Nerves Flashcards
What is the information processing/reaction arc
Stimulus
Receptors
Sensory
CNS
Motor
Effectors
Response
What do sensory receptors do
Convert stimulus energy into nerve impulses from electrical energy acting as a transducer
What happens when a receptor is at a resting state
There is a difference in charge between in and out of the cell generated by ion pumps and channels so there is a voltage or potential difference
What is the potential difference called when a cell is at rest
Resting potential
What happens to a cell when a stimulus is detected
The cell membrane is excited and becomes more permeable which allows more ions to move in and out of the cell altering the potential difference. Calling the pd the generator potential
What happens if the generator potential is big enough
It will trigger an action potential along a neurone but this will only occur if a certain level called the threshold is reached - not if the stimulus is too weak
What are Pacinian corpuscles
They are mechanoreceptors detecting mechanical stimuli such as pressure and vibrations
They are found in your skin and contain the end of a sensory neurone called a sensory nerve ending. This is wrapped in lots of layers of tissue (lamellae)
What happens when a Pacinian corpuscle is stimulated
The lamellae are deformed and press on the sensory nerve ending causing the stretch mediated sodium channels to deform. The sodium ion channels open and sodium then diffuses into the cell creating a generator potential which may trigger an action potential
At rest neurone cell membranes are…
Polarised - the outside of the membrane is positively charged compared to the inside due to a higher concentration
What is the voltage at resting potential
- 70 mv
How is the resting potential maintained
By sodium potassium pumps and potassium ion channels
What does the sodium potassium pumps a
Move out sodium ions of the neurone but the membrane isn’t permeable to sodium ions so they can’t diffuse back in creating an electrochemical gradient .
