W7 Neurology and Neurocytology (watch recording for slides 11/12) Flashcards
what structures make up a typical neuron?
cell body, dendrites, axon, pre-synaptic terminals a myelin sheath and a nucleus
what does the cell body do?
makes proteins essential for neuronal function
what do dendrites do?
receive signals from other neurons
what do axons do?
transmit electrical impulses to pre-synapatic terminals
what do pre-synaptic terminals do?
transmit signals to adjacent cells
what doe sthe myelin sheath do?
speeds up conduction
what are the three types of neuroglial cells?
microglia, astrocytes and oligodendrocytes
what do oligondendrocytes do?
form the myelin sheath (aka Schwann cells in the PNS)
what do astrocytes do?
serve as a barrier between neurons and is important in development and inflammation (protoplasmic (grey matter) / fibrous (white matter))
what are microglia responsible for?
responsible for cellular clearance after injury
what do axons end in?
a synapse or neuromuscular junction in muscle
axon terminal contains vesicles of neurotransmitters such as?
acetylcholine, noradrenaline, dopamine and serotonin
as nerve impulses travel down axons, vesicles fuse with what?
pre-synaptic membranes
what does a neurotransmitter diffuse across from and to?
diffuses from a synaptic cleft and interacts with a post-synaptic receptor
neurons have a resting potential but what happens when the threshold potential is reached?
the neuron will ‘fire’ - increased firing frequency increases intensity of the signal
do excitatory neurons move the resting potential towards or away from the threshold?
towards - inhibitory neurons move it away from the threshold
what are the 5 stages of action potential generation and propagation?
- there is stimulus (must reach over -55mV (the threshold potential) otherwise the initiation will fail)
- depolarisation occurs as sodium ions move in reaching an action potential of around +40mV
- repolarisation occurs as sodium ions move out
- hyperpolarisation occurs where the potential is below resting
- resting potential is reached again at -70mV
* this all happens in the space of few miliseconds
what is a refractory period?
if a second stimulus is applied to a neuron less than 0.001 second after the first it will not trigger another impulse. The membrane is depolarised and this is known as the refractory period
how does repolarisation occur?
it is first established by the opening of potassium channels and the facilitated diffusion of potassium out of the cell
how does repolarisation occur?
it is first established by the opening of potassium channels and the facilitated diffusion of potassium out of the cell
in some neurons the refractory period lasts only 0.001-0.002 seconds meaning that how many impulses can a neuron transmit per second?
500-1000
what are the first 6 stages of a synaptic transmission?
- uptake of the precursors
- synthesis of transmitter
- storage of transmitter in vesicles
- degradation of surplus transmitter
- action potential
- influx of calcium
what are the last 7 steps of a synaptic transmission?
- release of the neurotransmitter
- diffusion to post-synaptic receptors
- interaction with postsynaptic receptors
- inactivation of transmitter
- reuptake of neurotransmitter
- uptake of the neurotransmitter by non-neuronal cells
- interaction with pre-synaptic receptors
what is a neurotransmitter?
a chemical used for neuronal communication in the body, there are over 50 that have been identified and can be classified by chemical structure and functional role
