Pacinian corpsucle/ GP

Cells or proteins that detect a stimulus Proteins found in cell membrane Cells connected to nervous systemR

They convert the energy of the stimulus into electrostatic energy by creating an electrochemical gradient action potential which passes as an impulse along neurons

Nervous system receptor Mechanoreceptor - Responds to mechanical stimulus responds to mechanical tissue

A single sensory neurone (axon ending) at the centre. Surrounded by multiple concentric layers of lamellae (connective tissue). Each lamella is separated by a gel-like substance. The neurone has stretch-mediated sodium ion channels in its membrane Potassium sodium pump

A detectable change in the internal or external environment that is capable of causing a response.

A generator potential is a change in the potential difference across the membrane of a nerve cell that occurs in response to a stimulus (When the threshold isnt reached)

Be careful not to mix up generator potentials and action potentials; remember that generator potentials: only occur at the site of a stimulus differ in size depending on the size of the stimulus can lead to an action potential (Basically the start of the depolarisation of axon membrane )

When not being stimulated the inside of the cell is more negatively charged than the outside Potential difference across the membrane This is known as the resting potential and we say the membrane is polarised

Resting potential is around -70mv and is maintained by sodium potassium pump (requires atp) Sodium potassium pumps 2 K+ ions in the axon membrane and 3 Na + ions out of the cell membrane Potassium ion channels are open allowing facilitated diffusion of K+ ions out of the neuron down their concentration gradietn More positive ions outside of neurone than inside so inside remains more negatively charged

When a stiumulus is detected ( Pressure ), Sodium voltage gated channels start to open to make the cell membrane more permeable to Na+ ions. Causing cell membrane to become more permeable to Na+ ions Potential difference reduced so membrane becomes depolarised Bigger stimulus more channels will open creating larger change in voltage if threshold reached action potential arises

1) pressure distorts the layers of membrane, causing stretch-mediated sodium channels in the axon membrane to open 2) sodium ions enter the axon via facilitated diffusion 3) positively charged sodium ions cause the inside of the axon to become more positive (DEPOLARISATION); this is a generator potential

Over time touch receptors in the skin can become habituated to certain stimuli; this means that response to a stimulus decreases after repeated or prolonged exposure (Decrease in sensitivity)