4. Receptors Flashcards
How are receptors specific?
Only decent one particular stimulus.
Light
Glucose conc
Pressure
What can receptors be ?
Cells - photoreceptors
Proteins - cell surface membrane glucose on pancreatic membrane
Who do receptors in nervous system convert energy of stimulus into ?
Electrical energy used by neurones.
Name 3 stages of how receptors work ?
Resting potential.
Generator potential.
Action potential.
When a nervous system receptor is in return state, what’s the charge like ?
There’s a difference in charge of inside and outside of cell.
Inside - negatively charged relative to outside.
Because there’s a difference in charges across membrane , what does it mean ?
There’s a voltage across membrane.
Potential difference.
What is voltage also known as?
Resting potential .
How is the resting potential generated ?
By ion pumps and ion channels.
What happens when stimulus is detected ?
Cell membrane is excited and becomes more permeable.
Allowing more ions to move in and out of cell.
This alters the potential difference.
So the stimulus causes a change in what?
Potential difference.
The change in potential difference due to stimulus is called what?
Generator potential.
What does a bigger stimulus do ?
Excites membrane even more.
Causing bigger movement of ions and bigger change in potential difference -so bigger generator potential.
What is potential difference across membrane measured in?
Millivolts.
What happens if the generator potential is big enough ?
It will trigger an action potential - electric impulse along neurone.
However, when can an action potential only be reached?
When generator potential reaches threshold level.
How is the strength of action potentials measured ?
The frequency as the action potentials are all one size.
What happens if stimulus is too weak ?
Generator potential won’t reach threshold - no action potential.
What are pacinian corpuscles examples of ?
Mechanoreceptors
Decent mechanical stimuli
Pressure
Vibrations
Where are pacinian corpuscles found ?
Skin
What do pacinian corpuscles contain ?
End of sensory neurone , sensory nerve ending.
What is the sensory nerve ending wrapped around?
Lots of layers of connective tissue - lamellae
What happens when a pacinian corpuscle is stimulated ?
The lamellae become deformed and press the sensory nerve ending.
Sensory neurones cell membrane stretches, deforming stretch meditated
sodium ion channels.
Channels opens
Sodium ions diffuse into cell generating generator potential.
How did stretch mediated sodium ions get their name?
Because they only open and let sodium ions pass through they’re stretched.
When the stimulus is applied, which sodium ions open?
They open where the stimulus is being applied so sodium ions diffuse into cell.
Sodium ions however remain closed where stimulus is not present. So no diffusion here
The bigger the stimulus…
More pressure applied More sodium channels opens Creates bigger generator potential More likely to reach threshold More like to crest action potential
