Mr p bio 7 receptors Flashcards
how does a stimulus cause a generator potential?
causes the membrane of a receptor to become more permeable to Na+ which causes a change in potential difference
when will a generator potential lead to an action potential?
of it is large enough to reach the threshold
give an example of a pressure receptor
pacinian corpuscle
what is the state of the pacinian corpuscle in resting state?
stretch-mediated sodium channels are too narrow to let sodium pass through them
what happens to the pacinian corpuscle if pressure is applied?
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
what is the intensity of a stiumlus?
the frequency of impulses
where does light enter the eye?
pupil
what does the iris do?
controls the amount of light that enters
what does the lens do?
focuses light rays on to the retina which lines the inside of the eye
what does the retina contian?
the photoreceptor cells
what is the fovea?
an area of the retina where lots of photoreceptors are found
how do nerve impulses reach the brain?
carried from retina to the brain by the optic nerve (bundle of neurones)
what is the name for where the optic nerve leaves the brain?
the blind spot- no photoreceptors so not sensitive to light
describe the process that photoreceptors undergo?
- light hits the photoreceptors + is absorbed by light sensitive optical pigments
- 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
what are the two types of photoreceptors?
rods and cones
where are rods found?
mainly in the peripheral parts of the retina
where are cones found?
mainly closely packed together in the fovea
what do rods and cones contain to allow them to fulfill their function?
different optical pigments making them sensitive to different wavelengths of light
what type of information can rods give?
only give info in black and white (monochromatic)
what type of information can cones give?
give info in colour (trichromatic)
how many different cones are there and how do they differ?
3 each with a different optical pigment- red/blue/ green
what are rods sensitive to and why?
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
what are cones sensitivity?
less sensitive than rods because each bipolar neurone joins with only one cone, so takes more light to reach threshold and trigger an AP
describe visual acuity in rods
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
what is visual acuity?
the ability to tell apart points that are close together
describe visual acuity in cones
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
why is the cardiac muscle myogenic?
the muscle contracts and relaxes without receiving signals from the brain
describe the process of the control of heart beat?
- SAN in right atrium generates an AP, which spread across the atria causing the atrial muscular wall to contract
- 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 - causes ventricles to contract from the base up so max vol of blood is forced up the arteries
what does the medulla do?
subconsciously controls the rate of SAN firing
what detects pressure in the heart?
pressure receptors called baroreceptors that are stimulated by high and low bp
what detects changes in CO2 conc and pH in the heart?
chemoreceptors
describe the process involved when a high bp is detected?
-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
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??
sympathetic neurones are stimulated, which release noradrenaline, causing the HR to increase
what is the process after detecting low CO2/ high pH?
-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
