Receptors - B17 Flashcards
What is generator potential?
-a stimulus causes the membrane of a receptor cell to become more permeable to Na+
-causes a change in the potential difference
-a change in the potential difference in a receptor is called a generator potential
-if the generator potential is large enough to reach threshold, and action potential will be produced
What is the pacinian corpuscle?
-a pacinian corpuscle is an example of a pressure receptor and is mainly found in the skin
-it contains stretch mediated sodium ion channels
How is generator potential produced?
-when pressure is applied, the lamellae of the pacinian corpuscle are deformed
-causes stretch-mediated Na+ channels to open-> Na+ diffuse in
-causing depolarisation
-if threshold is reached a generator potential is produced
How does a stimulus feel more intense?
The greater the frequency of impulses, the more intense a stimulus feels
How do photoreceptors work?
-light hits the photoreceptors and is absorbed by light sensitive optical pigments
-light bleaches the pigments, causing a chemical change and increases the membrane permeability to sodium ions
-generator potential produced- if threshold is reached, an action potential is sent along a bipolar neurone
-bipolar neurones connect photoreceptors to the optic nerves which takes the action potential to the bran
What is the photopigment called in rod cells?
Rhodopsin
What are the two types of photoreceptors and where are they found?
-rods found mainly in the peripheral parts of the retina
-cones found mainly closely packed together in the fovea
-both contain different optical pigments making them sensitive to different wavelengths of light
What does it mean if rods are monochromatic?
They only give information in black and white
What makes cones trichromatic?
-give information in colour
-3 types of come each with a different optical pigments making- red/blue/green sensitive
-when stimulated in different proportions, you see different colours
What makes rods very sensitive to light?
-because many rods joint together to one bipolar neurone, so many weak generator potentials combine together to reach the threshold and trigger an AP
-this is called retinal convergence
What makes cones less sensitive than rods?
Because each bipolar neurone joins with only one cone, so it takes more light to reach threshold and trigger an AP
What is visual acuity?
The ability to tell apart points that are close together
Why do rods have low visual acuity?
Rods have low visual acuity because many rods join to the same bipolar neurone, so one action potential is sent to the brain for multiple rods, which means light from two points close together can’t be told apart
Why do cones have a high visual acuity?
-comes have a high visual acuity because cones are close together and one cone joins to one bipolar neurone so send separate action potentials to the brain
-when light from two pointe hits two cones, two Amps go to the brain, so you can distinguish two points that are close together as two separate points
What does it mean if the cardiac muscle is myogenic?
The muscle contracts and relaxes without receiving signals from the brain
What is the sinoatrial node?
A small mass of tissue in the wall of the right atrium, sends out a wave of electrical activity to the atrial walls, causing the atria to contract
What does the AV septum do?
The AV septum( a band of non-conducting collagen tissue) prevents the electrical wave from passing to the ventricles, instead they pass to the AVN
Describe how the heartbeat is controlled.
-SAN in the right atrium generates an action potential, which spreads across the atria causing the atrial muscular wall to contract
-a layer of non-conducting tissue prevents the depolarisation from spreading to the ventricles-to prevent simultaneous contraction of atria and ventricles
-the action potential 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
-an action potential then passes from the AVN down the Bundle of His and up the purkyne fibres
-this causes the ventricles to contract from the base up so maximum volume of blood is forced up into the arteries
How is information communicated between the heart and the brain?
-the rate of SAN firing is controlled subconsciously by the medulla
-animals must control the heart rate in response to internal stimuli e.g. low blood pressure or increased demand for O2
What are pressure receptors?
Called baroreceptors
-in the aorta and carotid artery are stimulated by high and low BP
What are chemoreceptors?
In the aorta, carotid artery, and medulla
-monitor CO2 concentration and pH(thereby controlling O2 conc.)
How is blood pressure decreased?
-high blood pressure
-baroreceltors im aorta/carotid artery detect high BP
-sends action potentials along sensory neurone to the medulla
-medulla sends more action potentials along parasympathetic nerve and less action potentials down the sympathetic nerves
-parasympathetic nerves secrete acetylcholine, which binds to receptors on the SAN
-SAN generates action potentials less frequently so the AVN fires less frequently, causing the ventricles to contract less frequently
-this causes the heart rate to slow, decreasing blood pressure
How does blood pressure increase?
-low blood pressure
-bark receptors in the aorta/carotid artery detect low BP
-sends action potentials along sensory neurone to the medulla
-medulla sends more action potentials along sympathetic nerve and less action potentials down the parasympathetic nerves
-sympathetic nerves secrete noradrenaline, which binds to receptors on the SAN
-SAN generates action potentials more frequent so the AVN fires more frequently, causing the ventricles to contract more frequently
-this causes heart rate to increase, increasing blood pressure
What happens if blood oxygen levels are too high?
(High O2, 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 parasympathetic nerve
-these secrete acetylcholine which binds to the receptors in the SAN
-this decreases HR bringing O2/CO2/blood pH levels back to normal
