stimuli and responses

Question 1

what is a stimulus

Answer 1

any change in external environment

Question 2

what are receptors

Answer 2

can be cells or proteins that detect a stimulus

Question 3

what are effectors

Answer 3

cells that bring about a response to stimulus to produce an effect

Question 4

what do sensory neurones do

Answer 4

transmit electrical impulses from receptors to the cns

Question 5

what do motor neurones do

Answer 5

transmit electrical impulses from the cns to the effectors

Question 6

what do relay neurones do

Answer 6

transmit electrical impulses between sensory and motor neurones

Question 7

describe nervous system

Answer 7

1- stimulus detected by receptor cell and electrical impulse sent along a sensory neurone

2-when electrical impulse reaches end of the neruones chemical neurotransmitters take info to next neurone which then sends electrical impulse

3-the cns processes the info and sends electrical impulse along motor neurone to effector

Question 8

what is a reflex

Answer 8

rapid automatic response to a stimuli

Question 9

explain hand withdrawal from heat reflex

Answer 9

• thermodetectors in the skin detect heat
• sensory carries impulse to relay neurone
• relay neurone connects to motor neurone
• motor neruone send impulse to effector
• muscle contracts to withdraw hand

Question 10

how is nervous system response localised

Answer 10

when electrical impulse reaches end of neurone neurotransmittors are secreted directly onto target cells

Question 11

how is nervous system communication short lived

Answer 11

neurotransmitters quickly removed

Question 12

what is a tropism

Answer 12

a plants growth response to directional stimulus

Question 13

what is a tropism

Answer 13

a plants growth response to external stimulus

Question 14

whats positive tropism

Answer 14

growth towards stimulus

Question 15

what is phototropism

Answer 15

plant growth in response to light

positively phototrophic means towards light growht

Question 16

what is gravitropism

Answer 16

growth of plant in response to grvaity

negatively gravitrophic if grows up

Question 17

what are growth factors

Answer 17

hormone like chemicals whihc speed up or slow down growth

Question 18

whats auxins and how does it work

Answer 18

a growth factor

stimulate growth of shoot by cell elongation

Question 19

what does high concentrations of auxin do

Answer 19

inhibit growth of root

Question 20

whats IAA

Answer 20

an auxin in tips of shoot in flowering plants

Question 21

how does pacinian corpuscle work

Answer 21

when under pressure the stretch mediated sodium channels become deformed

meaning they open and allow rapid influx of sodium ions

the positive charge on sodium ions causes membrane to become depolarised

results in generator potential being made leading to action potential. in the axon

Question 22

describe pacinian corpuscle

Answer 22

have single sensory neurone in middle of connective tissue called lamellae forming layers seperated by gel

Question 23

what are photoreceptors

Answer 23

light receptors in eye

Question 24

how is light recieved in the eye

Answer 24

light enters eye in pupil
amount of light controlled by iris
lens focuses light rays onto retina
Nerve impulses from the photo receptor cells are carried from the retina to the brain by the optic nerve

Question 25

what is the fovea

Answer 25

area in retina with lots of photoreceptors

Question 26

how do photoreceptors convert light into electrical impulses

Answer 26

when light hits photoreceptors they are absorbed by light sensitive optical pigments

light bleaches the pigments causing chemical change altering membrane permeability to na+

generator potential is created if reaches threshold nerve impulse sent along bipolar neurone

bipolar neurone connect photoreceptors to optic nerve taking impulse to brain

Question 27

what are the two photoreceptors found in eye

Answer 27

rod and cone cells

Question 28

details on rod cells

Answer 28

found in peripheral part of retina

only give information on black and white

Question 29

details on cone cells

Answer 29

packed together in the fovea
give info in colour
three types red green and blue sensitiove

Question 30

sensitivity and visual acuity of rod cells

Answer 30

sense- very sensitive to light as many rods join one neurone so many weak generator potentials combine to reach th threshold and trigger ap

va- low visual acuity as many rods join one neurone

Question 31

sensitivity and visual acuity of cone cells

Answer 31

sensitivity - low sensitivity as one cone joins one neurone so lots of light required to reach threshold and trigger ap

va- high visual acuity as only one cone joins neurone

Question 32

why can the heart be described as myogenic

Answer 32

can contract and relax without signals from nerves

Question 33

where and what is the SAN

Answer 33

in right atrium

like a pacemaker sets rythm of heart beat by sending out regular waves of electrical activity to atrial walls

Question 34

describe process of regualr beating of the heart

Answer 34

1-SAN sends out wave of electrical activity to atrial walls

2- causes both atria to contract at same time

3- band on non conducting collagen tissue prevents electrical activity to be passed on to ventricles

4- electrical activity transfered from san to avn

5-slight delay before avn reacts to make sure atria empty before ventricles contract

6-avn passes waves of electrical activity to bundle of his into purkyne tissue

7-purkyne tissue carries waves to both ventricle wallas making them contract