| What are pacinian corpuscles | found in the skin stimulated by pressure
found at the end of sensory neurones |
| How does a stimulation of pacinian corpuscles lead to a generator potential | Pressure (stimulus) is applied e.g. needle being inserted in the arm, being massaged, shaking hands, a tap on the head, etc.
The pressure on the skin stimulates the Pacinian corpuscles.
The pressure causes the layers of lamellae to become deformed (change shape/stretch).
This pressure also presses against the sensory nerve ending causing the axon membrane to stretch.
In the membrane, there are stretch mediated sodium ion channels. These channels only open when the membrane is stretched.
Sodium ions diffuse in, creating a generator potential.
If the generator potential passes the threshold, an action potential is produced |
| Pacinian corpuscles trigger words | Stimulated
Change shape
sensory nerve
Stretch
sodium ion chanels
generator potential
threshold |
| SAN does | produces it own electricity |
| AVN does | impulses travel from the AVN to the ventricles along Bundle of His |
| what is the Bundle of His | Bundle of his is a collection of purkyne fibres that run down the septum and up ventricular walls |
| What colours are receptors responsible for | Cones - red sensitve , blue sensitive , green sensitive = COLOUR VISION
Rod cell - black and white vision |
| Why do Cones have visual acuity | RECEPTORS STIMULATED light from 2 dots enter the eye and stimulates cone receptors
temporal SUMMATION each cone has its own bipolar connection so when two cones are stimulates ach is released to two bipolar neurones
SETS OF IMPULSES threshold is passed as sepearate sets of ach is released so two seperate impulses reach the brain causing you to see two dots
WHEREAS RODS HAVE SAME STEPS BUT AS ONLY TWO STIMULATED CONNECTED TO THE SAME BP ONLY ONE IMPULSE TRAVELS TO THE BRAIN SO ONE DOT |
| How do Rods have high visual sensitivity | DIM LIGHT stimulates the rods , light absorbed by pigments
ACH RELEASE ach released from each rod receptor diffuses across post sypatic membrane
as multiple rods are connected to one bipolar neurone , ach builds up so more NA+ gated channels open so NA+ diffuse in causing AS SPATIAL SUMMATION so THRESHOLD TO BE PASSED.
Action potentials move along the bipolar neurone to the optic nerve , causing high visual sensitivity
BUT CONES IT IS THE OPPOSITE AS CONNECTED TO THEIR OWN BP SO THRESHOLD NOT PASSED |
