Neuronal Communication Flashcards
Pacinian corpuscle
A pressure sensor found in the skin
Transducer
A cell that converts one form if energy into another/in to electrical impulse
Sensory receptors
Mostly transducers which can detect changes in our surroundings
Structure of the pacinian corpuscles
Oval-shaped consists of a series of consecutive rings of connective tissues wrapped around the end of a nerve cell.
What do pacinian corpuscles respond to?
Changes in pressure therefore stop responding when pressure is constant.
What can cause sodium channels to open
Changes in pressure/ any stimulus
What ion is inside the neurone
Potassium
What ion is outside the neurone
Sodium
Why can potassium ions leak out of the cell
The membrane is more permeable to potassium
What enhances the negative potential of a neurone
The presence of negatively charged anions
What effect the number of sodium channels opened
The intensity of the stimulus.
structure of neurones.
long, many gated ion channels, sodium potassium pump, dendrites
how many peripheral neurones in vertebrates are myelinated neurones.
one third
what does the myelinated sheath do?
prevents the movement of ions across the neurone membranes.
what is the polar state of the neurone?
-70mv
what is the threshold value?
-50mv
what causes voltage gated sodium channels to open after the threshold?
positive feedback loop.
what is the maximum potential of the neurone?
30mv
what causes the potential difference to be brought back to negative
potassium ions diffusing out of the cell.
the potential diff overshoots what is this?
hyperpolarisation
what is the refractory period?
the point were potassium and sodium are brought back to their original sides with the sp pump.
What is inside a cell body?
The nucleus many mitochondria and ribosomes
Why is the membrane more permeable to potassium ions the sodium ions when polarised?
Because some of the potassium channels are open
What is the rating potential of the membrane
-70mV
What is the threshold voltage?
-50mV
What is the maximum voltage?
30mV
What are local currents
When sodium ions are able to flow through the neurone causing depolarisation
How do local currents occur?
Through diffusion
Why don’t action potentials reverse in direction?
Because of the refractory period
What are the gaps between the myelin sheaths called?
Nodes of Ranviar
What is saltaory conduction
The jumping of action potentials from node to nod
How fast is saltatory conduction
Up to 120ms-1
What is the all or nothing rule?
All action potentials produce a depolarisation of 30mV
How is intensity of stimulus detected?
Frequency of action potentials
what is a cholinergic synapse
a synapse that uses acetylcholine as its neurotransmitter
how wide is a synaptic cleft?
approximately 20nm wide
what are the specialised features of the pre-synaptic bulb?
many mitochondria
a large amount of smooth endoplasmic reticulum.
voltage gated calcium channels.
how does the post synaptic bulb react to the presence of a neurotransmitter?
they have specialised sodium ion channels which can respond to the neurotransmitter.
what is the first step for the action of a synapse?
the voltage gated calcium ion channels open.
what is the first step for the action of a synapse?
the voltage gated calcium ion channels open.
what do the calcium ions cause inside the cell?
they cause the vesicles of neurotransmitters to move in the cell and bind with the membrane.
what happens after the neurotransmitter binds to the receptor?
it causes the sodium channels to open.
what is a EPSN?
a generator potential or a excitatory post-synaptic potential.
what is the role of acetylcholinesterase?
it is an enzyme found in the synaptic cleft. it hydrolyses the acetylcholine to ethanoic acid and choline
what is summation?
the effects of several excitatory post-synaptic potentials are added together.
what is the main role of a synapse?
to connect two neurons together so a signal can be passed along.
what is a summation?
occurs when the effects of several ESPN’s are added together.
what is temporal summation?
several action potentials in the same pre-synaptic neurone.
what is spatial summation?
action potentials arriving from several different pre-synaptic neurones.
what is the point of summations?
just one action potential isn’t enough to reach the threshold potential.
what can prevent the production of ESPN’s ?
by the action of a ISPN.
what would be useful in a reflex arc?
one presynaptic diverging innto many postsynaptic.
what does it mean to become habituated?
after repeated stimulation to a stimulus a synapse may run out of vesicles containing the neurotransmitter.
this means there is no longer a response.
