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Why are action potentials said to be all or none where as epsps and ipsps are described graded?
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Numerous nerve impulses arriving at a synapse at the same time exert a cumulative effect?
Kind of. Each neurone can have thousands of inputs from other neurones arriving at the same time. It all depends on the types of signal arriving from the other neurones. There are 2 types of incoming signal; 1. Excitatory Post-synaptic potentials (EPSPs) - These inputs depolarise the neurone (bring the negative voltage of the neurone closer to 0mV). 2.Inhibitory Post-synaptic potentials (IPSPs) - These inputs hyperpolarise the cell (make the neurone voltage more negative). Some of the inputs coming to the neurone will be EPSPs, some IPSPs. If all the inputs come in and there are more EPSPs then the neurone will depolarise. If the neurone depolarises to the firing threshold (around -40mV) then an action potential will be propagated and the neurone will transmit the message to the next neurone in the chain. If the majority of the inputs are IPSPs then the neurone will hyperpolarise and will not fire. If there are more EPSPs than IPSPs but the neurone still doesn't depolarise enough to reach the firing threshold then the neurone will not fire.
The site in the neuron where EPSPs and IPSPs are integrated is the?
The Axon Hillcock is the site where EPSPs AND IPSPs are integrated in the neuron.
Why are action potentials said to be all or none?
All or nothing response of an action potential (AP), refers simply to the fact that an AP will either occur, or not. There is no gradient, no half APs or double APs. The only option is AP, or no AP. Like in computer binary, the response is either 1 (an AP) or 0 (no AP). All the factors trying to induce (or inhibit) an action potential (i.e other action potentials, EPSPs and IPSPs) add up (summate) at the axon hillock, (aka the trigger zone). Here, if the stimulation is big enough an action potential will occur. If the stimulation is not big enough, no action potential occurs.
What is sub threshold Depolarization of nerves?
Subthreshold depolarization refers to a small increase in the membrane potential of a nerve cell that does not reach the threshold for generating an action potential. It is a graded response that occurs when the membrane potential of the nerve cell approaches but does not exceed the threshold for firing an action potential. Subthreshold depolarizations can summate or integrate within the cell to reach the threshold and trigger an action potential.
How is an action potential propagated along a axon?
A.P. propagation consists of the movement of the action potential along the axon, axon terminals and dendrites. A.P. propagation is non-decremental meaning that the amplitude of the A.P. remains constant throughout the propagation. Action potentials are also follow the principle of all-or-none fashion. Meaning if there is not enough summation(adding of EPSPs and mEPPs) to bring the stimulus to threshold, then no AP will be elicited
What EPSPs will summate to a sustained value above threshold?
Generate a string of action potentials
How action potential is propagated?
A.P. propagation consists of the movement of the action potential along the axon, axon terminals and dendrites. A.P. propagation is non-decremental meaning that the amplitude of the A.P. remains constant throughout the propagation. Action potentials are also follow the principle of all-or-none fashion. Meaning if there is not enough summation(adding of EPSPs and mEPPs) to bring the stimulus to threshold, then no AP will be elicited
Numerous nerve impulses arriving at a synapse at the same time exert a cumulative effect?
Kind of. Each neurone can have thousands of inputs from other neurones arriving at the same time. It all depends on the types of signal arriving from the other neurones. There are 2 types of incoming signal; 1. Excitatory Post-synaptic potentials (EPSPs) - These inputs depolarise the neurone (bring the negative voltage of the neurone closer to 0mV). 2.Inhibitory Post-synaptic potentials (IPSPs) - These inputs hyperpolarise the cell (make the neurone voltage more negative). Some of the inputs coming to the neurone will be EPSPs, some IPSPs. If all the inputs come in and there are more EPSPs then the neurone will depolarise. If the neurone depolarises to the firing threshold (around -40mV) then an action potential will be propagated and the neurone will transmit the message to the next neurone in the chain. If the majority of the inputs are IPSPs then the neurone will hyperpolarise and will not fire. If there are more EPSPs than IPSPs but the neurone still doesn't depolarise enough to reach the firing threshold then the neurone will not fire.
The site in the neuron where EPSPs and IPSPs are integrated is the?
The Axon Hillcock is the site where EPSPs AND IPSPs are integrated in the neuron.
Will any two EPSPs override one IPSP?
false
Why are action potentials said to be all or none?
All or nothing response of an action potential (AP), refers simply to the fact that an AP will either occur, or not. There is no gradient, no half APs or double APs. The only option is AP, or no AP. Like in computer binary, the response is either 1 (an AP) or 0 (no AP). All the factors trying to induce (or inhibit) an action potential (i.e other action potentials, EPSPs and IPSPs) add up (summate) at the axon hillock, (aka the trigger zone). Here, if the stimulation is big enough an action potential will occur. If the stimulation is not big enough, no action potential occurs.
What is sub threshold Depolarization of nerves?
Subthreshold depolarization refers to a small increase in the membrane potential of a nerve cell that does not reach the threshold for generating an action potential. It is a graded response that occurs when the membrane potential of the nerve cell approaches but does not exceed the threshold for firing an action potential. Subthreshold depolarizations can summate or integrate within the cell to reach the threshold and trigger an action potential.
EPSPs produced by many different presynaptic fibers converging on a single postsynaptic neuron causing summation on the postsynaptic dendrites and cell body best describes?
spatial summation
How is an action potential propagated along a axon?
A.P. propagation consists of the movement of the action potential along the axon, axon terminals and dendrites. A.P. propagation is non-decremental meaning that the amplitude of the A.P. remains constant throughout the propagation. Action potentials are also follow the principle of all-or-none fashion. Meaning if there is not enough summation(adding of EPSPs and mEPPs) to bring the stimulus to threshold, then no AP will be elicited
