Membrane potential, action potentials and synaptic transmission and perception Flashcards
what is a membrane potential
difference in charge between the extracellular fluid and intracellular fluid
What is the concentration of sodium inside and outside of the cell
out 150mmol
in 15mmol
What is the concentration of potassium ions inside and outside of the cell
out 5mmol
in 150mmol
What is the concentration of anions inside and outside of the cell
out 0
in 65mmol
what has higher permeability potassium or sodium ions
potassium
If the positive concentration gradient is directed outside the cell which way is the electrical gradient directed
inside the cell
what is the main cause for the resting potential.
K+ diffuse out of the cells which creates a positive charge outside the cell.
What is the formula to work out the membrane potential
E = 61 log conc out/ conc in
Na+ enter the cell from the outside(extracellular) which makes the potential more positive to overall charge. What is the potential differnence
-70mv
Quickly describe the process of an ap being generated- using the graph with certain channels opening etc
what is threshold potential to
At resting potential , stimulus cause NA to open and reach threshold of -55 positive feedback causes voltage. gated sodium channels to open from threshold to to peak.
Pd now at +30mv , Na volatge gated close which is triggered at threshold but slow.
Efflux of K+ causes repolarisation. Potassium channels( I gate) open at threshold potential put slow. Pd overshoots causing hyperolarisation where potassium channels close.
What is the refractory period?
what molecules restore this
Ap ions are in the wrong place so restored by PAMPS
this makes sure the cell can recover and AP are only transmitted in one direction
What is GABA
GABA is an inhibitory neurotransmitter which binds to the GABA a receptor and causes hyperpolarisation of the post synaptic membrane due to causing an influx of K+
GABAb - potassium efflux
GABAa - influx of CL-
Temporal summation
2 or more AP I quick succession release enough neurotransmitter to trigger AP on next neuron
Spatical summation
pre neurones simultaneously coverage to release small amount of neurotransmitter - multi stimuli in 1 response
soma
body of the neurone
what does the axon do
carries impulses from the body
axon hillock
soma binds to the axon- where the theshold potential is met , all or nothing potential
intensity of AP
firing frequency
difference between neurone and a nerve
Neurone is one cell and a nerve is made up from multiple nerves.
Excitable cells – can generate an electrical current through ion channels what are the two types of excitable cells
muscle and nerve
Neurofibrils are special features of neurones - what do they do?
provide cellular stability ad structure
- Chains of tuberin running along axon to cell body and axon terminal
- Moves vesicles along axon with foot like projections
What are neurotubules?
microtubule transport system ,
chains of tubulin that run from the soma to the axon terminal
and have transport molecules on the chains that move vesicles along the outside of tubules -foot like process
cell body —- axon terminal carries:
neurotransmitter vesicles, proteins and lipids on kinesis
axon terminal —– cell body carries:
cell debris on dynein - energy dependent
wha does myelin provide and where does depolarisation take place
electrical insulation - and depolarisation takes place at the nodes of ranvier
what is saltatory conduction
ions only diffuse at gaps. local currents elongated speeding up transmission
Describe what a Schwann cell is where it is found
- In peripheral nervous system, Schwann cell wraps around one neurone.
describe what an oligodendrocyte is and where it is found
- In central nervous system, oligodendrocyte has multiple arms which wraps around multiple axons.
grey matter
cell bodies
white matter
axons
grey matter is found where in the brain
peripherally but central in the spinal cord
what are glial cells
non-neuronal cells in the CNS
4 types of glial cells
oligodendrocytes
astrocytes
microglia
ependymal
what are astrocytes
maintain microstructure,
blood brain barrier
what are microglia and what do they produce
immune cell ( monocyte) produce growth factors
what are ependymal cells
produce CSF , line CSf spaces, cilia aid CSF movement
3 connective tissues of nerves
endoneurium - connective tissue around myelin sheath of ash myelinated nerve fibre in PNS
perineurium - surrounds bundle( fascicles) of nerve fibres within a nerve
fascicles - bundle of axons , nerve fascicle - PNS in CNS this is known as a nerve tract
epineurium - surrounds peripheral nerve -BV
3 main roles of peripheral nerves
motor, sensory and autonomic
efferent neurones
away from the CNS
afferent neurones
towards the CNS
what is fibre class based on
diameter and myelination
What are Adelta fibres function
fast pain and temperature towards the CNS
What are Abeta fibres function
afferent for touch and pressure
somatic sensory modalities (4)
tactile - pressure, touch and vibration
pain
proprioception - positions of limbs and static movement
thermal
mechanoreceptors
deformation and stretching
thermoreceptors
temp
nociceptors
pain
What are the 2 types of nerve endings
free nerve endings - dendrites sit in tissue where single detected
encapsulated nerve endings - deformed and enhances sensitivity - touch pressure and vibration
