Neuro physiology Flashcards
What are the types of gated channels
Mechanically gated channels: Channels open when the axolemma is deformed. closes when axolemma returns to noraml state
chemically gated channels: Opens when a neurotransmitter binds to the outside, opening the channel
voltage gated channels: opens when the membrain reaches threshold
where are the different types of channels located around the cell body
in the dendrites and cell body: chemically gated Na and K channels
in the axon hillock voltage gated Na and K channels
in the axon terminals voltage gated Ca channels
how is the concentration grandient of ions maintained
the K / Na exchange pump, 3 Na out of the cell while 2K pumped into the cell. uses atp in the process
what is a local poteintal and how are they summated
a local potential is the membrane potential at one area once on the cell body
these can be added up in the axon hillock in spatial or temporal manors,
spatial: there are AP comming in from multiple neurons
Temporal: there are multiple AP from the same neuron
these are either depolarizing or hyperpolarizing in the location, this is not an AP, they my sum to make acton potenials
what is the difference between IPSP and EPSP
Inhibitory post synaptic potentials: when the neurotransmitter signals to open K chemically gated channels, hyperpolarizing
Excitory post synaptic potenitals: when the neurotransmitter signals for Na chemically gated channels to open depolarizing
why is summation done in the axon hillock
due to a high concentration of voltage gated sensors to start an action potential when -60mV is reached
why do action potenitals not flow backwards
due to the absolute refractory period. when a voltage gated Na channel is opened it enters the absolute reforactor period until it starts to close, note that this only happens once the K channels have been open for long enough to adiquitly decrease membrane potenital, not when the Na channels inactivate.
after this period we reach relitive refractory where a second AP can be sent but requires a much larger thershold voltage
How does AP flow down myelinated axons compaired to unmyelinated axons
myelinated axons: The nodes of Ranvier are filled with lots of voltage gated channels. the Na diffuses faster the the mechanical opening and closing of gates. this cauases them to diffuse to the next node quicker, opening lots of channels to continue the AP
in unmyelinated axons: diffusion of the Na when it enters the axon will cause neighbouring Na channels to open which occours down the axon
where is the internode section of a myelinated axon
under the myeline, aka between the nodes of ranvier
what is the process when the AP reaches the axon terminals
1) Ap causes Ca gated cahnnels in the axon terminals to open
2) this tiggers the movement of vesicles with neurotransmiters to exocytose into the synaptic cleft
3) Neurotransmitters diffuse down the synaptic cleft to the chemically gated channels in the post synaptic axon dendrites and cell body
What occours when a neurotransmitter unbinds from the dendrites
enzymes in the synaptic celft break down the neurotransmitter
a second of this can be sent back into the cell to be remade into new neurotransmitters
describe the difference between neuromuscular junctions and neuron - neuron synapes
Neuromuscular juctions: between the effector muscle and post snaptic neuron, cause 1 large synaptic transmittion no summation required. ACh, always excitory
NN: small action potenital both IPSP and EPSP summed to reach threshold. variety of NT can be used
what is an electrical synapse
the use of gap junctions causes the action potenital to be continuous from 1 neuron to the next, is always the same sie as AP are always the same size. very consistant
Why does the second stimulus need to be so much larger than an inital stimulus in the refractory period
The influx of Na must overcome in the outflow of K repolarising the cell during the repolarisation phase
