurone?

Answer 3

-Transmits electrical impulses from receptors to the CNS

Question 4

What is a motor neurone?

Answer 4

-Transmits electrical impulses from CNS to effectors

Question 5

What is a relay neurone?

Answer 5

-Transmits electrical impulses between sensory neurones and motor neurones

Question 6

Why are simple reflexes involuntary?

Answer 6

-The pathway of communication doesn’t go through conscious parts of the brain

Question 7

What is phototropism?

Answer 7

-The growth of a plant in response to light

Question 8

How do roots and shoots grow in response to light?

Answer 8

-Roots=negatively phototropic
-Shoots=positively phototropic

Question 9

What is gravitropism?

Answer 9

-The growth of a plant in response to gravity

Question 10

How do roots and shoots grow in response to gravity?

Answer 10

-Roots=positively gravitropic
-Shoots=negatively gravitropic

Question 11

Where is auxin produced?

Answer 11

-In the tips of roots and shoots and diffuses down the plant

Question 12

What does auxin stimulate?

Answer 12

-Growth in shoots
-Inhibit growth in roots

Question 13

What does IAA stimulate?

Answer 13

-Cell elongation

Question 14

What is a resting potential?

Answer 14

-Outside of the membrane is positive and inside of the membrane is negative

Question 15

What is a generator potential?

Answer 15

-Membrane is stimulated and becomes excited and more permeable
-Allows more ions to move in and out of the cell
-Changes the potential difference
-Bigger stimulus=bigger change of potential difference=bigger generator potential

Question 16

What is an action potential?

Answer 16

-Generator reaches threshold level
-All same size, strength of stimulus is is measured by frequency of action potentials

Question 17

Describe the structure of a Pacinian corpuscle

Answer 17

-End of a sensory neurone wrapped in layers of connective tissues called lamellae

Question 18

What happens when a Pacinian corpuscle is stimulated?

Answer 18

-Lamellae become deformed and press on end of sensory neurone
-Sensory neurone membrane stretches
-Stretch-mediated sodium ion channels become deformed
-Channels open and sodium ions diffuse into cell
-Generator potential created
-If threshold reached->action potential

Question 19

How do photoreceptors work?

Answer 19

-Light enters eye
-Pigment in photoreceptor breaks down
-Membrane becomes more permeable to sodium ions
-Sodium ions diffuse in
-Generator potential
-If threshold reached->action potential

Question 20

What are properties of cone cells and where are they found?

Answer 20

-Found in the fovea
-Detect 3 colours->red, yellow and blue
-Sensitive to bright light
-High visual acuity as one cone joins to one bipolar neurone

Question 21

What are properties of rod cells and where are they found?

Answer 21

-Found in the peripheral parts of the retina
-Detect black and white light
-Sensitive to dim light
-Low visual acuity as many rods join to the same bipolar neurone

Question 22

What is visual acuity?

Answer 22

-The ability to tell apart points that are close together

Question 23

What does myogenic mean?

Answer 23

-The heart muscle can contract and relax without receiving signals from nerves

Question 24

Describe and explain how heart rate is controlled

Answer 24

-The sinoatrial node (SAN) acts as a pacemaker, causes right and left atria to contract at the same time
-Electrical signals are transferred to the atrioventricular node (AVN)
-Electrical signals passed onto the bundle of His
-Then onto the Purkyne tissue which carries the electrical signals into walls of ventricles causing them to contract from the bottom up

Question 25

Describe how high blood pressure is detected and what happens when it is

Answer 25

-Baroreceptors detect a change in blood pressure
-Impulses sent along sensory neurone to medulla
-Impulses sent along parasympathetic neurones
-Acetylcholine secreted
-Binds to receptors on SAN
-Slows down heart rate->decreases blood pressure

Question 26

Describe how low blood pressure is detected and what happens when it is

Answer 26

-Baroreceptors detect change in blood pressure
-Impulses sent along sensory neurones to medulla
-Impulses sent along sympathetic neurones
-Secrete noradrenaline
-Binds to receptors on SAN
-Increases heart rate->increases blood pressure

Question 27

Describe how high blood pH, high O2 or low CO2 levels are detected and how this is counteracted

Answer 27

-Chemoreceptors detect change
-Impulses sent along sensory neurones to medulla
-Impulses sent along parasympathetic neurones
-Acetylcholine secreted
-Binds to receptors on SAN
-Heart rate decreases->counteracts change

Question 28

Describe how low blood pH, low O2 or high CO2 levels are detected and how this change is counteracted

Answer 28

-Chemoreceptors detect change
-Impulses sent along sensory neurones to medulla
-Impulses sent along sympathetic neurones
-Noradrenaline secreted
-Binds to receptors on SAN
-Heart rate increases->counteracts change