Neurotransmission Flashcards
what are the components of a neuron?
dendrites - receive information
soma - cell body, controls cell processing
axon - carries info from soma to terminal boutons
terminal boutons - at the end of the axon, location of the synapse
what is the neuronal membrane made up of?
a lipid bilayer - hydrophillic and hydrophobic layers which only allow certain substances in and out of the cell
what is a membrane potential?
a potential gradient that creates the movement of particles across a membrane due to two forces
when the cell is at rest, what are it’s potentials?
the inside is more negatively charged than the outside
what is used to measure flow and strength of electrical voltage?
voltmeter
what causes there to be a membrane potential?
force of diffusion - molecules move from a high to a low concentration
force of electrostatic pressure - opposite charges attract and the same charges repel
describe how an equilibrium potential happens
- positive ions move across membranes by diffusion force
- as more positive ions move there is an increase in the electrical potential across the membrane
- eventually a point is reached when the diffusion force = the electrostatic force
what charge are organic ions?
negative
why does the membrane come to rest near the potassium equilibrium potential?
because more potassium channels are open than sodium channels, meaning that more potassium than sodium ions can diffuse
what does the Nernst equation?
it can calculate the equilibrium potential for any ion
what mechanism maintains the ionic concentration gradients across the membrane?
sodium potassium pumps
ATP (made by mitochondria) is broken down to release energy which forces the ions to move against their concentration gradient
what is an action potential?
a nerve impulse which travels down the axon and allows communication with the neuron.
it is generated at the axon hillock
it is generated by the summation of converging inputs from dendrites
what is hyperpolarisation?
when the membrane potential is more negative than the resting membrane potential, causing more positive ions to move out and negative ions to move in.
it inhibits action potentials
what is the term used to describe: the membrane is more positive than at resting membrane potential, more positive ions move in and negative ions move out.
depolarisation
what is decremental conductance?
when stimulated, depolarisation occurs which decays as it moves through the neuron
where does an action potential come from?
stimulation causes sodium channels to open, and NA rushes in. once depolarisation threshold is reached the AP is fired. an all or nothing response
describe voltage gated channels
there are two types:
- sodium channel: activated at rest and inactivated at the refractory period
- potassium channel: activated with lots of depolarisation, inactivated when too little depolarisation
describe the process of action potentials firing
- at resting membrane potential most of the voltage gated channels are closed
- a small depolarisation opens a few sodium channels leading to further depolarisation
- if the stimulation is above the action potential threshold most of the sodium channels open, more sodium moves in, further depolarisation
- some potassium channels open, potassium leaves through diffusion
- the inside of the neuron is now more positive so sodium channels become deactivated (refractory period)
- potassium continues to leave and makes the membrane potential negative (repolarisation)
- both channels close, hyperpolarisation occurs
- potassium channels close and external potassium is diffused away, resting membrane potential is restored
what are the two cells that create myelin sheaths?
oligodendroglial cells - cns
schwann cells- pns
what is the only place where action potentials can occur and why?
the nodes of ranvier - the only place sodium and potassium ions can pass, a gap in the myelin sheath
what are the two types of synapses?
electrical(rare)
chemical - chemicals released from presynaptic to postsynaptic neuron
what are the types of modulation of signal?
axodendritic, axosomatic, axoaxonic
what leads to neurotransmitter release?
influx of calcium ions
where are inputs summated?
soma
what are neurotransmitters?
chemicals used to transmit information from pre to post-synaptic neurons
what are the types of receptors on the postsynaptic membrane?
ionotropic receptor - fast transmission
metabotropic receptor - slower transmission
glutamate and GABA are part of what class of neurotransmitter?
amino acids
describe glutamate
a fast excitatory neurotransmitter in the CNS
describe GABA
a inhibitory neurotransmitter
can EPSPs be abolish/decreased?
yes, by IPSPs that are active at the same time
what are autoreceptors?
- located on presynaptic terminal
- respond to neurotransmitters in the synaptic cleft
- control neuronal communication
- negative feedback mechanism
what is the refractory period?
a period of time where the cell can’t repeat a particular action. happens after an AP is fired
