neurones definitions. Flashcards
what is meant by the term polarised?
a membrane that has a potential difference across it
depolarisation def?
loss of polarisation acrossa membrane
+40mV
refers to the period when Na+ channels open and Na+ ions diffuse by facilitated diff into the membrane.
resting potential def?
the pd of a neurone at rest when there is no action potential being transmitted.
-70mV
action potential def?
the depolarisation of the cell membrane
hyperpolarization def?
when the pd overshoots slightly and influx of K+ ions facilitated diff out of neurone membrane resulting in the membrane pd becoming more -ve than at restig potential of -70mv.
refractory period ?
The time after an action potential has passed + no more APs can be stimulated across the membrane as the Na+ channels are closed.
Na+/K+ pump is used to return the membrane back to resting to potential by redistributing the ions to their correct places.
threshold potential def?
a pd across a membrane at -55mv . If a stimulus does not reach threshold potential an action potential will not be generated.
generator potential def?
a small change in the potential difference within a cell due to some Na+ diffusing into the cell.
all or nothing principle def?
the principle that a stimulus must reach at least threshold potential (-55mv) for an action potential to be generated.
No matter how large the stimulus the action potential will always be the same size
repolarisation def?
when a membrane is restored back to its resting potential
saltatory conduction def?
when an action potential jumps between nodes of ranvier + depolarisation ONLY occurs at the unmylinated NOR
potential difference def?
the difference in charge inside + outside of a neuron
local current flow ?
movement of action potential down conc gradient inside the neuron membrane from high Na+ => low Na+
leads to +ve feedback as Na+ channels open leading to more Na+ ions diffusing into membrane.
potential def?
- the term used to be describe the movement of charged particles across a membrane of a cell.
nerve impulses?
an action potential potential that is along an axon to other end of a neuron.
what is a synapse?
a gap between 2 neurons
what is the synaptic cleft?
the space that separates the axon of one neuron and another dendrite
it is the space where NT are released by exocytosis + where they diffuse towards post synaptic neuron.
what is the presynaptic neuron?
the neurone wihch the AP is sent from / neuron where hte neurotransmitters are released by exocytosis from
what is the post synaptic neuron?
the neuron where the neurotransmitter binds to (on the receptors on the membrane)
what is the synaptic knob?
the swollen end of a presynaptic neuron where Mt and SER are present to make neurotransmitters which are released by exocytosis.
contains neurotransmitters
what is the synaptic vesicle?
the neurotransmitter receptor that the NT bind to on the post synaptic neuron.
what are neurotransmitter vesicles?
vesicles in the presynaptic neuron that contain the NTs
what are excitatory synapses?
a synapse where the NTs eg Ach bind to post synaptic membrane causing depolarisation so that an action potential can be propgated.
what are inhibitory synapses?
a synapse where neurotransmitters eg GABA hyperpolarise the membrane pf the post synaptice membrane ( ie making inside more -ve than RP) so that action potentials cant be fired
what is synaptic divergence?
when one neurone joins with many others to disperse info (APs ) to different parts of the body.
what is synaptic convergence?
when MULTIPLE neurons connect to ONE neuron so that info can be amplified.
give 5 examples of neurotransmitters?
serotonin epinephrine dopamine adrenaline Acetylcholine
function of Acetylecholinesterase?
enzyme that breaks down Ach in synaptic cleft to choline + acetic acid + choline by HYDROLYSIS.
what is summation?
why is it needed?
this is where the effect of NTs can be combined to stimulate an action potential
- summation may be needed when there is a WEAK STIMULUS (not a small AP bc all AP same size) that causes a few NTs to be released into the synaptic cleft. -> this may not be enough to excite the post synaptic membrane to threshold + thus may not be enough to stimulate an action potential.
temporary summation?
this is when multiple action potentials are fired rapidly in a quick succession one after the other within a short time frame.
why does the firing of AP across a neuron need to be in a short timeframe in temporal succession?
- so that the AP can add on to each other to reach threshold potential
spatial summation?
when action potentials on several different presynaptic neuron simultaneously arrive at the post syn neuron to reach threshold + trigger an action potential in the post synaptic neuron.
benefit of summation?
synapses can accurately process the information received.
how do synapses ensure that the impulses are transmitted one way only?
- receptors for the neurotransmitters are only found on the post synaptic neuron.
what are the 4 main roles of synapses?
unidirectional transmission from presynaptic neuron to post synaptic by having receptors o the POST syn only
- can cause multiple responses from one stimulus (divergent synapse)
- can receive multiple responses for one response (convergence synapse)
