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42 Cards in this Set

  • Front
  • Back
The two types of Neuron transmissions.
Synaptic and Membrane transmission
Synaptic Transmission is a?
Chemical process, the result of a chemical neurotransmitter.
Membrane transmission is?
The propagation of an action potential across a axon along the membrane of the axon.
Synaptic transmission are different then neuromuscular junction due to?
1)Transmission across the synapse does not necessarily result in an action potential. Instead, small potentials are produced which must add together in summation to produce an action potential.
2)Although ACh is a common neurotransmitter, there are many others and the exact effect at the synapse depends on the neurotransmitter involved.
3)Neurotransmitters can be excitatory or inhibitory. The result might be to turn off the next neuron rather than to produce an action potential.
Basic steps of synaaptic transmission.
1) impulse arrives at the axon terminus causing opening of Ca+2 channels and allows Ca+2 to enter the axon. The calcium ions are in the extracellular fluid, pumped there much like sodium is pumped. Calcium is just an intermediate in both neuromuscular and synaptic transmission.
2) Ca+2 causes vesciles containing neurotransmitter to release the chemical into the synapse by exocytgosis across the pre-synaptic membrane.
3) The neurotransmitter binds to the post-synaptic receptors. These receptors are linked to chemically gated ion channels and these channels may open or close as a result of binding to the receptors to cause a graded potential which can be either depolarization, or hyperpolarization depending on the transmitter. Depolarization results from opening of Na+ gates and is called an EPSP. Hyperpolarization could result from opening of K+ gates and is called IPSP.
4) Graded potentials spread and overlap and can summate to produce a threshold depolarizaton and an action potential when they stimulate Voltage gated ion channels in the neuron's trigger region.
5) The neurotranmitter is broken down or removed from the synapse in order for the receptors to receive the next stimulus.
Ach-E breaks down _____?
acetylcholine
Monoamine oxidase (MOA) is an enzyme which breaks down the _______?
Catecholamines (epinephrine, nor-epinephrine, dopamine), and epinephrine (which is an important autonomic neurotransmitter) is removed by the axon as well as a process known as reuptake.
Reuptake is a process in which?
Is the process in which Monoamine oxidase breaks down catecholamines, and norepinephrine and then removes these products from the axon.
_______ are small, local depolarizations or hyperpolarizations which can spread and summate to produce a threshold depolarization.
Graded Potentials
Depolarizations are called _______, because they tend to lead to an action potential which excites or turns the post-synaptic neuron on.
EPSPs, (excitatory postsynaptic potentials)
_______ the EPSPs and IPSPs will add together to produce a net depolarization (or hyperpolarization).
Summation
________ this is analogous to the frequency (wave, tetany) of the same neuron which is stimulated very quickly, analogous to summation discussed for muscle.
Temporal summation
Depolarization occurs when _______ results in a high frequency of EPSPs.
High intensity stimulus
Spatial summation means that many stimuli occurring simultaneously, their depolarizations spread and overlap and on one another to sum and produce _______
Threshold depolarization
______ when the brain causes an IPSP in advance of a reflex pathway being stimulated. (prior to hyperpolarization)
Inhibition
_____ When the brain causes an EPSP in advance of a reflex pathway being stimulated, it makes the reflex more likely to occur requiring less additional stimulation.
Facilitation
_______ are the result of athletic and other routine activities involving learned reflexes.
Learned Reflexes
Learned reflexes are reflex pathways facilitated by the ________.
Brain
_______ occurs when we perform a rote task or other repetitive action.
Post-tetanic potentiation
The _____ of a neuron is the region where the voltage gated channels begin.
trigger region
When summation results in ________ in the trigger region of a neuron, an action potential is produced.
threshold depolarization
There are both sodium and potassium channels. Each sodium channel has an ______ and an _____, while potassium channels have only one gate.
Activation gate

Inactivation gate
Resting membrane potential is around ____ inside the cell.
-70 mv
______ is when the sodium inactivation gates close and potassium gates open.
Repolarizing phase
Repolarizing causes ______to stop entering the cell and _______to leave the cell.
Na+ ions

K+ ions
Until the membrane is repolarized it cannot be stimulated, this is called the ____________.
absolute refractory period
Action potentials are ___________, and once started the action potential progresses along the axon membrane.
self-propagated
Action potentials are a _________ action, that is there are not different degrees of action potentials. You either have one or you don't.
all-or-none
A chemical such as the neurotransmitter ________ triggers a conformational change in the channel protein which allows Na+ ions to enter the cell causing depolarization.
Acetylcholine (ACh)
Most Na+ gated channels have _______ and _____gates. K+ channels have only _______gates.
activation and inactivation

activation
During the _________ period neurons cannot be stimulated because it is depolarized.
Absolute refractory period
During the ____________ period neurons require greater than normal stimulation because it is hyperpolarized.
relative refractory period
At the _______ the sodium activation gates are closed, sodium inactivation gates are open, and potassium gates are closed.
Resting state
Excess Na+ ions enter the cell causing _________ becoming briefly more positive on the inside of the cell membrane.
reversal of potential
Hyperpolarizations are called _______.
IPSPs (Inhibitory post-synaptic potentials)
In _____________ channels a change in the membrane potential toward depolarization triggers opening of the ion gates.
voltage-gated ion
Many EPSPs occurring in a short period of time (eg. with high frequency) can summate to produce threshold _______.
Depolarization
Spatial summation means that there are many stimuli occurring _________.
Simultaneously
When we anticipate a ________ we often facilitate the reflex.
Stimulus
When the brain causes an IPSP in advance of a reflex pathway being stimulated it reduces the likelihood of the reflex occurring by increasing the depolarization required. This is called ________________.
Inhibition
_______ is when the action potential begins with the activation gates of the sodium channels opening, allowing Na+ ions to enter the cell and causing a sudden depolarization which leads to the spike of the action potential.
Depolarization phase
________ is analogous to quantal summation in a muscle.
Spatial summation