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Which is greater - The extent of membrane polarization at threshold potential or that of the resting membrane potential?
Wiki User
∙ 15y ago
A cell is more depolarized at it's threshold potential than it is at it's resting potential. This is important because a nervous system where a random excitatory post synaptic potential (epsp) would trigger the next neuron would lead to an overly excitable nervous system (btw, this is why caffeine makes you jittery).
Wiki User
∙ 15y ago
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An action potential is triggered if?
If a neuron, or other excitable tissue, is stimulated by a stimulus of threshold strength or greater strength..
What determines if an action potential is initiated in the postsynaptic neuron?
Every time neurotransmitter is released from the presynaptic neuron it generates an excitatory post synaptic potential(EPSP) in the postsynaptic neuron. When the EPSP is greater than the threshold for excitation an action potential is generated.
The greater omentum arises from what part of the stomach?
peritoneal membrane
If the frequency of light is greater than the threshold frequency will photoelectric effect starts?
Yes - that's how it works.
What describes the potential energy diagram of an exothermic reaction?
The potential energy of the reactants is greater than the potential energy of the products.
An action potential is triggered if?
If a neuron, or other excitable tissue, is stimulated by a stimulus of threshold strength or greater strength..
What is the difference between a compound action potential and a single action potential?
Single action potentials follow the "all or none" rule. That is, if a stimulus is strong enough to depolarize the membrane of the neuron to threshold (~55mV), then an action potential will be fired. Each stimulus that reaches threshold will produce an action potential that is equal in magnitude to every other action potential for the neuron. Compound action potentials do not exhibit this property since they are a bundle of neurons and have different magnitudes of AP's. Thus compound action potentials are graded. That is, the greater the stimulus, the greater the action potential.
What is concentration polarization in membrane science?
Many electrochemical reactions produce or consume species in the solution. The rates of reactions involving dissolved species which participate as reactants in the rate-determining step(that stage in the reaction which controls its rate) will be dependent on the concentration of the dissolved species. As the dissolved species are consumed by the reaction, so a greater change in potential will be required to maintain the current, and this is known as concentration polarization. A reaction for which concentration polarization dominates is referred to as mass-transport or diffusion controlled.
What determines if an action potential is initiated in the postsynaptic neuron?
Every time neurotransmitter is released from the presynaptic neuron it generates an excitatory post synaptic potential(EPSP) in the postsynaptic neuron. When the EPSP is greater than the threshold for excitation an action potential is generated.
What are graded potentials?
Voltage impulses in neuronal dendrites which vary in strength. (and btw, the following previous DETAILED answer is WONDERFUL!!)Upon being stimulated (by another neuron or as a special receptor) the dendrites of a neuron produce a graded potential. Stimulation can occur in many ways, including chemical stimulation (neurotransmitters, etc.), mechanical stimulation (certain pain receptors, hair receptor, etc.), light stimulation (photoreceptors) and a few other methods. Regardless of the method of stimulation the same general result is effected. Certain receptor protein ion channels on the dendrites are activated, and opened. This causes an influx (or efflux) of whatever ion the receptor channel was geared for. Thus it can cause either a depolarization (an excitatory response that may lead to an action potential) or hyperpolarization (an inhibitory response which makes it harder for an action potential to occur) depending on the ion let in (or out). The more receptor protein ion channels that are stimulated the stronger, or more intense the signal. A slight stimulation of a receptor protein ion channel will often open the channel and let in ions. However in order for a depolarization of threshold strength to reach the axon hillock, it generally requires multiple depolarizing receptor protein ion channels to open. Because of this, graded potentials are said to summate. In effect the total polarizing effect of the ion channels adds together. This is important in that one channel cannot stimulate an action potential, it takes multiple channels working in concert to depolarize a membrane enough to cause and action potential. Graded potentials (or receptor potentials when they occur in receptor cells) are short lived depolarizations or hyperpolarizations of an area of membrane. These changes cause local flows of current (current reflects the movement of ions) that decrease with distance. The magnitude of a graded potential is a direct reflection of the intensity or strength of the stimulus. The more intense the stimulus, the more ion channels that are opened, and the greater the voltage change (hyper or de- polarization) and the farther the current flows. Once stimulated polarization occurs as ions rush in. These ions accumulate very close to the stimulated area. From there the surplus of ions radiates out in all directions, polarizing adjoining membranes. As this polarization spreads like a wave it leaves behind it a wake of formerly polarized membrane that very quickly returns to resting membrane potential. As the wave of polarization ripples across the membrane it either summates (adds or subtracts) with other polarization waves or quickly looses intensity. This is in part due to the ever present leakage channels . Because the current dissapates quickly and is short lived graded, potentials can only act as signals over short distances. However their purpose is only to drive the axon hillock to threshold membrane potential, at which point an action potential will be generated.changes in the transmembrane potential that cannot far from the site of stimulationamplitude of various sizes
Two layered serous membrane attached to the greater curvature of the stomach?
The greater omentum
Is threshold toxicity value greater or less than LC50?
Less.
How does an object affect the height of the object?
Directly. The greater the potential fall, the greater the potential energy.
The greater omentum arises from what part of the stomach?
peritoneal membrane
The size of the difference threshold is greater for heavier objects than for lighter ones?
Webers Law
What do pacinian corpuscles detect?
They are mechanoreceptors that detect pressure, and are found in the skin and also in joints and tendons. Naked nerve endings lie in the centre of the corpuscle surrounded by concentric layers of connective tissue separated by viscous gel (looks a little bit like an onion!).Mechanical stimuli are converted into electrical impulses as follows:Transduction occurs - the production of a small receptor potential of about 1mV across the receptor membrane when pressure is applied.The receptor potential is produced by deformation of the receptor membrane, which interferes with ion channels embedded in the membrane and causes leaks, allowing an influx of sodium ions.A generator potential is produced and an impulse is generated at the first node of ranvier. Electrical impulses are transmitted along the neurone.The presence of gel-filled lamellae in the Pacinian corpuscles provides a mechanical filter of the stimulus. If pressure is applied rapidly the membrane of the corpuscle is deformed for a few milliseconds until the gel flows and the membrane resumes its normal shape. If pressure is applied slowly the gel flows away from the stimulus so the membrane is not deformed, and no receptor potential is generated. The greater the pressure applied to the corpuscle, the greater the receptor potential. Once the pressure reaches a critical size (te threshold) an action potential is triggered.
The greater influx of sodium ions results in what of the membrane?
depolarization
