Mr p bio 7 receptors

Question 1

how does a stimulus cause a generator potential?

Answer 1

causes the membrane of a receptor to become more permeable to Na+ which causes a change in potential difference

Question 2

when will a generator potential lead to an action potential?

Answer 2

of it is large enough to reach the threshold

Question 3

give an example of a pressure receptor

Answer 3

pacinian corpuscle

Question 4

what is the state of the pacinian corpuscle in resting state?

Answer 4

stretch-mediated sodium channels are too narrow to let sodium pass through them

Question 5

what happens to the pacinian corpuscle if pressure is applied?

Answer 5

the lamellae of the pacinian corpuscle are deformed causing stretch-mediated Na+ channels to open and Na+ to diffuse in causing depolarisation. if threshold is reached a generator potential is produced

Question 6

what is the intensity of a stiumlus?

Answer 6

the frequency of impulses

Question 7

where does light enter the eye?

Answer 7

pupil

Question 8

what does the iris do?

Answer 8

controls the amount of light that enters

Question 9

what does the lens do?

Answer 9

focuses light rays on to the retina which lines the inside of the eye

Question 10

what does the retina contian?

Answer 10

the photoreceptor cells

Question 11

what is the fovea?

Answer 11

an area of the retina where lots of photoreceptors are found

Question 12

how do nerve impulses reach the brain?

Answer 12

carried from retina to the brain by the optic nerve (bundle of neurones)

Question 13

what is the name for where the optic nerve leaves the brain?

Answer 13

the blind spot- no photoreceptors so not sensitive to light

Question 14

describe the process that photoreceptors undergo?

Answer 14

1. light hits the photoreceptors + is absorbed by light sensitive optical pigments
2. light bleaches the pigments, causing a chemical change and increases membrane permeability to sodium ions
   3.generator potential produced- if threshold is reached, an action potential is sent a long a bipolar neurone
   4.bipolar neurone connects photoreceptors to the optic nerve which takes the action potential to the brain

Question 15

what are the two types of photoreceptors?

Answer 15

rods and cones

Question 16

where are rods found?

Answer 16

mainly in the peripheral parts of the retina

Question 17

where are cones found?

Answer 17

mainly closely packed together in the fovea

Question 18

what do rods and cones contain to allow them to fulfill their function?

Answer 18

different optical pigments making them sensitive to different wavelengths of light

Question 19

what type of information can rods give?

Answer 19

only give info in black and white (monochromatic)

Question 20

what type of information can cones give?

Answer 20

give info in colour (trichromatic)

Question 21

how many different cones are there and how do they differ?

Answer 21

3 each with a different optical pigment- red/blue/ green

Question 22

what are rods sensitive to and why?

Answer 22

they are very sensitive to light as many rods join to one bipolar neurone, so many weak generator potentials combine together to reach the threshold and trigger an AP. called retinal convergence

Question 23

what are cones sensitivity?

Answer 23

less sensitive than rods because each bipolar neurone joins with only one cone, so takes more light to reach threshold and trigger an AP

Question 24

describe visual acuity in rods

Answer 24

rods have low visual acuity as many rods join to the same bipolar neurone, so one AP is sent to the brain for multiple rods, which means light from two points close together cant be told apart

Question 25

what is visual acuity?

Answer 25

the ability to tell apart points that are close together

Question 26

describe visual acuity in cones

Answer 26

cones have a high visual acuity as cones are closer together and one cone joins the bipolar neurone so send seperate APs to the brain when light from 2 points hits 2 cones, 2 APs go to brain so you can distinguish 2 points that are close together as 2 seperate points

Question 27

why is the cardiac muscle myogenic?

Answer 27

the muscle contracts and relaxes without receiving signals from the brain

Question 28

describe the process of the control of heart beat?

Answer 28

1. SAN in right atrium generates an AP, which spread across the atria causing the atrial muscular wall to contract 2. a layer of non-conducting tissue prevents the depolarisation from spready to the ventricles- to prevent simultaneous contraction of atria and ventricles 3.AP travels to the AVN where there is a short delay this allows blood from the atria to fully empty into the ventricle and also prevents the atria and ventricles contracting simultaneously 4.AP passes from AVN to bundle of His and up the purkyne fibres 5. causes ventricles to contract from the base up so max vol of blood is forced up the arteries

Question 29

what does the medulla do?

Answer 29

subconsciously controls the rate of SAN firing

Question 30

what detects pressure in the heart?

Answer 30

pressure receptors called baroreceptors that are stimulated by high and low bp

Question 31

what detects changes in CO2 conc and pH in the heart?

Answer 31

chemoreceptors

Question 32

describe the process involved when a high bp is detected?

Answer 32

-baroreceptors in the aorta/ carotid artery detect high bp -send AP along sensory neurone to medulla -medulla sends more APs along parasympathetic nerve and less APs sent down the sympathetic nerves -parasympathetic nerves secrete acetylcholine which binds to the receptors on the SAN -SAN generates APs less frequently so AVN fired less frequently, causing ventricles to contract less frequently -cause HR to slow, decreasing bp

Question 33

how does the process after the detection of low bp differ from high and after detecting high CO2/ low pH differ from low CO2/ high pH??

Answer 33

sympathetic neurones are stimulated, which release noradrenaline, causing the HR to increase

Question 34

what is the process after detecting low CO2/ high pH?

Answer 34

-chemoreceptors detect chemical changes in the blood and sends an impulse along the sensory neurone to the medulla -medulla causes more impulses to pass along the receptors on the SAN -this decreases HR bringing CO2/ pH levels to normal