Membrane potential Flashcards
What is membrane potential?
Difference in electrical charge between inside/outside of cell
What is polarisation?
One side +ve one side -ve (-70, at rest is resting potential = sodium in extra cellular/ potassium in intracellular)
Ion channels?
Ions?
Special pores for passage of ions.
=ve /-ve charged particles (remove /add electron)
What is an atom?
Nucleus with protons and neutrons
What two processes change ion concentration?
Concentration gradient and electrostatic pressure (polarised cell membrane)
What is the difference between depolarise and hyperpolarise?
Depolarise - reduce polarisation of membrane eg goes down 70..65..63
Hyperpolarise - increases polarisation of membrane (70, 73, 77)
What does excitatory/ inhibitory postsynaptic potential do?
E- increases possibility of neuron firing as excites neurons, reaches threshold - action potential)
I - decreases PSP (takes away from threshold level)
What 3 things happen in PSP?
1) Graded response (intensity determines amplitude)
2) Instantaneous
3) decremental (less amplitude as travels along axon)
What is action potential?
The reversal of membrane potential from -70 mv to +30 - 50 mv, lasts 1 millisecond. Depends on EPSP being enough to male cell reach threshold.
What is threshold of excitation?
When membrane depolarised enough to create action potential generation (all or nothing response UNLIKE PSP WHICH ARE GRADED
What are two integration possibilities?
1) Spatial summation - simutaneous PSP sum to form greater PSP OR cancel eahc other out.
2) Temporal summation - PSP formed rapidly, as same synapse for greater potential (hyperpolarise as more accumulate, no time for resting potential)
What are most common axons?
Somatic and dendritic
What are directed and non directed synapses?
What is dendritic spine?
1) Release of neuro and site of neuro reception are close by
2) Opposite to 1
3) Nodules located on spine of dendrite.
How do small Neurotransmitters travel?
To golgi complex, packed into vesicles, go and cluster near presynaptic membrane , until exocytosis
Have effect on IONOTROPIC and METABO receptors. Involved in brief, effects on neuron. Released over directed synapse.
(Large (created on ribosomes) - golgi - microtubules - terminal buttons
What are receptors and ligands ?
1) Proteins on surface of PS membrane
2) Molecule that binds to another molecule
What is a large neurotransmitter?
Neuropeptide - short proteins (made up of amino acids) about 3 to 36 in length (short protein chains)
Released more diffusely, not directed synapse.
Bind to METAB receptors that release 2nd messengers. Effects longer lasting etc etc.
What do Calcium gated channels do
When action potential, open up - allow influx of calcium ions, causes small molecule NT vesicle to fuse with membrane and release content into synaptic cleft. BUT LNT - General level of calcium ions in intracellular fluid, not single action potential, more general rate/series of AP.
What influences a neuron to act?
NT bind to specific proteins on surface of synaptic membrane called receptors. Influence on neuron depends if has specific receptors that bind to specific NT.
Many Neurons bind to many N receptors.
What are two types of receptors?
1) Ionotropic - causes ligan gated ion channel to open/ close, ions flow into neuron or our (depending on NT and receptor being activated.) Can cause PSP, whether E or I depend on channel. eg. sodium channel in to neuron- excitatory.
2) Metabotrophic - more common– Not GATE. Signal protein has G protein attached - when released can a) break of and cause synthesis of 2nd messenger , this can go into cell nucleus and cause changes in DNA
OR b) can open /close channel
Compare metabotropic to Ionotropic receptors.
M = more common, have slower effects, last longer, and act over greater area (more diffuse) and more varied.
How are NT moved from synaptic cleft?
1) Reuptake - transporter mechanism reabsorb NT back into presynaptic neuron/
2) Enzymatic degradation. NT broken down by enzymes.
What are glial cells?
Non neurol cells in CNS and PNS
No axons or dendrites
Smaller but more numerous than neurons
Conduct signals
What are gap junctions and what do they do?
Narrow spaces between adjacent cells, bridged by tubular protein channels filled with cytoplasm (connexins)
Allow small molecules and electrical signals to pass between cells.
Quicker message.
Where is a NT created?
IN the cytoplasm of a neuron
