(14) Response to stimuli

Question 1

what do sensory neurones do

Answer 1

transmit electrical impulses from receptors to the CNS

Question 2

what do motor neurones do

Answer 2

transmit electrical impulses from the CNS to effectors

Question 3

what do relay neurones do

Answer 3

transmit electrical impulses between sensory neurones and motor neurones

Question 4

what is the peripheral nervous system

Answer 4

made up of the neurones that connect the CNS to the rest of the body and has 2 separate systems

Question 5

what is the difference between the somatic and the autonomic nervous system

Answer 5

somatic controls conscious activities and autonomic controls unconscious and has 2 divisions with opposite effects on the body

Question 6

what is the difference between the sympathetic and the parasympathetic nervous system

Answer 6

the sympathetic nervous system gets the body ready for action (fight or flight)
the parasympathetic calms the body down

Question 7

what are the 3 neurones involved in a simple reflex arc

Answer 7

sensory, relay, motor

Question 8

what is a tropism

Answer 8

the response of a plant to a directional stimulus

Question 9

what are growth factors

Answer 9

hormone like chemicals that speed up or slow down plant growth. produced in the growing regions of the plant and move to where they’re needed in other parts of the plant

Question 10

what do auxins do

Answer 10

stimulate the growth of shoots by cell elongation (cells become loose and stretchy so get longer) but high concentrations can inhibit growth in roots

Question 11

what is a taxes

Answer 11

organisms move towards or away from a directional stimulus eg light

Question 12

what is a kinesis

Answer 12

the organisms movement is affected by a non directional stimulus eg humidity

Question 13

what is a cells resting potential

Answer 13

the potential difference (voltage) when the cell is at rest due to ion pumps and ion channels generating a difference between the inside and outside of the cells

Question 14

what is an action potential

Answer 14

triggered if the generator potential is big enough and is an electrical impulse across a neurone

Question 15

what is a generator potential

Answer 15

a change in potential difference due to a stimulus

Question 16

how do you acheive a bigger generator potential being produced

Answer 16

a bigger stimulus excites the membrane more causing a bigger movement of ions and a bigger change in potential difference so a bigger generator potential

Question 17

what are pacinian corpuscles

Answer 17

receptors that detect pressure and vibrations in the skin

Question 18

how does a pacinin corpuscle trigger a generator potential

Answer 18

they contain the end of a sensory neurone wrapped in layers of connective tissue (lamellae) and when stimulated the lamellae are deformed and press on the sensory nerve ending which causes the channels to open and the sodium ions diffuse into the cell creating a generator potential

Question 19

how do photoreceptors convert light into an electrical impulse

Answer 19

light enters the eye hits the photoreceptors and is absorbed by light sensitive optical pigments , this causes a chemical change and alters the membrane permeability to sodium ions.
creates a generator potential and if the threshold is reached a nerve impulse is sent along a bipolar neurone which take impulses to the brain

Question 20

what are the 2 types of photoreceptor in the eye

Answer 20

rods and cones

Question 21

what are the differences between rods and cones

Answer 21

rods are mainly found in the peripheral parts of the retina and only give info in black and white but cones are packed together in the fovea and give info in colour

Question 22

explain the sensitivity of rods

Answer 22

rods- very sensitive to light (work well in dim) because many rods join one neurone so many weak generator potentials combine to reach the threshold and trigger action potential

Question 23

explain the sensitivity of cones

Answer 23

less sensitive (work best in bright light) because one cone joins one neurone so it takes more light to reach the threshold to trigger an action potential

Question 24

explain the visual acuity of rods

Answer 24

low visual acuity because many rods join the same neurone so light from 2 points close together can’t be told apart

Question 25

explain the visual acuity of cones

Answer 25

high visual acuity because cones are close together and when light from 2 points hits 2 cones, 2 action potentials go to the brain so you can distinguish 2 close points as separate

Question 26

define myogenic in terms of cardiac muscle

Answer 26

can contract and relax without receiving signals from nerves (controls the regular heartbeat)

Question 27

what is the bundle of His

Answer 27

a group of muscle fibres responsible for conducting the waves of electrical activity between the ventricles to the apex of the heart

Question 28

what is purkyne tissue

Answer 28

finer muscle fibres in the right and left ventricle walls that splits off from His bundle and then carries waves of electrical activity into the muscular walls of the right and left ventricles causing them to contract simultaneously

Question 29

what part of the brains controls the rate at which the SAN fires (heart rate)

Answer 29

medulla oblongata

Question 30

what are baroreceptors

Answer 30

pressure receptors in the aorta and carotid arteries- stimulated by high and low blood pressure

Question 31

what are chemoreceptors

Answer 31

found in aorta, carotid arteries and medulla-they monitor the oxygen levels in the blood and co2 and pH

Question 32

how is high blood pressure counteracted by the parasympathetic nervous system

Answer 32

detected by baroreceptors, impulses sent to medulla, send impulses along parasympathetic neurones which secrete a neurotransmitter to bind to the SAN. this slows heart rate and reduces blood pressire

Question 33

how is low blood pressure counteracted by the sympathetic nervous system

Answer 33

detected by baroreceptors, impulses sent to medulla which send impulses along sympathetic neurones, secrete noraderenaline which binds to SAN. increases heart rate

Question 34

how is high blood oxygen, low co2 or high pH levels counteracted by parasympathetic nervous system

Answer 34

detected by chemoreceptors, impulses sent to medulla, impulses sent along parasympathetic neurones which secrete acetylcholine which binds to SAN and heart rate decreases to return everything to normal level

Question 35

how is low blood oxygen, co2 or pH levels counteracted by sympathetic nervous system

Answer 35

detected by chemoreceptors, impulses sent to medulla, impulses sent along sympathetic neurones which secrete noradrenaline which binds to SAN and heart rate increases